Posted on 02/24/2007 4:59:17 AM PST by Pharmboy
A male chimpanzee feeds in Kibale National Park tropical
rain forest, 354km southeast of Uganda's capital Kampala,
December 2, 2006. A new study, certain to be controversial,
maintains that chimpanzees and humans split from a common
ancestor just 4 million years ago -- a much shorter time
than current estimates of 5 million to 7 million years
ago. (James Akena/Reuters)
Chimpanzees and humans split from a common ancestor just 4 million years ago -- a much shorter time than current estimates of 5 million to 7 million years ago, according to a study published on Friday.
The researchers compared the DNA of chimpanzees, humans and our next-closest ancestor, the gorilla, as well as orangutans.
They used a well-known type of calculation that had not been previously applied to genetics to come up with their own "molecular clock" estimate of when humans became uniquely human.
"Assuming orangutan divergence 18 million years ago, speciation time of human and chimpanzee is consistently around 4 million years ago," they wrote in their study, published in the Public Library of Science journal PLoS Genetics, available online at http://genetics.plosjournals.org/perlserv/?request=get-document& doi=10.1371/journal.pgen.0030007#toclink4.
"Primate evolution is a central topic in biology and much information can be obtained from DNA sequence data," Dr. Asger Hobolth of North Carolina State University said in a statement.
The theory of a molecular clock is based on the premise that all DNA mutates at a certain rate. It is not always a steady rate but it evens out over the millennia and can be used to track evolution.
Experts agree that humans split off from a common ancestor with chimpanzees several million years ago and that gorillas and orangutans split off much earlier. But it is difficult to date precisely when, although most recent studies have put the date at somewhere around 5 million to 7 million years ago.
Hobolth and colleagues from the University of Aarhus in Denmark and the University of Oxford in Britain looked at four regions of the human, chimpanzee, and gorilla genomes.
QUICK SPLIT
They used a statistical technique called the hidden Markov model, developed in the 1960s and originally applied to speech recognition.
What they found may contradict some other recent research. They found evidence that it took only 400,000 years for humans to become a separate species from the common chimp-human ancestor.
Just last May, David Reich of the Broad Institute at the Massachusetts Institute of Technology and Harvard Medical School's Department of Genetics found evidence that the split probably took 4 million years to occur, although his team put the final divergence at just 5.4 million years ago.
"I don't think it really contradicts our paper," Reich said in an e-mail exchange.
"We were focusing on a maximum time for the common ancestor of humans and chimpanzees, while they were focusing on a best estimate," added Reich, who reviewed Hobolth's paper before it was published.
Experts have long known that humans and chimpanzees share much DNA, and are in fact 96 percent identical on the genetic level.
And one year ago, Soojin Yi and colleagues at the Georgia Institute of Technology said they found genetic evidence that chimpanzees may be more closely related to humans than to gorillas and orangutans.
Their look at the molecular clock showed humans evolved one unique trait just a million years ago -- our longer life span and our long childhood that means humans reach sexual maturity very late in life compared to other animals.
Elaine Morgan is the Aquatic Ape Theory woman. She's a unique individual...
http://en.wikipedia.org/wiki/Punctuated_equilibrium
http://en.wikipedia.org/wiki/Phyletic_gradualism
But what about the Yugo/Hummer split or the Greyhound Bus/tank ancestry?
Primary Literature by Jonathan Marks
Benveniste, Raoul E. and Todaro, George J. (1976) Evolution of type C viral genes: Evidence for an Asian origin of man. Nature, 261:101-107. This study also applied DNA hybridization to the apes. They found a 3-way split.
socrates.berkeley.edu/~jonmarks/biblio.html
The inoperative Vitamin C gene in humans and apes is "junk". Since the last common ancestor to humans and apes lost the ability to fabricate Vitamin C (primates having a high Vitamin C diet, so the gene was not necessary for survival), that gene has acquired more DNA trash over the ages. Study of that specific gene sequence, and the number of mutations it has acquired away from a functional gene, can be used to map the evolution of primate species, and provide evidence for dating.
Evolution theory would predict that these mutations would map according to other morphological changes in primates, and the dates of the divergence. And indeed the changes do map the earlier conclusions. The predictive power of Evolution theory was demonstrated once again.
It's too bad that the ID hypothesis gives no predictions. It would be cool to know what the Designer of the universe had in mind, or perhaps what techniques we could deduce, and perhaps copy, from the Designer. Unfortunately that road is barren.
The amount of inoperative structural genes is extremely modest compared to the regulatory genes that MAKE them inoperative. Regulatory genes: that's the ticket.
The "Vitamin C" gene and it's mutations in primates has been well studied. If humans and primates required this gene to survive, then evolution would ensure that the gene stayed operative when individuals with mutations died. With an inoperative Vitamin C gene, allowed by a high Vitamin C diet, the gene began accumulating errors, and thus can map species splits and act as a timer.
Arguments about whether the rest of the genome is "junk" or are regulatory genes is irrelevant to studies of this specific DNA sequence.
One thing that IDers ignore is that DNA mutations *do* occur. Without the effects of evolution to correct these errors by allowing individuals with damaging mutations to die, then all "kinds" would have died off from harmful mutations, leaving the earth sterile. This is how evolution "guides" the species DNA along a path of survival, and the corollary is that if the path to survival (i.e. the environment) changes, that the species itself will be guided by the same survival mechanism to change.
Once you demonstrate that the environment via evolution "corrects" the genome to allow survival, and then demonstrate that the environment can vary over location and time, then the fact that evolution of species occurs is obvious.
That’s just not right.
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