Questioning the ‘Out of Africa’ Hypothesis and Human Migration

http://www.smh.com.au/national/education/out-of-africa-theory-of-human-evolution-under-fire-20140822-106o5e.html

In this article, Peter Spinks discusses how evidence may change the details of the ‘Out of Africa’ hypothesis. This is the hypothesis stating that our modern human ancestors roamed from Africa to other parts of the world nearly 60,000 years ago. However, teeth of early modern humans found in China and south-east Asia suggest that modern humans may have left Africa as early as 130,000 years ago. The research team responsible for the find was led by anthropologist Christopher Bae, who says that this evidence indicates that “the human evolutionary record… is more complicated than originally believed.”

Spinks highlights that although the find has caused some confusion in the ‘Out of Africa’ hypothesis, it also makes clear details regarding migration. For example, it gives more information regarding where humans initially went after migrating from Africa. It is now believed that humans travelled along the Arabian Peninsula before reaching south-east Asia, while a second group later dispersed into north-west Asia, moving into Europe and eventually to the Americas. This forces revision of the hypothesis as a whole, which Spinks paints as a positive situation, as it encourages change due to evidence found.

This evidence opens many new ideas regarding numerous migrations from Africa and encourages rethinking of existing timelines. It is believed that many cultural and technological advancements occurred in southern Africa between 55,000 and 75,000 years ago, making it easier for modern humans to survive in unfamiliar environments. Earlier studies uncovering Palaeolithic stone tools dating back to 125,000 years ago in the United Arab Emirates similar to those in east Africa support theories that early modern humans moved into Arabia straight from Africa instead of via the Nile as typically assumed. This suggests that modern human ancestors were fairly advanced in their ability to adapt to new environments and successfully migrate across continents.

Spinks’ goal is to present the evidence found to his audience in the context of what it means to evolutionary theory and the migration patterns of modern human ancestors. He presents factual information with analysis from experts in order to strengthen his argument: that “the textbook version of [human migration] almost certainly needs re-writing.”

But is his assessment correct? The teeth found in Asia provide new evidence, but what does it mean for evolutionary theory? Is this enough evidence to change and strengthen ideas regarding modern human evolution, giving more context to human migration? Or does it complicate and weaken evolutionary theory?

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18 Responses to Questioning the ‘Out of Africa’ Hypothesis and Human Migration

  1. gwuw2014 says:

    I think one of the key facets of scientific theory is that it is always in development. This new dental evidence does not weaken evolutionary theory but rather opens doors to theories. The article you linked to specifically calls into question the “Out of Africa” hypothesis, but another idea, the Multiregional Continuity Model, is also considered by human evolutionists. This article summarizes the differences between the two theories but doesn’t touch on any dental evidence:

    http://www.actionbioscience.org/evolution/johanson.html

    Maybe instead of weakening the entirety of human evolution, this dental evidence strengthens the Multiregional Continuity Model?

    • greyelephant1 says:

      gwu2014, I agree that the dental evidence would agree with the Multiregional Continuity Model but I do not think it would weaken the entirety of human evolution. I think the theory of human evolution may change with the evidence, however I do not think that will weaken the argument of evolution.

    • sunny2018 says:

      gwu2014, thank you for the article. I like that it presents both theories with archaeological and genetic evidence, and I agree that much of the evidence presented in Spinks article supports the Multiregional Continuity Model. However it is also possible that neither theories are completely accurate, and perhaps some combination of the two is more plausible than simply one or the other being true.

  2. greyelephant1 says:

    First, I really like this article, it is very intriguing. I am a little conflicted personally on what I believe. I can understand interbreeding occurring and that hominins were in other regions of the earth, including Asia. What I am not sure is how this affects our perspective of evolution. I do believe that with more evidence, Spink is correct in that the textbook version of evolution needs updating, but more evidence is needed. Usually, for something new to be accepted in the scientific community, there needs to be a lot of evidence, especially if the new ideas proposed disagree with current ideas. I think this data just changes how we specifically think humans evolved, but not the theory itself.

    • pigfish1116 says:

      I agree with greyelephant1, I don’t think the whole theory of evolution will be changed because of this find but I think the history that archaeologists have created around early human bones has to be revised.

    • macnplease says:

      In the context of the scientific method, you are correct; it is uncommon for a theory to change dramatically without a substantial disproof of the original theory or new proof of a different one. I find it interesting how you use the word “believe” in this context, too – it doesn’t really matter what we “believe” so long as we follow the implications of the evidence with as much integrity as possible.

  3. collegeblogger19 says:

    I think this new evidence doesn’t weaken the theory of evolution, but rather strengthens it. Whenever additional evidence is found, it enhances the theory. Finding the new dental evidence gives us more information on human migration–and even though it differs from previous human migration theories, it is always helpful to enhance and reform theories to make them stronger and evidence-based.

    • greyelephant1 says:

      collegeblogger19, I never thought of it as strengthening evolution, but that is an excellent point! I can understand that more evidence arising, no matter what it supports does strengthen the idea of evolution. Great point!

    • sunny2018 says:

      I agree with your assessment collegeblogger19; I see this new evidence as augmenting the theory. The real confusion is in piecing all of the evidence together to try and form a clear picture of what happened regarding migration and human evolution.

  4. pigfish1116 says:

    I am taking archaeology and right now we’re discussing inductive and deductive reasoning and how archaeologists either make generalizations about the evidence and artifacts they find or can come to extremely specific conclusions on the history of these artifacts. It will be interesting to see how the scholarly evolutionary community will collaborate and interpret these new finds.
    I think it will be a hassle making new middle school textbooks about this evolutionary find if scientists agree that these teeth can change the way we interpret early human migration! I believe it is important to keep the public updated on the new findings that prove evolutionary theory but what about school textbooks? First of all, scholars have to rewrite the textbook, then schools have to buy the new textbooks. The problem I see in the California school district is that schools don’t have enough funding to constantly buy new textbooks. I know this is taking a whole different turn but it’s interesting to think about how this information will reach young people who really don’t read up on archaeological finds but rather watch Kim Kardashian at the gym.

    • sunny2018 says:

      I hadn’t considered the effects regarding education. What do you think would cause new textbooks to be written? Is there a specific amount of evidence needed, or should major finds altering scientific theories automatically require a change, not necessarily in just textbooks, but in science education as a whole?

      • macnplease says:

        To try answering your question – I would think that once a hypothesis has established itself significantly in the scientific community, at least enough to be taken seriously, it should be included in educational texts. After all, we never will know if we have it absolutely right, so in the mean time we must update our educational texts as best we can. Obviously this is from a scientific idealist perspective, and the logistics of updating educational texts so often are mind-boggling. I see it as a standard to work towards.

      • pianokid123 says:

        sunny2018, anthropology is a field extremley prone to revision, and biology textbooks will most likely incorporate these findings into later editions if more evidence accumulates. For instance, Campbell Biology is constantly revising sections on biotechnology due to all of the exciting advances in the field, and my AP edition even mentioned Homo florensis, a species discovered only ten years ago! After all, these findings are not THAT shocking as a plethora of other hominid species have ventured out of Africa in previous waves such as Homo erectus and Homo heildelbergensis.

  5. This is a really interesting article and you’ve done a great job or forwarding the information concisely.
    The beauty of science is the fallibility of a hypothesis or theory; even evolution itself isn’t immune to this. However, the article points to an interesting addition to the theory and may even cause a revision in the overall timeline of human evolution, which in my opinion, is a pretty big deal. It really shouldn’t be a factor that weakens evolution though, because I don’t see it as something that disproves it in any way.

    Another interesting read along the same lines:
    http://io9.com/5915909/our-ancestors-may-have-originated-in-asia-not-africa

    • macnplease says:

      We posted our comments at about the same time and cover similar points, so obviously I’m inclined to agree with you!

      Concerning your link to the article, this would also be a groundbreaking discovery should their hypothesis be accurate. It’s curious, however, that these two vastly contradicting theories (Out-of- Africa being earlier than we thought vs. Out-of-Asia) do not address each other. Perhaps in time.

  6. macnplease says:

    What an interesting find! This would indeed make waves in the Human Evolutionary theory, as it presents numerous implications with a simple change of timing: The fact that there could possibly have been earlier migrations out of Africa would and could mean that hominids evolved in different ways than previously hypothesized, especially if they migrated initially through the Arabian Peninsula instead of Indo-Europe. It will be interesting to see if this new theory plays out and makes any substantial change to the current model. This is the beauty of science – new discoveries mean we can augment our knowledge of our universe.

    The blog poster did a good job of forwarding the information from the article by Peter Spinks. The blog poster does not just summarize the main points of the article, but includes Spinks’ goals in writing the piece. Well done!

  7. pianokid123 says:

    Anthropology, by nature, is an extremley fragile region of science. This is because many of the hypotheses regarding human evolution are based upon a few hominid skeletons and artifacts. One new discovery can greatly affect current scientific hypothesis surrounding human evolution. Not to fear, for this is merely science at work! For instance, in 2003 the new hominid genus Homo florensis was discovered in Indonesia. However, much debate remains as to whether this fossil is its own individual species, or merely a deformed human. (Check out the article here http://www.livescience.com/1282-hobbit-declared-species-debate-continues.html). These discoveries by no means reduce Darwin’s theory — we are looking at such a small branch of fossils that range only about eight million years, a mere glimpse in evolutionary time. Obviously, mistakes and overgeneralizations will be made when basing all the entirety of human evolution off a few fossils, and these errors have been foreseen by scientists who then approach these fields with caution. It is important to remember ideas surrounding hominid evolution are hypotheses, not theories. Evolution, on the other hand is a theory, and is what we use to predict where to find these fossils and artifacts in the first place!

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