杏吧原创

BY NOW, you would have thought scientists would have worked out why women
go through the menopause. Well, they haven鈥檛.

On the face of it, the claim that women who have children later in life tend
to live longer than normal (鈥淥lder mums age more slowly鈥�)
is simplicity itself. Women who have a later
menopause and can still have babies well into their 40s might do so because
their bodies as a whole are ageing more slowly than the norm. But why go through
the menopause at all? Men don鈥檛 experience such a precipitous loss of
fertility.

One suggestion is that menopause offers hidden benefits when it comes to
passing on genes. As a woman ages, her chances of reproducing safely decline to
the point where it is better for her to concentrate on raising her last child or
her grandchildren, rather than to continue having babies herself. The problem
with this idea is that detailed studies of hunter-gatherer societies have found
that older women don鈥檛 help others nearly enough to offset their own
reproductive loss.

The alternative view is that menopause is just one more meaningless aspect of
the physical disintegration we call ageing. This sounds bleak and unexciting but
it has a silver lining. According to this view, our female ancestors died before
menopause could happen. As a result, they were never exposed to low,
postmenopausal levels of oestrogen and progesterone, and never had to adapt
biologically to the consequences. By this logic post-menopausal hormone levels
are maladaptive and treatments that boost them ought to do more good than
harm.

The origins of menopause may be a mystery. But the world鈥檚 ongoing experiment
with hormone replacement therapy should one day point to an answer.