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I'm Kristen Hawkes.
I'm an evolutionary anthropologist
at the University of Utah.
And my topic is "Human Aging
and Menopause".
I'm an evolutionary anthropologist
and so that means
that I think in terms of natural selection
as the key to explaining
why things vary in the living world.
And if you think about natural selection,
aging initially looks like quite a riddle.
But, of course,
we're not the only ones that age.
Aging is a thing about living organisms.
And so evolutionary biology
has given us some crucial tools.
Hence, thinking about
how we live in a finite world,
all organisms do, it means that
there are always tradeoffs.
And because there are tradeoffs,
aging senescence is a necessary result
from natural selection.
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More is spent on maintenance and repair means
less can be spent on current reproduction.
And so the tradeoff between those two things
provides this wonderful leverage
for explaining variation.
This figure shows that tradeoff between
what's put into somatic maintenance
and repair on the one hand,
and what's put into current reproduction.
And if those parallel lines
represented lines of equal lifetime fitness,
the expectation is that selection
would adjust that tradeoff to hit the line
of highest lifetime fitness.
And it turns out to be
a very powerful toolkit
for explaining some of the variation
in rates of aging across the living world.
How much goes into maintenance
and repair depends on,
first of all, what the chances are
of surviving to older ages.
If the chances are very low,
if mortality is very high,
then that kind of investment won't payoff.
And so when mortality is low, it does.
And it also matters
what the reproductive payoff is
if you do survived to those ages.
