Posted on 01/23/2006 4:31:58 PM PST by PatrickHenry
Scientists at the Georgia Institute of Technology have found genetic evidence that seems to support a controversial hypothesis that humans and chimpanzees may be more closely related to each other than chimps are to the other two species of great apes – gorillas and orangutans. They also found that humans evolved at a slower rate than apes.
Appearing in the January 23, 2006 issue of the Proceedings of the National Academy of Sciences, biologist Soojin Yi reports that the rate of human and chimp molecular evolution – changes that occur over time at the genetic level – is much slower than that of gorillas and orangutans, with the evolution of humans being the slowest of all.
As species branch off along evolutionary lines, important genetic traits, like the rate of molecular evolution also begin to diverge. They found that the speed of this molecular clock in humans and chimps is so similar, it suggests that certain human-specific traits, like generation time, began to evolve one million years ago - very recently in terms of evolution. The amount of time between parents and offspring is longer in humans than apes. Since a long generation time is closely correlated with the evolution of a big brain, it also suggests that developmental changes specific to humans may also have evolved very recently.
In a large-scale genetic analysis of approximately 63 million base pairs of DNA, the scientists studied the rate at which the base pairs that define the differences between species were incorrectly paired due to errors in the genetic encoding process, an occurrence known as substitution.
"For the first time, we've shown that the difference in the rate of molecular evolution between humans and chimpanzees is very small, but significant, suggesting that the evolution of human-specific life history traits is very recent," said Yi.
Most biologists believe that humans and chimpanzees had a common ancestor before the evolutionary lines diverged about 5-7 million years ago. According to the analysis, one million years ago the molecular clock in the line that became modern humans began to slow down. Today, the human molecular clock is only 3 percent slower than the molecular clock of the chimp, while it has slowed down 11 percent from the gorilla's molecular clock.
This slow down in the molecular clock correlates with a longer generation time because substitutions need to be passed to the next generation in order to have any lasting effect on the species,
"A long generation time is an important trait that separates humans from their evolutionary relatives," said Navin Elango, graduate student in the School of Biology and first author of the research paper. "We used to think that apes shared one generation time, but that's not true. There's a lot more variation. In our study, we found that the chimpanzee's generation time is a lot closer to that of humans than it is to other apes."
The results also confirm that there is very little difference in the alignable regions of the human and chimp genomes. Taken together, the study's findings suggest that humans and chimps are more closely related to each other than the chimps are to the other great apes.
"I think we can say that this study provides further support for the hypothesis that humans and chimpanzees should be in one genus, rather than two different genus' because we not only share extremely similar genomes, we share similar generation time," said Yi.
Even though the 63 million base pairs they studied is a large sample, it's still a small part of the genome, Yi said. "If we look at the whole genome, maybe it's a different story, but there is evidence in the fossil record that this change in generation time occurred very recently, so the genetic evidence and the fossil data seem to fit together quite well so far."
The list of definitions I posted is not in any particular order--it grew as I added more and more definitions. I am repeating the pertinent ones again:
Theory: a well-substantiated explanation of some aspect of the natural world; an organized system of accepted knowledge that applies in a variety of circumstances to explain a specific set of phenomena; "theories can incorporate facts and laws and tested hypotheses." Addendum: "Theories do not grow up to be laws. Theories explain laws." (Courtesy of VadeRetro.)
Hypothesis: a tentative theory about the natural world; a concept that is not yet verified but that if true would explain certain facts or phenomena; "a scientific hypothesis that survives experimental testing becomes a scientific theory"; "he proposed a fresh theory of alkalis that later was accepted in chemical practices"
Law: a generalization that describes recurring facts or events in nature; "the laws of thermodynamics"
Note that a theory does not grow up to be a law. A law is very simple, and often a description of observed events. A theory attempts to explain the events and how they interrelate.
Also, a theory is not a starting point. You don't sit down and say, this is my theory in science. You propose hypotheses and test them. If you get a lot of successful tests you can form a theory from them. A well-tested and well-supported theory is the goal of science because it explains things.
This is where ID fails as a theory. There is no testing being done; there is simply nothing resembling the scientific method to ID.
At the most, there are hypotheses; where they could be tested at all, they have been shown to be incorrect. Don't pass go, don't advance to theory.
Again, thanks for responding and for being so persuasive. I hope to remember you this way. People do change, you know.
>If most of your education comes from FR and similar sites, please check out PatrickHenry's List-O-Links. There really is a lot of good information there. Unless your mind is made up.
I'm afraid if I do check PH's link I'll turn into a bitter and empty automaton, which is conducive to a life of alienation and dehumanization. No, thanks.
You can lead a horse to water but you can't make him think.
Could we be more closely related to grapefruits than to kumquats? Yes. However we are more closely related to animals than to plants.
"Chimps, orangutans, gorillas and gibbons all have an evolutionary history just like we do, but the Lucies, Australopithecus, Homo habilis, Homo erectus, Cro-Magnon man and the Neanderthals of their history aren't interesting in the popular press so the liberals leave them out and draw the line direct from chimps to hominoids. Besides, the explanation would be messy and convoluted if they put them in.
What makes you think they have been left out? They are in our direct line back to the shared ancestor of humans and Pan paniscus (Bonobos).
"And when you get right down to it, the liberals are going to say we're more closely related to those pygmy bonabo chimps. You know why that is don't you? It's because the bonabos ƒúçk like bunnies. Liberals worship at the alter of promiscuity you know.
We are more closely related to Bonobos because the molecular evidence says we are.
"Global warming, second hand smoke, chimp/human evolution, bad politically motivated science is the hallmark of liberalism.
The world is warming, the area of contention is the cause of the warming. Second hand smoke is deadly. Humans and Chimps share an ancestor from 5 or 6 million years ago. You sound upset that science is not doing what you want. Why?
>Wasn't it Heinlein who wrote:
Belief gets in the way of learning.
I don't know and don't care what someone else has said.
>Do you have any evidence that Chimps and Humans are not related?
Yes. I have a more developed brain than a chimp. Don't look or act like a chimp. I can type and read and speak and reason - something a brainless chimp cannot do.
Post 106 has potential. But I'm hoping for even better.
>Who are the "us" you speak of?
The "us" I speak of is the opposed of the "us" you spoke of. For me "us" = non-evolutionists.
Between theory and law? You mean you have come up with a completely new and separate category? You are important.
Just for your edification, theories do not graduate to laws, the two serve different purposes.
When I put up the rhetorical question about grapefruits and kumquats, I really didn’t think there'd be anybody dumb enough to take the bait, but as they say about liberals, "You can't make this stuff up!"
OK. Thanks.
So it goes from hypothesis to theory. But a law can stand on its own? I thought a theory when is tested and retested over and over again and is proven correct, it then becomes a law.
I'll try to remember this distinction between theory and law.
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