Archive for December, 2011

Earliest Precursors of the One-Drop Rule (C15)

December 19th, 2011

Uncovers the earliest hints that Americans around the 1830?s Ohio River Valley were starting to adopt an ideological rather than a biological concept of “racial” classification. This session traces the first emergence of this myth. This is session C15 of a series of topics on the emergence and triumph of the one-drop rule in U.S. history, discussed in lectures on “The Study of Racialism.”

Three Generations of Autosomal Mapping — A Case Study

December 12th, 2011

An opportunity recently arose to collect autosomal admixture mapping data for three generations of one family, a family that has European, subsaharan African, and Asian admixture. The results are educational. They exemplify the heredity of ancestry-informative DNA markers. They show, on the one hand, that the transmission of ancestry-informative markers from one generation to the next is predictable. On the other hand, they also show that each transmission is random, so that predictions must rely on probabilities. Such blending of randomness with predictability is usually hard to explain. The following case history makes it clear.