Posted on 08/08/2007 10:58:39 AM PDT by Domandred
Two hominid fossils discovered in Kenya are challenging a long-held view of human evolution.
The broken upper jaw-bone and intact skull from humanlike creatures, or hominids, are described in Nature.
Previously, the hominid Homo habilis was thought to have evolved into the more advanced Homo erectus, which evolved into us.
Now, habilis and erectus are now thought to be sister species that overlapped in time.
The new fossil evidence reveals an overlap of about 500,000 years during which Homo habilis and Homo erectus must have co-existed in the Turkana basin area, the region of East Africa where the fossils were unearthed.
"Their co-existence makes it unlikely that Homo erectus evolved from Homo habilis," said co-author Professor Meave Leakey, palaeontologist and co-director of the Koobi Fora Research Project.
The jaw bone was attributed to Homo habilis because of its distinctive primitive dental characteristics, and was dated to around 1.44 million years ago.
It is the youngest specimen of this species ever found.
The skull was assigned to the species Homo erectus despite being a similar size to that of a habilis skull. Most other erectus skulls found have been considerably larger.
But it displayed typical features of erectus such as a gentle ridge called a "keel" running over the top of the jaw joint. Analysis showed the skull to be about 1.55 million years old.
The new dates indicate that the two species must have lived side by side.
Sister species
If Homo erectus had evolved from habilis and stayed within the same location then both must have been in direct competition for the same resources.
Eventually, one would have out-competed the other.
The particularly small Homo erectus find, shown from above with the large skull from Olduvai (Tanzania) to demonstrate the gorilla-like size variation of the species. Credit: National Museums of Kenya There may have been a large size difference between the sexes "The fact that they stayed separate as individual species for a long time suggests that they had their own distinct ecological niches, thus avoiding direct competition," Professor Leakey explained.
Professor Chris Stringer, head of human origins at London's Natural History Museum, said: "Both were apparently stone tool-makers, but one possibility is that the larger and perhaps more mobile erectus species was an active hunter, while habilis scavenged or caught small prey."
It is most likely that both species evolved from a common ancestor.
Other possibilities
But the linear, ancestor-descendent relationship between the two species cannot be ruled out altogether.
Fred Spoor, professor of developmental biology at University College London, and co-author of the paper, told the BBC News website: "It's always possible that Homo habilis lived, let's say, 2.5 million years ago and then in another part of Africa, away from the Turkana basin, an isolated population evolved into Homo erectus."
After a sufficient amount of time to allow both species to develop different adaptations and lifestyles, Homo erectus could have then found its way to the Turkana basin.
With separate "ecological niches", both species could co-exist without direct competition for resources.
"But that is a much more complex proposition," Professor Spoor explained, "the easiest way to interpret these fossils is that there was an ancestral species that gave rise to both of them somewhere between two and three million years ago."
Not so similar
The fossil record indicates that modern humans (Homo sapiens) evolved from Homo erectus.
However, to some researchers, the small size of the erectus skull suggests that species may not have been as similar to us as we once thought.
On average, modern humans display a low level of "sexual dimorphism", meaning that males are females do not differ physically as much as they do in other animals.
The scientists compared the small skull to a much larger erectus cranium found previously in Tanzania. If the size difference between the two is indicative of the larger one being from a male and the smaller being from a female, it suggests that erectus displayed a high level of sexual dimorphism - similar to that of modern gorillas.
Sexual dimorphism can relate to reproductive strategies and sexual selection.
If erectus was very sexually dimorphic it may have had multiple mates at a time. This differs from the more monogamous nature of modern humans, indicating that Homo erectus was not as human-like as once thought.
The researchers dismiss the idea that the small size of the skull could be a result of it belonging to a youngster.
"By studying how the skull bones are fused together we discovered it belonged to a fully grown young adult rather than a developing juvenile erectus," said Professor Spoor.
creationists have been saying habilis and erectus were living side by side many times over the last decade or more...
but we were mocked, and ridiculed....
Their co-existence makes it unlikely that Homo erectus evolved from Homo habilis
You don't say.
Its simply more chronic masturbation from the academic set.
New evidence in China, which appeared on this site this week, suggests
that we evolved out of an Asian ancestor.
One things is for sure: someone is CLEARLY wrong. And just
because one is clearly wrong does not make the other one right.
Academia! Isn’t it wonderful! You do not need to be conclusive,
just argumentative!
MV
I think it was Mark Twain who said that only in science can you reap such a wholesale return of conjecture from such a tiny investment of fact.
Why am I not surprised that the first 4 posts mock science.
but we were mocked, and ridiculed....
Creationists have been saying a lot of things, including that all science that conflicts with the bible is BS, evolution is impossible, the age of the earth is under 10,000 years, and Homo erectus and Homo ergaster evolved from Noah's descendants after the flood, etc.
Until creationists actually spend the years of study and research that it requires to have a valid scientific opinion in these matters, they will not be paid any attention.
You’re wrong. All you need to study is the Bible. You don’t need any research. You don’t need science books - or history books either for that matter. Throw them away.
What are you, anyway? A socialist evolutionist God-hater?
/sarc
That sure was easy to say. Maybe these scientists will even find some actual evidence that such an alleged species ever existed. That's not quite as easy though.
interesting, no one disputed that we creationists have been saying that habilis and erectus coexisted as humans....hmmmm
instead, attempts at insults, how utterly civil of all of you...
That sure was easy to say. Maybe these scientists will even find some actual evidence that such an alleged species ever existed. That’s not quite as easy though.
DING, DING, DING
WE HAVE A WINNER!!!!!
so why would this stop us from mocking and ridculing creationists? ha.
Noah’s flood? The earth is under 10,000 years old?
thank god the Inquisition is not around!!! We would have to burn a lot of scientists at the stake!
Not science, just evolutionism.
Read them again. They say “academia.” Sorry, the Earth isn’t 6000 years old, it’s not even 60000 years old... We need a couple of more orders of magnitude.
Actually only one refers to "academia" of which science is a subset.
Sorry, the Earth isn’t 6000 years old, it’s not even 60000 years old... We need a couple of more orders of magnitude.
I have no idea how old the earth is. I am unable to measure that, but then so is everyone else.
When he was good, he was very good.
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