"Fuzziness" (Continuity and classification)

Curtis Clark jcclark at CSUPOMONA.EDU
Thu Jul 26 11:26:26 CDT 2001

At 01:19 AM 7/26/01, Richard Pyle wrote:

>Bottom line:  The boundaries between "species" (populations of individuals)
>will always be more "fuzzy" and subject to human interpretation than the
>boundary between a parent individual and its offspring individual.

Unfortunately, the line between parent and offspring is just as fuzzy. I'll
leave aside all the organisms that don't conform to our anthropocentric
view of parent/offspring (many plants, fungi, invertebrates come to mind)
and concentrate on humans.

Barbara Ertter's post about paraphyletic species reminded me of Henrietta
Lack. For those of you unfamiliar with her, her ovarian cancer lives on as
HeLa cells, the most durable and weedy human cells in existence, common
contaminant of mammalian cell cultures. Ms. Lack is dead; Ms. Lack is
immortal. HeLa cells are human; HeLa cells are a new species. They are her;
they are her offspring. Our narrow views of human individuality and
ancestry don't cope well with the situation.

You could argue that this is a special case, and that it doesn't really
relate to the question at hand. So let's move on. Many humans suffer from
autoimmune diseases: one's immune system starts to attack parts of one's
own body. It had been noted that autoimmune diseases are most common in
women who have had children. It occurred to a researcher that this might be
the result of residual fetal cells remaining in the mother and triggering
the response. It turns out that it is not unusual for fetal cells to
migrate into the mother and take up residence (and function) in many
organs. The researcher devised a way to genetically screen for these cells
(I don't remember the details) and found that they were more common in
women with autoimmune diseases.

Men and childless women can sometimes get autoimmune diseases, and it turns
out that maternal cells can invade the fetus, which may account for that.
So it seems that at least some of us are chimeras of ourselves and our
children, or ourselves and our mothers, or perhaps our mothers, ourselves,
and our children all at the same time.

Tell me again how it is that individual humans are less "fuzzy" than species.

Curtis Clark                  http://www.csupomona.edu/~jcclark/
Biological Sciences Department             Voice: (909) 869-4062
California State Polytechnic University      FAX: (909) 869-4078
Pomona CA 91768-4032  USA                  jcclark at csupomona.edu

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