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0:00
I'm Lynette Leidy Sievert.
I'm a biological anthropologist.
I'm currently a Professor
of Anthropology
at the Department of Anthropology
at UMass Amherst.
And I study human variation
in age menopause,
and human variation and symptoms
during the menopausal transition.
And I work all over the world,
asking women who are 40 to 60
about their menopause,
and the rest of their life.
And I've become interested
in the evolution of menopause
and what makes us different
from other animals.
So today, I'm going to be talking
about "Setting the Second Stage:
the Evolution of Menopause,
and Post-Reproductive Life."
0:44
So I'm going to be talking about
the second stage of adulthood.
And I'm using a quote here,
from Mary Catherine Bateson
from her book
"Composing a Further Life:
The Age of Active Wisdom."
And the reason I like this quote
is because
I've always thought
about the evolution of longevity
as tacking on this extra piece
on to the lifespan.
But Mary Catherine Bateson
points out that,
"humans have inserted
a new developmental stage
into the life cycle."
She calls it,
"a second stage of adulthood,
not an extension
tacked on to old age."
And this helped me to think
about this age as being inserted
and we're still healthy during
the second stage of adulthood.
So this is what I've become
interested in thinking about.
1:36
The next slide is about menopause.
We're gonna define menopause
here two ways.
First, by the WHO definition:
"The permanent cessation
of menstruation,
due to the loss
of ovarian follicular activity."
And that is unique to humans,
in the sense,
that every human female
is going to stop menstruating
by at least the age of 60 or 62.
I've never met a woman
who is able to menstruate
beyond the age of 62.
I've never found in the literature
any woman menstruating
beyond the age of 62.
This is a human universal
among females.
The reason we need
a different definition
for other mammals is because
not all mammals menstruate.
So Cohen suggested this definition:
"The irreversible loss
of the physiological capacity
to produce offspring,
due to
intrinsic biological factors."
So, it's a little more vague
about what's going on.
But the way you determine
if an animal
has been through menopause,
is by looking to see
what is their inter-birth interval.
And so you see offspring,
offspring, offspring.
And then when you would expect
another offspring,
you wait another
two standard deviations
beyond the normal
inter-birth interval.
And if another offspring
doesn't appear,
you can say, "Oh, that female
must be at menopause."
And that gives us a nice definition
that can be applied across species.
