If you’ve ever received an email from me composed on my iPod
you may have seen one of my favorite quotes.
The excerpt is from a The Lives of a Cell by Lewis Thomas and the
extended passage reads as follows.
“Nothing would save me and my
liver if I were in charge, for I am, to face the facts squarely, considerably
less intelligent than my liver. I am, moreover, constitutionally unable to make
hepatic decisions and I prefer not to be obliged to, ever. I would not be able
to think of the first thing to do."
I like the respect
and admiration for the complexity and internally programmed aptitude of the
human body Lewis expresses, but I’m most impressed with the humility that comes
from an appropriate view of science. In
light of the quote, and the light it sheds, why create a post title that depicts
the body with such contempt? My text book told me so.
When reading in Essential
Cell Biology about how genes and genomes evolve, the first point the
authors make is that in terms of evolution our body doesn’t matter, only our
germs. Again a clarification is needed.
There are two basic
types of cells in humans (and mammals and other organisms): somatic cells and
germ cells. Somatic cells make up the
bulk of the body including skin, kidney, liver, heart, brain and bone.
Basically everything except sperm and eggs are somatic cells. So that just
leaves sperm and eggs in the category of germ cells. Germ cells are the reproductive agents of the
body and therefore the only cells of any consequence when passing on genetic
information. As my textbook puts it, “In
this sense, the somatic cells can be considered to exist only to help cells of
the germ line survive and propagate.”
Of course germ
cells have all of the information that lead to somatic cells, but anything that
happens after the line blossoms into a body will not have an impact on the next
generation of reproductive cells that follow. The only events that can impact
the germ line are sex and mutation.
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