Anthropology 100, September 19th 2012
Mapping Biological Diversity
Human pops differ fin the frequency of alleles, not by the presence or absence of
While some alleles produce discrete variation, many produce continuous
what really separates pops is not that some have alleles others don't, it is just that
the frequency of certain alleles is much higher in some pops than others.
*height and skin colour are examples of CONTINUOUS variation. continuous
variations pose a problem when trying to classify people because you have to
MAKE CATEGORIES, and those become arbitrary.
*DISCRETE variation means there are relatively few variations of a particular
allele, making it very easy to categorize and determine these features when doing
analysis. Examples: Blood Type. PROBLEM with discrete variation, sometimes
there are actually far too few categories (ear wax, only two categories. limiting).
When something is too limiting, it doesn't tell you much about the people these
when we put these alleles on a map we usually see CLINES, showing allele
frequencies in different populations drifting from one place to another gradually.
(CLINES are gradual changes in the freq. of genotypes or phenotypes over
Australians are dark, even though they are further from the equator, because of
genetic drift from papua new guinea where australia was settled from. Philippines
are lighter cause of multitude of trees that make for a ton of shade.
The cline is different for the americas because they migrated only 20000 years
ago from northern european descent. with more time they may have become darker
near the equator. the shades had changed but not all the way to africa dark, not
Skin colour is in some ways no longer selected for what with our control of
vitamin d and of sunscreen. Skin colour doesn't tell us anything about individuals
except how much their ancestors need protection from the sun or rather needed
exposure to the sun to activate vit.D in