Posted on 04/11/2002 3:37:12 PM PDT by Ahban
The World's No.1 Science & Technology News Service
Scientists sort the chimps from the men
19:00 11 April 02
NewScientist.com news service
A team of molecular biologists have taken a step towards defining what makes us human. It is not so much our differing gene sequences that distinguish us from our primate cousins, but how active those genes are, the team has discovered.
Chimp and human genomes vary by only 1.3 per cent and only a tiny fraction of this actually affects genes. The new research shows how variation in the amount of product of a gene may be as significant to our recent evolution as structural changes.
The greatest changes in gene expression have been in the brain, say the researchers, perhaps explaining why human mental capabilities have evolved so rapidly.
"This is the first open door to understanding how humans became humans and chimps became chimps," says Wolfgang Enard, of the Max Planck Institute for Evolutionary Anthropology in Leipzig, the study's first author.
Hidden changes
"Expression patterns are certainly the key to the differences between chimps and humans," says Chris Stringer of the Natural History Museum in London. "And these changes have been hidden up to now."
But Walter Messier, director of Evolutionary Genomics, Denver, Colorado told New Scientist: "It's sometimes difficult to devise an adequate control when you do expression pattern work. Let's face it, expression patterns can change after one has had lunch, for example. But it is a very valuable approach."
Evolutionary Genomics is trying to identify differences between chimp and human gene sequences, for example in relation to HIV susceptibility.
Five-fold changes
The new analysis compares gene expression patterns in blood cells, liver and brain tissue from chimps and humans, and also orangutans and monkeys for reference. The researchers used a molecular tool called a DNA chip to detect the products of up to 12,000 active genes.
The greatest variations in gene expression patterns were found in the brain. The researchers estimate that there have been more than five times the number of changes in human brains than chimp brains since their evolutionary lines diverged.
This may explain how humans have developed such unique mental capabilities as language, culture and planning, the researchers say. But changes in gene expression must in the end originate from DNA changes and the researchers do not yet know which groups of genes are responsible.
Disease genes
So far only two genetic differences have been biochemically characterised, one affecting cell surface structure and one that may affect hair structure.
Identifying which genes are responsible could help us to learn more about the genetic basis of diseases, says Enard, if we can correlate gene expression patterns with differences in susceptibility to cancer, Alzheimer's or AIDS.
Finally, Enard cautions: "The question of what makes us human can be answered in so many different ways. Never will molecular biology tell us everything."
Journal reference: Science (vol 296, p 340)
Helen Phillips
This story is from NewScientist.com's news service - for more exclusive news and expert analysis every week subscribe to New Scientist print edition.
How do human brains go through five times the changes of chimp brains in the same amount of time, even though we have over double the life span?
These are the questions. I doubt we will get definitive answers, but the speculating is kinda fun!
I agree genetic scientist may have been missing something fundamental. Perhaps nucleic DNA may just provide the basic framework of what we are to be.
Perhaps mitochondrial DNA plays a large role in development than suspected.
No, I think the article says the genes that affect the brain mutated 5 times as much in humans as did chimps' brains' genes since we split off from each other.
I, too, have had this feeling for a few days. Perhaps they have the cart before the horse. They may be going down a dead-end alley.
Even a trip down a dead end alley is progress. Once you get to the end you go back to the beginning knowing that you went the wrong way.
What the article says is that the genes for the brains of chimps and humans are basically the same. What has occurred is that the way in which those genes are interpreted has changed 5 times fasted in humans as in chimps.
The greatest variations in gene expression patterns were found in the brain. The researchers estimate that there have been more than five times the number of changes in human brains than chimp brains since their evolutionary lines diverged.
With mammals, this is more critical. The mothers body and how she "reads" the DNA is just as important as what the DNA says. This is analogous to the diskette. How the computer reads those bits and bytes is just as important as what they say.
All from the same maker - they become obsolete – and the software is not compatible.
The comparative data suggest that during the evolutionary process, humans somehow altered the process of gene expression in their brains, accumulating expression differences at least five times faster than chimpanzees and distancing themselves from their nearest cousin. A similar trend appeared when the scientists examined differences in brain protein levels.
To determine if the differences between humans and chimps were indeed more than expected between such closely related species, the researchers also analyzed gene and protein expression in two mouse species that are about as genetically different from to each other as humans are to chimps. They found fewer differences in gene expression levels among the mice, further suggesting that the human-chimp discrepancy marks a special evolutionary process
Whatever could they mean by 'special evolutionary process'? Didn't they have a hard time explaning how known mutation rates for both species could have produced the differences already observed between the two? How much bigger is this problem now?
I also think that this study is a point in favor of special creation of humans. See my #14 where a quote from the other story about this study highlights this. They are evolutionists so they call it "special evolution". I guess that is what they call evolution that they have no other explanation for, but count on them to scream 'its not science' every time we say the evidence points to special creation.
When we dare to look at the big picture and use scientific deductive reasoning, Intelligent Design is a very logical conclusion. We like to pretend that we have more knowledge than we actually have or even understand.
To use deductive reasoning to determine that there is no intelligence behind our very own intelligence should make Dawkins laugh. Instead the selfish gene mocks the god that he claims to be…
The problem might be getting bigger the more is known. They are drowning in data already, and who has the time to look across disciplines? The Middle East solution might be simpler.
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