Posted on 03/08/2006 3:25:00 PM PST by Pharmboy
How can humans and chimpanzees, who share about 99 percent of the same genes be so different?
Scientists in the United States and Australia say changes in the gene expression, not just genes, is a big part of what separates humans from their nearest relatives.
Gene expression is the process by which genes are turned on or off. Not all of the estimated 30,000 genes in humans are activated at the same time in every cell.
"We think gene expression is a major part of what separates chimps and humans," said Kevin White, an associate professor of genetics, ecology and evolution at Yale University in the United States.
White and researchers from the University of Chicago in Illinois and the Hall Institute in Parkville, Victoria in Australia looked at gene expression in humans, chimpanzees, orangutans and rhesus monkeys.
They used new gene-array technology to compare the level of expression of 1,056 genes in the four species.
"When we looked at gene expression, we found fairly small changes in 65 million years of macaque, orangutan and chimpanzee evolution," said Dr Yoav Gilad of the University of Chicago, lead author of the study.
But he said it was followed by quick changes in specific groups of genes known as transcription factors, which control the expression of other genes, since humans diverged from their ape ancestors during the last 5 million years.
"This rapid evolution in transcription factors occurred only in humans," Gilad added in a statement.
The research, which is published in the journal Nature, supports a 30-year-old hypothesis by scientists Mary-Claire King and Allan Wilson who suggested that key differences between humans and chimpanzees might be found in the way they express their genes.
Until the mapping of the human genome and the development of gene array technology that allows for large-scale analysis of gene expression, it has not been possible to test the hypothesis.
Gilad, White and their colleagues used samples of liver tissue from five adult males from each of the four species in their study.
They found about 60 percent of the genes had consistent levels of expression in humans and the primates.
But genes for transcription factors were more likely to have changed their expression patterns than the genes they regulate.
"Specifically in the human lineage the transcription factors are changing or evolving in their expression at a faster pace than in the other lineages, particularly as compared with chimps," White said.
The researchers do not know what caused the shift in gene expression in humans but they suspect it could be due to changes in the environment, the acquisition of fire and a preference for cooked food.
They plan to use other types of tissue to look at large arrays of genes in future studies.
Turning on or off various genetic subroutines (i.e. genes) is also called "better programming."
Looking at those quad walkers from Turkey got me thinking. People and animals that live in the dirt with their hands are probably ingesting a goodly amount of lead with all it's dumbing down properties. Could people and chimps and the like be the victims of poor hygiene as the principal reason for their retarded development? As man went upright and erect he probably gained many many IQ points as a result of not poisoning himself constantly. hmm.
Beer. It was beer.
"As man went upright and erect he probably gained many many IQ points as a result of not poisoning himself constantly."
I was thinking maybe a better view of what was trying to sneak up on him.
Yes, my first reaction was, "Duh!" However, it's always good to get solid confirmation.
Hey, put that thing down. No one needs to get hurt.
And pretzels, popcorn and chips. :-)
How do they know what genes were doing 65 million years ago?
Rather obvious yes -- but I hate these PR releases. They really distort and lionize.
As far as gene regulation, the transcription, yes, but it's not at the transcription factor level. Everything is indicating it is chromosomal and epigenetic much more than any mutated genes.
Does this say that environmental changes could actually be the cause of rapid evolution, rather than rapid evolution being a response to changes in the environment?
Of course fire and cooking are man made changes in the environment. Don't know what different that might make, but certainly it seems there is at least a possibility for some kind of positive feedback mechanism there.
More like 96.2% difference last I heard.
What changes in the environment could it be?
Both man and chimp live in relatively same environments.
Acquisition of fire? Fireflies have bioluminescence,
did that stimulate them to become sometin' else?
This sounds quite "Lamarckian" i.e. an organism adapts
to one sort of behaviour because one of its ancestors
did it..like a proto-giraffe eating leaves off of the top of a tall tree, and its offspring get longer necks....I believe "Lamarckianism" is pretty well discreditied in most
biological circles...no?
Ping.
It all depends on how you measure it. Which makes discussions about these numbers rather confusing.
Not to worry. According to the brainy scientific materialists, this means that any monkey can become a liberal if given enough time and creature comforts.
LOL!! How'd you know that was me??
Chimp needs some ear protection!
Hey--he's a frickin' chimp! He can't read the NRA safety guidelines (but I will tell him next time we go shooting together).
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