Humanity's Genetic Diversity on the Decline
jd writes "In a study covering five different periods of history, from 300 AD to the present day, and geographically spread across much of Europe, scientists have extracted the mitochondrial DNA from a sizable number of individuals in an effort to examine changes in diversity. The results, published in the Royal Society journal is intriguing to say the least. 1700 years ago, three out of every four individuals belonged to a different haplotype. In modern Europe, the number is only one in three. The researchers blame a combination of plague, selection of dominant lineages and culturally-inflicted distortions. The researchers say more work needs to be done, but are unclear if this involves archaeology or experiments involving skewing the data in the local female population."
Most importantly, it is the correct combination of genes that makes a successful organism as well as individual genes. 'Mixing' of groups of people is hugely advantageous for this reason.
Secondly, genes do not become lost when they combine with genes from another person to make a child. There is just a new combination of genes which can contribute to the whole genetic diversity of mankind. For example, we could take the idea that races should not interbreed a little further and say that people should not breed outside of their immediate family. The problem with this would be that genetic diversity could hardly ever increase, and by attrition mankind would be doomed. By separating races one creates several smaller separate gene-pools each of which is smaller than the original whole and hence more vulnerable.
Thirdly, by separating the societies it would become genetically/evolutionarily advantageous for one race to think of or treat the others as subhumans. By this argument I claim that you have implicitly invoked Godwin's law.
Also, I wish you luck procreating with your sister...