Race by unknow

Author:unknow
Language: eng
Format: epub
ISBN: 9781119472414
Publisher: Wiley
Published: 2019-11-22T00:00:00+00:00

Updating Lewontin 2: The Structure of Genetic Variation Today

Lewontin had it mostly right. However, if he made one error, it was in not being able to consider that one group might actually vary more than another. Lewontin surely knew this, but his statistical model could not both consider the size of the genetic variation in groups and the amount of variation within and among groups.

Increasingly, researchers had observed that Africans were very much more variable than the rest of us. However, Lewontin's statistical procedure did not consider this fact. Besides, he was measuring blood group polymorphisms, not human genetic variation directly.

To end this story, let's turn to the work of Ning Yu and colleagues. With the advent of modern genetic technologies, it has become possible to read a long portion of an individual's genetic code. Yu and colleagues did this, and published their results in a 2002 paper, three decades after Lewontin. They compared a long sequence of DNA from individuals who were identified as “European,” “Asian,” and “African.” The DNA section sampled consisted of 25 000 single nucleotide polymorphisms (SNPs). They then tabulated the number of differences between any two individuals of the total of 30 (10 from each so‐called race).

What Yu and colleagues found is that the average difference between any two Europeans and any two Asians was slightly greater than 0.6/1000, or about 15 in total (Figure 10.2). This is not so surprisingly low, as it has been crudely estimated that about 99.9 percent of SNPs are identical between any two individuals. They found very little difference between an Asian and a European. Again, this makes sense, as the dividing line between these continents is permeable and rather arbitrary. More variation was found between an African, on the one hand, and either a European or Asian, on the other: right about 1.0/1000. The shocker comes next: the greatest variation was found between two Africans: about 1.2/1000. Said slightly differently, there is more variation among Africans than between Africans and non‐Africans.

Download

Copyright Disclaimer:
This site does not store any files on its server. We only index and link to content provided by other sites. Please contact the content providers to delete copyright contents if any and email us, we'll remove relevant links or contents immediately.