Friday, July 27, 2007

A small break for a new fact

As I continue this discussion with Marcsana about evolution, one of the joys of the effort lies in the fact that I am constantly finding new and wonderful facts (something, alas, that would threaten creationists rather than delight them!)

I ran across a random fact this evening in a Science Week article- a mention that "
It is of interest that a cell-surface sugar modification that is lost in the human lineage due to genomic mutation is reported to reappear in human cancers."

Hmmm- interesting! And not something I had heard before. So I delved a bit more into this fascinating statement- and here is what I found.

Cells are covered with chains of complex sugars. At the end of these chains are often various compounds called sialic acids, which help, among other things to regulate water metabolism in cells.

One particular sialic acid, N-glycolylneuraminic acid, is found widely throughout the animal kingdom, including in the great apes. However, humans do not normally produce this particular sialic acid. This isn't because we have lost or never had the gene necessary to do so; instead, this gene has been deactivated by a mutation, and genetic analysis showed that this mutation is approximately 2.9 million years old- after we split from the branch of the primate tree that went on to become chimpanzees and bonobos, and about the same time that a tremendous growth spurt in hominid brain size occurred.

Several scientists have speculated that this mutation helped allow the growth of human brains and also may have allowed human populations to grow due to conferring some disease resistance.

In another fascinating implication, scientists studied the prevalence of variants of this gene in different human populations , which supported a multiple African origin for all human races.

Research has also shown that some tumors can turn the gene back on and produce
N-glycolylneuraminic acid.

So there you have it. One short sentence led to a world of discoveries, all supporting evolution in varied and interesting ways. Life is so much richer when you are open to new knowledge, rather than fearing it as something that may threaten your worldview.

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