On 3 Jan 1997 05:12:18 GMT, Ram Samudrala <ram at mbisgi.umd.edu> wrote:
>B. Moosang (bmoosang at uoguelph.ca) wrote:
>>>OK, just trying to settle an argument between two non-science people -
>>how long would something like menstruation take to evolve? The argument
>>that I have been presented with is that woman began menstruating (rather
>>then doing what other critters do (which I can't remember the scientific
>>term for but is basically go into heat))
>>I would like a reference to this. As I understand it, this
>discharing of blood and tissue occurs in primate females also.
Yes, but for most other mammalia (IIRC) this is a *yearly*
process, reducing the reproductive rate (though, come to
think of it, rabbits may destroy this general line of thought).
The argument, as I understand it, was how would a monthly
cycle have evolved in humans? While a monthly fertility cycle
would have advantages in expanding the birth rate, how would
this have provided enough of a selection pressure to eliminate
the yearly fertility cycle...
Mind you, I'm not all that well educated in Biology (other
than by observation of my wife and childbirth).
>>after people began living in more fixed shelters between - let's say
>>for arguement sake between 5000-15000 years ago. Would this be enough
>>time for this to evolve?
>>Humans have been around a bit longer than that. Assuming a mechanism
>for transporting the egg to the uterus, for the lining of the uterus,
>and for getting rid of debris, didn't exist, it boggles my mind to
>think how long such a function would take to evolve in the first place
>(going from 0 frequency to >0 frequency), let alone be naturally
He's thinking that the monthly cycle was selected for in the last
15K years. Beats me, though I'd think it unlikely; I don't see
how there's enough selection pressure to eliminate the yearlies
around the globe; After all, the australian aborigines were
isolated far longer than that and the trait is consistent...
Though, once again, I've a specific lack of knowledge in details.
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