Dear squirrels-ga,
Good day!
Heritability measures the degree of genetic determination of a
characteristic (e.g., skin color) within a population. It gives no
genetic basis of differences between the populations (whites, colored,
etc.). It is a common mistake to assume that if a trait is heritable,
it is adaptive. The opposite is generally the case!
Skin color is a quantitative trait having the following
characteristics:
- varies in the population along a continuum.
- is controlled by many genes (polygenic)
- is strongly influenced by environment
- is controlled by addictive genes with nodominance
During human evolution, as different "people groups" were exposed to
different environments, natural selection resulted in certain genetic
traits to be enhanced for adaptability (for example: darker skin
pigmentation for environments with more intense sunlight due to the
genetic "potential" to increase more melanin). As these groups were
isolated and intermarried with each other, they eventually lost
certain genes that were not needed for adaptability. People in the
Nordic region are genetically more homogeneous than people living in
regions with high diversity (e.g., Asians).
That is why, the Norwegians who go to the tropics for vacation do not
change to another (darker) color - they have simply lost the genetic
potential to do so. The UN workers, on the other hand consitute a
diverse population with many variations of the genes that control the
skin color. This increases the possibility of heritability of skin
color even if these people have never left NY.
There is also a molecular biology interpreation of the heritability of
skin color! There are at least three genes involved in skin color and
several alleled of each gene producing differing amounts of melanin.
If we assume 4 alleles per gene, there are a total of 12 different
alleles which could be combined in 144 different ways!
Hope this answer satisifies your query :)
Thanks & regards,
reeteshv-ga
Additional links:
An explanation of skin color and quantitative inheritance in common
parlance is available at:
http://www.bio.miami.edu/dywang/skincoloriqquantative.html
An informative article written by Edward H. Hagen, Institute for
Theoretical Biology, Berlin, is availabe here:
http://www.anth.ucsb.edu/projects/human/epfaq/heritability.html
Search strategy:
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