Slashdot Log In
Humans Evolved From a Single Origin In Africa
Posted by
kdawson
on Thu Jul 19, 2007 10:18 AM
from the 6,000-skulls dept.
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."
This discussion has been archived.
No new comments can be posted.
The Fine Print: The following comments are owned by whoever posted them. We are not responsible for them in any way.
Full
Abbreviated
Hidden
Loading... please wait.
Not so fast (Score:5, Informative)
"John Hawks of the University of Wisconsin-Madison says the paper is mistaken. A major flaw is that the current research is largely based on skull variability. "You can't find the origin of people by measuring the variability of their skulls," Hawks said.
"Differences in skull features are related to genetics, and genetic variation depends on how much mixing occurs with other populations. "The main problem with the paper is that it takes some assumptions from genetics papers of 10 to 15 years ago that we now know are wrong," Hawks said.
"Other scenarios, besides the single-origin theory, could account for the link between distance and skull variability. "Africa is ecologically diverse, and cranial variation is a function of environments," he said. In environments supporting hardy foods such as roots, people would need bigger jaw muscles, and thus larger areas for muscle attachments.
"Also, correcting for climate is not a good idea, according to Hawks. "The most important feature that is related to climate is skull size. So by correcting for climate, they are subtracting a major component of variability," he said.
"In his own research, Hawks is finding that natural selection has led to changes in thousands of genes during only the past few thousand years.
"I'm really thinking just the opposite of this paper," Hawks said. "There are differences in the skull between populations, including their variability, but it is mostly due to very recent effects and not the origin of modern humans."
"At the end of the day, a resolution to the "Out of Africa" debate may be impossible, he said. Most of the evidence can be interpreted as supporting both human-origins theories. "It's really hard to find observations that distinguish the two," Hawks said.
"The multiregional idea is identical to the recent African origin idea, except for its prediction that Europeans and Asians were part of the single population of origin and didn't become extinct."
Re:Not so fast (Score:4, Interesting)
I think it's down right now, but I'd recommend it!
Parent
Re:Not so fast (Score:5, Funny)
2) Get first post on said story noting the debunking.
3)
4) Profit? Karma?
Parent
Re:Not so fast (Score:4, Informative)
Parent
Re: (Score:3, Interesting)
An opposite argument is possible. Let's say you had butte
Re:Not so fast (Score:5, Insightful)
Anyways, some anthropologist took this population/genetics research and applied it to human populations. First off, they had to show that there was more diversity in Africa. They did this with genetics. So then if Africa has the most human diversity, and the above postulate about populations and diversity is true, then humans must have originated in Africa.
Parent
Re:Not so fast (Score:5, Insightful)
And it is nice to see another anthropologist on Slashdot. I have my degree in anthropology (focusing in archaeology), with a minor in statistics.
Parent
Re:Not so fast (Score:5, Interesting)
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:
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.
Parent
Re: (Score:3, Informative)
That's now how it works. "Turning into humans" (or any other species) is a long, involved process that entails some random genetic mutations being advantageous enough for you to spread them around. Then there's some separation that blocks interbreeding between populations. Evolution continues in both populations until they speciate--i.e. they can no longer interbreed because they have separately evolved for long enough. While parallel evolution does happen, the "parallel" species are still different species
Re:Not so fast (Score:5, Informative)
Parent
Re: (Score:3, Informative)
It seems here that we have a researcher who started with a conclusion and is trying to find data to support it, rather than starting with a hypothesis, gathering data, and forming a conclusion
While I don't know much about the research in question, this statement struck me as wildly wrong. Theories are quite often developed before there's data to support that theory. The most well known of those is special and general relativity. At the time Einstein created these theories there was very little data to su
Re: (Score:3, Insightful)
I should further clarify perhaps, that GOOD science runs from hypothesis to data gathering, testing, and conclusion, while POOR science starts with the conclusion, then gathers evidence, rarely tests (or does not test rigorously enough, or only tests certain applications in which the original conclusion would prove to be true while avoiding or dismissing other testing which might find flaw with it).
"good" science? It's a perfectly valid methodology to devise a theory that isn't supported by evidence and th
Re:Not so fast (Score:4, Insightful)
How exactly do you submit a retraction for a slash article?
I would rather have Unicorn posting his own update than having someone ripping the original to pieces.
His(her/it) actions are commendable in my book.
Parent
Re: (Score:3, Funny)
Re:Not so fast (Score:5, Informative)
It looks like my OP is going to be modded -1 Troll anyways, since some people seem to think that there are only 2 theories: Evolution and Creationism, and that if I'm saying "Not so fast", I must be spouting creationist nonsense.
Hilarity ensues.
Parent
Re:Not so fast (Score:4, Interesting)
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.
Parent
Re: (Score:3, Informative)
Re: (Score:3, Insightful)
Re:Not so fast (Score:5, Funny)
Parent
Re:Not so fast (Score:5, Funny)
Parent
Re:Not so fast (Score:5, Informative)
Parent
stupidity supports racism (Score:3, Informative)
What about future cross breading? (Score:3, Interesting)
Re: (Score:2)
Re:What about future cross breading? (Score:5, Funny)
Parent
Re: (Score:3, Funny)
Are you attracted to gay bees?
Disclaimer: I realize that not everyone here watched SNL in the early 80s. If you didn't, I'm sorry you don't get the joke -- but I don't mean to offend any gays or bee fetishists.
Re: (Score:3, Insightful)
I don't think it's that unusual. There are plenty of species complexes out there. Probably the most familiar example is genus Canis (dogs). A large number of the members of this family are reproductively compatible, and gene flow between variou
I'm from Kansas (Score:5, Funny)
There, fixed it for you.
Re:I'm from Kansas (Score:5, Funny)
Parent
One source for all life (Score:3, Interesting)
Re: (Score:3, Insightful)
Perhaps one day, when life started out, there were many different types of bacterial lifeforms. Turns out that only a handful managed to stay alive in the ever-changing environment. Some of those just happened to have the bad luck of being wiped out by a meteor shower. And one of few remaining ones was a bloodthirsty killer that ate the few remaining other species; we decended from that guy.
Perhaps something completely different happenned. The chances of a lifeform being succesful in
Re: (Score:3, Insightful)
Re: (Score:3, Informative)
Re: (Score:3, Interesting)
Because there really was just one source (Score:5, Informative)
Yes, and that ancestor is a very simple RNA-based bacterium. And this evolved into DNA-based simple bacteria. Then bacteria which included other simple and ultra-specialized bacteria (cloroplasts and mitochondria). Which evolved into simple multi-celular life forms like sponges and extremely simple worms (hardly more than essentially an elongated torus whose surface was a bacterial film.) Which further evolved into more and more complex stuff.
And some figured out how to eat the others. E.g., fungi evolved to take another cell apart for food. And then some of those managed to, well, more or less do agriculture with other bacteria: the lichen are more or less a combination of a fungus and a bacteria, where the fungus traps the bacteria and helps fixate water and minerals for it, then scoop the food the bacteria produced. Or sometimes just destroy and eat those bacteria for food.
So there you already see the early split between plants and animals: one branch of the fork relied on photosynthesis to produce its own food and energy, using solar energy for it, and the other branch of the fork evolved to be basically parasites on the first one. Whether literally parasites eating the live plants (mostly plankton and algae at that point), or eating the corpses.
But before that fork, they evolved from the same ancestor, hence why they're still similar inside.
And from there it was often a race between species, driven by natural selection. E.g., the lignin based plants of the carboniferous era had a major temporary advantage, in that bacteria and fungi didn't yet exist which could digest this adaptation. However, that also applied to dead plants, which is why there's so much coal left from that age (and gave the age its name.) There simply was noone around which could eat a dead plant. But then bacteria evolved that could take apart lignin and celulosis. And then some animals evolved compartmented stomachs where they could store such bacteria so they could eat plants. (Don't think just literally animals. Some insects, e.g., termites, do exactly the same.)
And so on, an so forth, branching wildly ever since, and punctuated by some extinctions that trimmed the tree.
But, yes, once you trace all the branches back, it all leads to that first primitive bacterium. That's why it's all so similar at a chemistry level. Each step was a tweak of what already existed. Each step evolved more complex proteins, or just different proteins, and more specialized roles, but it was still based on the same reactions that worked before.
E.g., it still had enzymes which copied a strand of RNA, between a "START" and an "END" marker, to a protein. Even in DNA based cells, it's still not that horribly different: there's just an extra step of transcribing the DNA to RNA, so then you can transcribe the RNA to a protein. (As to why that more complicated mechanism evolved by natural selection: because breaking a single strand of DNA, for example by radiation or some chemicals, can still be fixed, while the same break in RNA means cell death. So the DNA based mutants were hideously more survivable than their RNA based ancestors.) Anyway, we essentially we still use the same mechanism of producing the proteins as that original proto-bacterium ancestor.
Where did that original bacterium come from? Well, probably from something even simpler. A bacterium is nothing more than a drop of sea water with a membrane. It makes it easier to keep the contents isolated from the rest of the world, much like a test tube does. But ultimately you just have some reactions in liquid water inside. So probably some chemica
Parent
Re: (Score:3, Insightful)
Perhaps several different biochemistries developed, with one becoming too successful and displacing others.
And it had astronomically many tries (Score:3, Informative)
That said,
1. While chlorophyll does match that spectrum well, the original photosynthesis was done by cyanobacteria, which _don't_ match that spectrum too well. So there you go, a less perfect solution was perfectly viable too, and the better solution appeared later.
So give me
Re: (Score:3, Interesting)
Highly unlikely, given that life appeared on earth virtually the instant (geologically) that there was solid ground and liquid water.
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)
Finally (Score:4, Funny)
Confusing Creationists (Score:3, Funny)
Only confusing the stupid ones (Score:5, Insightful)
Seriously, though, the creationists I respect go to the Bible/Koran/Talmud and say "God created the heavens and the earth" then go to a science textbook to figure out how he did it.
Parent
Interesting points, poor grasp of english (Score:5, Interesting)
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.
Parent
Um, why is this even in question? (Score:4, Insightful)
Given that two identical populations can drift away from the ability to interbreed through nothing more than isolation, how likely would it be that one species, scattered across many environments, could independently evolve into a new species whose members could interbreed? That seems a bit off!
I do think that hybrid species are pretty cool, even though they don't occur too often in nature. We had the polar/kodiak hybrid shot a year or so back. Zoos also have many examples of lygers, tylons, etc. Wolves and domestic dogs can interbreed, the same goes with cyotes and jackals as well. It does make one wonder how far humans could drift apart if several populations were isolated for 20,000 years. I wonder if they'd all still look alike except for different bumpy foreheads?
Re:Um, why is this even in question? (Score:5, Interesting)
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.
Parent
At least wait for the ID people to post ... (Score:3, Interesting)
... 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:At least wait for the ID people to post ... (Score:4, Insightful)
When I read the article, the first thing I thought was 'I thought we could all agree on this?' That's the 1 big (important) thing the ID and Evo people agree on: We came from a single source.
Of course, I still haven't ruled out that possibility that evolution is controlled by God. It kind of muddies things a bit.
Parent
Re:At least wait for the ID people to post ... (Score:4, Interesting)
It was on television, so no reference.
Parent
I'd really expect the truth to be more like... (Score:4, Funny)
Perhaps the real questions are regarding time lines and why evidence either exist or does not. Rate of deterioration under what conditions?
This whole Darwin vs. god vs. intelligent design is all rather silly.
Its like right to life vs. freedom of choice. Want to know the truth about that? Ask a starving child!
Likewise, the evolution of conscious beings is probably a mix of Darwin, god (the right conditions existing - father physics and mother nature) and intelligent design, even though intelligence can sometimes be stupid (selective breading and external intelligence influence)
Anyone who wants to divide what actually is, is looking to create a problem that doesn't really exist.
Re: (Score:3, Insightful)
The sooner they are relegated to obscurity, the better -- then most people will consider them the crackpots that they are. Giving them attention before they even appear doesn't help.
Re: (Score:3, Interesting)
"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 Pe