Biomedical Engineering Reference
In-Depth Information
such characteristics is environmental. He offers four arguments. First, he
maintains that “exposure to a new environment inevitably causes an
adaptation to it.” Variations in skin color as well as body shape and size
are adaptations to temperature and humidity. Second, explains Cavalli-
Sforza, “There is little climatic variation in the area where a particular
population lives, but there are significant variations between the climates
of the Earth. Therefore, adaptive reactions to climate must generate
groups that are genetically homogeneous in an area that is climatically
homogeneous, and groups that are very different in areas with different
climates.” His third point is that “adaptations to climate primarily affect
surface characteristics.” Fourth, “We can see only the body's surface, as
affected by climate, which distinguishes one relatively homogeneous pop-
ulation from another.”
10
Others note that perhaps .01 percent of our
genes are responsible for our external appearance and that we differ
“from one another only once in a thousand subunits of the genome.”
11
It is clear that there are many differences between humans and human
groups. But these differences do not constitute a race: “a group of indi-
viduals that we can recognize as biologically different from others,” in
Cavalli-Sforza's words. Such differences would have to be statistically
significant and biological. He continues “Because genetic divergence
increases in a continuous manner, it is obvious that any definition or
threshold would be completely arbitrary.”
12
And while such information
might logically demonstrate the uselessness of classification—for
example, efforts to establish some sort of superiority—Cavalli-Sforza
does indicate one justification for genetic classification: to identify groups
with a genetic similarity that, because of common ancestry, increases
their probability of having similar diseases and, therefore, the possibil-
ity of developing drugs responsive to these diseases. Here the motive for
classification is therapeutic and justified by the humanitarian need to cure
disease.
Another argument against the concept of race and racism is the
common origin of all modern humans from a population in Africa. The
separation of chimps and humans occurred about five million years ago,
and modern humans arose in Africa about one hundred thousand years
ago. The age of this so-called African Eve or, more precisely, mitochon-
drial Eve was calculated by counting “the number of mutations that dif-
ferentiate two living individuals, and identify when their last common
