If Darwin came back today, what would he be
most excited by in modern science?
I think it would be the whole world of genetics.
That’s the answer to all the big questions
he had – how does variation emerge?
And how could that be transmitted?
Let’s return to our brown bears stranded
in the Arctic to consider the impact of genetics
on our understanding of evolution.
Each bear is made up of cells.
And if we take a brown bear cell, and tunnel
into its nucleus, we find DNA – the molecule
with the genetic instructions for building,
in this case, a brown bear, written in a four-letter
code.
Now, the thing about DNA—it’s not perfect.
When it’s copied, mistakes get made.
Mutations, in other words, that sometimes
affect an organism’s traits and that sometimes
can be passed from parent to offspring.
So the variation at the heart of evolution—it’s
genetic variation.
Slight differences in DNA that—for example—could
make some bears a bit lighter in color, a
bit more insulated against the cold, and a
bit more capable of digesting fattier foods
like seals.
Evolution is essentially any change in the
genetic composition of a population.
Mutations are random, so they’re not always
helpful.
But the bears with mutations that gave them
some advantage for Arctic living survived
and reproduced more often than bears without
them.
They passed the genes responsible for those
adaptations onto their cubs.
Over generations, more bears inherited and
elaborated on these and other changes in the
DNA.
The eventual result – a polar bear.
And when we tunnel into its cells, we find
polar bear DNA.
Think of DNA as the raw material that—across
billions of years—evolution has molded and
built into countless forms of life.
We are all related, tied to one another by
the most spectacular of double helical threads.
