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Thread: Human-chimp Difference May Be Bigger

  1. #1

    Human-chimp Difference May Be Bigger

    Human-chimp Difference May Be Bigger

    Science Daily — Approximately 6 percent of human and chimp genes are unique to those species, report scientists from Indiana University Bloomington and three other institutions. The new estimate, reported in the inaugural issue of Public Library of Science ONE (Dec. 2006), takes into account something other measures of genetic difference do not -- the genes that aren't there.

    That isn't to say the commonly reported 1.5 percent nucleotide-by-nucleotide difference between humans and chimps is wrong, said IUB computational biologist Matthew Hahn, who led the research. IUB postdoctoral researcher Jeffery Demuth is the paper's lead author.

    "Both estimates are correct in their own way," Hahn said. "It depends on what you're asking. There isn't a single, standard estimate of variation that incorporates all the ways humans, chimps and other animals can be genetically different from each other."

    By studying "gene families" -- sets of genes in every organism's genome that are similar (or identical) because they share a common origin -- the scientists also provide new information about the evolution of humanness. After surveying gene families common to both humans and chimps, the researchers observed in the human genome a significant increase in the duplication of genes that influence brain functions.

    "Our results support mounting evidence that the simple duplication and loss of genes has played a bigger role in our evolution than changes within single genes," Hahn said.

    That finding complements reports by University of Colorado and University of Michigan researchers in the journals Science and PLoS Biology earlier this year, in which researchers showed that both gains and losses of individual genes have contributed to human divergence from chimpanzees and other primates.

    Hahn and his research partners examined 110,000 genes in 9,990 gene families that are shared by humans, common chimpanzees (Pan troglodytes), mice, rats and dogs. The scientists found that 5,622, or 56 percent, of the gene families they studied from these five species have grown or shrunk in the number of genes per gene family, suggesting changes in gene number have been so common as to constitute an evolutionary "revolving door."

    The researchers paid special attention to gene number changes between humans and chimps. Using a statistical method they devised, the scientists inferred humans have gained 689 genes (through the duplication of existing genes) and lost 86 genes since diverging from their most recent common ancestor with chimps. Including the 729 genes chimps appear to have lost since their divergence, the total gene differences between humans and chimps was estimated to be about 6 percent....

    http://www.sciencedaily.com/releases...1219201931.htm

    Interesting. I wonder what those 689 genes that are unique to humans are responsible for?

  2. #2
    Banned adi chicago's Avatar
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    some homo sapiens sapiens males cannot control their libido and sexual behaviour [rape],maybe one of them long time ago met in the jungle a female monkey...the result ...who realy knows?just joking.
    very interesting subject .the missing link.
    Last edited by adi chicago; 12-22-2006 at 09:27 PM.
    • Dum spiro, spero.
      • Translation: "As long as I breathe, I hope."

  3. #3
    Genes change. That is the truism that analysis of the genes of different species has shown. Genes change at a certain rate but their change rate increases with greater selective pressure. For example, the emperor penguin has shown a much higher rate of gene change than most other species, presumably because of the very high selective pressure being placed on these birds by their extreme environment.

    Because humans and chimps have not exchanged genes for a long time (probably hundreds of thousands of years), a 6% average difference of genes is not surprising. To me there are three estimates that are missing from this analysis. First, are all the gene differences significant? Many gene changes are trivial and don't change the function of the proteins that they encode. It is possible that 90% or more of the gene changes have no effect whatsoever. Second, is the rate of gene change higher or lower than expected from the time that the human and chimpazee species have diverged? If the rate is higher, it it because of an accelerated rate of human gene change or chimpanzee gene change? One can argue that humans have been under greater selective pressure than chimpanzees for past 100,000 years. Chimpanzees have not migrated all over the world and exposed themselves to the same environmental extremes as humans. Third, what genes are different? One of the most interesting factoids that I have heard is that close to a third of the our genes is related to development of the brain. Is this where most of the differences are?

    Analyses of genes have provided the most compelling for evolution. Darwin had no access to genetic analysis when he was proposing the theory of evolution based on "survival of the fittest". If he were here today, I believe that he would immediately recognize the power and the value of genetic analysis for evolutionary theory. Gene changes don't just occur because of survival of the fittest. Genes change with time. Selective pressure influences the rate of change and the consequences of the changes. The difference of genes between two species just indicate how long a given species has been separated genetically from another species and the selective pressure that has been placed on one or the other species. Why should it be surprising that chimps have some different genes from humans? It would be astonishing if our genes are the same. They are different from us, very different, in many ways. Nobody would mistake a chimp for a human or vice-versa.

    Wise.

  4. #4
    Dr. Wise, why do your replies to articles 90% of the time make more sense then the article?

    I'm not trying to stroke your ego..but it's true.

    In gene research just like any type of complicated beyond belief research needs leaders that see the forest and the trees.

    Are there enough of this type of leader to go around?
    We have seen some not so ethical activities in the dog gene world. Test being created by people that have jumped to premature conclusions. And other blatant falsehoods even.

    I don't know if what you and others are inside can be taught. That's frightening.

    Have a wonderful Christmas. And don't plan to retire until your 90 or so..the world needs your type of professional more now then ever.
    Life isn't about getting thru the storm but learning to dance in the rain.

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