The possibility of an earlier modern human migration out of Africa—at least as far back as 220,000 y

Discussion in 'Biology & Genetics' started by geek, Feb 12, 2019.

  1. sculptor Valued Senior Member

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    =

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    said to be sapiens sapiens from over 300kybp
    what is shown is a composite; assembled from fragments
    This video shows the skull with jaw attached


    again
    composite

    I ain't so sure
    what do you think?
    sapiens?
    neanderthal?
    other?
     
    Last edited: Feb 21, 2019
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  3. iceaura Valued Senior Member

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    We know for sure that not only anatomically but culturally, ecologically, modern humans were widely spread 60k ago. They almost certainly had boats of some kind, for example.
    A couple of hundred thousand years for that to develop is not a stretch.
     
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  5. Yazata Valued Senior Member

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    I'm not sure what to think about that. The Jebel Irhoud specimens seem to be what we might call proto-anatomically modern humans I guess. Their date comes after the hypothetical divergence date of the modern human and neanderthal lines, so these Moroccan specimens might be early examples from the line that would produce the anatomically modern humans.

    I wrote more about them in posts # 22, 23, 24, and 53 in this interesting earlier thread, where you made lots of posts as well:

    http://www.sciforums.com/threads/new-evidence-of-homo-sapiens.159503/page-2
     
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  7. geek Registered Member

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    Whats special About Africa?
    When our planet was inhabited all across by animals , perhaps a 100 times more in specimen than now.( Humans might have thought of living together much after those creatures , with there era gone extinct, and it was safe enough to do so).

    When none of any of other species there are , whom science talks about Migrations out of any one continent,_regarding there origin- why is it only human species have their origin and then migrates out of Africa.

    Why couldnt humans have had their independent origins all across the planet, just like every other species both plant and animals did?
    What is special about Africa: Air, more things to eat? good soil, what is it?
     
  8. iceaura Valued Senior Member

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    They didn't.
     
  9. Yazata Valued Senior Member

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    The way that current anthropological orthodoxy seemingly has it, all of the evolution that went into the development of modern humans took place in Africa. Which suggests that either --

    1. human evolution doesn't take place outside Africa, or

    2. if it does, then all of human evolution outside Africa was abortive, leading to varieties of human that later became extinct (Neanderthals, Denisovans and the Flores Island hobbits perhaps).

    The first is unconvincing to me for biological reasons. Reproductive isolation and introduction into new ecological niches are drivers of evolution. Early hominins expanding their range into Eurasia would seem to have increased both conditions. So one would expect the pace of human evolution to pick up after these populations left Africa. (Like Darwin's finches evolving new species as they colonized new islands in the Galapagos.) One wouldn't expect the pace of evolution to cease as they spread out.

    The second seems unconvincing to me too, simply for reasons of likelihood.

    I think that we do see fairly distinct biota appearing on different continents. An example is the giant carnivorous flightless birds that were apparently the apex predators in South America for millions of years after the demise of the dinosaurs. (And obviously filling some of the same ecological niches with similar anatomies.)

    https://en.wikipedia.org/wiki/Phorusrhacidae

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    Even today, Australia serves as a refuge for marsupial populations that are unusual elsewhere. (It's also a refuge for human types like JamesR and Bells.)

    The variable that seemingly determines how unique a continent's biota is, is how isolated that continent is. South America wasn't always connected to North America and seems to have been home of many unique species. (Still is.)

    Maybe (I'm just speculating now) Africa hit the sweet spot. Isolated enough to generate a unique biota, but close enough that more determined species could leak out and spread into broader Eurasia.

    Well, human beings do have so many anatomical similarities that common ancestry is strongly suggested. We do seem to derive from the same ancestral interbreeding population (not necessarily the same individuals in that population, so I'm skeptical about the 'genetic Eve' idea that has all of us the decendants of one particular woman) and that population does seem to have been located among the rift valleys of east Africa. That's millions of years ago.

    Then we seem to see earlier models of hominin such as Homo erectus leaving Africa and becoming established all over Eurasia. (Peking man, Java man...) Later we see much more modern sorts of populations (Neanderthals, Denisovans) in Eurasia. I don't know where they originated, but I'm not totally opposed to the idea that they evolved from the earlier populations right there in Eurasia.

    If early anatomically-modern man first appeared in Africa and spread into Eurasia roughly 100,000 years ago in a new out-of-Africa episode, did they replace the variants who were already living in Eurasia, by driving them to extinction? Or did these populations interbreed, forming a hybrid modern type?

    These are questions that are hugely moralized and politicized in our current climate, touching as they do on race. So as is increasingly the case these days, it's often difficult to distinguish between objective science and rhetoric that takes the form of science.
     
    Last edited: Mar 6, 2019
  10. James R Just this guy, you know? Staff Member

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    The evolution of human beings is convoluted. I suspect that the fact that modern humans evolved in Africa is partly due to favorable environmental conditions, and also due to the contingency of having the "right" kind of ape ancestors there, which is more or less accidental.

    Primate evolution has been traced back 65 million years, after the mass extinction event that wiped out the dinosaurs. There were some primate-like species in North America, some in China, but many have been found in Eurasia and Africa. One theory has it that the early primates that eventually involved into modern apes migrated south from Europe to Africa, or else came across from western Asia. From there, the species diversified, producing the great apes and human beings. Several species of human beings then migrated out of Africa to various other places. It appears that Homo sapiens out-competed Homo neanderthalensis (which some argue is a subspecies of Homo sapiens) for a similar ecological niche, leading to the eventual extinction of the latter species.

    The Hominoidea (apes) superfamily, including the Hominidae family of which modern humans are a species, diverged from the Hylobatidae (gibbon) family about 15-20 million years ago. African great apes (subfamily Homininae) diverged from orangutans (Ponginae) about 14 million years ago. Humans, chimps and some extinct bipedal species diverged from gorillas about 8-9 million years ago. Chimps diverged from humans and their biped ancestors about 5.6-7.5 million years ago.

    Bearing in mind that Homo sapiens is a very young species in evolutionary terms, and that human geographical diversification has taken place only very recently, with a lot of genetic mixing of regional groups, it is not particularly surprising that human beings have, for the most part, not split into distinct species since leaving Africa.

    Absolutely we do, particularly where there is geographical or ecological isolation.

    The marsupial populations of Australia are not just unusual. They are natively found nowhere else in the world. Think kangaroos, koalas, wombats, echidnas, platypus, antechinus, bilby, quokkas ... the list goes on and on.

    But every continent has species that are unique to that continent.

    On a smaller geographical scale, genetic isolation can happen in lots of different ways, leading to species whose ranges are restricted to very small areas indeed. For example, using an Australian example again, if you're a mountain pygmy possum then you can't survive the temperatures that exist below a certain level on the mountains where your species evolved. That makes it very difficult, if not impossible, to spread your population even to the next-door mountain range, let alone to a different continent.

    Also worth mentioning is that how isolated the continent has been in the past is also relevant. The continents aren't in the same places today that they were 100 million years ago, for instance. You have to take continental drift into account. Also, with continental drift comes changes in climate, which can be fatal to many species. Antarctica used to be near the equator.

    There is some evidence of genetic bottlenecks in Homo sapiens. Our DNA as a species is actually less diverse than we would expect if we had maintained largish populations over the whole lifetime of the species.

    Those are good questions, and the subject of ongoing research, I believe.

    I don't really see how matters of human evolution over millions, or even hundreds of thousands of years, could possibly involve the somewhat arbitrary modern idea of "race".
     
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  11. Write4U Valued Senior Member

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    There are many more human arti-facts than human fossils.
    Because it was not that long ago. From your link.
    consider that there are much older more primitive species which already used tools, albeit simple tools.

    One of the oldest known human settlements is on the southern tip of Africa.
    This is significant in view of the prevailing global climate at those times.
    https://en.wikipedia.org/wiki/Pinnacle_Point
     
    Last edited: Mar 7, 2019
  12. Write4U Valued Senior Member

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    OK I'll say it. It is physically impossible that "modern 23 chromosome humans" could have lived 2 billion years ago. That was before our 24 chromosome common ancestor appeared on earth.
    More importantly, they did not have time travel yet.

    It is possible that life could have originated 2 billion years ago, but not on earth.

    The proof lies in the earth's chemistry, the formation and evolution of bio-molecules during the various "ages" which allowed for the eventual formation of living patterns. This takes time.

    Fortunately the Earth provided a chemical rich environment.

    But if the intent of this OP is to suggest that human lived at the time of dinosaures it is way, way, wayyyyyyyyy off in factual science.

    Again, all I can do is recommend Robert Hazen's lecture on Origins at the Carnegie Institute. If one takes the time to consider his presentation, you will find a vast body of knowledge presented in a clear and engaging condensed history of the possible origin of life on earth.

    His lecture allowed me to start finding confirmations from independent but related research in chemistry and the evolution of
    , to bacterial "Quorum Sensing"
    https://en.wikipedia.org/wiki/Quorum_sensing

    The chemical processes are relatively simple and on earth may well fall in the range of 2 trillion, quadrillion, quadrillion, quadrillion progressive chemical reactions, but the odds are small.

    The evidence shows that the 23 chromosome "modern" human emerged somewhere around 200,000 years ago.

    But one thing is clear, humans could not have lived in a oxygen-free atmosphere. That was the time of the prokaryotes
    , such as cyanobacteria which produced the oxygen which allowed the explosion of Eukaryotic organism and greater cellular complexity.
    https://www.sciencedaily.com/releases/2013/01/130117084856.htm

    You believe that fully evolved humans could have existed 2 billion years ago?
     
  13. ForrestDean Registered Senior Member

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    Most likely. But I didn't mention anything about modern 23 chromosome humans.

    Today's "factual science" is still extraordinarily limited.

    It's very possible. Makes sense.

    You believe we are fully evolved now? Evolution is an ongoing process. It is possible we could've devolved over 200,000 years ago and we are working our way back up. Relying on scientific evidence based on our current modern day scientific equipment as definitive proof of how organic life lived and evolved throughout this planet's entire history is folly.
     
  14. Write4U Valued Senior Member

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    I introduced it because it is overwhelming evidence that man and ape had acommon ancestor which had 24 chromosomes. Adam was the first hominid to be born with a mutated gene, a fusion between two adjacent chromosomes.
    All humans have only 23 chromosomes, all apes still have 24 chromosomes, it is the defining moment of the split from a "common ancestor" into Homo sapiens and other Great Apes.
    Not this important fact:

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    http://www.evolutionpages.com/chromosome_2.htm

    No you cannot rewrite natural evolutionary processes, undo certain things and expect the same results. Ice ages, meteor bombardments, volcanic activity, reversal of the poles.

    Change any of this in the past and we cease to exist, as human anyway.

    Humans are the result of deterministic albeit probabilistic sequence of earthly events. Our research shows periods of an alien environment, periods of a very friendly environment with rapid evolutionary biological growth, followed by extinction periods and renewed beginnings.

    What is devolvement? This is not allowed in nature. Devolvement results in natural selection to the junk heap of extinction. The only way out is up, up. Ever greater specialization and adaption to the immediate environment or death.

    It remains to be seen if humans can stand that test. We know insects can......hehe.....

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    They have done it for billions of years!!! The insect has seen it all and lived to tell the tale.

    Humans are the new guys on the block.
     
    Last edited: Mar 7, 2019
  15. sculptor Valued Senior Member

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  16. ForrestDean Registered Senior Member

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    You see, this is just more "evidence" that current, modern science is an endless series of corrected mistakes and false, flawed assumptions because the evidence provided by our current physical scientific instruments we use today are shallow at best and can only give us the face value of Earth's history leaving us with nothing more than theory and speculation. Some of it may be accurate, some of it may not be. That's why it's still just a theory. Sure, our technology is more advanced and complex than it was centuries ago, but to claim beyond any doubt about who or what evolved on this planet at certain times excluding all other possibilities simply because it has not been discovered by our current, "limited" technology, is no different at all to those scientists of just a few centuries ago who "knew beyond a doubt" that the Earth was flat, and was also the center of both the solar system and Universe based on scientific evidence at that time. Those scientists were no less correct than contemporary physical sciences, for the same fundamental reasons.
     
  17. iceaura Valued Senior Member

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    Bullshit.
    Which have proved far more accurate and worthwhile bases for decision making than anything else available.
    You don't know what a scientific theory is.
    They don't exclude "all other possibilities" - they exclude just some of them, the ones in too direct conflict with too firmly established discovery and evidence.

    When they are functioning.
     
  18. Michael 345 New year. PRESENT is 69 years old Valued Senior Member

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    So because in the past people made observations about the world with no evidence it's OK today to make claims with no evidence

    Well done

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  19. ForrestDean Registered Senior Member

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    LOL well yeah of course. People should be free to make any claims they like, which of course they do all the time, but it doesn't mean their claim is correct. And of course, people should be free to disagree with those claims, which of course back then those who disagreed with the majority were not treated so fairly and had to endure unpleasant consequences regardless of the evidence they had to disprove the commonly accepted belief.

    There are some Christians today who claim the Earth is only 10,000 years old regardless of overwhelming evidence that shows otherwise. The Flat Earth Society claim to this day that the Earth is flat. Evidence can be extremely useful, especially if we are to progress and evolve.
     
  20. Michael 345 New year. PRESENT is 69 years old Valued Senior Member

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    but it doesn't mean their claim is correct

    Hold that thought every time you think about making claims you appear to pick out of thin air

    AND
    I don't think your examples are this bat shit crazy

    ????
    Have to agree. You appear not to understand the use of the word "theory" in science which is different in everyday common use

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  21. ForrestDean Registered Senior Member

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    Hmmm, maybe. I always thought a scientific theory was just an examination and interpretation of the facts. From what I understand, facts and theories are two different things. If I remember correctly from what I learned in school, within the scientific method, there is a clear distinction between facts, which can be observed or measured, and theories, which are scientists' explanations and interpretations of the facts. I always thought theories can change, or I should say the way in which they are interpreted can change, but the facts themselves remain the same. At least that's my understanding of a "theory".
     
  22. sideshowbob Sorry, wrong number. Valued Senior Member

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    The problem is where you said, "... it's still just a theory." A theory is always "just" a theory, like a fact is just a fact and a unicorn is just a unicorn. Theories don't morph into something else. They just become better explanations (or they're replaced by better theories).
     
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  23. Michael 345 New year. PRESENT is 69 years old Valued Senior Member

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    The point I was trying to make

    You just did it better

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