The best thing about bacteria is that they multiply very fast.
Put antibiotics on a Petri dish with enough bacteria,
and a few days later you'll find that a lone bacterium
one that happened to be resistant to the drug's effects —is now recolonizing the plate.
It's natural selection in action.
You can see clearly that they are constantly evolving
as the normal bacteria became antibiotic- resistant bacteria.
As little as a few hundred years ago, the same was true for humans,
but what about now?
Nowadays, with the availability of better healthcare,
food, heating and hygiene the number of ‘hazards’ we experience in our lives has dramatically reduced.
In scientific terms, these hazards are referred to as selection pressures.
The question is, now we have fewer selection pressures and more help in the form of medicine and science,
will evolution stop altogether for humans?
Has it stopped already?
According to Meredith F. Small, associate professor in the anthropology department at Cornell University,
humans haven't really changed the rules of natural selection.
We might think that because we have culture-and with it all kinds of medical interventions and technologies
that we are immune from natural selection, but nature proceeds as usual.
Evolution is defined as a change in gene frequencies over time,
which means that over generations, there will be changes in the gene pool,
and humans experience those changes as much as any other organism.
Some people live and some people die,
and some people pass on more genes than others.
Therefore, there is a change in the human gene pool over time.
Here are some of the most recent quirks — and even superpowers —
we've acquired thanks to the power of selection.
1. Drinking milk as adults:
One easy-to-understand example how humans have evolved over recent centuries is how,
on some continents, our bodies have adapted to tolerate the most abundant food sources common to that region.
However, in most parts of the world,
after weaning, adults are unable to drink milk
because their body switches off the intestinal production of lactase, an enzyme that digests the sugar in the milk.
As these people cannot digest the lactose sugar
they suffer symptoms including flatulence, diarrhoea, nausea, or vomiting.
Yet, more than 70 per cent of European adults can quite happily drink milk.
This is because they carry a regulatory change in the region of DNA
that controls the expression of the gene that codes for lactase.
This DNA change enables the lactase gene to be switched
on and lactase production to continue, even after weaning.
We can see evidence of this evolution today
because the European people has a long tradition of dairy farming- are much more tolerant of lactose in their diet
than Asian people that do not have a heritage of dairy farming.
This may seem nutritionally inconsequential (though delicious),
but the ability to digest incredibly calorie-dense dairy products
was incredibly useful for humans surviving the cold winters of Europe.
2. Missing wisdom teeth:
It's not just oral surgeons who are removing wisdom teeth (third molars) from human mouths
— evolution is playing a part too.
Like most mammals, humans' ancestors had four sets of three molars
(for a total of 12, with six in both the upper and lower jaw) used to help chew and grind food.
Unlike other mammals, however, humans underwent a period of evolution in which the brain greatly expanded in size.
This created an architectural problem;
with a much larger brain case, the jaw had to become narrower
so that it could still connect to the lower part of the skull.
As our heads and jaws were changing, some cultural shifts were taking place as well.
With bigger brains, man got wise to fire and its ability to soften food.
Overall, man's diet became much more processed;
compared to the roots and raw meat our ancestors ate,
we might as well be eating strained applesauce.
In fact, we wouldn't necessarily need any teeth at all to survive today,
though dining out would be a dull affair.
This meant our jaw muscles didn't grow as strong as they used to,
keeping the wisdom teeth beneath the gums increasing the risk of painful and deadly infection.
A few thousand years ago, a mutation popped up that prevented wisdom teeth from growing at all.
Now one in four people are missing at least one wisdom tooth.
Sure, those wisdom tooth lackers may claim they're more highly evolved
because they don't have to go through a few days of misery,
but what do they talk about at boring parties?
3. Disease resistance:
Evolution is about the survival of the fittest —
and a big part of evolutionary fitness is not dying from a disease before you've had children.
So it makes sense that evolution would be giving us a boost against some common diseases.
A genetic mutation that protects people from a common form of malaria
spread like wildfire in sub-Saharan Africa about 42,000 years ago, according to a new study.
That makes the mutation one of the swiftest, strongest changes to the human genome yet seen
though it remains a mystery why this particular disease sparked such a dramatic evolutionary response.
However, it's not just malaria
— evolution has helped spread adaptations that protect against leprosy,
tuberculosis, and cholera in certain populations as well.
Some scientists have suggested that living in cities helps this process along.
In conclusion, evolution is persistent, everywhere,
pushing our species forward in tiny increments.
We in developed nations may think we are immune from natural selection
because we are so surrounded by
material goods and high technology,
but this immunity is an illusion.
Technology protects us from nothing,
and medicine surely hasn't cured all the diseases.
