'Out of Africa' Seriously Debunked?

Discussions unearthing human history including cultural anthropology, linguistics, etc.

Re: 'Out of Africa' Seriously Debunked?

Postby line on February 18th, 2016, 10:14 am 

I knew the OOAf theory is BS long time ago, without the benefit of the hindsight. I did not say anything since I don't want to become the target of acedemic bashing here. I have antagnized enough people by posting what I had to post for myself anyway.
How do I know it? The interpretation is absolutely anti-logic. Africa got the greatest genetic diversity (or whatever), and so they think it is the source of all the other less diversed regions. But what about New York City? I think it is more diversed than any countries in Africa, or even the entire Africa, because you can find Africans from all parts of Africa in NYC, plus some from Asia, Australia, Europe, and America. So NYC is the origin of human evolution by their logic (if there is any).
For their kind of interpretation to be valid, many unproved hypotheses have to be introduced: (1) there is only one origin; (2) the diversity must mostly if not always occurred before dispersion; (3) the origin (Africa) must satisfy a condition to allow such diversities to occur and yet remains largely stable and undisturbed, etc. Enough is enough! all these preconditions are against the common sense. Such is the quality of science in our time. It seems that as the technical capacity goes up, the thinking capacity goes down at the same time. I am too ashame to call myself a molecular biologist.
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Re: 'Out of Africa' Seriously Debunked?

Postby moranity on February 18th, 2016, 10:53 am 

the main thing to remember with this whole topic is that new evidence comes in pretty much daily that rewriteslarge portions of homo sapiens sapiens history.
We now have 1-4% neanderthal dna in european ancestry, 1-5% of neanderthal dna and 1% of another hominid in asian ancestry and that was meant to have occured around 40 thousand b.p., but then there's this:
Neanderthals mated with modern humans much earlier than previously thought
that shows evidence for either an earlier migration of homo sapiens sapiens or interbreeding between them and neaderthals in africa

also, mitochondrial dna studies seem not to be as robust as nuclear dna studies, i think thats the consensus
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Re: 'Out of Africa' Seriously Debunked?

Postby zetreque on February 18th, 2016, 3:11 pm 

NYC is not even close to a comparable analysis. We have technology right now bringing together people from anywhere the world in less than 24 hours. Things are very different. :)
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Re: 'Out of Africa' Seriously Debunked?

Postby moranity on February 18th, 2016, 5:49 pm 

the reason for the "out of africa" theory is that the oldest hominid fossils come from africa, not the level of genetic diveristy in africa
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Re: 'Out of Africa' Seriously Debunked?

Postby Paralith on February 19th, 2016, 5:56 pm 

line » Thu Feb 18, 2016 8:14 am wrote:I knew the OOAf theory is BS long time ago, without the benefit of the hindsight. I did not say anything since I don't want to become the target of acedemic bashing here. I have antagnized enough people by posting what I had to post for myself anyway.
How do I know it? The interpretation is absolutely anti-logic. Africa got the greatest genetic diversity (or whatever), and so they think it is the source of all the other less diversed regions. But what about New York City? I think it is more diversed than any countries in Africa, or even the entire Africa, because you can find Africans from all parts of Africa in NYC, plus some from Asia, Australia, Europe, and America. So NYC is the origin of human evolution by their logic (if there is any).
For their kind of interpretation to be valid, many unproved hypotheses have to be introduced: (1) there is only one origin; (2) the diversity must mostly if not always occurred before dispersion; (3) the origin (Africa) must satisfy a condition to allow such diversities to occur and yet remains largely stable and undisturbed, etc. Enough is enough! all these preconditions are against the common sense. Such is the quality of science in our time. It seems that as the technical capacity goes up, the thinking capacity goes down at the same time. I am too ashame to call myself a molecular biologist.


line, if you were indeed a molecular biologist, I would hope you'd understand that the levels of genetic diversity in question were assessed by looking at the genomes of people we can be reasonably sure are indigenous to the area in which they currently live. Therefore, estimates of the genetic diversity of people in the Americas is NOT done by looking at the genomes of all people currently living in New York City. It is done by looking at the genomes of people who we are quite certain are 100% indigenous Native Americans. It is this indigenous population, not the currently admixed population of New York City, which displays much lower levels of genetic diversity than similarly indigenous populations in Asia, Europe, and Africa.

If you don't want to be "academically bashed", then you shouldn't bash academics without having a clear understanding of what their research actually says.

moranity wrote:the reason for the "out of africa" theory is that the oldest hominid fossils come from africa, not the level of genetic diveristy in africa


No, the reason is both, moranity. No good scientific explanatory framework is based solely on one source of evidence. And, because of the fossils, there is little argument that the oldest of hominin ancestors arose in Africa. But the question today is more about the origin of the anatomically modern Homo sapiens species. Because multiple non-Homo sapiens hominin species made it out of Africa before Homo sapiens came on the scene. The question is if Homo sapiens arose primarily in Africa and then migrated outwards like other hominin species before it, or if Homo sapiens is the result of a large population spanning both Africa and Europe and maybe also Asia evolving synchronously into modern humans. And as I stated earlier in this thread, the answer is probably somewhere in the middle of these two ideas. The pattern of genetic diversity in particular suggests that a goodly portion of the founding population of Homo sapiens was in Africa, but evidence like the inclusion of Neandertal DNA in our genomes suggests that newly emerged Homo sapiens interbred quite freely with the species that came before it. And when populations begin to interbreed, they begin to evolve together. And, only people with ancestry that is not indigenous to Africa have Neandertal DNA in their genomes.
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Re: 'Out of Africa' Seriously Debunked?

Postby BioWizard on February 19th, 2016, 8:32 pm 

Paralith » 19 Feb 2016 04:56 pm wrote:
line » Thu Feb 18, 2016 8:14 am wrote:It is this indigenous population, not the currently admixed population of New York City, which displays much lower levels of genetic diversity than similarly indigenous populations in Asia, Europe, and Africa.


Hey Para. I guess you meant higher.
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Re: 'Out of Africa' Seriously Debunked?

Postby moranity on February 20th, 2016, 3:01 pm 

Hi Paralith,
So a species has highest genetic diversity in its area of origin?
i would have thought that genetic diversity was more a reaction to circumstance, such as intra-species competition, niche specialisation or some such? not just because they have been there longer than anywhere else?
A change in environment could render an area un-livable, for instance
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Re: 'Out of Africa' Seriously Debunked?

Postby BioWizard on February 20th, 2016, 4:14 pm 

moranity » 20 Feb 2016 02:01 pm wrote:Hi Paralith,
So a species has highest genetic diversity in its area of origin?
i would have thought that genetic diversity was more a reaction to circumstance, such as intra-species competition, niche specialisation or some such? not just because they have been there longer than anywhere else?
A change in environment could render an area un-livable, for instance


You're looking at it backwards. It's the moving of a small subset of that original population to establish a new population in a new area that causes the new population to have less genetic diversity relative to the original population. Why? Because the subset that moved out represents only a fraction of all the genetic diversity present in the original area.

Think about it this way. Assume you have a book with 120 pages. Assume all the pages in the book are unique, each has a different text on it. I ask you to make a copy of the book, then destroy the previous copy, over and over. At any given time, you have 120 unique pages in your copy. Thus, even though the actual physical book is in flux, the information in the book is maintained over time. Now suppose I tear 118 pages out of the book and give you the remaining two. You can copy these two pages 60 times to recreate a 120-page book, then resume what you were doing. But now your entire book is made up of only two unique pages. Thus, by forcing you to replenish your page count (re. population size) from only 2 pages out of the original book (re. subset of move-out population), I strongly decreased the information content (re. genetic diversity) in your book.

This is why bottlenecks decrease genetic diversity in a population and cause strong drift effects, even in the absence of any kind of selective forces. When a few individuals move out of a population of origin and go on to establish a new population somewhere else, the population goes through a genetic bottleneck (since the new individuals no longer have access to the entire original gene pool and can only interbreed with each other now).
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Re: 'Out of Africa' Seriously Debunked?

Postby BioWizard on February 20th, 2016, 4:23 pm 

Finally, to complete the thought, remember that neutral drift steadily increases genetic diversity within a population over time, again even in the absence of selective forces (it's like a DNA ticker, and can actually be used to date populations relative to each other). These are just mutations that appear and spread within the population unchecked by selection. So yes, the longer the population exists with its individuals having reproductive access to the entire population, diversity is passively increased. Over time, the diversity in a bottlenecked population will slowly start to increase again. But since the unbottlenecked population never stopped, it will always have more diversity (unless some extremely strong selective pressure or natural disaster change that).
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Re: 'Out of Africa' Seriously Debunked?

Postby moranity on February 20th, 2016, 4:35 pm 

Hi Paralith and Biowizard,
that makes good sense, i assumed that what would increase speciation would also increase genetic diversity with in a population. If anything it does the opposite, by the sounds of it.
So a great factor in maintaining and then increasing genetic diversity within a population is equal access to mates?
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Re: 'Out of Africa' Seriously Debunked?

Postby BioWizard on February 20th, 2016, 4:43 pm 

moranity » 20 Feb 2016 03:35 pm wrote:So a great factor in maintaining and then increasing genetic diversity within a population is equal access to mates?


It allows for maximum efficiency in the spread of new genetic variants (which increases genetic diversity). It doesn't have to be equal access at the level of every individual. But the smaller the barrier to the spread of any variant, the faster it spreads.
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Re: 'Out of Africa' Seriously Debunked?

Postby BioWizard on February 20th, 2016, 4:53 pm 

Think about it as the population having access to new (and old) variants, rather than vice versa.
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Re: 'Out of Africa' Seriously Debunked?

Postby wolfhnd on February 28th, 2016, 11:46 am 

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Re: 'Out of Africa' Seriously Debunked?

Postby Fuqin on September 8th, 2016, 9:25 am 

Wolfhnd:-"Over the last two hundred thousand years we have seem a rapid increase in brain volume and over the last ten thousand years a significant reduction in brain volume both almost exclusively tied to culture. Culture I would argue is the most defining human characteristic".

Fascinating I know isn't the main thrust of the discussion , but I've never heard this before, while there is a correlation , is there a theroy that describes as to why the development of culture might be linked to a reduction in brain size? Technology, diet , langage , record keeping springs to my mind .
Anyone know cheers :)
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Re: 'Out of Africa' Seriously Debunked?

Postby wolfhnd on September 8th, 2016, 6:24 pm 

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