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Tuesday, August 30, 2005

Homo Sapiens: Fewer Genes Than Rice

And why this may limit future evolution;

Research published in the July issue of Trends in Immunology, shows how a more advanced immune system in humans could explain why the human genome may have only a slightly greater number of genes than the plant Arabidopsis thaliana, and probably less than rice, Oryza sativa.

Dr Andrew George, from Imperial College London and based at the Hammersmith Hospital comments: "Although humans are normally thought to be considerably more complex than organisms, such as plants, rice, yeast and earthworms, this is not reflected in their number of genes, with humans having less genes than other supposedly less complex organisms."

Dr George suggests that the limited number of functional genes in the human genome may be a result of the presence of a more advanced immune system. The immune system is designed to protect us from disease, but it is important that the cells of the immune system do not recognise our own tissues or cells, as this would lead autoimmune disease.

Autoimmune disease is avoided by killing off any immune cells that recognise molecules produced by the body (self-molecules). This means that the larger the genome, the more self-molecules the immune system needs to tolerate.

As a result, the immune system has to kill more immune cells. If there are too many genes then this results in the vast majority of immune cells dying, paralysing the immune system, and leaving the body unable to fight off disease or infection.

Dr George adds: "The limited size of the human genome could make further evolution for humans difficult. Fortunately, the human genome has been able to create genes which have multiple uses, thus making the best use of a limited number of genes."

Posted by Kate McMillan on August 30, 2005 in Science | Permalink

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Comments

Has anyone stopped to consider that there is zero evidence for species evolving through mutation into other species? There has only ever been observed slight modifications of already existing structures and biochemistry. It is a huge and untenuous leap to suggest that you merely have to multiply this effect to explain the diversity of life. Humans will not "evolve" beyond being humans. (worms - worms, chimps - chimps etc.)

Posted by: jack | 2005-08-30 5:40:44 PM


I agree with Jack; there is really no evidence for the traditional Darwinian theory of evolution by gradual mutation...and Natural Selection.
There's a lot of hot debate about this. I don't mean between the creationists and the Darwinists; I mean among biologists who don't accept that the Darwinian theory is a complete theory and who suggest alternatives.

I don't agree with a Designer (I'm an atheist), but I do agree with informational networking that produces changes (it would take too long to describe here..).

By the way, a basic reason for the small size of the human genome, is possibly that humans in particular have large numbers of what used to be called 'junk DNA' or 'introns'. It now appears that these introns, which are of a very high number in humans, enable strong adaptive capacities. So, in humans, you have a system that has a limited number of 'innate' properties (the regular genes)..and provides for a large number of 'learned', informational, capacities.

It's all..as I said, a hot debate.

Posted by: ET | 2005-08-30 6:31:05 PM


One of the difficulties with even discussing the topic is that most people who do still have an understanding of genetics from the last decade. So much has changed, so many former "facts" set on their head.

Half of the time, I hear self-described experts in biology basing arguments on genetic premises that are now proven false.

Posted by: Kate | 2005-08-30 8:00:12 PM



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