>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. And
the estimated lifespan of humans before the advent of civilization
falls into the 20-30 year range. There was absolute *no* evolutionary
advantage to living longer than that. The same can be said for any
species, not just us. Most species live just long enough to
successfully produce the next generation. Long life has had no
evolutionary advantage until now, for us.