Posted on 08/15/2007 2:51:14 PM PDT by blam
Not breeding obvious in splits of human evolution
Simon Grose
15 August 2007
ABOUT 353,000 babies will be born into the world today, about 700 of them in Australia. Same as yesterday and same as tomorrow. Many of their parents will worry about being able to properly feed them, or whether they may have contracted HIV in the womb. Whatever circumstances today's new children and their families face, every birth evokes a degree of hope. Firstly, that the baby is fit and well. Beyond that, a myriad of hopes can be evoked to lead their nation, to be rich, beautiful, a sporting champion, and so on. But no parents cradle their newborn child and wonder if they have spawned a new species. For the estimated 150,000-200,000 years that our species has trod the globe, its members have made billions of babies and none have broken the Homo sapiens mould.
Within that mould there has been much genetic variation. Some individuals are much taller or shorter than normal, others markedly more or less intelligent than normal, and people with Down syndrome carry one more chromosome than is normal. But none of these variations are sufficient to define them as other than Homo sapiens.
It happens though. The uncountable millions of species of plants and animals living now or in the past were all the product of a genetic shift from their forebears. For Homo sapiens, the fossil record contains evidence of at least 14 species who preceded us on the evolutionary pathway over the past 4.6million years, either as direct ancestors or as relatives of those ancestors. Fossil finds from the banks of Lake Turkana in Kenya, revealed in the science journal Nature last week, opened a window on to this process, as well as exposing different interpretations by experts and how the media can be led to exaggerate the implications of scientific research.
"The discovery of two fossils has challenged the belief that our ancestors Homo erectus evolved from Homo habilis, according to a new study [that] suggests that the two species may in fact have co-existed for some 50,000 years in East Africa," Agence France-Presse said in a report indicative of coverage around the world.
However, towards the end of the Nature report, the authors acknowledge that "it is nonetheless possible that H.erectus evolved from H.habilis elsewhere, and that the Turkana basin was a region of secondary contact".
For Professor Colin Groves, of the Australian National University's School of Archaeology and Anthropology, the findings are interesting but untoward. "It just shows that habilis was there till much later than we thought and reinforces that primitive species live alongside their descendants," he said yesterday. "I don't know whey they puffed it so much."
Nor do the Nature paper authors deal with the fact that the fossil they classify as Homo erectus would be classified by others including Groves as Homo ergaster.
This highlights ongoing differences over classification of ancient species in the fascinating area of human evolutionary theory. Whereas Groves and others see sufficient variation between fossils to classify Homo ergaster and Homo erectus as separate species, others see sufficient similarities to classify them both as Homo erectus.
For those who classify them separately, Homo ergaster existed from 1.8 to 1.2million years ago and Homo erectus branched off from this line about 1.3million years ago, possibly surviving till as late as just 100,000 years ago. For the other camp, it was the same species all along. If the first theory is correct, Homo erectus was not a direct ancestor of ours because our line branched off from Homo ergaster after Homo erectus branched off. If the second is true, Homo erectus was one of our direct ancestors.
It's all a matter of degree because the longer a species survives, the more it changes. Although, in his judgment, Homo erectus existed as a species for about 700,000 years less than the Nature authors believe, Groves says "the end ones certainly are strikingly different from the early ones", particularly in the larger size of their brains. This process of evolution within a species is termed anagenesis.
The more dramatic event, when a species divides into two, is known as cladogenesis. For this to occur, a group of individuals must become geographically isolated. "When a small part of a lineage becomes separate from the rest, changes occur very quickly in that small group until finally new characteristics become fixed," Groves said.
Isolation is necessary for cladogenesis and time. The fossil record between us and what most believe to be our immediate ancestor, Homo heidelbergensis, includes two dated at 195,000 years ago of which Groves says one has several characteristics akin to Homo sapiens. These individuals were single genetic steps in a process that took tens of thousands of years, triggered by isolation of a core group.
So new parents should not expect their babies to be anything other than Homo sapiens. And with about 200,000 more births than deaths each day around the world, there is a diminishing likelihood that any group of Homo sapiens will become sufficiently isolated to kick-start a new breed.
Simon Grose writes on science and technology.
So... pygmys don’t count?
< < Sigh! > > Now, you are really confusing me!
Congratulations, you've almost figured out why evolution is just another form of junk science. The whole thing is driven by information and the only information there is in humans is that of humans. The information to have a kid with horns and poison fangs simply isn't there.
I want to say that at some point they found some Aboriginal group that had a different number of autosomes normally.
The discovery of two fossils has challenged the belief that our ancestors Homo erectus evolved from Homo habilis,
Cultural anthropologists have learned that Homo erectus migrated in large numbers to San Francisco.
Genes.
I think your understanding of the science is... a bit imperfect.
One of the explanations for racial diversity is that the small migration out of Africa spread to Central Asia, India, and down the coast toward Australia. The Toba eruption triggers global cooling, and destroys much of India. THe human population falls from tens of thousands to 1-10,000. Small populations with great isolation = lots of room for mutation/adaptation.
The groups isolated in east Asia develop the typical asian traits. Those in Australia are the ancestors of the aboriginies. Those living in Central Asia adapt to the cold grasslands, growing lighter in complexion and becoming Proto-European.
If they’d been isolated for another couple dozen millenia, those racial groups could have become species.
"The last glacial period was preceded by 1000 years of the coldest temperatures of the Late Pleistocene, apparently caused by the eruption of the Mount Toba volcano. The six year long volcanic winter and 1000-year-long instant Ice Age that followed Mount Toba's eruption may have decimated Modern Man's entire population. Genetic evidence suggests that Human population size fell to about 10,000 adults between 50 and 100 thousand years ago.
"The first group to arrive are held to have come from the north because the cranial measurements of the surviving skulls of this type are affinial with the skulls of the Afanasevo culture in particular, which was located in the Sayan-Altai/North Mongolia area, and with the skull types of steppe people living much further to the west. This group is called "Proto-European" by Mair and Mallory, and it can be dated to have arrived in Xinjiang about 1800 B.C.E. or somewhat earlier. "
Very interesting. The author does a pretty good job of explaining those latest findings. Thanks for the post!
Makes shape alone rather like hard and soft fingernails.
On the other hand, it's in the proportions of torso to the long bones of the arms and legs that the greatest differences are found, and those differences appear closely related to the mean annual temperature at different latitudes.
When it comes to your liver, though, that's directly related to the amount and quality of the meat your ancestors ate. Seal eaters had to "evolve" systems to purge excess iron buildup. Same for those who followed reindeer herds, and at a later date, those who engaged extensively in raising hogs.
Up until quite recently (1901 let's say) human populations remained quite divided in terms of food availability ~ both in quantity and in kind. Eskimos rarely if ever ate bananas. Today, it's feasible for them to eat bananas every day. No doubt they will die early from Type II diabetes for engaging in a diet heavy in starch.
Sounds like making excuses and, as excuses go, that one's about as lame as is possible. Punctuated equlibria has its own set of problems which is worse if anything than the pure Darwinism it was meant to replace. If nothing else, as has been noted, you need a certain level of population before you'd ever see a "beneficial mutation", assuming such a thing were ever to happen, and the tiny "peripheral" groups which Gould and others postulate would not supply them.
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Whew, I was worried
As a man of faith I’d like to believe that God’s hand was in the Toba eruption...
Simon Grose:
ELECTRIC UNIVERSE IN THE NEWS
Simon Grose, Canberra Times, 12 April 1999.
http://www.kronia.com/thoth/ThoIII08.txt
http://home.planet.nl/~gkorthof/kortho39.htm
Are retrogenes changing Darwin’s Natural Selection Paradigm?
Retrogenes: genes that don’t behave - Reverse transcription: who needs it?
a review by Gert Korthof
21 Feb 1999 (updated: 29 Feb 2004 )
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