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Biotech Science

Humans Evolved From a Single Origin In Africa 461

Posted by kdawson
from the 6,000-skulls dept.
Invisible Pink Unicorn writes "Researchers at the University of Cambridge have combined studies of global human genetic variations with skull measurements worldwide to show conclusively the validity of the single origin hypothesis. The alternative hypothesis contended that different populations independently evolved from Homo erectus to Home sapiens in different areas. The lead researcher explains, 'The origin of anatomically modern humans has been the focus of much heated debate. Our genetic research shows the further modern humans have migrated from Africa, the more genetic diversity has been lost within a population. However, some have used skull data to argue that modern humans originated in multiple spots around the world. We have combined our genetic data with new measurements of a large sample of skulls to show definitively that modern humans originated from a single area in Sub-saharan Africa.' The article abstract is available from Nature."
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Humans Evolved From a Single Origin In Africa

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  • by jellomizer (103300) * on Thursday July 19, 2007 @11:20AM (#19914707)
    I am wondering if this information may or may not discount the theory the Homosapians and Neanderthalls in Europe may have cross breaded?
  • by tsa (15680) on Thursday July 19, 2007 @11:26AM (#19914791) Homepage
    A bit off-topic, I know, but what often puzzles me is that all living things basically work with the same chemistry. All have DNA, and there are many proteins that are physically very similar between different species, even between animals and plants. This leads me to conclude that all life must have come form one ancestor that materialized somewhere on the planet. But the earth is a big place. To me it seems very unlikely that life hasn't occurred in more than one place and more than one time. So how is it possible that all life, on a chemical level, is more or less the same?
  • Re:Not so fast (Score:4, Interesting)

    by Moridineas (213502) on Thursday July 19, 2007 @11:33AM (#19914895) Journal
    Just FYI, Hawks has an interesting blog at http://www.johnhawks.net/weblog [johnhawks.net]

    I think it's down right now, but I'd recommend it!
  • Re:Not so fast (Score:0, Interesting)

    by Anonymous Coward on Thursday July 19, 2007 @11:47AM (#19915117)
    Can you prove that?
    Does a black man gradually become lighter over the years?
  • Re:Not so fast (Score:3, Interesting)

    by wytcld (179112) on Thursday July 19, 2007 @11:49AM (#19915153) Homepage
    Can more variation in Africa really prove anything beyond ... more variation in Africa? Consider: There are more tribal cultures, more languages, more language families, more diverse environmental niches. When you look at a globe rather than our typical equatorial-land-cheating map projections, Africa is a huge place. But does the existence of more variations on a theme in a particular space prove that it was the location of the original of the theme?

    An opposite argument is possible. Let's say you had butterflies everyplace but Africa, with each (sub)species displaying designs that worked best for camouflage/mate selection/whatever in its home territory. Over time many of these (sub)species reach Africa. Because it's a large, ecologically diverse space, a considerable number of them find successful niches. The subsequent conclusion that the range of different butterfly designs in Africa proves their ultimate origin there would be exactly wrong in this scenario.
  • by E++99 (880734) on Thursday July 19, 2007 @11:56AM (#19915229) Homepage

    - Life might be hard to bootstrap: something that occurs once every billion year per galaxy.

    Highly unlikely, given that life appeared on earth virtually the instant (geologically) that there was solid ground and liquid water.

    - Even if life reoccurs at a different time, one type is likely to be vastly superior and outcompete the other.

    That doesn't seem to be the case. Bacteria, for example, are biologically vastly superior to humans, and out-compete humans in most measurable ways, but we (for the most part) have no trouble surviving as a species alongside them. The incredibly vast number of species on the planet argues against the idea that out-competed species, are as a rule, eliminated.
  • by lawpoop (604919) on Thursday July 19, 2007 @11:57AM (#19915243) Homepage Journal

    To me it seems very unlikely that life hasn't occurred in more than one place and more than one time. So how is it possible that all life, on a chemical level, is more or less the same?
    Maybe because there's only one chemical formula for life to exist, so that no matter where it arises, it's always the same chemical formula.
  • by Bob-taro (996889) on Thursday July 19, 2007 @12:07PM (#19915363)

    ... before you start bashing them, okay? I believe in intelligent design, but I don't see that this post has much to do with it. Those of us who believe in a literal interpretation of Genesis obviously don't believe that humans came from multiple sources, we believe all humans descended from one couple. However, even if you could conclusively prove that all humanity came from one population - that doesn't disprove evolution (which is probably why you didn't immediately get the ID crowd all posting "see! see! we were right!". In fact, I'd think that even from an evolutionists POV, the chance of a species evolving independently from multiple populations is low.

    Now if someone said they'd proven that humans couldn't have evolved from one population, I might be inclined to look at their findings more closely.

  • Re:Not so fast (Score:4, Interesting)

    by notasheep (220779) on Thursday July 19, 2007 @12:09PM (#19915381)
    "1. Dark pigmentation is a protection against the sun.
    2. When people migrate north were the sun is weaker, over time, the need for sun protection disappears and people lose the pigmentation, hence becoming lighter."

    Close, but not quite right. Sun + skin = creation of vitamin D, very important to the human body. Dark-skinned people created less vitamin D in this manner than light-skinned people, but also have better protection from the sun. A good trade-off in equatorial plains regions. As people migrated north they had less exposure to sun and therefore had less natural vitamin D so the sun-blocking benefits of dark skin became a negative to their survival. Lighter-skinned people could create more vitamin D in the northern regions so that became a plus for their survival - so skin became lighter over time in those regions. (Lighter-skinned people lived longer to reproduce.)

    At least according to most programs I've caught on the Discovery Channel.

  • Re:Not so fast (Score:0, Interesting)

    by Anonymous Coward on Thursday July 19, 2007 @12:34PM (#19915807)
    His comment is crude and overgeneralized, but his message is generally correct. I'd like to see someone attempt a refutation of the idea that the humans who came out of Africa and eventually made their way into the colder parts of Europe did not have some significant biological changes. Its pretty well documented.

    Sitting here and telling people they are dumb for correctly interpreting biological data is not I am hoping for.
  • by DarenN (411219) on Thursday July 19, 2007 @12:42PM (#19915951) Homepage
    I remember hearing that it's been proven genetically that there is one common male ancestor and one common female ancestor for humans. the problem was, they were about 100,000 years apart.

    It was on television, so no reference.
  • by the phantom (107624) on Thursday July 19, 2007 @12:48PM (#19916049) Homepage
    The Multiple Origin Hypothesis is really misnamed, if you ask me. The model states that H. erectus migrated out of Africa, and that populations of H. erectus interbred, keeping variation down, or at least keeping interbreeding possible. Thus, modern H. sapiens evolved all over the place, in a direct line from the H. erectus ancestors already in place.

    The Single Origin or Out of Africa Hypothesis states that H. sapiens evolved in Africa, and migrated out from there.

    In both cases, there is an acknowledgeable that human ancestors first evolved in Africa, then moved out from there. The difference, as I see it, is really the time at which this happened. Out of Africa is much more recent than Multiple Origins.
  • Re:Not so fast (Score:5, Interesting)

    by msaavedra (29918) on Thursday July 19, 2007 @01:28PM (#19916853)

    I have a degree in anthropology. I recall some mathematical work...I didn't really understand it, but it was highly mathematical.

    Typical anthropology major (I kid, I kid. I have a degree in anthropology, too).

    I believe I've read the same or similar material. Here is a little more detailed explanation:

    Population geneticists have observed more genetic variability within the African population than in other areas. This by itself doesn't mean anything, though. It could just be that the environment in Africa in the old days was pleasant enough that mutant genes had a decent chance of survival, while harsher environments in paleolithic Europe, Asia, etc could weed out genes much more efficiently through very vigorous natural selection.

    There is another piece to the puzzle, though. Not only does Africa have a huge amount of variability, but that variability encompasses nearly all the variability found in other places as well. That is, the gene pools of Europe, Asia, etc are basically sub-sets of the African gene pool. Consider the following scenarios that could explain this:

    1. The populations in various locations split apart, and evolved somewhat independently. By luck or some unknown process, those new mutations arising in Europe and Asia also arose in Africa. However, those arising in Europe did not arise in Asia, and vice versa.
    2. The populations of the various continents split apart, but there is sufficient gene flow for mutations originating in one part of the world to spread to another. By coincidence or some process I'm not familiar with, the mutations arising in Africa spread to Europe and Asia, and those arising elsewhere spread to Africa. However, Europe and Asia have less genetic exchange, even with Africa acting as an intermediary.
    3. Modern humans developed almost exclusively in Africa, fairly recently in geological time. They spread through the world, replacing earlier populations with little if any interbreeding. The migrating populations lost some of their genetic variability through natural selection in their new environments, or through forces such as the founder effect.

    If think if you put this into mathematical language, you'd find option #3 is definitely the most likely. I wouldn't call it conclusive, though. After all, options #1 and #2 could be correct, if we discover some unknown processes that make them work without resorting to blind luck. In the meantime, though, my bet is on #3.

  • by fsmunoz (267297) <fsmunoz AT member DOT fsf DOT org> on Thursday July 19, 2007 @01:34PM (#19916961) Homepage
    Eheheh, that reminds me a perl of anglo-saxon racial mythology:

    "Which leads me to add one Remark: That the Number of purely white People in the World is proportionably very small. All Africa is black or tawny. Asia chiefly tawny. America (exclusive of the new Comers) wholly so. And in Europe, the Spaniards, Italians, French, Russians and Swedes, are generally of what we call a swarthy Complexion; as are the Germans also, the Saxons only excepted, who with the English, make the principal Body of White People on the Face of the Earth." Benjamim Franklin

    So, to ol' Ben you're "tawny". I'm even in worse conditions, since I would probably be a hit-n-miss between tawny, swarthy, "hispanic" or "latino" (this last two by name alone).

    That being said "white" is an historical construct onlyif you use the WASPish and/or nordicist redefinition of the term. It was already - and still is in most of the world - used to denote people of European descent. While there are grey areas the range itself (i.e. europoid people leaving outside of Europe) is more or less well defined in a racial sense. In general the discoverers you mention did view both africans and native americans as different in a racial perspective, going so far has having precise names for the resulting offspring according to the "mixture".
  • by paladinwannabe2 (889776) on Thursday July 19, 2007 @01:38PM (#19917035)
    Scientists, as you point out, often have a 'religious' view of certain theories. We saw it back when the Big Bang theory was first proposed; the scientists of the day saw it as 'thinly veiled creationism'. What drives science forward, though, is when you have two groups of fanatics screaming at each other, the non-fanatics generally cluster to the side with the better arguments and better evidence. That's why the Big Bang theory is now taught in schools, and the various steady state theories are discarded, as are most of the 'Big Crunch' ideas.

    Anyway, as far as your 4 theories go:
    1. The Universe came into existence completely from nothing, by itself. There was nothing, then everything over time. Start with nothing & work forward.
    I believe that Hawkings is actually espousing this idea. It seems highly unlikely to me, since it violates the First Law of Thermodynamics, without which all Chemistry, Physics, and Biology is meaningless.
    2. The Universe always existed
    Seems highly unlikely, given that a) the universe is expanding with no sign of collapsing and b) the Second Law of Thermodynamics.
    3. The Universe is an illusion
    Possible, but a pointless theory. Even if true, the universe behind the illusion still has to follow one of the other 3 possibilities (but #1 and #2 might be possible in a universe with different laws)
    4. The Universe was created.
    Almost certainly the case, the question is just by what. Perhaps another universe is unaffected by the Second and/or First law of Thermodynamics, and our universe was created there as an experiment/toy/prop. Perhaps our Universe was born from a black hole in another universe- and the black holes in our universe are also creating more universes. God creating this universe seems at least as likely as anything else, but that merely tells us he's insanely smart and/or powerful. He may care about our universe, but not care about us.

    Our best science tells us that we can't know how the universe was created. Unless we get the opportunity to witness another Big Bang or talk to God, it seems likely we will never even have that good of an idea.
  • by sasdrtx (914842) on Thursday July 19, 2007 @01:55PM (#19917385)
    Evolution is the theory that humankind is descended from the best rapists and killers.

    OK, I see their point.
  • by leonem (700464) on Friday July 20, 2007 @09:02AM (#19925731) Homepage
    A possible rebuttal:

    I've read an account of the development of early civilisations which stresses almost the opposite explanation. The mediterranean basin is an easier place to grow food (if not hunt/gather), leading to more sedentary leisure time, thus more pondering, thus more technological developments, thus even more leisure time and so on. Consider: the Egyptians relied on a uniquely ideal environment around the Nile.

    An analogy could be made with Britain and the industrial revolution. Success was not driven by hardship and necessity, but by ideal environmental conditions (rivers and coastline) for developing manufacturing and naval industries.

    It is possible that the initial impetus to move from hunter-gatherer to arable farmer was driven by greater need in cooler climes, but then again how would one survive long enough to work out how to farm if the envrionment didn't provide enough food to live at least several years? (I suppose simply storing autumnal wild foods might do, actually).

    Anyway, I don't think the 'forced to be inventive' thing can be a complete explanation, as even if it were briefly true, the necessity of invention ended the moment agrarian society was established, and that was thousands of years ago at least.

The clearest way into the Universe is through a forest wilderness. -- John Muir

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