Kristin Wintermute: On over for us and get started with tonight's critical minds evolution of the human mind and brain.
Mark Reimers: Thank you. Kristen. Thank you, Emily. Can y'all hear me fine.
Great.
Mark Reimers: Then let's start with
Mark Reimers: What do we want to know, well,
Mark Reimers: You know we are a relatively weak a would not recommend arm wrestling with a chimpanzee or a gorilla, but we have as a species managed to dominate the whole planet for good and frill
Mark Reimers: So what is our secret sauce. What's the secret of our success in a, in a way, why have we
Mark Reimers: dominated the planet, whether that's for good or for ill in ways that other animals have not
Mark Reimers: And we think that there's something special about the human brain is it something that's like a special cell type or special circuit and that leads into a question that is at the heart of a lot of political debates and that is what is human nature really
Mark Reimers: So let me start with some brain basics.
Mark Reimers: This will take about five minutes, a quick review, but I'd like to ask you two questions. First, how much do you think your brain ways
Mark Reimers: And how you know how much space does it fill. But let's start. How much weight do you think it has. And how many cells do you think are in it.
Mark Reimers: So take a second write down an answer or think about an answer.
Mark Reimers: Well, if you're an adult, your brain weighs about three pounds and fills the space of about 80 cubic inches.
Mark Reimers: Now there's roughly 200 billion cells in your brain.
Mark Reimers: But only about a third of them are neurons. The cells that we think of as the main actors in the brain.
Mark Reimers: And the rest of them are you can think of is like the stage hands, but they're important to make keep the show on the road, but they're not the stars.
Mark Reimers: Now, oddly enough, we think of our brain as mostly this area and we kind of forget about this little area tucked in here called the cerebellum, but actually most of your neurons are in the cerebellum.
Mark Reimers: They're very small
Mark Reimers: But you can live without the cerebellum and some people have walked into a clinic and it's been discovered that they have no cerebellum.
Mark Reimers: So it's quite possible to live a relatively normal life without one. So you're mostly living your life using perhaps about 20 billion neurons in the majority of your brain.
Mark Reimers: So what do these neurons look like, Well, here's a picture on the left of about 20 different neurons that are
Mark Reimers: Actually a small percentage of all the neurons in the area that's being pictured, but only about 20 of them have been colored
Mark Reimers: So that you can see their shapes the rest of them are transparent so they are small cells. They're about 1250 microns across sometimes a little bigger. And they so that's 12 or 15 millions of a meter, very small.
Mark Reimers: But they have these long branching processes thousands of these branches. They're called dendrites thats related to the Greek word for tree.
Mark Reimers: And these dendrites receive inputs from other neurons. So all of these branches are about communicating with other neurons and where these dendrites touch the
Mark Reimers: Other neurons coming from other cells. They have a sin apps and that sin apps works by sending chemicals we call neuro transmitters, but some chemicals in one 1,000th of a second. These chemicals can
Mark Reimers: Travel the slow of a be a very short distance between one setups and another it's much exaggerated in this picture.
Mark Reimers: So it's almost as fast as the electrical impulses that are coming along the neurons themselves.
Mark Reimers: So these things happen very quickly.
Mark Reimers: Now, let's talk a little bit about human evolution and, in particular, about how human evolution has affected the brain.
Mark Reimers: So just, again, a quick review.
Mark Reimers: We are a member of the family, the family we think is about 30 million years old and humans split from our common ancestors with our closest cousins, the chimps and bonobos, we think something like 7 million years ago. These dates are all approximate
Mark Reimers: So, give or take a million years.
Mark Reimers: Now, oddly enough, there have been over a dozen distinct human species in the last 2 million years. We're the only ones left.
Mark Reimers: So what if we compare our brains to a chimpanzees brain.
Mark Reimers: Well, so on the left is a diagram or picture of a chimpanzee brain on the right is a diagram of a human brain.
Mark Reimers: Well, it's pretty obvious. The human brain is bigger, it's actually about three times as big in volume.
Mark Reimers: And wait
Mark Reimers: A little more than that and
Mark Reimers: But if you look at this, shapes, they're pretty much the same. You can find all the same, you know, lobes and fishers on the chimp brain as you can on the human brain. Well, okay, so it looks the same, is it organized the same way.
Mark Reimers: Well, it seems that just about any distinct area that you can find on the human cortex. You can also find corresponding area.
Mark Reimers: And what do we mean by that, it means that has the same kinds of cells. The same kind of layering in which the cells or arranged. I am the same kinds of connections to the other parts of the brain. Same kinds of inputs, same kinds of outputs.
Mark Reimers: And so we can find for any just about any area of human cortex, we can find a corresponding structure on a monkey brain and certainly on a chimpanzee brain.
Mark Reimers: And so that makes us think maybe we're not maybe our brains aren't quite so special.
Mark Reimers: Well, let's return to the question of size. Maybe it's just that they're bigger maybe we're we're smarter. Just because we have bigger brains. And that's been a common idea.
Mark Reimers: So let's first discuss the relationship of brain size to body size. So this is a beautiful picture that I've crypt from Scientific American article
Mark Reimers: And
Mark Reimers: I would highly recommend this article. It's a good good summary of brain size and body size, but you see all of these pictures of individual mammals here from mice and bats. Sorry. That's my son that's bowls bats to blue whales and sperm whales here so
Mark Reimers: Along the whole of the mammalian order.
Mark Reimers: brains get bigger as bodies get bigger in an almost predictable fashion. We are a bit of an outlier ships are also an outlier. Although less so. Dolphins are quite an outlier.
Mark Reimers: But actually, elephants are right on the line and blue whales and start blue whales and sperm whales are actually bit below the line.
Mark Reimers: And so we can see that, overall, there's this relationship between brain size and body size. So let's start with comparing ourselves to a chimp. So we have roughly
Mark Reimers: Twice the body weight of a chimp. So if we scaled up
Mark Reimers: A chimp sprain to human body size because it's a non linear scaling it would be about half of our brain size.
Mark Reimers: And actually that's about the size of the brain of a gorilla gorilla has about the same body size and body weight as a human being, but a brain about half as big. So our brains are about twice as big as an ape our size should have
Mark Reimers: So we're we are definitely an outlier.
Mark Reimers: And when do you suppose that happened you suppose that happened, you know, near the beginning of the divergence from chimps and bonobos, or maybe more recently.
Mark Reimers: Well, in fact, we have enough skulls. Now that we can actually find out pretty much exactly when it did happen. So for the last, you know, 10 million years. Up until the about a million and a half years ago.
Mark Reimers: Our ancestors brains were about the right size for their bodies compared to any other ape.
Mark Reimers: They had brains that were Nope. No. We're different from an essentially a gorilla would have the same size.
Mark Reimers: But about a million and a half years ago there was a sudden inflection point and we are brain size took off dramatically. And here's a sort of more detailed picture of the last million and a half years.
Mark Reimers: And you can see that
Mark Reimers: This this huge inflection this more than doubling in size has occurred, primarily in the last million years.
Mark Reimers: So we want to ask why, what's different about human biology in the last million or million and a half years. Well, there's two important differences.
Mark Reimers: And we'll get to those in just a minute.
Mark Reimers: But I want to start with the hypothesis that was pretty common 50 years ago. In fact, it was so common that we were not me, but a professors used to teach this as this was a scientific fact that we got bigger brains, or I ancestors got bigger brains, so that they could use stone tools.
Mark Reimers: And making us stone tools, but there's a bit of a problem with that hypothesis, and that is that, in fact, if you look at the brain areas that are actually used in the fine motor control for making stone tools.
Mark Reimers: Those are the motor and sensory areas in our brains and they are the same size in humans and chimps. Now remember the rest of our brain has doubled. So proportionally.
Mark Reimers: That area has actually shrunk in humans. So that doesn't seem to fit this idea of, you know, getting bigger brains in order to use stone tools.
Mark Reimers: And that hypothesis is not very commonly held today there are still some people who believe. So the most common hypothesis or idea today.
Mark Reimers: Is that we are a social species and social doesn't mean just niceness. It also means people have moves and sometimes you have enemies or you often have enemies and you want to keep track of them.
Mark Reimers: And the more friends and enemies and the more variable their moods and how their lives change with having children or having, you know, fights with other with other apes. You have a lot more and keep track of.
Mark Reimers: And it turns out that even monkeys keep track of all of the relationships.
Mark Reimers: Between within their group, not just their relationships with other monkeys. They keep track of, you know, all the relationships between other monkeys that they are friends or enemies with. They want to know what's happening.
Mark Reimers: And so you can imagine that that place is quite a strain on the brain.
Mark Reimers: And here's a picture that sort of famously made this point Robin Dunbar's article and science little over 20 years ago 20 years ago 10 years ago.
Mark Reimers: Where he
Mark Reimers: Showed that at least among monkeys and apes, there seemed to be pretty close correlations between the sort of typical group size that these primates live in and what he called their cortical rate neocortical ratio, which is basically how much of their brain is given over to neocortex.
Mark Reimers: So that's the leading idea. Now, it's not the only idea. There are some other ideas, but I think this is the idea of it is the most support among scientists at present.
Mark Reimers: And I'd like to give you a little more evidence of a different sort. And that is if you look proportionally at which areas of the human brain seem to have expanded, let's say, a little bit out of proportion to
Mark Reimers: A chimpanzee then
Mark Reimers: You see that one of the areas, not the only area, but one of the areas that has particularly expanded is these ventral ventral means toward the stomach or toward the bottom and medial which means toward the middle these regions of our prefrontal cortex.
Mark Reimers: And those areas seem to have expanded, perhaps even more in human beings.
Mark Reimers: That then the rest of the brain. And these regions are particularly active in social relationships, particularly strong attachments. So if you are thinking of someone you love.
Mark Reimers: Then that area will be active. If you are thinking perhaps even about some bad thing that's happened to someone you love that area will be particularly active
Mark Reimers: If you are feeling guilty about something if you felt let somebody down, especially someone you care about that area will be active.
Mark Reimers: So I think, and I'll show you some more evidence to suggest that maybe a lot of the evolutionary changes have been driven by our more complicated sociability
Mark Reimers: So I'm going to pause here for just a few minutes, and if there are any questions, Emily. If you'd like to read them out and then we'll go further.
Kristin Wintermute: I can, I can do that. This is Kristen, I do have a question from me. She asked How do Bonobos fit into all of this.
Mark Reimers: What elbows. Yes. So they are what you might call a sister species of a chimp. So let me just get back here. We are so I'm
Mark Reimers: One of those are
Mark Reimers: Very much like chimpanzees. Think of a chimpanzee with a better haircut.
Mark Reimers: And they live only south of the Congo River and they seem to be generally a nicer eight but not entirely. They're still, they still have violence.
Mark Reimers: But they diverged from chimpanzees about a million years ago. So we diverged from their common ancestor about 6 million years before that.
Mark Reimers: Great. Next question.
Kristin Wintermute: Oops, sorry. We have another. I don't have any other questions. Do people have any other questions I want to ask at this time, feel free to put it in the Q AMP a
Kristin Wintermute: Oh, here's some more.
Kristin Wintermute: Philip as any idea what drove the increase 1.5 million years ago.
Mark Reimers: So any idea what
Kristin Wintermute: What drove the increase
Kristin Wintermute: 1.5 million years ago.
Mark Reimers: So we'll be talking about that in a bit, but brought but roughly speaking, it's the emergence of a complex cooperative society. So by large chimpanzees have politics, but their politics is who gets to boss around who
Mark Reimers: They don't cooperate very much in the wild they do a little bit and they certainly don't have specialized roles. But one of the key changes in human society.
Mark Reimers: That happened sometime between 2,000,001 million years ago, is the emergence of specialized roles and specialized skills and people being cooperative and helping each other do tasks, particularly hunting, but also gathering
Mark Reimers: And we think that part of, well, I like it. I can answer more of that later.
Kristin Wintermute: Okay. I have a question from a fan. She says, I have heard, perhaps erroneously that the human brain is limited in size by the birth canal IE humans brains cannot be larger than the birth canal, even though the human brain continues to develop somewhat after birth.
Mark Reimers: Could you hold on for 10 or 15 minutes and
Kristin Wintermute: So will he'll get to that point. So I'll move on to David's question for a long while the disproportionate disproportionate size of PFC in humans seemed controversial.
Kristin Wintermute: A quick Google search finds some p A's article suggests that the original claim of a relatively larger PFC has good evidence. Now is that true
Mark Reimers: So there has been a lot of controversy there remains some controversy. So in terms of
Mark Reimers: I gave you that logarithmic plot and I tell told if you read the fine print to you read that there was a sort of exponential increase or sort of power law increase in the
Mark Reimers: Brain size relative to body size, it wasn't linear
Mark Reimers: So within a brain, there's also these kind of non linear scaling relationships and generally speaking with primate grains, the bigger the primate brain, the bigger the proportion of cortex of our prefrontal cortex is
Mark Reimers: And so Susanna pergola who sell as a Brazilian neuroscientist who's done the most extensive comparisons of brains from different mammals.
Mark Reimers: argues that the proportion of neocortex in our brain is not outrageous, given the size of our brain.
Mark Reimers: And I, by and large, by that argument, but the size of our brain is is an outlier. And I would argue that the sum of the
Mark Reimers: specific regions that have expanded sort of disproportionately
Mark Reimers: Are not are not predictable from the kind of size relationships that she's investigated.
Kristin Wintermute: And so john as is serotonin molecular Lee, the same between close species.
Kristin Wintermute: Yes, that's
Mark Reimers: Serotonin is the same molecule down to a please. Yeah, fruit flies and and
Mark Reimers: Across the animal kingdom.
Kristin Wintermute: And
Mark Reimers: We should probably good. Maybe one more than we can move on.
Kristin Wintermute: One more, and then just so everybody knows I will keep your Q AMP. A in the
Kristin Wintermute: If I haven't. If we haven't answered it. So we can come back to it. Maybe at the end or at a later point we're going to have two more breaks. So, one more question. Why have giants. Pretty much diminished in today's day and age, why
Mark Reimers: What
Mark Reimers: To pretty much dominions giants.
Mark Reimers: Um,
Mark Reimers: It's not. I mean, there were times when human beings were fairly tall like six feet was relatively normal for some of our ancestors. Some of it has to do with nutrition.
Mark Reimers: We actually don't eat as well as our ancestors on until the last maybe the last 50 years but maybe you can explain more what you mean in the Q AMP. A after after the full talk
Mark Reimers: So let's, so I'd like to
Mark Reimers: Uh, to move on to the next part of the talk.
Mark Reimers: And that is
Mark Reimers: Some of the genes and connections that are different. So what's one thing that we do that you've never heard your pet dog do
Mark Reimers: Well, we're having a conversation with words and speech.
Mark Reimers: And why can we do this, whereas it seems that our close cousins, the chimpanzees cannot
Mark Reimers: And one of the main differences is the extension of a long group of axons or connections between you can think of these like the information superhighway of the brain.
Mark Reimers: So there's about 20 of these really long distance thick connections. You can think of them like you know the internet cables.
Mark Reimers: Fiber optic cables or whatever you want, but these are the connections that take information from one part of the brain to another part that's maybe you know 10 or 20 centimeters away.
Mark Reimers: And they're 10 to 15 centimeters away. And one of the
Mark Reimers: big differences between human beings and chimps is this area this tract here.
Mark Reimers: That we technically called the Arctic fish calculus, but you don't need to remember that for the exam.
Mark Reimers: So this carries information from our Broca's area which is critical for producing speech or Verna keys area which is critical for interpreting the speech we hear
Mark Reimers: And this real this rapid connection gives us real time feedback on what we're saying. So I can hear myself speak. And if I'm not quite making the sound. I thought I was going to make. I can correct it within a fraction of a second. So you hardly notice it.
Mark Reimers: That's an important thing for learning speech because you have to be able to hear yourself talk and
Mark Reimers: Chimpanzees basically can't do that because they don't have very much feedback. They certainly don't have the rich rapid feedback.
Mark Reimers: Between these areas that we have and a monkey has no no hope of doing that.
Mark Reimers: So that's one kind of new connection that's certainly important for them. One of the most obviously human distinct characteristics but here's another one.
Mark Reimers: And I bet I told you that I would say more about the these expanded areas that remember have to do with human relationships, especially close relationships.
Mark Reimers: So not only are the areas expanded, but their connections there outputs to the rest of the brain are also greatly expanded so that this area has become
Mark Reimers: A hub for the human brain. And I'm just going to point out a couple of places it connects to so it connects forward to these areas of your cortex that are involved in making quick judgments and
Mark Reimers: You know, responding to things that are pleasant or meaningful or important to you, but they also extend and this is almost entirely unique to human beings. They extend
Mark Reimers: Laterally and to the back in to the side into areas that are associated with regulating emotion and also areas that are
Mark Reimers: Important for memory and even recognizing what something is, and so that's a part gives you the possibility of learning something like language that social cues your interactions with other people can influence how you understand
Mark Reimers: What you're seeing and
Mark Reimers: What what you're hearing
Mark Reimers: I want to also point out that there are several new kinds of cells that are greatly expanded in human beings and one of them is so called spindle cell and this picture makes both sort of look kind of little bit like runs not very attractive, but actually the spindle cell.
Mark Reimers: Is has a very, very thick axon very, very thick wire, if you will, that connects it to other cells. So this is what gets information from one area of the brain to another area very very quickly by very, very quickly. I mean, a few thousands of a second.
Mark Reimers: So you can have a whole conversation back and forth in your head so you know 10 or 20 times per second and
Mark Reimers: And the spindle cells are particularly important for that. And the interesting thing is, again, they mostly run from these areas that I've been mentioning as sort of involved in social relationships and greatly expanded in human beings.
Mark Reimers: They mostly run from those areas to the whole rest of your brain. So there. You're all the rest of your brain has information about, you know, the social meaning of things in real time.
Mark Reimers: Okay, so those are some important changes in connections. I also should mention that there are some other animals that have lots of these kinds of spindle cells and you've
Mark Reimers: Probably heard that they're quite intelligent animals like dolphins and elephants have very high number of these kinds of cells.
Mark Reimers: Now I'd like to take another topic, very quickly, and that is changes to our genes that made some of these things possible
Mark Reimers: And this, we're still sorting this out. In fact, one of these pictures is from a paper that appeared in Science Magazine last week. That's this picture at the top right here.
Mark Reimers: And I'm just going to mention there's there's several genes that are involved in in making our brains bigger. This is very technical. So if you don't like you know don't like molecular biology, feel free to get up and get a drink.
Mark Reimers: But
Mark Reimers: There's two important changes that seem to have made the most difference to our bigger brains and they both have something very unusual in common.
Mark Reimers: So,
Mark Reimers: One of those genes is
Mark Reimers: A duplication of gene that monkeys and apes have which I won't even try to pronounce for you. But this is a for those of you who really like molecular biology. This is a row GDP is associated protein 11 ok so now you can forget that for the rest of the talk.
Mark Reimers: And
Mark Reimers: This is a what we have, we have an extra copy of this gene, but that copy is broken.
Mark Reimers: And what that broken copy does is it interferes with the function of the original gene. So, it slows it down. Okay, just so what does the original gene do well it's it puts the brakes on neuron proliferation.
Mark Reimers: So the brakes are released or, oh, a little looser in human beings that in apes. So our neuron progenitors our stem cells for neurons go on proliferating a bit longer. And that makes us have thicker courtesies. And so how do we know that it's this gene well
Mark Reimers: Oops, sorry this so what they've done is they've put
Mark Reimers: That gene into a marmoset and watch its brain grow. So here's a on the same scale is the thickness of the cortex from the bottom to the top of a normal Marvel set. And here is the bottom to the top of a
Mark Reimers: Of a marmoset with that one human gene introduced and that gene basically interferes with a marmoset version of the
Mark Reimers: Of the gene, which is very similar. And that really sort of loosens the brakes. The brakes don't get up get get applied more gently so you get more of these cells being born and they fill out more before tech. So in fact, this brain is about 70% bigger
Mark Reimers: Than the normal marmoset brain so that accounts for some of the fact that our brain is substantially bigger. Whoops.
Mark Reimers: We also have another group of duplications among a group of genes called Mbps. And that just stands for neuroblastoma
Mark Reimers: I think a breakpoint family and as the name suggests, there are associated with a particular kind of cancer.
Mark Reimers: And I bring this up so that they're also important for
Mark Reimers: For human brain expansion, then I bring this up because gene duplications are a kind of crude strategy. Most of evolution proceeds by sort of slow modifications of
Mark Reimers: existing regulatory sites and existing jeans gene duplications generally don't survive because they have damaging side effects and
Mark Reimers: Be interesting thing is that these duplications and there's actually more have survived in human beings, which indicates that the benefits of having a large brain were certainly worth the side effects.
Mark Reimers: And the side effects are among other things, these, these neuroblastoma us. And there's other kinds of damage that we have to our brain cells that that we think is due to this.
Mark Reimers: The action of this gene.
Mark Reimers: So,
Mark Reimers: So that's one. You know, that's the general strategy seems very unusual that so something very important must have been driving the rapid expansion of the human brain.
Mark Reimers: Now another gene that you've probably heard of is a gene called Fox P two or F box protein p two.
Mark Reimers: And that's a sort of master regulator of other genes. So it's it by its action, it turns on and off several dozen other genes.
Mark Reimers: And at the bottom here, I have a sort of a schematic from the people who did the work.
Mark Reimers: And published it in nature about 18 years ago showing the differences between the different versions of the same gene and different species. So
Mark Reimers: Basically this is a gene that has had almost no substantive changes for 100 million years. And then suddenly, meaning in the last 7 million years it's had two important changes just in the human lineage.
Mark Reimers: And
Mark Reimers: That seems rather unusual. And it turns out that that gene controls the genes that are expressed in circuits that control not only
Mark Reimers: Our speech, but also our fine movements of our hands and so speech itself requires some very fine movements. We don't know what the at this point, what difference that actually makes except we know that people who have a mutation in Fox P to almost always have trouble speaking
Mark Reimers: Interestingly Neanderthals had our changed version of Fox P, too. So it's possible they could be. They could have had language. We don't know.
Mark Reimers: So I've talked about to sort of big kinds of changes, but the majority of the changes have been sort of the typical kinds of evolutionary changes barely relatively subtle relatively slow and lots of them.
Mark Reimers: And in particular, although you often hear that we're 98 and a half percent chimpanzee that's based on our, our proteins, but the the DNA has had
Mark Reimers: The proteins are only a small part of DNA, and most of what's changed is the regulatory switches that turn on and off the proteins. So we've had lots of changes in these regulatory switches
Mark Reimers: It's been, you know, slow in the sense that it's happened over six or 7 million years, but
Mark Reimers: Relative to the changes in these switches in let's say robots or in other branches of primates, we've had lots more changes. So there have been lots of genes that have been turned up or turn down or more commonly have been
Mark Reimers: control logic has changed. They revoked in different circumstances. And we will talk about just a few of those a little later. So let me pause for a few more questions. And first, I'll let you take over again.
Kristin Wintermute: Sure. Um, what evidence, if any, do we have that lends itself to the hypothesis that our brains grew because of social nature.
Mark Reimers: Okay, that's a good question. Always challenge a scientist. When he says something dogmatic
Mark Reimers: So, that is, there are still there's still a lot of debate about that. I would say the majority of scientists think that
Mark Reimers: The evidence about how hard monkeys work to keep track of social relationships is
Mark Reimers: Is is sorry you didn't ask about brain size. You asked about
Mark Reimers: For for dominance. You know, I will say a little bit more about that in the next two parts of the talk. But very briefly, it's
Mark Reimers: That we can build up culture, we can learn from not only the mistakes of our ancestors. But there you know what they did. Right.
Mark Reimers: And it's a slow process of accumulation. But in the last hundred years. It's really accelerated.
Mark Reimers: But we have been able to sort of you know you and I could not invent modern computers by ourselves, but it's you know it's the building on what other people have done so we'll get to that in just a few minutes.
Kristin Wintermute: we're to the point where was the saying anthropoid anthropoid found seen
Mark Reimers: Seen dancer posts. You mean
That
Mark Reimers: Okay, that's actually quite a ways back. I won't go back that far. Um, so that's, um,
Mark Reimers: That's an older term, I believe that
Mark Reimers: Someone will have, you know, I forget that is that is now a different species of prominent and I can't remember which one. Someone can probably look it up. Google it and find it.
Mark Reimers: But yes, that's one of the different
Mark Reimers: I'm not sure if seeing that surplus was a homeless species or
Mark Reimers: Asked Australopithecus
Mark Reimers: But
Mark Reimers: Yeah, someone can look it up, and I
Mark Reimers: But I don't remember, but there you know several they're more than a million years back there quite a bit further back.
Kristin Wintermute: Um, so
Kristin Wintermute: Next question. I think I had read or heard that human brain development took a big step forward when humans started eating cooked animal flesh. Is this true
Mark Reimers: Great comment.
Mark Reimers: Great. Sure, so
Mark Reimers: Again, there's quite a bit of debate about that. But I think the evidence is now coming in fairly strongly to the cooking hypothesis. So remember I
Mark Reimers: Said that the human brain size is really taking off about a million and a half years ago. So the oldest fires, we have evidence of our are, you know, less than a million years old.
Mark Reimers: So, you know, that's as much as far back as we can place fires and cooking. But of course, people didn't necessarily, you know, try to leave it you know monuments to their heart fires that would last 2 million years.
Mark Reimers: So it's very likely that that cooking was going on, sometime before that. And there's some indirect evidence
Mark Reimers: Having to do with carbon isotope ratios, which I won't go into here. But if you know if we take if we take a course you know I can go into a lot
Mark Reimers: That suggests that human beings were eating a lot of cooked meat, particularly as well as some cooked vegetables, perhaps a million and a half years ago. So Richard rang him at Harvard has written and very nice book on this, which I highly recommend
Mark Reimers: One more question and then we should move on.
Kristin Wintermute: Okay. Um, are there any other competing hypothesis, other than social and tool use
Mark Reimers: Sure, so
Mark Reimers: I guess you might say the second place hypothesis right now is foraging complexity by the Environment complexity unfortunate. So if you
Mark Reimers: Have to remember where foods have different types are at different times of the year. So chimps, for example love figs, but figs are only going to be in season, a few weeks a year.
Mark Reimers: And or I should say a particular fig tree is only going to be in season, a few weeks a year, making figs. So they have to remember when each fig tree in there, you know,
Mark Reimers: 20 square mile territory. Actually, it's coming into season. So that's a complex foraging problem.
Mark Reimers: And so, you know, we would argue that human beings are omnivores. So they're they're having to keep track of where
Mark Reimers: You know, the, the deer are they have to keep track of where the roots are they have to keep track of where water is and they're doing this as they're moving around the landscape. So that's a complex foraging problem as well. Um,
Mark Reimers: You know,
Mark Reimers: I
Mark Reimers: I don't think it's more complex than the problem chimps have to solve.
Mark Reimers: But, you know, how would you measure that. I don't know.
Mark Reimers: There's also some indirect evidence, you know, and I'm running over time on this question, but there's some indirect evidence from other species that social complexity precedes foraging skill so
Mark Reimers: That's much lot there's much more to answer on that. But let's let's go on to the, the third part of the thought the third quarter, and I want to talk now about
Mark Reimers: And I'm going to get back to the question was asked earlier. But why we are so impressionable and why we learn so readily from each other. Both good things and bad things. And I'm going to start with something a little indirect
Mark Reimers: Okay, so, and that is, remember that we got our start
Mark Reimers: By walking on two legs quite early, and only got particularly smart much later.
Mark Reimers: And there's various reasons why we think human beings started walking up right but we think Lucy, for example, could walk up right although she was still pretty much at home in the trees and could
Mark Reimers: It wasn't probably could not run very fast.
Mark Reimers: Okay, so what are the consequences that of that.
Mark Reimers: Well, one of the consequences that probably half of you on the call makes you know either have or may experience is that
Mark Reimers: It's much harder for human women to give birth and for a chimpanzee female
Mark Reimers: You may have wondered why chimpanzee females, you know, managed to regularly give birth without having to have midwives, or go to the hospital or doctor's appointments or anything like that. Well, here's a good part of the reason, not the whole reason but a good part of it. That is that
Mark Reimers: Here's on the right is a chimpanzee pelvis. You can see there's a lot of space for birth canal.
Mark Reimers: And on the right is modern human pill or in the left modern human pelvis, and then we can see that even Lucy had the same kind of fill are very similar kinds of films much flatter pelvis.
Mark Reimers: Why do we have that well because it helps us walk upright. Chimps can walk up right for maybe a not really up right but they can walk on two legs for maybe 100 yards and that's quite an accomplishment.
Mark Reimers: Alright, so to get back to one of the questions that was asked, it sure does make a difference.
Mark Reimers: And so we, you know, it's much harder to fit a an infant's head through the birth canal.
Mark Reimers: And so, like all problems that are desperate.
Mark Reimers: There's, there's got to be some evolutionary solution. But again, it's a workaround. It's not, you know, it's not the way we would design it if we were designing human beings, but it's it's it's a way to do it. And that is what we just have birth much at a much earlier stage.
Mark Reimers: So this means that human infants are born at a less developed state then chimpanzee infants and very roughly, you know, there's lots of different time scales, but very roughly
Mark Reimers: Um, human infant at the age of nine months is about as physiological physiologically mature as a chimp newborn, you know, after just a few days.
Mark Reimers: And of course if you watch monkey babies or chimpanzee babies. They're learning to crawl in a matter of a few weeks or months and their cognitive tests show that they also outperform human babies cognitively for the entire first year of life.
Mark Reimers: So okay, so we're doing this so that on our sort of board all human beings are born in some sense of it prematurely, and our heads are only a quarter of the full size, whereas a gym.
Mark Reimers: A Gimp infants head is almost half their full size. So we're getting more and it roughly the same size of brain, but ours is going to go get swollen about twice as much
Mark Reimers: Okay, so some of the consequences of that are really important to remember this happened first. This happened because we walked up, right, which happened starting about 4 million years ago that the brain did not get bigger until about a million and a half years ago.
Mark Reimers: Okay, so as a consequence because our brains are born at such an immature state.
Mark Reimers: Our circuitry. The wiring inside our brains remains more flexible, more plastic is the technical term.
Mark Reimers: But we do much more rewiring our brains during the first 10 years of our life than let's say a chimpanzee baby does
Mark Reimers: In fact, the chimp baby gets the, the large, the most synapses of its entire life.
Mark Reimers: Remember the synapses are the connections. So that's where the information is in the brain, the connections between the neurons and a chimp baby has
Mark Reimers: To achieve maximum connections at about one year of age, a human being, gets maximum connections at seven years of age, and then they die back. So if you're if you're over seven. I'm sorry. It's all downhill from here, but
Mark Reimers: You know, that's why your seven year old niece or nephew can tell you the names and habitats of 100 dinosaurs or maybe 100 Pokemon characters, whereas you you know you would be hard pressed, you'd have to study to learn 20
Mark Reimers: Okay, so we have lots of have
Mark Reimers: Lots more plasticity in our, in our brain structure and they're turned out to be several entirely independent mutations that
Mark Reimers: All act together to delay snaps maturity. And again, most of these are the sort of destructive mutations.
Mark Reimers: They, they, are they break a gene or they do something that that sort of breaks, it's normal function. These are not evidence of, of, you know, sort of slow, steady selective pressure. This is evidence of something really, really, really sharp selective pressure for some period.
Mark Reimers: So we
Mark Reimers: You know, we end up with many more synapses or connections between our brain cells then do, then the apes or monkeys do
Mark Reimers: Okay, now
Mark Reimers: Maybe I'll just, I'll skip this and then talk a little bit about what does that plasticity, give us
Mark Reimers: Or what are some of the changes that that we have and I want to draw the connection between this the changes in our brain and our new sort of unique advantage in cooperation and cumulative culture.
Mark Reimers: So one of the things that I think you've probably heard of, if you've been reading neuroscience is a phenomenon called mirror neurons or I like to call it mirror functionality.
Mark Reimers: Is there not a special type of neuron, but there. It's been found that if you record from a monkey's brain or human brain. You can often find cells that
Mark Reimers: Risk that are active that fire a lot when let's say the monkey does something or when that monkey watches.
Mark Reimers: Another monkey or a human being, doing, you know, a very similar thing. So here the monkeys picking up. It looks like a rock. Not sure. Not sure what it is and then watching the human being. And these are
Mark Reimers: These are records of the firing of that neuron. So you if you go along one
Mark Reimers: Trace here like this every little spike here every little dash vertical dash is representing a time when that neuron that's being recorded was firing.
Mark Reimers: And you can see you know this. So it's firing maybe 20 or 30 times in one second, mostly in the first half second as the monkeys reaching out, but it will also fire as he's watching the monkeys watching this man reach out for the for the stone.
Mark Reimers: And so we can see, you know, again, a very specific. It's hardly firing at all before, but it seems to be very
Mark Reimers: very engaged by either doing or watching someone else do a particular action. And we think that that's very important for
Mark Reimers: Learning actions and
Mark Reimers: So most of these neurons that have these properties are in the sensory or motor parts of the brain.
Mark Reimers: But the, the important thing is that human beings have a lot more of this mirror response.
Mark Reimers: Or at least more of their neurons have this kind of mirror response than neurons recorded from monkeys. So you basically see this response.
Mark Reimers: In the motor cortex and some of the monkey and not very were very many other places but human beings. You see it in the dorsal lateral cortex. So areas that are involved in what we would call thinking and making choices as well as in the motor areas and some of the areas
Mark Reimers: Further back in the brain.
Mark Reimers: So we think that those kinds of properties of ourselves, which have to do with plasticity in early life.
Mark Reimers: Are important for the compulsive imitation. So here, this is a sort of meant to be a humorous picture but you know this this little boy so earnestly trying to be like
Mark Reimers: Presumably, his father and a friend or a father and uncle.
Mark Reimers: So that's it. We say Monkey see, monkey do. But in fact, human beings are much more compulsive imitators then
Mark Reimers: Ben monkeys are apes. So apes, will you know will watch you do something and then they'll try to do something with themselves, but they don't you if you watch them. You see that they don't have the right rhythm. So if you, you know, if you
Mark Reimers: Pick up a saw one of the favorite activities in some of the Indonesian sanctuaries for running attends is to have them saw what I don't know why.
Mark Reimers: And so if you know they'll watch someone saw and they'll pick up the saw and they know they have to hit the wood with it and move it, but they never seem to actually get it.
Mark Reimers: They don't seem to be able to make it bite and stay in the same position but human children will pick that up fairly quickly. And part of it is sort of picking up the rhythm and the
Mark Reimers: way of approaching something as well as getting the idea of doing the action but human beings, take this to an extreme when they're trying to solve problems when they're learning to do a new thing. And I'm going to just pause this for
Mark Reimers: So I'm going to stop sharing. I'm going to pause and then I'm going to get going to get you show you a video. And now we'll start sharing a grant again.
Mark Reimers: And here we are, so
Mark Reimers: So here, this experimenter in the black shirt is showing this little boy and the green TURTLENECK NOT turtleneck green vest. How to do, how to open the box to get a treat. So there's a candy bar inside and the experimenter is showing him how to do it. Now watch what he does.
Mark Reimers: And you'll hear that
Mark Reimers: So he's showing them how to get the treat. Now he leaves the room.
Mark Reimers: Notice that the child is doing everything
Mark Reimers: Exactly the same way, or at least trying to imitate every action that the adult did
Mark Reimers: So,
Mark Reimers: So the
Mark Reimers: Trial does everything that the Seattle does and
Mark Reimers: Let's get the
Mark Reimers: So whereas if you if you show that same whoops. Let's try this again.
Mark Reimers: So if you show that if you do exactly the same thing with the chimpanzee they figure out very quickly that it's only the last step that matters. They don't have to go through all the mumbo jumbo but a large fraction of human children will learn how to do all of the mumbo jumbo first
Mark Reimers: So,
Mark Reimers: So that sort of ability to learn from others is one important
Mark Reimers: Ability, but another is our ability to cooperate and
Mark Reimers: What's really striking is how much we cooperate, both to solve problems, but also you know when we're working on sort of the same kind of task in parallel, we will learn from each other. How to do it better and a number of studies with both chimpanzees and
Mark Reimers: monkeys have shown that they don't really pick up from other other animals, very quickly, and they don't cooperate so these boys here have been hunting, they have they caught a bird that they're serving up and they are that kind of cooperation is really the key to
Mark Reimers: To human activity. So I'm going to pause here and
Mark Reimers: Take questions for just take a couple of questions and then we should probably move on and do the last little part of the talk.
Kristin Wintermute: Sure. And then the question. Two questions from Joel and john
Kristin Wintermute: Because they're fairly similar and humans have 23 chromosomes why other apes have 24 was one chromosome lost or did two chromosomes fuse somehow
Mark Reimers: Yes. So our chromosome to is a fusion of an eighth two of the Apes chromosomes and I can't remember which numbers, but to have a smaller apes chromosomes fuse to give us our one large chromosome to so he do not have
Mark Reimers: A single you know there are chromosome three is there chromosome two and they have several smaller chromosomes that fuse to make our chromosome two
Mark Reimers: So we have a sort of more or less the same total amount of DNA. Okay.
Kristin Wintermute: Is it true that mimicking a smile actually does release serotonin and makes you happy. Oh gosh.
Mark Reimers: Um, can I plead that it's beyond my expertise is such a
Mark Reimers: That would take us pretty far afield, there has been some
Mark Reimers: Some studies showing that it seems to have a small effect and some studies showing no effect and
Mark Reimers: I, I don't know. I suppose it really matters.
Mark Reimers: What context, you do it, it
Mark Reimers: You know, it's not it's not a big effect.
Mark Reimers: If it's there but but we don't know.
Kristin Wintermute: What is the function of Gilliam's. See, I'm not saying that right so
Kristin Wintermute: We'll cells. And why are there proportionally so many
Mark Reimers: Sure, good question.
So,
Mark Reimers: Remember I you introduced them a slice the stage hands. You know, if you think of the neurons as the actors there, you know, sort of doing the stuff that bit that we have our focus is on
Mark Reimers: The glial cells are sort of the stagehands there, you know, making things work behind the scenes. They're helping the actors change clothes all of those kinds of things.
Mark Reimers: And one of the
Mark Reimers: Other kinds of changes from let's say mammals generally to primates to human beings is an increase in the number of glial cells. So what we've done is in some sense offloaded
Mark Reimers: A lot of neuron functions onto glial cells and, you know, we might think that maybe the neurons have become more streamlined or more efficient at their job. That's just speculation.
Mark Reimers: But it's generally true that a lot of the functions that
Mark Reimers: But let me, let me start again.
Mark Reimers: So, for example, rats actually have bigger neurons than we do.
Mark Reimers: And they have very few glial cells. So their neurons are some sense doing more of a work.
Mark Reimers: Whereas our neurons are very much like thoroughbred horses. They depend for it. They can't even feed themselves. They basically depend on the astrocytes which is one type of we'll sell to spoon feed them.
Mark Reimers: So anyway, for whatever metaphor, take that for what it's worth. Okay. Um, maybe I should go on to the last part of the talk. And then we can have a good 15 minutes of quick Q AMP. A at the end.
Kristin Wintermute: Sure. Sounds good. We have about 30 questions. So just keep that in mind.
Mark Reimers: Okay, I'll try to, I'll try to be quick. So I want to talk about us attention and sustained effort.
Mark Reimers: So one of the really distinct things about human beings is what's shown in these two pictures that we can concentrate
Mark Reimers: For some length of time on something that's not immediately rewarding or stimulating and we do it best with other people and we can share. We can look at the same thing, like this little girl is looking at what her mother showing her and
Mark Reimers: Able to focus jointly on that.
Mark Reimers: If you try to do that with a chimp or a monarchy. They just don't get it.
Mark Reimers: Um, you can try to indicate, you know, let's look at this together. Nothing. They're not going to play.
Mark Reimers: They, by and large, you know, they, they don't have the idea that you might share an intention with them, they see you as a competitor, you know, they see other apes as largely competitors. They are very reluctant to make really trusting
Mark Reimers: friendships and relationships, whereas that's critical for, you know, for this child learning from mother or also for these young adults, you know, trying to work together to figure something out.
Mark Reimers: Now, one of the big changes and this is
Mark Reimers: One that I'm I guess I'm particularly interested in because I was on this paper is that human beings Jenner have generate a lot more dopa mean
Mark Reimers: In some of these higher order cortical areas that I've mentioned sort of the so called them association areas where many different inputs are coming together and decisions are being made choice, you know, the distinctions are being made.
Mark Reimers: We have a lot more
Mark Reimers: Dopamine synthesis
Mark Reimers: Relative to apes and
Mark Reimers: So human beings show less modulate sorry I want, sorry. My apologies. I, I thought I had taken this slide out and replaced it with the next slide. My apologies. Okay, I'm gonna start again.
Mark Reimers: So, you know, one of the important things about human behavior is that we're capable of sustained effort and
Mark Reimers: That effort seems to depend on a neuro chemical called dopamine.
Mark Reimers: And that enables you to just, you know, that enables you know these poor guys to to, you know, do the back breaking Labor Day after day and it enables you to slog at your
Mark Reimers: At your coursework, or to you know put in a nine to five at the office doing, you know, things you may or may not like. And one of the key differences is that human beings have a lot more dopa me
Mark Reimers: In areas to do with memory emotion and association, as I mentioned, then monkeys are rapes, so this is a graph from our paper and
Mark Reimers: The human levels of adult me and synthesis Aryan read the chimpanzee levels are in blue and the monkey levels are in green. And you can see that, especially in areas like the amygdala.
Mark Reimers: The street in which is where we have a sort of quick habits and sort of it. Part of this got chopped off the hippocampus, we have a lot more
Mark Reimers: So we're able to sort of motivate ourselves, both to do work and to put in hard work, thinking which other apes have a harder time doing apart now that also has a downside.
Mark Reimers: So I'm just going to say that one of the the the odd things about human brains is that we actually consume about twice as much energy as a brains. So our, our brains are three pound brains draw about
Mark Reimers: 20% of our of our total oxygen usage and energy use.
Mark Reimers: But that's about twice as much as an ape brain does and
Mark Reimers: If you, if you look at what's happening in a human brain when someone's not you know necessarily engaged fully in something which is you know face it most of the time.
Mark Reimers: It turns out that the social brain regions that I mentioned this, this picture may be hard to figure out. But this is looking at sort of the inside view of one half of the cortex. And this is looking at the outside view one half of the cortex. So this is like a midline view.
Mark Reimers: And these orange areas are these areas that are active in this so called default mode which is basically what your brain where your brain is burning energy when you are just, you know, not
Mark Reimers: Engaged with what's around you. You're, you're sort of ruminating or thinking on your own. And so we have a lot more internal dialogue than apes do as far as we can tell, our internal activity.
Mark Reimers: And that has a real dark side. So when people are obsessive or when they're depressed or psychotic there'll be a lot more of this internal dialogue and it turns out they are also
Mark Reimers: Generating a lot more dopa me. So there's a much higher level of doping meaning in their brains.
Mark Reimers: So again, this is something that's given us a tremendous advantage as a species, but comes with significant drawbacks and significant problems. So I'd like to, to wrap up with some some perspective and and some prospects. So I often get asked if our brains are still evolving. Well, you know,
Mark Reimers: What timescale, are we talking about here. So, you know, we might say arbitrarily, but let's say still evolving means the last hundred thousand years.
Mark Reimers: Which is a long, you know, that's a long time by our historical standards, but that's, you know, that's only 3000 generations. That's not much by evolutionary standards.
Mark Reimers: And so yeah, there have been changes. Some of them are not very complimentary. So our brains are actually about 10% smaller than our ancestors. A 50,000 BC.
Mark Reimers: And we've also had some variants like you've heard of the old timers disease gene AICPA we for so the AICPA we
Mark Reimers: For is actually the ancestral form that we share with chimps and and monkeys, but I'm be able, be able to see two and three. The other variants
Mark Reimers: That protect against all simers seem to have originated and spread in the last sometime in the last 80,000 years perhaps
Mark Reimers: So again, you ask why. Why would we, you know, something that's convinced stayed stable so long change in the last hundred thousand years. Well,
Mark Reimers: We think that that's when grandparents became important. There's also maybe a change in diet. So this is not you know consensus, but this is the most
Mark Reimers: The most common idea right now. So this is sort of a timescale, that's, you know, relevant for evolutionary time but that's much longer than we most likely to think, what about the last 10,000 years or 20,000 years
Mark Reimers: Well, there is some again it very indirect evidence and weak evidence
Mark Reimers: It suggests that we are getting some
Mark Reimers: Changes again in those regulatory sites.
Mark Reimers: One of the interesting things in my research is that there's a key scaffolding protein that holds all of your sort of
Mark Reimers: Inhibitory receptors, the ones that sort of calm you down in place to hold them in place and there seem to be different variants being selected in East Asia versus US, Europe, so there's there's evidence of recent evolution, even in behaviourally relevant genes. So we might ask, okay,
Mark Reimers: Will we evil will our brains evolve in the future. I mean, of course, if you'd asked someone 50,000 years ago, they would have said, of course, where the pinnacle of evolution, if they knew about evolution.
Mark Reimers: So we always like to think that we're, you know, the latest, the last word, but we're just the most recent work if that and
Mark Reimers: It seems that human genome has evolved much more rapidly in the past 10,000 years than in the previous any previous 10,000 year period.
Mark Reimers: And we are also getting to the point where we could actually influence our own evolution, we could engineer some human genes.
Mark Reimers: And, you know, some people are talking about should we engineer genes that will actually change how we behave
Mark Reimers: I'm leaving that as a question that's much smarter than we can do it and 30 seconds. I'd like just to leave you with a little bit of further reading, if you
Mark Reimers: If you're interested in some of these topics and you'd like some reading, I recommend these four books at present, I keep updating this you know every time.
Mark Reimers: This is beautifully written this really focuses on although it's a little out of date this central book evolution of childhood really focuses on the soap the social experience. And there's another good book by Sarah blaffer 30 with a very similar theme mothers and others.
Mark Reimers: And then this is a very recent book sort of looks at the whole of the evolution of the brain, not just from
Mark Reimers: 7 million years ago splitting with chimps. But, you know, from the beginning and then there's another book that
Mark Reimers: I didn't get a cover for about cooperation and human evolution and success. So with that, I'm going to thank you for your attention. Glad you stayed with me and all the rest of the famous questions and answer discussion.
Kristin Wintermute: So I will open it up and start reading some questions. Did the development of a more sophisticated linguistic skills correspond to this 1.5 million inflection point
Mark Reimers: Um, we don't know is the short answer.
Mark Reimers: We think that the linguistic skills.
Mark Reimers: Probably coincided with the changes to that gene Fox p two. I showed you, but we don't know when those changes occurred, except well let's let's put it this way. We do know they occurred prior to half a million years ago.
Mark Reimers: But we don't know if they occurred, you know, 600,000 years ago or a million years ago were 2 million years ago. And that would be what we would really like to know. So a million and a half is as good a guess as any we have right now.
Kristin Wintermute: Okay, um,
Kristin Wintermute: Question from john isn't lattice, would it be the same and the plant kingdom. Molecular. Molecular Lee. Oh boy, my tongue is Ty, sorry.
Mark Reimers: It is what the same in the plant kingdom.
Kristin Wintermute: And it's in the lettuce.
Mark Reimers: Lettuce.
Mark Reimers: Yeah, I'm sorry, what
Kristin Wintermute: I'm not sure I understand that either. And maybe john can send me another chat or put something in the chat so we can clarify that question.
Mark Reimers: Yeah, let's come back.
Kristin Wintermute: Here. Here's another question. It's no
Kristin Wintermute: Is it known whether the connection between bronchus. And we're Nikki's airy areas is responsible for our quote internal voice.
Mark Reimers: Ah,
Mark Reimers: That is a good question and I don't know the answer. And I have never
Mark Reimers: Heard anybody or read anybody
Mark Reimers: give any plausible argument for that.
Mark Reimers: I'm inclined to believe that because speech is so important.
Mark Reimers: To us, we are more likely to imagine
Mark Reimers: Aspects of hearing voices and there are people for whom that so vivid that it sounds like an external voice.
Mark Reimers: So I'm guessing that it probably does. But I don't know. I mean, we'd have you have, there's no way to do the experiment of chopping out somebody. Well, I guess there probably are some people with damage, just to that area, but I don't know what their what their what their results are
Mark Reimers: So, good question. But we don't know the answer.
Kristin Wintermute: Our
Kristin Wintermute: Next question, follow up to my original question spindle cells could be some evidence for this. Any others.
Kristin Wintermute: I can't remember what embers original question was, I have to go back and look
Mark Reimers: Let me go back and look and see
Kristin Wintermute: Like, come on, that'll take me a moment. So we'll come back to that.
Kristin Wintermute: Is the AR HD a p 11 duplication unique to humans.
Kristin Wintermute: Yeah. Any idea how long ago, the duplication event happened.
Mark Reimers: Um, yes it is unique to humans. And we have some idea that it's probably at least a million years old. Because there's actually more than one duplicate
Mark Reimers: Yeah.
Mark Reimers: It's a while back.
Kristin Wintermute: Does the mention at our age gap 11 difference modify the structure of core tool layers as well as overall size.
Mark Reimers: Another good question that I was just thinking about this afternoon and wished thinking. I bet somebody sports going to ask me them. And I don't know, squirt.
Mark Reimers: Um, there are more granular cells in the human brain. Then in the human cortex. So they're particularly found and layer for human cortex.
Mark Reimers: Then in let's say in a brain.
Mark Reimers: So that's very possible but
Mark Reimers: You know they're they're made relatively late, so that's when this slowing down the brakes would probably have an impact, but
Mark Reimers: You know until we have an experimental test. It's just speculation. So, good idea. Why don't you become a scientist and do a PhD thesis on that it's
Mark Reimers: All here for now for doing that.
Kristin Wintermute: I cannot take staten drugs because they scavenge the brain cholesterol and prevent natural thinking the majority of people are not effective, because the status, do not cross the blood brain barrier.
Mark Reimers: Barrier. Yeah.
Kristin Wintermute: Is it true that brain cholesterol is needed for the sin that says connections to occur.
Mark Reimers: So cholesterol is an important building block of all of lipids cell membranes. So neurons. Just have a look an awful lot of cell membrane, an awful lot of membrane real estate relative to their size of, you know,
Mark Reimers: Sell reloads you know cell volume. So yeah, they need a lot of cholesterol.
Mark Reimers: Yeah, you might have that checked out if if just those are things that shouldn't really you know you shouldn't have a lot of
Mark Reimers: crossing a blood brain barrier. I mean, as you get older, you get more of that but but it's not something I'm middle aged adults should have a lot of
Mark Reimers: Okay, did you find embers earlier question.
Kristin Wintermute: I did. And so, Amber, if you can put it in the chat where your earlier question is, um,
Kristin Wintermute: But I can go on to another question, because we have quite a few we have like
Mark Reimers: 40. Am I staying a few minutes past eight but but
Mark Reimers: I'll leave that up to you.
Kristin Wintermute: Know I'm good, I'm good. If people are enjoying the conversation. So we have whole genome sequences of Neanderthals homo. I'm gonna I'm gonna
Mark Reimers: Start over. That's okay. The discipline, sir.
Kristin Wintermute: Yeah. Now are these changes and regulatory sequences found in our closest relatives or just and modern humans.
Mark Reimers: You know, again, another good question. Um,
Kristin Wintermute: So,
Mark Reimers: When I did the comparison of the regulatory regions. A the Neanderthal and dismissive and seek sequences were not available, so on and I don't have time to do it now, but that would be a great question to ask to to answer. I think we could answer that now.
Mark Reimers: I I've not seen anybody actually
Mark Reimers: Make that specific comparison, the sort of broadly. A lot of the regulatory region changes, you know, affecting things like hair and skin color and body density both have those many of those occur and innocence and in Neanderthals.
Mark Reimers: So my guess is that a lot of the
Mark Reimers: brain changes the regulatory changes also occurred in the halls, but which ones in particular. I don't know.
Kristin Wintermute: Sorry, I didn't get Amber to respond. Her first question was, what evidence, if any, do we have that lends itself to the hypothesis that our brains grew because of social nature and then her question. Follow up question was spindle cells can be some evidence for this. Any others.
Mark Reimers: Thank you. Okay, now I get it. Now I get it. Sure.
Mark Reimers: And yes spindle cells. I think are some additional evidence. And that's why I put them in there at few slides after the brain.
Mark Reimers: X expansion, because I think they are, they're suggesting that the, you know, there's the seem to be a variety of different evolutionary selective pressure sculpting
Mark Reimers: Different aspects of this social brain system and that suggests you know convergent Lee that they the bats was one of the major posts. I have evolutionary pressure, you know, the others being that
Mark Reimers: You know the the sort of not only the spindle cells, but also the arc of the unscented Fisichella said that, you know, very thick layer that is very much thinner and apes, that goes back into the regulation of the emotional and and sort of social recognition areas of the brain.
Mark Reimers: But you know there's there's a lot more to say about that but that would, you know, you'd have to think of course it's it's it's quite a bit.
Kristin Wintermute: So I got a kind of a long question and the G chat and I do apologize. We can't get to everyone's questions and I really appreciate the questions.
Kristin Wintermute: And mark does his best to answer off the top of his head as much as possible and hopefully we can continue these conversations to go more in depth, but on the question that I got on the chat was
Kristin Wintermute: What does brain dead me. What happens to the brain as the body dies.
Kristin Wintermute: Said,
Kristin Wintermute: That some people cannot tell the right from their left. So there's kind of two different
Mark Reimers: Several questions in there.
Kristin Wintermute: Yeah, yeah. So if you could kind of
Mark Reimers: So what, there's a lot of argument over what really brained, it should mean and how it should be defined, we
Mark Reimers: usually think of it as either the cells are dead or the
Mark Reimers: You know, the, the, the cells have basically lost all their electrical activity and to sell some of the cells may still be alive and if it actually a recent experiment by one of my colleagues Nana just done it. Yeah, I'll show that you could actually
Mark Reimers: Revive some cells of pigs brain after it had been dead eight hours.
Mark Reimers: So, you know, it takes it takes a while to die and
Mark Reimers: I don't know if we ever get to, if I ever do the talk on the biology of religion. I'll talk about the near death experiences and the
Mark Reimers: You know what have brain recordings of animals that having those near death experiences. I'm Kristin, you want to mention several people several people have asked questions that are very technical, you want to mention that the the seminar series.
Kristin Wintermute: Yes, I'm Mark is going to do a three part series as a part of our further reflection instruction led courses and it's a further exploration of the topic we address today on brain evolution and he has
Kristin Wintermute: Three different areas that he will address the registration is up on the AJ Center for Education website. I can put that in the chat if people are not familiar, you can register. There's a small fee, it will start august 25. Am I correct on that.
25th.
Kristin Wintermute: So if you're interested, please register. We've already done one course with Mark and it's been. It was a great experience.
Kristin Wintermute: I thought I was going to tune out and I ended up being really engaged. So I think the next more in depth discussion on brain evolution and the three part series will be really interesting. For those of you who won a little bit more meat to the topic. So, um, I'll put that in the chat. Now,
Mark Reimers: Great. Thanks, Kristen.
Mark Reimers: Yeah, happy, so I'll be I'll be talking a lot more about the specific genes that and this, you know, specific cell types.
Mark Reimers: And you'll be reading some scientific articles or at least a good summaries of scientific articles. But, you know, we'll, we'll talk through it and look at
Mark Reimers: You know it's able to cover a lot of the same material, but in very in a lot more depth and you'll get to argue with me and ask questions. So let's have maybe 10 or 12 minutes more questions and then we'll wrap it up.
Kristin Wintermute: Sure, um, next question. Has the brain in general developed more intelligently with the adaptations of modern technology, what parts of the brain do we use more now than before modern technology such as computers.
Mark Reimers: Well, two good questions.
Mark Reimers: I wish I had time to give really good answers, but I'll give crude answers.
So first,
Mark Reimers: We don't think that brain structure has changed detectable at all in the last, you know, several centuries.
Mark Reimers: Probably, your brain is working a little better than, let's say your grandparents brains just because you're better nourished.
Mark Reimers: There has been. For most of the 20th century, a steady increase in IQ scores. In fact, they had to basically recalibrate the IQ table every you know 20 or 30 years
Mark Reimers: And because people were getting better and better at these. And so we think that, you know, having experience with some of the, you know, more people were literate, more people were using a variety of abstract communication methods that that improved.
Mark Reimers: At least the abilities to do those kinds of tasks, even if without changing the brain structure. Now, one thing that's concerning is that the last 20 years IQ scores have started to go down.
Mark Reimers: So maybe technology of some sort, helps especially my opinion is that sort of active technology helps where you're, you know, writing and doing things are moving your body
Mark Reimers: Whereas it seems the last 20 years we've had more passive technology and that doesn't seem to, you know, doesn't seem to be helping, at least in so far as correlation is causation, which, of course, as you know, is just a guess. But something has been lowering IQ scores in the last 20 years
Mark Reimers: Um, let's take the next question.
Kristin Wintermute: Chair, and if a person
Kristin Wintermute: underwent a stroke.
Kristin Wintermute: And typing is broke broken area was affected does worn a key area goes down with the two because of the thick fast bridge connection between the two.
Mark Reimers: I only
Mark Reimers: The cells don't. And what if you have a stroke that basically deprives the cells of oxygen in one area and they die.
Mark Reimers: Now, what happens is, well, okay.
Mark Reimers: Yes and no. How about that you should always, you should always be a little suspicious of scientists who say yes and no. Like final answers, but
Mark Reimers: Be
Mark Reimers: So it actually one of my colleagues Kelly pellet has shown that actually the areas that receive input from a dead area.
Mark Reimers: And also suffer some loss of function. They don't do as well. They don't die.
Mark Reimers: But they, you know, because they've lost some of the inputs that they were used to and counting on they are somewhat disturbed and they try to sort of make
Mark Reimers: make up for that. So the Vernon keys area won't die, but it will it will have a little bit of a harder time, we think, but people with strokes and brokers areas often can understand speech quite well.
Mark Reimers: Next question.
Kristin Wintermute: Sure, um, his our ability just went over most of our body driven human evolution, not just bipedalism per Born to Run or the Terra Houma a tribe, if I remember their tribal or
What
Mark Reimers: Yeah.
Mark Reimers: So our ability to sweat has probably made it possible for us to run. It's not clear what direct effect that's had on the brain and
Mark Reimers: You know, we think of ourselves as maybe if you're thinking really hard. You don't usually have a hothead
Mark Reimers: Whereas if you're, you know, run, you know, you run for five minutes. Under the African sun and you really need to sweat.
Kristin Wintermute: Is
Kristin Wintermute: Kind of this kind of interesting. Please address the point of what comes first, the chicken or the egg social structure proceeds brain development brain developed proceeds social structure functions. That's one of those psychology nature nurture.
Mark Reimers: Code is and I'm, you know,
Mark Reimers: And it's, I think the answer is sort of like the chicken and egg problem is, well, there was a sort of chicken and a sort of, you know, and an egg and then there was a somewhat more like a chicken and and the more like a chicken egg.
Mark Reimers: That they sort of bootstrap and this, this is
Mark Reimers: Joe Henrik and his book The secret of our success goes into this in some detail.
Mark Reimers: And there's another good book, whose name I'm forgetting right now that oh and
Mark Reimers: Kevin Alonzo book.
Mark Reimers: That sort of go into this sort of bootstrapping that, you know, as you know, as society changes and it becomes more cooperative or board, you know, you get more done by being being cooperative then that exerts pressure you know that, then people whose brains.
Mark Reimers: predispose them to be more cooperative will have more children, and then they
Mark Reimers: You know venue, more people with brains that are more predisposed you know have those kinds of attributes will cooperate in different ways, you know, more, more richer and more extensive ways. So I think that there's lots of
Mark Reimers: Ways that that the to ratchet each other. But that's, you know, that's, that's, of course, in evolution.
Mark Reimers: Okay, Kristin, you're muted.
Kristin Wintermute: Sorry, I just want to make sure that everybody knows about tomorrow's ha virtual conference, you can still register, there's going to be lots of good conversation good talks and so i hope to see some of you there.
Kristin Wintermute: Thank you all for coming tonight. This has been great. And if Mark wants to take a couple more questions. And people are interested in want to hang in there. I am totally there to read more questions. It's just been really fun to be a part of this and we are definitely going to do more.
Kristin Wintermute: Critical mind and some instructed further reflection courses, there's more stuff coming up. So look at our website. Look at the H a website, check us out on social media. And that's my advertisement for now.
Kristin Wintermute: If you want more questions. I'm more than
Mark Reimers: I can stay for another you know maybe till you know for another 10 minutes or so. Maybe he like sounds good. Okay, I'm going to stop my video but I will continue to ask question.
Mark Reimers: Great.
Kristin Wintermute: And Bonobos tend to walk upright upright more like humans to our their birth canal is closer to human than chimps.
Mark Reimers: You know, I don't know the answer to that. I mean, they, they may be slightly better at it than ships are
Mark Reimers: But they can't maintain it for for very long periods of time and they can't run
Mark Reimers: on two legs for any period of time.
Mark Reimers: Okay, how about next one.
Kristin Wintermute: Yeah, I'm here, I'm what I know we got the brain dead I we answered that if human infants are less mature at birth. What would happen if birth was delayed.
Mark Reimers: Well, let's you know let's not talk to the mother about that.
Mark Reimers: That's a good question. So
Mark Reimers: I mean, some of those superficial things would be that, you know,
Mark Reimers: Babies would be born with their skulls more fully formed like jump babies are born. But, you know, the human babies are born with this big soft spot because their, their plates haven't grown together yet. Um, but
Mark Reimers: I guess one of the things that would be different if we could manage to give birth.
Mark Reimers: Much later, would be that
Mark Reimers: At least with the genes we have now that we would on our
Mark Reimers: children's brains would be less plastic they'd be more rigid
Mark Reimers: Less, you know, malleable and less interested in
Mark Reimers: Or at least less malleable.
Mark Reimers: And and plus you know a changeable by experience.
Kristin Wintermute: Okay, just a few comments, so I want to get to a question.
Kristin Wintermute: Last week I saw talk by Dr. Celia Hayes Oxford
Mark Reimers: Oh, yes.
Kristin Wintermute: Mm hmm.
Kristin Wintermute: who argued that a number of core human cognitive capabilities depend more on culture than some have originally asserted for
Mark Reimers: Example, she's I think she's fully right about that. Yeah, look for work.
Kristin Wintermute: Yeah, so I want to finish this question to make sure I do due diligence. So, for example, she argued that most of our ability to learn from invitation only arises due to particular child care practices.
Kristin Wintermute: That are common in human culture, perhaps many Nero mirroring responses arise during development in the current Community of evolutionary neuroscientist how controversial that claims of Dr. Hayes
Mark Reimers: Okay. So I think, I think, Cecilia Hayes is is got a lot of good original ideas, but she is a little bit off the main street. I mean, I think I happen to like a lot of I think she's right about a lot of things where she's bucking the consensus, but
Mark Reimers: You know she is bucking the consensus and
Mark Reimers: Part of my responsibilities to say both what I think. And also what the consensus. You know what the majority think
Mark Reimers: So,
Kristin Wintermute: Um, so I wanted, I did you finish your question.
Mark Reimers: Yeah, well,
Kristin Wintermute: Okay, so, um, I love taking this question because this is a person who I haven't heard from for years. He's a graduate of the humanist Institute. Hello, Calvin shallows, what would you say that chimps engage in parallel play rather than cooperative play
Mark Reimers: So a lot of their play is rough and tumble. So that's, that's not parallel, but it's not really cooperative either
Mark Reimers: But they tend not to. They tend not to, let's say, do what human children will do where they'll
Mark Reimers: Play with an object together where they have rules like you can have a play with your dog where you throw a ball and the dog.
Mark Reimers: Gets you know, grab goes runs out, gets the ball and brings it back to you and then you throw the ball again and you sort of
Mark Reimers: You know you trade places with the ball, so to speak, but it's hard to play a game like that with a chimp.
Mark Reimers: Not because they can you know because they're just really reluctant to, you know, pass something on so you don't have chimps playing catch. For example, they are excellent pictures and excellent catchers, but they would, they never play catch
Mark Reimers: Because that requires the sort of cooperation.
Mark Reimers: You know, even some birds will play catch, but they but but chimps don't so so those are the kinds of
Mark Reimers: cooperative games that that they could play but they don't. And they don't you know some chimps carry around little, little objects that looked vaguely like something and we think they're like
Mark Reimers: You know, like little kids with with their pet animal or their goal, you know, with their, their, you know, their stuffed animal or teddy bear their goal. We don't know, of course, but it's sort of touching, but they never share those they never played with an object pretending that it is something
Mark Reimers: So those are two kinds of cooperative place that we see in
Mark Reimers: In people that we don't see in chips.
Kristin Wintermute: We probably can take one more question, and I just love having you all here. And again, I'm just going to repeat that we will do more of these.
Kristin Wintermute: And Mark has been
Kristin Wintermute: I've pushed him into doing happy hours we have more open discussion. So if you're interested, and a happy hour from Mark, maybe I can push him into doing another
Kristin Wintermute: But for sure if you're the further reflection will go more deep and I think it's more discussion oriented because it's a
Mark Reimers: So that'll be a back and forth question and
Kristin Wintermute: Yeah yeah so
Kristin Wintermute: Yeah. So the last question is do you think human marrying contributes to superstition I III, we see too many patterns and mimic them and superstitious Lee make the wrong conclusion.
Mark Reimers: You know, um,
Mark Reimers: I think it's more likely that it's our, our overactive social brains that we see intentions. We see people behind things and we see purposes and intentions were purposes aren't
Mark Reimers: So it's not clear to me that the mirror neurons by themselves with at least the mirror function.
Mark Reimers: They don't come with labels, saying, you know, this is a mirror neuron and that one's not. But the mirror that sort of mirror functionality of many neurons seems
Mark Reimers: You know, it's possible. I just, I just don't know of any, any way to sort of tell whether it has an N, whether that is an important part of superstition or not, but I think we can say that the sort of social brain is an important part of superstition.
Kristin Wintermute: So,
Kristin Wintermute: Before we end, Mark, do you want to say a few more words are
Mark Reimers: Sure, actually. One thing that I meant to say right at the end is something that I think has a lot of bearing in our current
Mark Reimers: Sort of distress and in America that is that one of the biggest mistakes that I think European and Western thinkers generally have made is assuming that you know what's our essence our human essence is entirely our individual cells, what's in our skulls.
Mark Reimers: And you know in in medieval Western Christian thought that essence was the soul for modern Western scientists, they think of it as the brain, but they think that, you know, that's what special. It's something inside the skull.
Mark Reimers: Whereas most widely, let's say, many other cultures recognize that human beings are sort of embedded in social media, social relationships which affect who they become and their development.
Mark Reimers: And I think the, I think that the important to take away from this is that the key to human
Mark Reimers: Let's say success or domination as a species is not that our individual brains are in some way superior to an ape sprain, but rather that we have evolved to sort of take
Mark Reimers: So much from other people to internalize other people's ways of thinking and feeling and like most of human evolution.
Mark Reimers: That has been in one hand, a tremendous advantage, let's say in the Stone Age, but it can also be a liability, you know, as we look around to the modern media circus maybe that same trade is perhaps
Mark Reimers: Also a liability.
Mark Reimers: So that's, that's where I'll ended and
Mark Reimers: I hope to see some of you on the course AND MAYBE WE CAN. KRISTEN I will talk about maybe a return engagement for for a larger public
Kristin Wintermute: Thank you, everyone. And I hope you have a wonderful night and I hope to see you guys tomorrow.
