Replacement and Multiregional models for the origins of anatomically modern humans?

Question

How do they compare?What are their central hypothesis, what predictions do they make, which has more evidence to support it? Be sure to use evidence from the fossil and archaeological records, as well as genetic data.

Answer 1

Some parts of the out of Africa model are flawed IMO because it also must assume no migration in populations and it assumes that the we have adequate fossil evidence to conclude humans came out of Africa simply because our oldest modern human fossils come from there.  In reality, the DNA evidence doesn't suggest we came out of Africa IMO.  The fossil evidence is too sparse to say that modern humans didn't evolved simultaneously in Eurasia.  Clearly, we don't have homo erectus, Neanderthals and ergaster evolving simultaneously into Homo sapiens.  That is a ridiculous and totally discredited notion.  It still doesn't mean we came out of Africa.  In my opinion the zeal of those pushing an out of Africa borders on racism, whether consciously or not.  Darwin suggested our ancestors might be found in Africa since the closest relatives, Chimps and Gorillas were there.   Ever since it has become an obsession for some, or so it seems to me.  There could very well have been populations of modern humans in Asia but because of location and habitat, fossil were rare and none simply have been found.   The actual fossil evidence is a lot more scarce than most realize.  Paleontologists are constantly theorizing things which far outstrips the evidence and rarely do they admit to what they don't know which is almost everything.

Answer 2

Both models have their pros and cons. One thing to get out of the way before I go into detail about the 2 models is the fact that the Mitochondrial DNA used to support the Out of Africa theory is flawed. The MtDNA used comes from a small sample of skeletons (not every fossil found is suitable for MtDNA extraction). Also it assumes that the MtDNA remained constant throughout Homo evolution (no mutations occurred in MtDNA over a time span encompassing roughly 2 million years).

The Multiregional Model:

This model is based on the idea that the first group of hominids to leave Africa about 1.8 million years ago (see Damansi Find in Republic of Georgia) consisted of interconnected populations, meaning gene flow still occurred between the populations preventing speciation. If this is valid the multiple species grouped as Homo found to date from 1.8 MYA would all have been capable of interbreeding; consisting of both branching and merging populations with no major speciation events occurring. Also, it assumes the variation in the fossil record would simply be due to geographic regionality. The one main problem I have with this theory is the fact that a situation involving vicariance (a geographic barrier such as glaciations, mountain ranges, rising sea level, etc..) could create a situation in which a single population over time could become split and with time result in 2 different species.

Main supporters of this model are Milford Wolpoff and colleagues

Out of Africa Model:

This model is based on the idea that erectus, ergaster, and other homo species left Africa around 1.8 MYA and populated other parts of the world. Afterward, a relatively recent population (last 200,000+ years) migrated out of Africa  during the late Pleistocene. This anatomically modern population competed with and replaced the already established populations of erectus, ergaster, heidelbergensis, etc.. in Asia and Europe. If this is true it would minimize the amount of parallel evolution required to produce the widespread appearance of Homo sapien characteristics. This model is somewhat supported by the fossil record considering some of the older sapien finds are in Africa (I would caution that more finds in the future may contradict this) and would help account for a later appearance of Homo sapien in parts of the far east.

Main supporters of this model are Chris Stringer and colleagues

I tried to present this as unbiased as possible and have left it up to you to decide which one you think is correct (unfortunately it was not presented unbiased to me back in my college years, so I researched it on my own, just like you are.)

Jonmcn49

Hey, this is only Yahoo Answers. If you don't agree with someone’s answer that's what the thumbs down is for. No need to attack people. That is what you did and I also did the same. It was all in the heat of the moment, no hard feelings here.....I just had to defend myself. I'm sorry if I offended you. Also, I would suggest reading the book I listed below it is very good and is right up your alley as far as biology and chemistry. Anyway, I just reflected on the matter and thought I should post this in return. Cheers, I have a lot of work to get done.  

P.S. I never said I supported the Multiregional model, you just assume things way too much. On a lot of the topics I didn't want to go into too much depth, after all we have to keep in mind that we are more educated then a lot of people using this service.

Answer 3

The out of Africa model has the most support! But I do have to disagree with poster #1. The total number of skeletal remains used in MtDNA extractions and all other DNA related extractions to date are only 7, however there are a total of something like 26 skeletons suitable for MtDNA extraction but the museums that have them in their possession are afraid they will be damaged and will not allow extraction (I hate politics). So I don't know about you but 7 DNA extractions are not enough to convince me 100%. Also, poster #1 said it himself, the mutation rates are still estimated, and therefore they would NOT hold up in a court of Law. Even if they still were compared to modern populations that would assume a somewhat constant and is not adequate enough to be backed by the science community as a whole (more people refute this data vs. except it)  As a side note, both poster #1 & #2 seem like complete a******s.

Jon:

I may not be an expert, but I do know what the books say. You call me a coward, yet you sit behind a computer and verbally assault any person who does not agree with you. I think that top contributor junk has gone to your head. If you really are what you claim a zoologist, then why do you sit behind a computer on Y.A. all day? Shouldn’t you be doing research or something related to your field? Don't even try to tell me you're retired because real scientists never retire. Here is my opinion, a while back you went to college and took a couple biology classes and either flunked out or dropped out. So now you have a personal vendetta against anyone who doesn't agree and or contradicts you. Not all scientists agree with each other but educated people try to teach others not in their position, they don’t verbally attack them.

Answer 4

The complete replacement model is the " out of Africa " model and has the best support in hard genetic science. The multiregional model says that human evolved in place and has not as hard of factual support. For instance; the multiregionals makes the claim that because Chinese have the same facial bone structure of the Homo erectus of the area, that this supports the multiregional model. This is not good data, as environmental factors are always changing morphological features by location. They also have a compromise position that posits inbreeding with those out of Africa and local populations; pure conjecture. On the other hand, the genetic trail, both mitochondrial and Y chromosome have given the " out of Africa " camp evidence that the multiregional model can not equal.

Chris J. Mutational rates are pretty well understood and estimated. The sample size that geneticists used was more than adequate and quite supportive of the " out of Africa " theory. The multiregional theory uses many suppositions about breeding that are not supported by any evidence at all. I will assume you are a social scientist and not a biologist. The theory has wide support among geneticists and not just mitochondrial. You failed to mention Y chromosome data and you failed to mentioned  that tracking took place in today's populations based on well understood mutation rates.

You social scientists rarely are informed of the latest and best in genetics or biology. I had to audit a biological anthropology class for a local university as part of a study on teaching methods. I was quite suprised at what passes for scholarship in social science; even is this day and age

You put forward no evidence to back your spurious claims, just BS. I have a PhD in Zoology and need not respond to childishness, except to say, scientist usually attack others ideas, not others. You, though, are a pompous ***. It is laughable to peruse your pretentions. Your " disipline " needs to be reduced into biology, if you are a prime example of it. That is the true problem with your disipline; you people have too many positions and no solid conclusions.

John A. You are the typical YA coward who posts an answer well after the fact, hoping not to be noticed. Aside from the fact that you understand nothing of genetic tracing in MODERN populations and rules of evidence, you are  an ineffable twit!