On human evolution

[Mark Buchanan]

Ian Tattersall (curator of the Spitzer Hall of Human Origins - American Museum of Natural History) has written an up to date survey of the latest in human evolution: 'Masters of the Planet: The Search for our Human Origins'

http://www.amazon.com/Masters-Planet-Search-Origins-Macsci/dp/023010875X

Some of the interesting ideas discussed:

- the closing of the Isthmus of Panama caused an acceleration of primate evolution. The closing triggered the onset of modern glaciation which caused variation in the climate of Africa. As the climate of Africa went through several cycles the various primate species were often separated, displaced, and decimated - good conditions for variation and speciation.

- a large volcanic eruption ~75 thousand years ago in the Philippines might have triggered the out of Africa migration of modern humans.

- 'humans' were anatomically human with all the right hardware in place before language was 'discovered'. Symbolic language was likely discovered by children.

The book might make a good summer read for those interested.

Mark

[Ron O]

"Adversity is the mother of invention." Changing environments alter
the adaptive peaks and change the direction of allele frequency
changes sue to natural selection. Fragmentation of populations
increases the rate of genetic change and results in things like
founder effects that can push evolution into weird directions just due
to the genes that the small population is stuck with by the
individuals that started the population. Around 80,000 years ago
things got pretty desperate for our ancestors. We are confronted by
how our own activities have pushed many species to the brink of
extinction, but the human population went through a bottle neck in
population size so severe that we only have around 1/5 the genetic
variation as most other species. The chimp popultion has been
decimated and yet it has around 4 times the genetic variation found in
humans. The estimates for how desperate things got range down to an
effective population size of only around 1000 people in the whole
world (which for them was likely only one corner of habitable
Africa). From that point where we nearly didn't make it our ancestors
moved out of Africa and inhabited the rest of the world.

Ron Okimoto

[Steven L.]

I would have thought that earlier hominids had at least developed the
rudiments of language--and that as they evolved toward higher
intelligence, so did the sophistication of language.

Homo heidelbergensis was a good hunter with nearly as large a brain as
Homo Sapiens, and they worked in coordinated teams. Why couldn't they
at least have had a simple language to help them do that?

The evolution of language may have started even further back, with
gestures having some symbolic meanings to many different species of
earlier hominid. We know that chimpanzees--once it's explained to
them--can communicate well in that way.



--
Steven L.

[Mark Buchanan]

Could there have been multiple small separated groups at the same time and only one of them by luck or conquest continued on?

Mark

[Mark Buchanan]

Tattersall argues that modern human symbolic thought is orders of magnitude greater than chimps. Chimps can have empathy - i.e. know what another chimp is feeling/thinking, but humans can go much further. For example I can think about what you think about someone else.

Tattersall also makes the point that there is no way we can even conceptualize what it would be like to not be able to think symbolically.

In the archeological record evidence of symbolic thought appears abruptly - long after modern humans were anatomically all there.

Mark

[jonathan]

"Ron O" <roki...@cox.net> wrote in message
news:35a25cd0-f560-4481...@o4g2000yqk.googlegroups.com...

Using a more abstract view, you can use an earthquake as
an analogy for spontaneous evolutionary jumps. Both earthquakes
and evolution follow a power-law distribution of events.
Which is a combination of countless minor events, leading
up to the rare 'big one', which forever alters the previous
landscape. And increasing stress is the underlying cause.
But it doesn't have to be some kind of damage to an ecosysem
to create the stress.

If some ecosystem has been completely filled, where almost
every niche is occupied, and can accomodate little more, then
spontaneous large evolutionary jumps can result. The fractal
instability, or self-similarity across scale of self-organizing
systems usually result from a fully occupied and hence
stressed system.

Abstractly called the 'sudden expansion into the adjacent possible'.
This large evolutionary step from a fully filled and stressed
ecosystem often create entirely new possibility spaces
essentially overnight.

For instance, with the evolution of intelligence, the ecosystem
suddenly can support a huge new increase in life that
wasn't possible just before.

Emergence and Evolution - Constraints on Form

"The view of evolution as chronic bloody competition among
individuals and species, a popular distortion of Darwin's
notion of 'survival of the fittest,' dissolves before a new view
of continual cooperation, strong interaction, and mutual dependence
among life forms. Life did not take over the globe by combat,
but by networking."

http://www.calresco.org/emerge.htm


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> Ron Okimoto
>

[Ron O]

That is what happened. There were at least three Homo populations
alive at the time, possibly more. Modern humans, Neandertal and
Denisovans. We have a little Neandertal DNA in our genomes from
interbreeding with them after modern humans left Africa and New Guinea
populations have a bit of Denisovan DNA in them where Denisovans must
have inhabited that region at the time that Modern humans started
island hopping. The Neandertal and modern human populations had been
separated for around half a million years before we met them again in
the Middle East. The Denisovans split from Neandertal around 300,000
years ago, but also interbred with them more recently than that (there
is a bit of Denisovan DNA in the Neandertal genome). What surprises
me is how the Neandertal and Denisovan populations remained separate
for so long when they inhabited the same land mass and seemed to have
overlapping territories.

There might have been other populations in Africa, just like there
were Neandertals and Denisovans in Asia and Europe, but they went
extinct or we didn't interbreed with them when we spread out over the
rest of Africa and took over what territory they may have had.

Ron Okimoto

[jillery]

Thank you for this recommendation. Apparently Ian Tattersall has
written a number of books relating to evolution. I intend to read
them all.