New fossil findings challenge current theory of evolution
Offline Fossils challenge old evoluton theory
By SETH BORENSTEIN, AP Science WriterWed Aug 8, 5:57 PM ET
Surprising research based on two African fossils suggests our family tree is more like a wayward bush with stubby branches, challenging what had been common thinking on how early humans evolved.
The discovery by Meave Leakey, a member of a famous family of paleontologists, shows that two species of early human ancestors lived at the same time in Kenya. That pokes holes in the chief theory of man's early evolution — that one of those species evolved from the other.
And it further discredits that iconic illustration of human evolution that begins with a knuckle-dragging ape and ends with a briefcase-carrying man.
The old theory is that the first and oldest species in our family tree, Homo habilis, evolved into Homo erectus, which then became human, Homo sapiens. But Leakey's find suggests those two earlier species lived side-by-side about 1.5 million years ago in parts of Kenya for at least half a million years. She and her research colleagues report the discovery in a paper published in Thursday's journal Nature.
The paper is based on fossilized bones found in 2000. The complete skull of Homo erectus was found within walking distance of an upper jaw of Homo habilis, and both dated from the same general time period. That makes it unlikely that Homo erectus evolved from Homo habilis, researchers said.
It's the equivalent of finding that your grandmother and great-grandmother were sisters rather than mother-daughter, said study co-author Fred Spoor, a professor of evolutionary anatomy at the University College in London.
The two species lived near each other, but probably didn't interact, each having its own "ecological niche," Spoor said. Homo habilis was likely more vegetarian while Homo erectus ate some meat, he said. Like chimps and apes, "they'd just avoid each other, they don't feel comfortable in each other's company," he said.
There remains some still-undiscovered common ancestor that probably lived 2 million to 3 million years ago, a time that has not left much fossil record, Spoor said.
Overall what it paints for human evolution is a "chaotic kind of looking evolutionary tree rather than this heroic march that you see with the cartoons of an early ancestor evolving into some intermediate and eventually unto us," Spoor said in a phone interview from a field office of the Koobi Fora Research Project in northern Kenya.
That old evolutionary cartoon, while popular with the general public, is just too simple and keeps getting revised, said Bill Kimbel, who praised the latest findings. He is science director of the Institute of Human Origins at Arizona State University and wasn't part of the Leakey team.
"The more we know, the more complex the story gets," he said. Scientists used to think Homo sapiens evolved from Neanderthals, he said. But now we know that both species lived during the same time period and that we did not come from Neanderthals.
Now a similar discovery applies further back in time.
Susan Anton, a New York University anthropologist and co-author of the Leakey work, said she expects anti-evolution proponents to seize on the new research, but said it would be a mistake to try to use the new work to show flaws in evolution theory.
"This is not questioning the idea at all of evolution; it is refining some of the specific points," Anton said. "This is a great example of what science does and religion doesn't do. It's a continous self-testing process."
For the past few years there has been growing doubt and debate about whether Homo habilis evolved into Homo erectus. One of the major proponents of the more linear, or ladder-like evolution that this evidence weakens, called Leakey's findings important, but he wasn't ready to concede defeat.
Dr. Bernard Wood, a surgeon-turned-professor of human origins at George Washington University, said in an e-mail Wednesday that "this is only a skirmish in the protracted 'war' between the people who like a bushy interpretation and those who like a more ladder-like interpretation of early human evolution."
Leakey's team spent seven years analyzing the fossils before announcing it was time to redraw the family tree — and rethink other ideas about human evolutionary history. That's especially true of most immediate ancestor, Homo erectus.
Because the Homo erectus skull Leakey recovered was much smaller than others, scientists had to first prove that it was erectus and not another species nor a genetic freak. The jaw, probably from an 18- or 19-year-old female, was adult and showed no signs of malformation or genetic mutations, Spoor said. The scientists also know it isn't Homo habilis from several distinct features on the jaw.
That caused researchers to re-examine the 30 other erectus skulls they have and the dozens of partial fossils. They realized that the females of that species are much smaller than the males — something different from modern man, but similar to other animals, said Anton. Scientists hadn't looked carefully enough before to see that there was a distinct difference in males and females.
Difference in size between males and females seem to be related to monogamy, the researchers said. Primates that have same-sized males and females, such as gibbons, tend to be more monogamous. Species that are not monogamous, such as gorillas and baboons, have much bigger males.
This suggests that our ancestor Homo erectus reproduced with multiple partners.
The Homo habilis jaw was dated at 1.44 million years ago. That is the youngest ever found from a species that scientists originally figured died off somewhere between 1.7 and 2 million years ago, Spoor said. It enabled scientists to say that Homo erectus and Homo habilis lived at the same time.
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On the Net:
Nature: http://www.nature.com
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Sorry about the botched job of pasting the article. Thanks for fixing it!
So you don't wind up with html script that stretches the page out, with yahoo articles I usually click 'printable view' at the bottom of the article and copy the text from there. That removes all of the formatting from the regular view.
Just a friendly tip from BGH.
Ah, thank you for the tip. And thanks again for being on the ball!
Of course... a creationist will see the tittle and will say: "Oh see? They disproved evolution" When in reality all this is saying that two species that where believed to live on different time periods, are now found on the same time period. Evolution is does not take only one path, and science doesn't claim to have knowledge of every single path. Findings like these do not disprove evolution... they just help us understand it better.
That's probably true, but by posting this I wasn't trying to say that evolution had been disproven, not at all. It's empirical information that demands some modifications of the current theory. It's the kind of thing that science is built on, so I just figured some folks here would be interested.
My response was just what I gathered from having this discussion on a different forum. People actually believe this article disproves evolution O_o (the discussion had about 30 pages, and there was nothing we could say to change their minds ;P )
Oh see? They disproved evolution!
I don't actually see why this finding has any impact on the ladder view of human evolution at all. Why could erectus and habilis not have been living in the same area at the same time? Maybe a population of habilis evolved into erectus then moved back into an area where there were still habilis around. Saying that this couldn't happen is like the old theist drone of "if people evolved from monkeys, why are there still monkeys"?
Is this the original AP article? Because if it is, I have a serious issue with my local newspaper. They changed the language in several places to talk about the findings "discrediting" parts of the theory of human evolution. Fucking fundies are taking over this town.
Lazy is a word we use when someone isn't doing what we want them to do.
- Dr. Joy Brown
The fact that they co-existed means they had already diverged enough from their common ancestor to be different species.
if you imagine evolution like a tree, with each species being a branch off from ancestors (big tree!), it's the difference between one branching off from the other (previously thought) and both of them branching from somewhere else (now believed).
It's impossible to co-exist with creatures that are your ancestors because evolution must act on them. Finding out that these species co-existed means one couldn't be the ancestor of the other.
The flaw in asking the monkey question is 1) we didn't evolve from monkeys, we evolved from a chimpansee-like creature and
2) what we evolved from no longer exists (as is evidenced by findings like this), simply because our common ancestor has evolved into us/chimpansees (depending on how far back you go a number of other things).
So, if the creationists wanted to ask the question more appropriately, it would go, "if we evolved from a chimpansee-like creature, then why do chimpansee-like creatures still exist?".
The answer is: those particular creatures don't.
I hope that makes sense.
Doublethink means the power of holding two contradictory beliefs in one's mind simultaneously, and accepting both of them.
George Orwell.
What if you have two populations of habilis, one valley A , and one in valley B a few miles away. Population A's valley is drier and there's less vegetation, so they gradually evolve to do more hunting and end up evolving into erectus. Meanwhile, population B is living it up on succulent valley fruit and sees no reason to change and remains habilis. After a while, population A is so successful with this new hunting thing that they outgrow the valley and a group of them colonize valley B. A million years later scientists find bones of erectus and habilis living together.
Lazy is a word we use when someone isn't doing what we want them to do.
- Dr. Joy Brown
Someone can correct me if I'm wrong, but as I understand it: natural selection is still going to act on population B. In the time that population A changed so dramatically to become a different species, population B would have changed significantly as well.
If population B is living it up on "succulent valley fruit", they will still be selected for certain attributes. If there is so much abundance of food that they need not worry(and no predators), they will still be selected for social attributes (altruism, confidence, things like that).
These things will still change the species over that period of time. They would probably develop bigger brains, better immune systems against bad fruits, and more of an upright posture (that allows for easier manipulation of tools and such, but (I believe) slows the animal down). So, they just wouldn't "stay habilis".
edit:
note that, despite all of our technology, etc, natural selection still operates on humans to some degree. Non-natural selection as well (we select each other).
Despite, in opulent areas of the world, our ability to feed and protect the weakest members of our species almost perfectly, we are still developing in certain ways.
So, in 100,000 years you or I may be incompatible with our ancestors. Assuming animal life lasts that long, there will be some arbitrary point where scientists will have to declare us a new species. It's hard to draw a parallel because we have near global community and there are many new factors taking place that will affect evolution. Trying to speculate about this hurts the brain.
But scientists definitely do pay attention,and last I heard, we are selecting for bigger brains still, believe it or not.
edit 2:
and other things change as well.
Many of the superfluous things about our species will be lost or changed over time (goosebumps, coccyx, extraneous body hair, shitty spine improvisation, etc).
So in 100,000 years, the creatures that came from us directly might have no coccyx or goosebumps or shitty paranasal design (made for quadrapeds), maybe taller and smarter, and we wouldn't be able to mate with them.
Doublethink means the power of holding two contradictory beliefs in one's mind simultaneously, and accepting both of them.
George Orwell.
Only if there's pressure on the population that forces a change in the current design. Look at crocodiles and sharks. They are mostly the same now as they were 100 million years ago. If population A came under intense evolutionary pressure and population B did not, it seems to me entirely conceivable that the one population would evolve rapidly and the other wouldn't.
Remember that we are looking for species-level changes here. For all we know, population B evolved tie-dye fur so that the unsightly fruit stains wouldn't show, but the fossil record wouldn't show that.
For the record, I do like the "stubby bush" model better. It seems to me more likely that evolution would proceed in a burst when a common ancestor would suddenly get an opportunity to exploit multiple niches, perhaps because of a large extinction due to disease or climate change. We have seen this phenomenon in several species that move into new territory, like volcanic islands.
Here's a scenario: small, tree-climbing common ancestor suddenly finds himself alone in an area where disease has killed off most of the other large mammals. Over just a few million years he evolves into large tree-climbers (chimps), big vegetarians (gorillas), beachcombers/swamp waders (homo sapiens), big-game predators (Neanderthals), smaller game predators (erectus) and scavenger opportunists (habilis).
Weird, huh? Valley Of The Primates.
Lazy is a word we use when someone isn't doing what we want them to do.
- Dr. Joy Brown
I think you're right. I think it's an issue of speed.
But I still don't think there's any reason to believe that, if there was significant environmental pressure a few miles away to change Population A, then POP B wouldn't change.
If the environment was set up in such a way, then wouldn't POP A just find POP B? Animals don't tend to immediately change habitat without sudden significant other changes. It seems you are looking at it as if POP A and POP B are rigidly stuck in their habitats.
So I guess what you're saying is possible, in a sense, but I think that they would have to find evidence to support it before assuming that it were true.
There would still be changes within POP B, given the amount of time it would take POP A to make such a change to become another species, that I think POP B would still be at least ALMOST another species by the time they were wholly differentiable.
if species X survives from year 0-100,000ish
and they find fossils of species Y which appeared around 90,000-250,000ish, they may have "co-existed", but there would be
good reason to believe that Y came from X (if it appeared to be so).
I think it would be this clear cut in almost any circumstance.
If someone dug up a fossil of species Y that's from around year "20,000" in this example, then it would change the consensus that Y came from X directly.
So I guess I agree that you could be right,
I think that the evidence probably speaks for itself. So I don't see anything wrong with these scientists changing their viewpoint on this particular issue.
Doublethink means the power of holding two contradictory beliefs in one's mind simultaneously, and accepting both of them.
George Orwell.
Is this a new discovery? The Leakey Foundation site lists Mauve as having made discoveries that caused in increased view of "bushiness" in the human family tree back in 1999. I know it's a new story, but AP is often waay behind the curve.
Actually I thought it was already established and common knowledge that different kinds of homonids lived near each other at various times in history. It's consistent with what we know about speciation in organisms that are still around today--that populations get separated geographically and there's a genetic drift, or that catastrophies or migrations cause the reproductive isolation that can lead to speciation. It would be suspicious if we *didn't* find that in the fossil record for humans because it would suggest that something different happened.
"After Jesus was born, the Old Testament basically became a way for Bible publishers to keep their word count up." -Stephen Colbert
I think you're right, Textom. I seem to remember hearing about this "bushiness" theory a long time ago.
You know why I think AP picked it up now? Because somebody sexed up the press release with language that makes it look, at first glance, like there's something wrong with the theory of evolution in humans.
Lazy is a word we use when someone isn't doing what we want them to do.
- Dr. Joy Brown
Here is PZ Myers take on the new fossils. It is very well stated!
Two new Homo fossils
Category: Evolution • Fossils • Organisms
Posted on: August 9, 2007 1:45 PM, by PZ Myers
Two new Homo fossils are described in this week's Nature, and here they are.
This is KNM-ER 42700. It's a very well preserved brain case, it has been dated to 1.55 million years ago, and it has been positively identified as belonging to Homo erectus. It's a little unusual in being particularly small, but otherwise, definitely H. erectus.
a, Anterior, b, left lateral, d, superior and e, inferior views of KNM-ER 42700 (scale bar, 5 cm).
This is KNM-ER 42703. It's a broken maxilla, or upper jaw, and it has been dated to 1.44 million years ago — it's over 100,000 years more recent than the KNM-ER 42700. This specimen has been identified as Homo habilis.
f, Anterior, g, occlusal and h, right lateral views of KNM-ER 42703 (scale bar, 2 cm).
This is very cool and there are some interesting things to learn about human evolution from them. Unfortunately, one fact seems to be dominating the news about them, and is being consistently misinterpreted: the H. erectus specimen is older than the H. habilis specimen, yet the most common models of human evolution have H. habilis giving rise to H. erectus which in turn was the progenitor of H. sapiens. Even the Nature news summary makes a big issue of this difference.
And further, it gets twisted and accentuated yet further in the popular press, with articles claiming that Finds test human origin theory and Evolution doubt after fossil find.
These are all wrong (I think; I don't hang out with anthropologists much—they don't really see evolution in that simplistic and linear fashion, I hope?). These discoveries do not put any seriously held theories in doubt. They do nicely demonstrate that a linear progression is not to be seriously held.
Just as your mother's life most likely substantially overlapped with your own, the persistence of a parental species so that it overlaps in time with its daughter species is not a challenge to evolution at all. That's the case here; the authors certainly do not regard this work as casting any doubt on the evolution of humans at all. Here's their conclusion:
To translate,
The two species are anatomically distinct, and they don't see signs of a blending between the two.
The two species were sympatric, or living in the same territory at the same time. This suggests that they probably had different lifestyles, or conflict would have driven out one or the other.
They did not have an anagenetic relationship, that is, one species did not gradually and imperceptibly change into the other. The Homo lineage had branched at some earlier date.
That branch occurred elsewhere and earlier, and the H. habilis→H. erectus→H. sapiens line of descent is still tenable; it's just that KNM-ER 42703 would then be a member of a dead-end branch that did not leave descendents in modern times (of course, KNM-ER 42700 is probably also not a direct ancestor — it's representative of a population that may have led to us.)
Experience tells me that this concept, that individual fossils can't be arranged in a simple, linear, lineal relationship, is going to be very hard for many people to grasp, and is going to fuel quite a few creationist shouts of triumph in the near future, and the media aren't helping. It's misplaced. Evolution predicts a great many branches, with only a few twigs here and there preserved in the fossil record, exactly as we see in this discovery.
Spoor F, Leakey MG, Gathogo PN, Brown FH, Anton SC, McDougall I, Kiarie C, Manthi FK, Leakey LN (2007) Implications of new early Homo fossils from Ileret, east of Lake Turkana, Kenya. Nature 448:688-691.
Thanks for that awesome article BGH! It is as I thought: the stubby bush model would seem more likely to fit these findings, but the old linear model is not abolished by any means. We could be looking at the last survivors of habilis hanging in there on a diet of nuts and berries long after erectus drove them off the hunting grounds.
Lazy is a word we use when someone isn't doing what we want them to do.
- Dr. Joy Brown
Yeah, thanks, BGH. I guess it is a new story.
I think it looks like another case of the media being out of touch with current scientific thinking. Even people with a little bit of scientific literacy still seem to choke on the idea that the parent species doesn't automatically go extinct for no reason whenever speciation happens.
"After Jesus was born, the Old Testament basically became a way for Bible publishers to keep their word count up." -Stephen Colbert
Wow, that's interesting. I'm going to have to go back and read the article more thoroughly.
It's not surprising, though. Any time a "transitional" fossil is found, it's actually more likely that the fossil is more indicative of the kind of "missing link" rather than the link itself. Millions of species have lived on this planet and only a tiny fraction managed to get themselves fossilized.
It's likely Neanderthals and Cro Magnon existed at the same time...why not habilus and erectus?
I just got done re-reading Lord of the Flies by William Golding. I really would like to read another of his books, The Inheritors, which was (I think) the first novel that suggested our ancestors wiped out Neanderthals. It's very possible.
Golding's view of human nature was rather dim, but I suspect he might be right. As a species we have a lot of "saving graces" like music and art, but we are terribly violent and it's hard for us to change. I often wonder if we will be able to change before we wipe ourselves off the face of the earth.
I've been thinking about this a lot during the past few years and my mind has been especially focused on the issue in light of the "official" extinction of the Yangtze River dolphin. The very traits that led to our success as a species may very well lead to our downfall.
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Thanks, BGH. I was going to ask jmm for a link, but I think I'll have a look at yours if I can find the time.
I find paleontology endlessly fascinating.
Books on atheism, purchases on Amazon support the Rational Response Squad server.
There was a story not long ago about a find of a girl skeleton that had mixed Neanderthal and Homo sapiens features. So there's a possibility that the Neanderthals weren't wiped out but just bred back into the general population.
Lazy is a word we use when someone isn't doing what we want them to do.
- Dr. Joy Brown
Well it didn't take AiG long to go and do exactly what we predicted they'd do with this information:
http://www.answersingenesis.org/articles/2007/08/11/news-to-note-08112007
According to AiG's slant on the news item, "The question is, then, after such reversals, does the ordinary individual view with any greater skepticism evolutionists’ stock teaching? For example, after this complete reversal, how much faith will people place in this evolutionary assurance"
"After Jesus was born, the Old Testament basically became a way for Bible publishers to keep their word count up." -Stephen Colbert
This is what I was afraid of. We all knew that some Christian organizations would latch onto this finding and proclaim that "evolution is a lie" and that "a magic man done it", but that's honestly not why I posted this article. I just thought it was an interesting find.
Just thought I'd break down AiG's garabage for fun:
Reversal? What reversal? Science has found evidence supporting one of two competing theories for how man evolved. We now know mre than we did before. This is tremendous forward progress and a victory for paleoanthropology.
Begs the question that ordinary individuals view evolution with skepticism. Bullshit rhetoric, nothing more.
Did they read the article? The whole point is that there is NOT a "stock teaching" of evolution and that these findings give weight to one model over another. As in any large, complex field of study, there are controversies and this is a sign of health and progress. Their dissatisfaction with the fact that everything is not graven in stone and immutable down through centuries betrays their own flawed methods of deluding themselves into thinking they know something.
They felt the need to use the word "reversal" twice, so they must think this is a strong point. Unfortunately for them, even if you accept that the linear model was once some kind of canon (which it wasn't), the fact that the model has been challenged and dealt a setback is STILL evidence of the superiority of the scientific method and evolutionary theory over religious thought. On what grounds could any religious person challenge some detail of the story of Genesis, for instance, and force people who believe the story to admit they may be wrong? None. There is no way for this to happen. All that can happen is that some religious person may decide that their faith leads them to a different interpretation of Genesis than someone elses. There are no grounds for discourse, no grounds for discovery, no grounds for adding to the community fund of knowledge. The two parties must agree to disagree, creating schism, or fight to destroy the other point of view, usually only possible by destroying the person who holds that view.
Hopefully none. Rational people don't hold beliefs based on faith. They have reasons for believing what they believe and those reasons can be connected through logic to evidence from the real world. AiG makes the mistake of thinking that evolution fails if people don't have faith in it. This is projection; it is THEIR beliefs that require faith to stay alive. Evolution survives regardless of people's faith or lack of faith in it because no matter how many times you look at the data, it remains the best explanation.
Evolution doesn't make assurances. Assurances are for priests and con men, assuming one can tell the difference. Evolution is proven through reference to the facts.
Lazy is a word we use when someone isn't doing what we want them to do.
- Dr. Joy Brown
I find the claim made by theists – that science is untrustworthy because it is constantly changing – quite ironic when you consider what science actually says and does, with that theism says and does. Science seeks progression and revision and scientists admit when it was mistaken and/or needs to adapt a previous idea. So the criticism that science changes is really no criticism at all. Theists on the other hand claim the ultimate source, god, so any change or revision for them undermines their entire foundation.
Take the bible, which is considered to be the word of god, or just divinely inspired, either way the claim is that the book is extra special… so the book should be more accurate, reliable, and predictable than any other book or source we have. So why then do we see theists do a complete reversal in doctrine (and here we do have an actual reversal) and either no longer consider things literal which once were, or no longer accept commands in their bible?
So their claim seems to really be nothing more than a projection of their own faults onto science.
"It is far better to grasp the universe as it really is than to persist in delusion, however satisfying and reassuring" -- Carl Sagan
Exactly. And in doing so they reveal their real attitude toward knowledge. Knowledge for these theists isn't something with intrinsic value, or even something with which to gain control over their world. It exists only for its emotional value as a security blanket. Knowledge that changes and updates all the time is useless to them. They want knowledge to be a static icon that they can look at and be reassured that everything is safe, that they are right and that they needn't exert themselves to learn or think or change their own beliefs.
Basically we are dealing with some people with major insecurity issues who are so self-absorbed that they see the world only in terms of its impact on them.
Lazy is a word we use when someone isn't doing what we want them to do.
- Dr. Joy Brown