Posted on 03/06/2002 7:38:41 PM PST by ValerieUSA
A new piece of evidence—one sure to prove controversial—has been flung into the human origins debate.
A study published March 7 in Nature presents genetic evidence that humans left Africa in at least three waves of migration. It suggests that modern humans (Homo sapiens) interbred with archaic humans (Homo erectus and Neandertals) who had migrated earlier from Africa, rather than displacing them.
Ancient Origins
In the human origins debate, which has been highly charged for at least 15 years, there is a consensus among scientists that Homo erectus, the precursor to modern humans, originated in Africa and expanded to Eurasia beginning around 1.7 million years ago.
Beyond that, opinions diverge.
There are two main points in contention. The first is whether modern humans evolved solely in Africa and then spread outward, or evolved concurrently in several places around the world.
The second area of controversy is whether modern humans completely replaced archaic forms of humans, or whether the process was one of assimilation, with interbreeding between the two groups.
"There are regions of the world, like the Middle East and Portugal, where some fossils look as if they could have been some kind of mix between archaic and modern people," said Rebecca Cann, a geneticist at the University of Hawaii.
"The question is," she said, "if there was mixing, did some archaic genetic lineages enter the modern human gene pool? If there was mixing and yet we have no evidence of those genes—as is indicated from the mitochondrial DNA and y chromosome data—why not?"
Alan Templeton, a geneticist at Washington University in St. Louis who headed the study reported in Nature, has concluded that yes, there was interbreeding between the different groups. "We are all genetically intertwined into a single long-term evolutionary lineage," he said.
To reach his conclusion, Templeton performed a statistical analysis of 11 different haplotype trees. A haplotype is a block of DNA containing gene variations that researchers believe are passed as a unit to successive generations. By comparing genetic differences in haplotypes of populations, researchers hope to track human evolution.
Templeton also concluded that modern humans left Africa in several waves—the first about 1.7 million years ago, another between 800,000 and 400,000 years ago, and a third between 150,000 and 80,000 years ago.
Alison S. Brooks, a paleoanthropologist at George Washington University, is more cautious about Templeton's conclusions. "Archaeological evidence supports multiple dispersals out of Africa," she said. "The question has always been whether these waves are dead ends. Did all of these people die? Templeton says not really, that every wave bred at least a little bit with those in Eurasia.
"This has not been the majority viewpoint of geneticists up to this point," said Brooks.
Dueling Theories
The fossil record shows that about 100,000 years ago, several species of hominids populated Earth.
Homo sapiens could be found in Africa and the Middle East; Homo erectus, as typified by Java Man and Peking Man, occupied Southeast Asia and China; and Neandertals roamed across Europe.
By about 25,000 years ago, the only hominid species that remained was Homo sapiens. Scientists have conducted a considerable amount of both genetic and archaeological research in an effort to understand how this outcome occurred.
....More at link......
You know if the two species were breeding so much were they really different species? Reproductive isolation is one of the defining characteristics of a "species". I think this supports the theory put forth by some anthropologists that Homo erectus and Neandertals were actucally separate Homo sapien tribes, and not other species. I personally think this throws a monkey wrench into the puzzle that is "human evolution".
Gunnar Heinsohn of the University of Bremen is one of Germany's foremost scholars and a key player in the chronological revisions of near-Eastern stratigraphy and historiology which you read about, if you read about that sort of thing. I once asked him how long he figured the white race had been on the planet, the topic at hand actually being the dispersion of caucasian languages and whether or not there'd actually been time for it.
Heinsohn's reply:
Mueller-Karpe, the first name in continental paleoanthropology, wrote thirty years ago on the two strata of homo erectus at Swanscombe/England: "A difference between the tools in the upper and in the lower stratum is not recognizable. (From a geological point of view it is uncertain if between the two strata there passed decades, centuries or millennia.)" (Handbuch der Vorgeschichte, Vol I, Munich 1966, p. 293).
The outstanding scholar never returned to this hint that in reality there may have passed ten years where the textbooks enlist one thousand years. Yet, I tried to follow this thread. I went to the stratigraphies of the Old Stone Age which usually look as follows
modern man (homo sapiens sapiens)
Neanderthal man (homo sapiens neanderthalensis)
Homo erectus (invents fire and is considered the first intelligent man).
In my book "Wie alt ist das Menschengeschlecht?" [How Ancient is Man?], 1996, 2nd edition, I focused for Neanderthal man on his best preserved stratigraphy: Combe Grenal in France. Within 4 m of debris it exhibited 55 strata dated conventionally between -90,000 and -30,000. Roughly one millennium was thus assigned to some 7 cm of debris per stratum. Close scrutiny had revealed that most strata were only used in the summer. Thus, ca. one thousand summers were assigned to each stratum. If, however, the site lay idle in winter and spring one would have expected substratification. Ideally, one would look for one thousand substrata for the one thousand summers. Yet, not even two substrata were discovered in any of the strata. They themselves were the substrata in the 4 m stratigraphy. They, thus, were not good for 60,000 but only for 55 years.
I tested this assumption with the tool count. According to the Binfords' research--done on North American Indians--each tribal adult has at least five tool kits with some eight tools in each of them. At every time 800 tools existed in a band of 20 adults. Assuming that each tool lasted an entire generation (15 female years), Combe Grenals 4,000 generations in 60,000 years should have produced some 3.2 million tools. By going closer to the actual life time of flint tools tens of millions of tools would have to be expected for Combe Grenal. Ony 19,000 (nineteen thousand) remains of tools, however, were found by the excavators.
There seems to be no way out but to cut down the age of Neanderthal man at Combe Grenal from some 60,000 to some 60 years.
I applied the stratigraphical approach to the best caves in Europe for the entire time from Erectus to the Iron Age and reached at the following tentative chronology for intelligent man:
-600 onwards Iron Age
-900 onwards Bronze Age
-1400 beginning of modern man (homo sapiens sapiens)
-1500 beginning of Neanderthal man
between -2000 and -1600 beginning of Erectus.
Since Erectus only left the two poor strata like at Swanscombe or El-Castillo/Spain, he should actually not have lasted longer than Neanderthal-may be one average life expectancy. I will now not go into the mechanism of mutation. All I want to remind you of is the undisputed sequence of interstratification and monostratification in the master stratigraphies. This allows for one solution only: Parents of the former developmental stage of man lived together with their own offspring in the same cave stratum until they died out. They were not massacred as textbooks have it:
monostrat.: only modern man's tools
interstrat.: Neanderthal man's and modern man's tools side by side
monostrat.: only Neanderthal man's tools
interstrat.: Neanderthal man's and Erectus' tools side by side
monotstrat.: only Erectus tools (deepest stratum for intelligent man)
The year figures certainly sound bewildering. Yet, so far nobody came up with any stratigraphy justifiably demanding more time than I tentatively assigned to the age of intelligent man. I always remind my critiques that one millennium is an enormous time span--more than from William the Conqueror to today's Anglo-World. To add a millenium to human history should always go together with sufficient material remains to show for it. I will not even mention the easiness with which scholars add a million years to the history of man until they made Lucy 4 million years old. The time-span-madness is the last residue of Darwinism. This "most misleading Englishman" (Velikovsky) needed millions of years to let invisibly small alterations do the big visible changes. It is quite funny to observe catastrophism combined with darwinizing time spans. Yet, I see it all over neo-Catastrophism.
Note that Heinsohn is not claiming that he has proof that the changeover to modern man from neanderthal was 3500 years ago per se; he is merely stating the fact, as he sees it, that there is no real basis in evidence to assign any greater age than that to the changeover. Emmet Sweeney and Heinsohn put the construction of the great pyramids somewhere around 900 BC and the flood, presumably, around 1200 or 1500 BC. Sweeney's two little books, "The Pyramid Age" and 'Genesis of Israel and Egypt" are major pieces of academic work and astonishing tour de forces.
Basically, you've never even thought about having the kind of credentials to debate any of the issues Heinsohn is involved in.
The biggest problem generally with your "revolutionary sciences" that overthrow everthing we think we know is that they offer no corresponding edifice in the place of everything we think we know, nothing that has any evidence for it or useful content of any sort.
Do you really think that anyone capable of fooling around with Janet Reno is even capably of sentient thought, let alone the ability to articulate it in written or spoken words?
- Atlantis - Donovan 1970's
Some things never change.
Now THAT'S something that should definitely be kept in a zoo (under armed guard).
I think this cuts to the heart of the question. Considering the amount of new evidence about human origins and migrations appearing almost daily, I think it's far too early to try to advance some grand "final" theory. Speculation is fun but we need to know a whole lot more before running out on any particular limb of the Tree of Man. Consider the phenomenal amount of new information being amassed about just DNA alone, not to mention the entire field of biology. Those data will eventually put to good use in associated scientific fields like anthropology and archaeology. I'm not terribly old but I recall vividly the exciting discovery of the "double helix" by Watson and Crick. That was just a microsecond ago in terms of of Man's history on earth. Yet I think the secrets being revealed by DNA research will change our future -- and our understanding of the past.
Did you mean to say there's some left over DNA in her jeans from the past? (YUK)
Alison S. Brooks, a paleoanthropologist at George Washington University, is more cautious about Templeton's conclusions. "Archaeological evidence supports multiple dispersals out of Africa," she said. "The question has always been whether these waves are dead ends. Did all of these people die?"
No, Allison, (you twit) they are all working at WalMart as greeters.
Like I say, they did not find it, and they are not laughing.
Not speaking for myself but I'm told this occurs quite frequently during those "college drinking" years.
Yep..., had to chew my own arm off, once.
But he did contemplate it.
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.