Re: Why do humans live so long?
- From: Kermit <unrestrained_hand@xxxxxxxxxxx>
- Date: Thu, 31 Jan 2008 10:57:00 -0800 (PST)
On Jan 30, 2:58 pm, Vend <ven...@xxxxxxxxxxx> wrote:
On 30 Gen, 20:05, JDT <jdtat1...@xxxxxxxxx> wrote:
On Jan 30, 5:37 am, Strange Creature <strangecreatu...@xxxxxxxxx>
wrote:
Two questions:
Is is reasonably well established that
the lifespans of human beings are
longer than those of the great apes,
and that this is due to genetics, and
not the environmental factors of
humans living in human civilization
and not in zoos or in the wild?
If the answer to the first question
is yes, what specific selection
pressures over the course of
several million years have lead to
a longer lifespan among humans
in comparison with the lifespan
of chimpanzees?
In "The Third Chimpanzee", Jared Diamond speculated on these
questions. This might be especially interesting if it is true that
Neanderthals only lived to 50 or so while early moderns had much
longer lifespans (as claimed by Diamond in that book).
Early moderns probably lived to 60 or so. Doesn't seem much longer.
There is one
important distinction to make:
"average lifespan" vs. "maximum longevity". HIgh infant mortality (and
high rates of death at all ages) give short average lifespans but
there are always a few people, even in hunter-gatherer societies, who
live to long age (maximum lifespan). A possible selective advantage of
that is having people around who remember how the group survived some
crisis 40 yrs ago or whatever.
Why wouldn't this selective advantage apply to Neanderthals, or chimps
for what matters?
It does. One consideration is that tweaking the genes so that humans
live longer is not simple - it's not like reducing pigmentation, or
growing coarser and thicker hair.
Small things that go wrong lead to various aging problems and eventual
death. Humans live a long time for two primary reasons (just-so
alert!): it takes a long time to learn to be a human, with a childhood
of 18 years or so, and it is advantageous to have a third generations
still active. As human culture became more complex, and like developed
language, the old folks not only could do many of the complex tasks
developing in human society, but also be a respository of knowledge.
Orangutans' bones heal very quickly from fractures. Why? Because they
are the only great ape who lives routinely high in the trees. When
they fall, they break. The difference between healing in three days or
33 days means passing on one's genes or not. We other great apes could
use this talent, but our need is not so great. It's a tricky process
to heal bodies, and the selection pressure has to be strong.
This, BTW, is why I argue that there is no simple treatment to extend
maximum human lifespan. There is no "death gene" that can be turned
off, or there would be the occasional long-lived mutant. There aren't
any that I know of, altho there are albinos and furry people and
giants. No 200 year-old longevity "giants".
It will happen in time, but multiple processes will have to be
monitored and controlled.
Grandparents participating in rearing
grandchildren could also play a role. Humans not only live longer than
other apes, women go through menopause--something that chimps tend not
to do.
JDT
(posted from Google so do I have to fnord?)
Kermit,
who wouldn't mind seeing such advances real soon
.
- References:
- Why do humans live so long?
- From: Strange Creature
- Re: Why do humans live so long?
- From: JDT
- Re: Why do humans live so long?
- From: Vend
- Why do humans live so long?
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