Posted on 02/28/2008 4:21:27 AM PST by Renfield
CHICAGO (AFP) - French fossil hunters have pinned down the age of Toumai, which they contend is the remains of the earliest human ever found, at between 6.8 and 7.2 million years old.
The fossil was discovered in the Chadian desert in 2001 and an intense debate ensued over whether the nearly complete cranium, pieces of jawbone and teeth belonged to one of our earliest ancestors.
Critics said that Toumai's cranium was too squashed to be that of a hominid -- it did not have the brain capacity that gives humans primacy -- and its small size indicated a creature of no more than 120 centimetres (four feet) in height, about the size of a walking chimp.
In short, they said, Toumai had no right to be baptised with French researcher Michel Brunet's hominid honorific of Sahelanthropus tchadensis -- he was simply a vulgar ape.
Toumai's supporters used 3D computer reconstructions to show that the structure of the cranium had clear differences from those of gorillas and chimps and indicates that Toumai was able to walk upright on two feet, something our primate cousins cannot do with ease.
If Toumai is truly an early human, that means that the evolutionary split between apes and humans occurred far earlier than previously thought.
And pinning down his age is key to redrawing the evolutionary map.
"The radiochronological data concerning Sahelanthropus tchadensis ... is an important cornerstone both for establishing the earliest stages of hominid evolution and for new calibrations of the molecular clock," Brunet wrote in a study which will appear in the March 4 edition of the Proceedings of the National Academy of Sciences.
"Thus, Sahelanthropus tchadensis testifies that the last divergence between chimps and humans is certainly not much more recent than 8 Ma (million years ago.)"
Toumai also probably lived "very close in time to this divergence contrary to the unlikely 'provocative explanation,' which recently suggested a 'possible hybridization in the human-chimp lineage before finally separating less than 6.3 (million years ago)," the authors concluded.
If Toumai -- the name means "hope of life" in the local Goran language -- is accepted as a human, the implications are profound.
The fossil was found some 2,500 kilometers (1,500 miles) west of the Great Rift Valley. If that is still seen as humankind's ancestral home, it implies the early hominids ranged far wider from East Africa, and far earlier, than previously thought.
The discovery also implies hominids evolved quickly from apes after they split from a common primate ancestry.
Hominids are considered the forerunners of anatomically modern humans, who appeared on the scene about 200,000 years ago.
Still unclear, though, is the exact line of genealogy from these small, rather ape-like creatures to the rise of the powerfully-brained Homo sapiens.
Hopefully more examples will turn up.
They more than like used K-Ar aging of the dirt right on it to roughly determine the age. K-Ar dating has a greater age rage the C-14. There are also other means, such as Uranium-lead dating, which can be fairly accurate to 4.5 billion years.
Carbon date Bob Byrd. I’m just sayin’.
There are a couple of dozen different radioisotopes that can be used in dating. The effective range of each depends on the half-life.
Radiocarbon has a half-life of 5,730 years, and thus has a maximum effective range of about 50,000 years. (They are working on counting methods to extend this, but it won't be extended too far.)
Other radioisotopes have far longer half-lives, and are suited for dating objects of far greater antiquity.
Here is a good link:
Radiometric Dating: A Christian Perspective by Dr. Roger C. Wiens.
I just looked and I guess they used Be-10/Be-9 dating, which doesnt make sense ince it has a shorter life than the time period used. But I am no expert in this sort of dating.
“Toumai’s supporters used 3D computer reconstructions to show that the structure of the cranium had clear differences from those of gorillas and chimps and indicates that Toumai was able to walk upright on two feet”Yeah, right. They can tell all that from the structure of the brain.
Let’s see the rest of the skeleton and then maybe it can be determined whether it walked upright or not.
Upright posture can be inferred from the location of the foramen magnum (though which the spinal cord passes).
In four-legged critters it is near the back of the skull. In critters that walk upright it is at the bottom. Take a look at a cat or dog vs. a human and you will see how this works.
See the article I linked to in post #25.
Radiometric dating works to many multiples of the half-life. For example, radiocarbon dating works back to nine or ten half-lives. I assume it is the same for the radioisotope used here.
I quickly misread it earlier, I thought it said it was accurate to 1.5 million years, not that its half-life was just 1.5 million. No morning coffee effect yet, soon though soon.
Actually, when I look into my dog's eyes I see there's somebody home too. I guess it comes down to what really makes us human. Besides a soul, that is.
EosimiasTiny Fossil AnimalFossil bones of an animal no bigger than a shrew and weighing less than an ounce have been identified as belonging to the earliest known relative in the primate lineage that led to monkeys, apes and humans. The wee animal lived 45 million years ago in a humid rain forest in what is now China... The paleontologists who announced the discovery yesterday said the fossil animals, named Eosimias for "dawn monkey," were the best evidence yet for fixing the time and place of one of the more fateful branchings in evolution. Eosimias appeared to be a transitional figure when lower primates, known as prosimians, went their separate way, developing into today's lemurs, lorises, bush babies and tarsiers, while the diverging higher primates, anthropoids, evolved into more prepossessing creatures, eventually including human beings... scatterings of fossils point to the earliest primates of any kind appearing about 55 million years ago, mainly in Asia. But when the two lines of primates diverged had seemed to be lost in the wide gaps in the fossil record... This was further evidence that, although the more immediate human forebears arose in Africa, their earliest primate ancestors appeared to come from Asia. Somehow primates then migrated to Africa. Dr. MacPhee said the Euroasian origin of primates was now generally accepted by scientists, "thanks in part to Beard's work," but "why that should be is itself controversial now."
May Link Lower Primates
With Humans
by John Noble Wilford
March 16, 2000
Spread Of Endogenous Retrovirus K Is Similar In The DNA Of Humans And Rhesus MonkeysAccording to paleontologic and molecular studies, the chimpanzee (Pan troglodytes) is the closer relative to the humans (Homo sapiens) and that both lineages had a common ancestor at 5 to 7 million years ago.
adapted from Public Library Of Science materials
ScienceDaily
Friday, October 12, 2007
Moreover, the human-chimp lineage split from that of the rhesus monkey (Macaca mulatta) around 25 million years ago. However, by studying the population dynamics of complete copies of primate endogenous retrovirus family K (ERV-K) in the genomes of humans, chimpanzee and rhesus monkey, a surprising pattern was observed.
The study by Romano and colleagues being published this week on PLoS One revealed that human ERV-K had a similar demographic signature to that of the rhesus monkey, both differing greatly from that of the chimpanzee. The data suggested that the humans and rhesus have been purging ERV-K copies from their genomes while the chimpanzee ERV-K population kept the signature of increasing numbers of ERV-K amplification in the genome of ancestral primates during the last 20 million years.The Chimp Genome Reveals A Retroviral Invasion In Primate EvolutionSearching the genomes of a subset of apes and monkeys revealed that the retrovirus had integrated into the germline of African great apes and Old World monkeys -- but did not infect humans and Asian apes (orangutan, siamang, and gibbon). This undermines the notion that an ancient infection invaded an ancestral primate lineage, since great apes (including humans) share a common ancestor with Old World monkeys... Eichler and colleagues estimate that gorillas and chimps were infected about 3-4 million years ago, and baboon and macaque about 1.5 million years ago. The disconnect between the evolutionary history of the retrovirus and the primates, the authors conclude, could be explained if the Old World monkeys were infected by "several diverged viruses" while gorilla and chimpanzee were infected by a single, though unknown, source... As for how this retroviral infection bypassed orangutans and humans, the authors offer a number of possible scenarios but dismiss geographic isolation: even though Asian and African apes were mostly isolated during the Miocene era (spanning 24 to 5 million years ago), humans and African apes did overlap.
adapted from Public Library Of Science materials
ScienceDaily
Tuesday, April 5, 2005Retrovirus Struck Ancestors Of Chimps And Gorillas Millions Of Years Ago, But Not Ancestral HumansWhat researchers don't understand is why the virus affected the ancestors of chimps, gorillas, and Old World monkeys, but didn't affect the ancestors of humans or of Asian apes like orangutans and gibbons. The infections took place independently, and did not originate in a common ancestor of humans and apes. The event also took place between three and four million years ago, well after the separation of humans from apes. That split is estimated to have occurred five to seven million years ago.
adapted from University Of Washington materials
ScienceDaily
Wednesday, March 9, 2005The Scars of Evolution"The most remarkable aspect of Todaro's discovery emerged when he examined Homo Sapiens for the 'baboon marker'. It was not there... Todaro drew one firm conclusion. 'The ancestors of man did not develop in a geographical area where they would have been in contact with the baboon. I would argue that the data we are presenting imply a non-African origin of man millions of years ago.'"
by Elaine Morgan
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Thanks Renfield. |
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Either way, it voted in the last four presidential elections.
Most of the show-biz chimps are Bonobos. The regular chimps are too big and powerful to trust around actors.
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