01-20-2010, 10:29 AM
This is an old article but it was recently brought to my attention. Anyone have any more information on this? Thanks.
The ancestors of modern humans came from many different regions of the world, not just a single area, according to a University of Michigan study published in the current (Jan. 12) issue of Science. The study, by U-M anthropologist Milford H. Wolpoff and colleagues, is one of just a few to base its controversial conclusion about the origin of the human species on a comparison of actual human fossils---early modern and archaic fossil skulls from around the world.
Edit: Sorry posted it in the wrong sub-forum...
01-20-2010, 12:13 PM
It is about "multiregional hypothesis" (http://en.wikipedia.org/wiki/Multiregional_origin_of_modern_humans), theory which says that modern humans descend from Homo sapiens coming out of Africa who then interbred with more primitive humans on other continents. In contrast, the prevailing "out of Africa" hypothesis holds that modern humans are the direct descendants of people who spread out of Africa to other continents around 100,000 years ago.
01-21-2010, 01:37 PM
The Fuerle book on Human Origins addresses this directly at some length. Chapter 19 (http://erectuswalksamongst.us/Chap19.html) discusses the "African Eve" theory phenomenon.
I paste some of it below:
The executive summary is that the Out-of-Africa enthusiasts had a bad case of Confirmation Bias. They stack reckless assumption on top of reckless assumption. Why? So that they can get the as-is unreliable genetic data (for various technical reasons) to fit tightly into their paradigm [which has slowly become "Our" paradigm over the past 20 years]. The OoA'ers boldly claimed that mathematical models proved their case--when in fact the models said the African-origin theory, as-proposed, was one of many (over a billion) possible storylines for tracing Humanity back to "Eve".
Eve could have lived over a million years ago, or a mere 10 millennia ago -- both are predicted by the models based on available data and after accounting for various technical issues.
From the anthropology text "Erectus Walks Amongst Us" (http://erectuswalksamongst.us/Chap19.html) by Richard Fuerle (2008)
“Eve” is a metaphor that the afrocentrists have given to our ancestral mother, who they believe lived in Africa about 150,000 ya (Shreeve, 2006), and from whom all living humans derived their mtDNA. “Eve” was not a single woman, however, since at least a thousand breeding pairs would be needed for a viable population. 1 According to the afrocentrists, all the women in that founding population either had the same mtDNA or, if they had different mtDNA, did not have daughters.
As support for Eve living in Africa, and for her date of 150,000 ya, afrocentrists point to studies of mtDNA in living people. Cells were collected from people all over the planet and were analyzed to determine the A-C-G-T base sequences (see Appendix) in their mtDNA; people within each geographically separated population tend to have many of the same A-C-G-T sequences, but those sequences are different in other populations. 2 For example, at a particular location (“locus”) on an mtDNA string, Europeans may have an A while Asians have a T. Differences in the A-C-G-T bases at a locus are called “SNPs” (single nucleotide polymorphisms). 3 Now the scientists had to decide what was the original base (A, T, C, or G) at each locus and which base (A, T, C, or G) is the mutation; the population with the original base was then be presumed to be the older, ancestral population from which all other populations descended. However, as we shall see, that reasoning may not be valid.
So the scientists programmed a computer that created millions of “trees,” with different populations at the bottom and on the various branches, based on “A’s” changing to “T’s” and “T’s” changing to “A’s” and so on. The assumption was made that the “correct” tree, that showed the actual changes that occurred in the bases over at least tens of thousands of years, would be the simplest tree, the most “parsimonious” tree. 4 The computer compared all these different trees and picked out the simplest tree and, low and behold, it was the tree with the Africans at the bottom, just as OoA had predicted.
The tree in Figure 19-1 (from Wikipedia) is imposed on a map of the world to show human migrations (black arrows) under the OoA theory. The blue lines represent the boundaries of areas covered in ice or tundra during the last ice age. The colors in the list on the right of the map are for the circles and the numbers for the colors in that list give the number of thousand years BP, i.e., before 1950. The letters and numbers inside the small white circles are for the groups of mtDNA alleles (“haplogroups,” see next chapter) that people living in those areas have. 5
The tree begins with an upside-down Africa in the tail of this weird-looking bird, then spreads to Asia (body) and Europe (left wing – orange circle), down to Australia (foot – red circle) and across the Bering Strait to North America (neck- blue circle) and South America (head – green circle). Unfortunately, the bird didn’t fly because the biologists who did the calculations were not mathematicians and, when a mathematician checked their work, he flunked them. The OoA tree was not the simplest tree. In fact, there were over a billion parsimonious trees. 6
So the mtDNA analysis does not show that Eve was an African. Can it at least tell us how long ago Eve lived? Since scientists now have all these mtDNA sequences and know how many SNPs there are, if they can assume that (1) every mutation that has occurred in Eve’s mtDNA is represented by a SNP in the data they have and (2) the mutation rate is constant (i.e., one mutation every X years), then they can easily calculate how long ago Eve lived, the “coalescence” date. 7 But are those two assumptions reasonable?
As to the first assumption, there are several reasons why the number of SNPs observed may be greater than the number of mutations that have actually occurred. Occasionally, during fertilization, the tail of a sperm will enter the egg along with its head, thereby adding the father’s mtDNA to the mother’s and possibly ending up in her daughter. (Hagelberg, 2003). If the father’s mtDNA is different from the mother’s, the scientists may count those differences as additional mutations, making the coalescence date seem farther in the past than it really was. Also, some of our male ancestors may have interbred with a female of another subspecies of Hs. If the daughters were accepted into our lineage, the scientists would count these additional SNPs as mutations and conclude that the coalescence date occurred much farther in the past than it did.
The number of SNPs may also be less than the number of mutations that have actually occurred. A mutation may occur, then later a second mutation may occur at the same location that reverses the first mutation, for example, A→T, then later T→A. The scientists don’t see any SNP at that location and they count no mutation, when really two mutations occurred, and therefore the coalescence date is older than they think it is. Also, two or more mutations may have occurred at the same site. Suppose A→T→G. All the scientists see is an A→G, so they count only a single mutation when there were really two mutations, and they again think that the coalescence date is more recent than it actually was.
Scientists have obtained ancient animal mtDNA 8 from fossil bones and teeth and date those bones by chemical and physical means. They can compare that mtDNA to mtDNA obtained from living descendants of those animals and count the number of SNPs. After adjusting as best they can for all the possible sources of error mentioned above, they divide the number of mutations by the number of years, which gives them the mutation rate, the number of mutations per year. They can then take the number of mutations in all living humans (as estimated from the number of SNPs), divide by the animal mutation rate and determine when all those humans started out with the same mtDNA (i.e., the coalescence date, the date that Eve lived).
But even if the number of SNPs is correctly adjusted for all the possible sources of error described above, the second assumption, that mtDNA mutates at a constant rate, must still be made. If, for example, hundreds of thousands of years go by and the mtDNA does not mutate at all and then there is a shower of cosmic rays or a volcano spews mutagens into the atmosphere, causing a large number of mutations, the mtDNA clock is not going to be accurate because it will be slowing down and speeding up. 9 And, when fossil bones are used to determine the mutation rate, additional assumptions must be made. The humans who lived at the time of the fossils and those who lived today were not genetically the same and may not have had the same resistance to mutations. After the Industrial Revolution, thousands of additional mutagens that never before existed were spewed into the atmosphere and the drinking water, so since about 1750 there may have been a higher number of mutations, making the date for Eve appear older than it was.
For these reasons, until technical problems are overcome, the mtDNA data cannot be relied upon for either the location of Eve or her date. 10
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