>CurtAdams <CurtAdams@aol.com> writes:
>
>>If the gains
>>from increasing telomerase exceeded the risks, evolution would
>>already have cranked it up.
>
>This doesn't follow at all, at least if you assume that the only
>advantage of increased levels of telomerase is increased lifespan. To
>reproduce during most of homo sapien's history on this planet, an
>individual needed only to live long enough to produce and raise a (few)
>healthy offspring. This doesn't need more than about 20-25 years.
It follows from the fact that in all continuously reproducing species,
evolvable genetic variation in lifespan has been virtually eliminated.
Remember that selection is very powerful. If living a few more years
adds only a 1 in a 1000 chance of having another child, or successfully
raising one you've already had, selection can readily fix it. This
is one of the problems with research in evolution - evolution can
readily fix characteristics we can't even detect with normal scientific
research.
Since humans have recently expanded from an tight genetic bottleneck
and recently had major changes to lifespan, it's possible that evolution
"missed" some things during that bottleneck. However, even then it's
unlikely to miss much and it's had 5-10,000 generations with a much
larger population to fix its errors.