Posted on 04/11/2002 3:27:46 PM PDT by Nebullis
A team of international researchers from Germany, the Netherlands and San Diego may have shed light on why chimps and humans are so genetically similar (nearly 99 percent of shared DNA sequences), and yet so mentally different.
In a study published in the April 12, 2002 issue of the journal Science, the scientists noted that the striking difference between these primate cousins is most evident in their brains. The disparity appears to be the result of evolutionary differences in gene and protein expression, the manner in which coded information in genes is activated in the brain, then converted into proteins that carry out many cellular functions.
The brain differences are more a matter of quantity than quality. Differences in the amount of gene and protein expression, rather than differences in the structure of the genes or proteins themselves, distinguish the two species.
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One does not change one's own brain. But one can improve the brain of his children be selecting the smartest mate.
The article implies that intelligence in humans serves as an attractant, like the plumage on the birds of paradise.
Blinded by the ideology. That is why evolution is so bad, it is stupifying. It keeps people from seeing what is truly amazing. The fact is that no other species performed the same transformation. The same could have/should/have happened with other species but it did not.
Further, humans are far different from all other species. It is the only species that has art. The differences between humans and chimps are not just of degree, but of quality.
You are completely misrepresenting my statement. I said man is unique and we have known so for a long time. It is not a religious argument and it is not about tax dollars. This study verifies how unique man is.
I don't know how that can be determined when the article itself states---
Why these evolutionary differences occurred is still unknown.
"They found five times as many changes in gene expression -- actual activity by the genes -- in the human brain than would be predicted by evolution."
[NOTE: - If that characterization of the study is accurate, then consider this; here is a finding by Varki and Paabo of an Institute where they are PAID to look for evidence supporting the theory - which is what they were looking for - but found the opposite. I find it interesting that where any hint of a notion that there might be the slightest possiblility that perhaps evolution from one species to another might not have taken place is completely and utterly unthinkable, the automatic reaction to data that shows the opposite of what is being sought (evidence of evolution) is not to re-examine the basic premise, but to simply come up with some new 'predictions' to try to make the data fit the paradigm.] < /rant > < flame retardant="on" >
Study: Creative Use of Genes Makes Humans Unique By Maggie Fox, Health and Science Correspondent
WASHINGTON (Reuters) - What makes humans different from chimps, apart from a little extra hair? It might be a more creative use of the genes that affect how the brain works, a study published on Thursday suggests.
Humans and chimps share 98.7 percent of their DNA, but are clearly very different. Scientists have long tried to determine how just over 1 percent of our genes can make such a difference.
It may not be an issue of quantity, but of quality, an international team of genetics experts reports in this week's issue of the journal Science. And the differences seem to lie mostly in the brain.
"When you look at blood, you don't see a lot of differences. Chimps look very, very much like us," Ajit Varki of the University of California San Diego, who helped direct the research, said in a telephone interview.
"But when you look at brain you see a lot of differences."
The findings could go a long way to soothing humans flustered at learning that we have fewer genes than even some plants. Public and private teams who sequenced the human genome estimate that we have only about 30,000 to 40,000 genes as compared to, for instance, 50,000 for rice.
Genomics experts say it is not how many genes you have that counts, but what you do with them -- in this case the protein products of genes.
The work by Varki and colleagues, including noted genetics expert Svante Paabo of the Max-Planck-Institute for Evolutionary Anthropology in Leipzig, Germany, supports this.
They found five times as many changes in gene expression -- actual activity by the genes -- in the human brain than would be predicted by evolution.
"If two species have been apart for 5 million years, you expect a certain amount of differences," Varki said. But there are many more differences in the human brain than expected.
"Whereas if you look at liver and blood, you don't see that," Varki added.
The researchers look at messenger RNA, which is what translates the genetic recipe found in DNA into a final product -- a protein. Every cell contains a full complement of DNA, but what makes one cell become a liver cell and another function as a brain cell depends on what genes are expressed.
They took many different samples of tissue from human cadavers, chimps and orangutans that had died of natural causes, monkeys and mice, and compared them.
GRAY MATTER SHOWS GENETIC DIFFERENCES
In the case of the brain, they took gray matter from the left prefrontal lobe, one of the areas involved in thought as opposed to controlling movement or bodily function.
Using a gene chip, they checked to see which genes were actually being expressed by looking for messenger RNA.
The gene expression patterns of the chimpanzees and the macaque monkeys were more similar to one another than they were to humans. But the genes expressed in blood and liver were very similar in humans and chimps.
In addition, humans differed more from one another than chimps differ from one another, they found. As genomics experts predicted, it seems that humans mix and match their proteins, so that while there are only 30,000 genes, there are an estimated 250,000 different human proteins.
"With an understanding of the differences between humans and chimpanzees, we may be able to learn more about the genetics underlying diseases that seem to harm humans but not chimpanzees," Varki said. For instance, chimps do not die from AIDS or malaria and do not get Alzheimer's or cancer in the way that humans do.
In 1998 Varki and colleagues documented the first genetic difference to be found between humans and chimps -- a cell-surface carbohydrate molecule called sialic acid that chimps have but that humans do not.
"The thing about this topic -- I never met a human being who was not interested in it," Varki said. "
Cordially,
The difference is not all that great ... particularly in some people.
Agreed. Chimps are capable of much more cogent argument than many humans.
It's stunning, sometimes, how poorly written the press stories are. Do these writers ever read the original article or talk to the researchers?
When human and chimp DNA is compared and average rates for genetic differences are calculated, a genetic evolutionary speed is inferred. But the cognitive difference between humans and chimps is greater than this genetic difference would imply. It has long been hypothesized that this difference is due to differential gene expression. That is, the difference is an amplification in the downstream transcription and translation of small coding differences seen between humans and chimps. This is the first study which demonstrates this difference in activity of genes in the brain. There is very little, if any difference in expression levels of other systems like liver and blood.
If no difference in expression levels had been found in this study, as Edwin McConkey says: "...we should all have to take a course in metaphysics, and religious fundamentalists would be dancing in the streets."
Oh come on now, the argument would be made that this is evidence of the common ancestry of chimp and man and is conclusive evidence of Darwinian evolution.
"They found five times as many changes in gene expression -- actual activity by the genes -- in the human brain than would be predicted by evolution.
"If two species have been apart for 5 million years, you expect a certain amount of differences," Varki said. But there are many more differences in the human brain than expected. "Whereas if you look at liver and blood, you don't see that," Varki added
There are direct quotations. Apparently the writer has has at least listened to the researchers.
I don't see how the text of the article is much different than your statements that "when human and chimp DNA is compared and average rates for genetic differences are calculated, a genetic evolutionary speed is inferred. But the cognitive difference between humans and chimps is greater than this genetic difference would imply." How is that much different than saying that they found many more differences in the human brain than they expected? And why did they expect certain results? They were expecting different results because they were inferring a "genetic evolutionary speed", as you correctly point out.
Cordially,
Cordially,
Cordially,
There's still an enormous gap in understanding of expression from gene sequence, especially in multicelled organisms. At each major level, starting with transcription through RNA processing, through translation and post-translational processing, there is an amplification of possibilities, cascading of effects, networked feedback loops, and so forth. You can see how this becomes complicated very quickly and how it's difficult to tease out one aspect of it.
Identical sequences end up affected differently in different cell types. The brain expresses different proteins than the liver. We already know about the differences between different cell types. This study shows that there is a species expression difference between same cell type.
All this can't be separated from development. The signals at the unicellular stage start the program of expression patters with morphogenic gradient fields.
!
A fascinating book is Calvin's Throwing Madonna
The idea is that our ancestors adopted throwing stones to hunt for food. In order to get accuracy it is necessary to release the stone at a precise time. This requires lots of neurons working together. Hence our large brains. He also discusses handedness.
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