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Posted on 07/11/2002 4:13:07 PM PDT by jennyp
After a decade of digging through the sand dunes of northern Chad, Michel Brunet found a skull 6-7 million years old. He named it Toumaï.
Toumaï is thought to be the oldest fossil from a member of the human family. It's a dispatch from the time when humans and chimpanzee were going their separate evolutionary ways. A thrilling, but confusing dispatch1,2.
Sahelanthropus tchadensis - Toumaï's scientific name - was probably one of many similar species living in Africa at that time. "There must have been a group of apes knocking around between 5 and 8 million years ago for which there's a very poor fossil record," says anthropologist Bernard Wood of George Washington University in Washington DC.
Toumaï is the tip of that iceberg - one that could sink our current ideas about human evolution. "Anybody who thinks this isn't going to get more complex isn't learning from history," says Wood.
"When I went to medical school in 1963, human evolution looked like a ladder," he says. The ladder stepped from monkey to man through a progression of intermediates, each slightly less ape-like than the last.
Now human evolution looks like a bush. We have a menagerie of fossil hominids - the group containing everything thought more closely related to humans than chimps. How they are related to each other and which, if any of them, are human forebears is still debated.
Most members of the group are less than three million years old. After Toumaï, the next-oldest hominid is the 6-million-year old Orrorin tugenensis. But Orrorin is known only from a few teeth and bone scraps, and its evolutionary allegiances are controversial.
Our knowledge of Toumaï's period is "at the 1963 stage", says Wood.
Feature story
"When I first saw the skull I thought: 'Gee, it's a chimp'," says anthropologist Daniel Lieberman of Harvard University. Toumaï's brain, for example, was roughly chimp-sized. A closer look "blew my socks off", he recalls.
Sahelanthropus has many traits that shout 'hominid'. These include smaller canines, and thicker tooth enamel than apes. And the point at the back of skull where neck muscles attach suggests that Toumaï walked upright.
Many of Toumaï's advanced features are missing from later fossils such as Australopithecus, but reappear in still later species that are classified as Homo.
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Based on this, we might have to question some species' place in the hominid club. If Australopithecus looks more ape-like than a much older fossil, how can it belong to the human family? "Anything with a more primitive face has to have its membership reviewed," says Wood.
No groups will be expelled on the evidence so far. The real lesson, says Wood, is that appearances are a bad guide to evolutionary relations. Hominid and ape species probably mixed and matched from a set of features, he says, with the same traits evolving independently on multiple lineages.
Toumaï has other features that are just strange. "It's got a massive brow ridge, the size of a large male gorilla, and yet it's just a little hominid," says Lieberman. This heavy brow leads many to believe that Toumaï was male.
Family feud
Where then does Toumaï fit on the family tree? He could belong on the chimp or hominid lines, or he could be part of a different branch of the family, more distant from both chimps and humans that either is from the other.
"I'm willing to bet some money that this is a hominid," says Lieberman.
Palaeoanthropologist Tim White of the University of California, Berkeley, agrees. He thinks that Toumaï might belong to Ardipithecus, a group defined by fossils dating from about 5.5-4.5 million years ago.
But Wood takes a different view. "My guess is that it's neither a chimp nor a human ancestor - it's a creature that was living at the same time."
To solve the mystery we need more fossils from the same period. Unfortunately our relatives' habits may be against us. The forests favoured by chimps, and apparently by early hominids, are not conducive to fossil formation. Chimps, for example, have no fossil record.
On the bright side, Toumaï's discovery suggests that, even if they were rarely fossilized, ancient apes and hominids roamed right across Africa. "Finding hominids in the Sahara was a bit of a long shot," says Wood. So far, most fossil hominids have turned up in the east, with a few further south.
But desert-bound palaeontologists be warned: "There are brutal field conditions," says Lieberman.
Chad?
g
LOL! And THAT thread had an "already posted", too!
They should have had a "Name That Sahelanthropus Tchadensis" contest. My choice would have been "Skully."
Or another four or five. Upon review, this article does state something about which I have wondered.
Chimps, for example, have no fossil record.
A very interesting find. And it's so well preserved! I'm sure the debate is going rage now in paleoanthropological circles. That brow definitely looks ape-like to me. And the brain is so small.
But look what we've accomplished! First-rate science takes great imagination and great courage. Scientists shouldn't be denigrated because an ignorant public demands certainty when there is none.
The point I am trying to make is that evolutionist theory is still trying to fight creationists and in doing so may be holding on to some very false premises. The Earth ain't 8000 years old. But I also think evolution theory as it is now can't be supported even by the weight of it's own evidence. The theories get more convoluted every day. But then again- I am just an amateur science page reader.
The point is, the transitions at this point look very gradual to me, as along a continuum.
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Yup, until the next pseudo-man is dug up
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I was trying to say this is really hard stuff. A scientist looks at the new skull and tries to fit it into his existing theories. If he can't he's got to come up with new ones. The only alternative is to throw out the evidence and keep the theories. That's a real loser .
huh, odd
Personally, I think evolutionists have gotten away with unwarranted speculation for far too long. The fossil record either shows a continuous development of life from the presently extant organisms to the extinct ones of the past, or it doesn't.
If it doesn't they should just deal with it.
Simply explaining away the absence of fossil evidence in the form of transitionals or conjuring up stories to fill in the gaps is not science.
Brian.
But if evolution is thrown out because it can't explain new evidence I very much doubt we'll return to theories that couldn't even explain the old evidence. A good theory will have to explain all the current evidence and stand up, at least for awhile, to new discoveries.
Funny, that doesn't look like Strom.
Throw in a Neanderthal skull and you'll really show how tough it is to cram these fossils into a linear chain. I suspect that hundred years from now the bush of hominid evolution will appear much more overgrown than we'd ever believe now.
If you doubt this, consider the fact that all of the useful and practical knowledge derived from the theory [anti-microbial resistance, pesticide resistance etc] can be summarized as micro-evolution.
Micro evolution can be [and is] assimilated by either creationism or ID, so if all of the science establishment were to suddenly become born again Christians and begin to promote a young-earth world view, the sky would not fall, as medicine, biology, genetics etc., would proceed on as nothing ever happened.
Brian.
I can't throw out anything because I'm not a scientist...and I never forget that. I have only a rough understanding of most scientific theories and the evidence that supports them. When I pick up the leading journals and try to follow the evidence and arguments supporting or disputing competing theories I can't do it. I'm reduced to popularizations.
That being said I have no interest in attempts to present the Bible as science. Seems to me that what we're seeing now with evolution is pretty much a reply of what happened to the heliocentric theory three or four hundred years ago. Also the whole approach is wrong. Creationists are clearly motivated by a desire to prove the truth of the Bible rather than a desire to find a theory which best fits the facts.
Just my two cents as an ordinary citizen.
A quick reference to this dispute.
You've either grossly misunderstood hominid paleontology, or you're purposely misrepresenting it.
No one has ever claimed that there will be "one" human lineage without offshoots, dead ends, and branches. Hell, even Darwin back in 1872, before *any* significant fossils to speak of were available, pointed out that the tree of life should be very "bushy", with many "dead branches" that didn't survive to present day. Here's the only figure in his On the Origin of Species book:
This represents a slice of time, with the oldest period at the bottom and new newest at the top. The branching lines in between represent life forms that branch, often die out (each "twig" that stops in the middle of the diagram represents an extinction), and a few of which survive throughout the period of the chart (by reaching the top).
Part of his discussion of this diagram uses a metaphor:
The affinities of all the beings of the same class have sometimes been represented by a great tree. I believe this simile largely speaks the truth. The green and budding twigs may represent existing species; and those produced during each former year may represent the long succession of extinct species. At each period of growth all the growing twigs have tried to branch out on all sides, and to overtop and kill the surrounding twigs and branches, in the same manner as species and groups of species have tried to overmaster other species in the great battle for life.In other words, each family of creature branches off into many variant forms (species or subspecies), yet most of them die out and only the most successful survive to a future date to begin the cycle anew.
Darwin thus predicted that there would be numerous extinct humanoids, *most* of which would not be on a direct ancestral line to modern humans. This is pretty obvious when you consider how evolution works.
So why are so many folks still unclear on this 130-year-old concept?
Many humanoid fossils will be from offshoots of the human tree which succeeded for a time, but eventually perished. We're the only branch that managed to survive to modern times (although it can be argued that the Australian aborigines are an offshoot which is still hanging on from when they split off about 600,000 years ago).
The reason that new humanoid fossils are great discoveries is that they help fill in our family tree, about which little was known a 100 years ago -- *not* that they may necessarily be our precise ancestor (instead of a great-great-great-etc.-uncle), although some will be and we'll know better which is which after we discover more samples from the tree.
Yes, there are hundreds of missing links which have been unearthed, with more being found all the time (contrary to what the creationists would have you believe). But once they're discovered they're no longer missing.
Of *course* it does. Transitional fossils will have features that are similar to *all* their offshoots, which is one of the ways we can positively identify it as a common ancestor to several lineages.
The common ancestor between all apes and man will have some "apish" features, and some humanoid features. This one's a pretty decent candidate. You've pointed out some of the "apish" features, now here's a post I wrote on annother thread to make clear the humanoid features (and how well filled in the "from there to here" line has become):
Both, just as the article says.
I can tell just by looking at the photo that the skull has striking features in common with *both* the human *and* the chimp skull. But then, that's exactly what one would *expect* to see in a "missing link".
You're obviously only looking at the *differences*. People tend to see differences more readily than they see similarities. It's like the time I was watching a film with a Chinese friend of mine (I'm American, of European ancestry). There was a scene making a point of the fact that one of the characters was half Chinese and half American. I remarked that the guy looked mostly Chinese to me. My friend replied that to her he looked mostly American.
We tend to notice most what's different from ourselves, and mentally give less credit to what we're already used to seeing.
Here, try this sequence, presented in chronological order:
Newly found skull (7 million years old): 
Australopithecus africanus (3.3 million years old):
Australopithecus afarensis (3 million years old):
Homo Ergaster (1.9 million years old):
Homo Erectus, (1.7 million years old):
Cro Magnon Man, (30,000 years old):
Australian Aborigne (found in 1905, age of specimen not given):
Modern Man (present day):
Note that, just as evolution predicts, it's a steady progression from first to last:
1. The brain case steadily grows and takes up more and more of the skull.
2. The eyebrow ridge shrinks and fades into the skull.
3. The slope of the face starts with a heavy slant and them becomes more vertical.
4. The jaw (when available) starts massive (especially at the hinge) and becomes more gracile. Even the two earliest specimens with no jaws obviously leave a *lot* of room open for jaw attachment.
5. The curve of the chin begins very rounded and "undercut", then gradually pulls forward until it's finally sharp and directly below the teeth.
6. The ridge of bone that connects the bottom of the eye sockets (even with the nose) to the sides of the skull (there's a name for it, I forget it right now) begins massive and protruding, with a pronounced depression above it, then gradually shrinks and fades into the skull until it has almost vanished (but is still present) in modern man.
7. The nasal cavity starts out almost round and gradually become triangular.
8. The earlier specimens have 5 molars behind the canine, the latter ones have 4 (the fifth has become an impacted wisdom tooth).
9. There's a noticeable "peak" on the top of the skulls that gradually fades into a rounded crown.
And so on.
Looking at three from the side, each shown true relative size to each other (oldest on left), we have:
I could do a similar transition from the 7 million year old skull to the chimp skull as well (except that it would take longer, there aren't as many non-hominid primate skull photos on the web, because people are more fascinated with hominids), which would show a similar progression over time, indicating that the 7 million year old skull is probably an ancestor, or near ancestor, to the chimp family as well. (Chimp DNA differs from human DNA by only 2%, we're 98% identical and are pretty close relatives, I'm sorry to have to inform you).
The 7 million year old skull has some similarities to the chimp skull (just as it has some similarities to human skulls), but there are big differences there as well, showing plainly that the 7MA skull is hardly just an ancient chimp.
Meanwhile, consider the far greater differences between the following skulls and the 7MA skull than between *either* the human or chimp skulls versus the 7MA skull:
Lowland Gorilla (note the "crest" on top of the skull, not present on the 7MA skull, and the very thick bony "ring" around the skull):
Orangutan (do I really need to point out the unique features?):
Baboon (ditto):
Howler monkey:
Mandrill baboon:
Gibbon:
The 7MA skull is clearly not just a random "ape" skull, it's obviously far closer to a humanoid skull than to the above apes.
I used to argue in favor of a creation-oriented theoretical basis for the science of origins, until I became persuaded that creationism carries with it a prior assumption just as darwinism does. In a very real sense, they are both assumptions in search of evidence.
Though I am an evangelical Christian who believes the Bible for what it says, I don't hold to the position that science should be used to prove either the existence of GOD, or the infallibility of the Bible. If GOD is real [I speak rhetorically] then science, if allowed to proceed on its just course, will do nothing to dissuade an honest observer from coming to the knowledge of the truth of GOD.
In terms of science with respect to origins, I would describe myself as a proponent of ID, as this requires no prior assumption regarding either materialistic or theistic notions.
Brian.
Brian.
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