Kind: captions
Language: en
[Music]
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
transmittent?
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 pass 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.