In article <9205071558.AA18138 at genbank.bio.net> ODONNELL at ARCB.AFRC.AC.UK (Cary O'Donnell) writes:
>>How did longevity evolve in humans, or indeed any species?
> ... speculation of the evolution of longevity among Irish ancestors
As Austad points out in the 2/92 history of Natural History, longevity
evolves when you develop special protection against or an environment
isolated from natural enemies. Long lived species include many bird
species, some fish species, flying squirrels, porcupines and many turtles.
His particular area of interest is the opossums on Sapelo Island off
the Georgia coast. In 4,000 years (several thousand opossum generations)
they may have evolved a lifespan 30-40% longer than those who live
in an environment where there are predators. I suspect that there
is too short a period in "historical times" for the human lifespan to
have undergone this type of evolution. It is clear though that in the
several million years since our divergence from the other primates
we have evolved a life span which is 100%+ greater. This is a very
fast change in evolutionary terms indicating that lifespan is probably
under the control of only a few genes and that being "smart" has a
strong advantage in preventing death from enemies. I suspect that
our ability to avoid death from predators has contributed to the
lengthy development time allowed to download "software" into our children.
Other species do not have this luxury and have much more genetic hardware.
>>>NB: It has been observed that those organisms with the highest cellular
>DNA content are the longest lived (with the inevitable exceptions).
>But - this could be just the end result of evolution, rather than the
>driving force of longevity.
>Bunkum, the DNA content, chromosome number, etc. are in no way related to
a species lifespan. (The mouse, frog and shark all have about 3 Bbp vs.
the human 2.8 Bbp while the newt and bean have 10x and the lily 30x that
amount). You can accumulate a huge amount of DNA if you have active
retrotransposons that are duplicating DNA in a nondestructive way.
This is not going to affect your lifespan much in either direction.
You can also look at the large amount of DNA which serves no purpose
and see that we could eliminate alot of the non-coding, non-regulatory
sequences and suffer no significant decrease in lifespan.
--
Robert Bradbury uunet!sftwks!bradbury
