On Mon, 20 Jan 1997 J de Lyser <gd33463@glo.be> Wrote:
>>John:
>>the important thing is the line of decent that uniquely led
>>to humans, as opposed to some other animal. This line is
>>much shorter than thought 20 years ago, it's only 5 or 6
>>million years old. That lends support to the idea that the
>>Evolution of humans was not an inevitable outcome but a
>>lucky accident.
>J de Lyser
>True, but it's just as 'lucky' an accident that other species
>didn't develop intelligence. Any omnivorous species with
>smalll gestation size, and relatively long gestation time,
>theoretically could have.
Theoretically yes, but I don't think the evolution of intelligence is easy
and I don't thing it's inevitable. Life started almost 4 billion years ago,
but for 99.95% of that time there was nothing much smarter than a chimp.
>name one big cat who lived 5 million years ago in africa !
Make that 3.9 million years ago, that's when our fist bipedal ancestor,
Australopithecus Afarensis (Lucy) came along. Although it's somewhat after
this period, there is evidence that both the gracile and the robust
australopithecine were harassed by predators, and both had a brain 50% larger
than Lucy had. Bite marks made by Leopards have been found in many of the
skulls of these animals, and there is even evidence that they carried the
carcass into trees to eat them. I'm mot saying that the same species of
Leopard was around in Lucy's day but I'll tell you one thing, I've never heard
of an ecosystem, past or present, that had prey species but no predators,
and besides Lucy there were many other types of tasty meat running around,
several varieties of pigs and a sort of dwarf hippopotamus among others.
>all the big predators in the late miocene were Aquatic.
I very much doubt that "all" were, but we do know that Lucy lived near a lake
that was full of crocodiles.
>Acinonyx [...] like smilodon, they were nowhere near as
>intelligent or as sophisticated hunters as modern big cats
>[...] Smilodon and early acinonyx, were stupid cats! [...]
>more dangrous to Afarensis would have been hyenids, of course
>also underdeveloped, and not to be compared with todays hyena
>species [...] You were putting up chimps against modern
>predators, not prehistoric homonids against prehistoric
>predators !
You're assuming that because we are enormously smarter than Lucy was then
present day predators must be enormously smarter than the predators of Lucy's
day. It's not so.
Yes, if you plotted the average brain size of all animals from the extinction
of the Dinosaurs to now you would find a modest increase, but there is nothing
modest that happened to the human line. The brains of our ancestors got almost
5 times as big in just 3 million years, and nothing even close to that has
ever happened in Evolution before. This huge explosion in brain size started
at the same moment we developed bipedalism and a hand that can make complex
motions. I don't believe this is a coincidence, and that's why I think the
bipedalism question is so important.
John K Clark johnkc@well.com
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