At the sister blog.
“There’s all this variability in DNA at the individual level, and the differences between people of so-called different races are predictive of appearance, of skin colour, and whatever other superficial differences we use to distinguish races. They actually are not predictive of anything else”
Are there any geneticists who believe that? Disease resistance varies significantly by population/region because there are different disease prevalences in those areas. “Superficial” traits are not that special from the standpoint of natural selection (although admittedly there could be sex selection snowball effects where different superficial traits come to dominate different places), they are just the easiest ones to recognize. To give another example (although perhaps these groups are not large enough to qualify as classical races, I don’t know what criteria she’s using) people who have long lived at certain elevations have adaptations for dealing with the reduced oxygen content, and just like differential disease resistant this hampers the ability of other people who move in and thrive in such environments.
Excellent point. Certain biological features do vary non-randomly with respect to population/region, and I probably should have pointed that out. The problem is that people way overestimate the tightness of the link between these features and “race”. So, for example, although blacks are more likely to get sickle cell than whites, sickle cell is actually associated with malaria belts rather than race. See this cite for a brief summary:
One stark example of the essentialist exaggeration of race is that, in a national survey, most adults agreed with the statement ““Two people from the same race will always be more genetically similar to each other than two people from different races” (Jayaratne, 2001).
“Two people from the same race will always be more genetically similar to each other than two people from different races”
Greg Cochran (a professor of anthropology who has published on population genetics) has said that is in fact correct. Or something very close to that, I can’t remember exactly. Unfortunately the comments thread in which he said that can no longer be found on the internet.
See here: http://entitledtoanopinion.wordpress.com/2010/07/25/greg-cochran-on-genetic-diversity/
Well, if you compare indigenous people from, say, Austria and Nigeria, they will indeed always be genetically more similar to their own group than to the other group. This was shown in a paper by Witherspoon et al.:
Thus the answer to the question “How often is a pair of individuals from one population genetically more dissimilar than two individuals chosen from two different populations?” depends on the number of polymorphisms used to define that dissimilarity and the populations being compared. The answer, can be read from Figure 2. Given 10 loci, three distinct populations, and the full spectrum of polymorphisms (Figure 2E), the answer is 0.3, or nearly one-third of the time. With 100 loci, the answer is ~20% of the time and even using 1000 loci, 10%. However, if genetic similarity is measured over many thousands of loci, the answer becomes “never” when individuals are sampled from geographically separated populations.
Some earlier studies had suggested that this was not the case, but that was due to their using too few genetic markers.
Of course, this is not necessarily true for admixed populations such as races in America.
And since she mentions Hutus & Tutsis:
Do I understand it correctly that according to the author we should be careful using the category “human” – since evolution is all about “transitions” and “family resemblances”, speaking of “humans” tout court is just another example of vicious “essentialism”. In reality, I take it, some organisms are “more” and some are “less” human – it’s all depends on the combination of the genes and the environment.
No, I don’t see anywhere that she says we should avoid using the category “human.” It should be possible to use that category while still recognizing the variation to which you refer.
It seems to me that the common usage of the category “human” precludes statements of the kind “X is 85% human” or “Y is human enough to drive a car but not human enough to vote” – an organism is either human or not (appropriate age or developmental restrictions do not seem to change the “essential” humanity). “Anti-essentialist” approach would in that sense go against the common usage, it would effectively change the meaning of the word.
I was also wondering how do we decide what is the appropriate threshold and/or how do we center the “similarity clusters”? Do we have to postulate the existence of a prototypical human ( as well as prototypes for other categories mentioned in the piece)? A lot might depend on these decisions and I was wondering what scientific guidelines we should follow in making them.
Anonymous: Thanks for the question. I certainly wouldn’t say we should avoid using the category “human”. We need categories to survive, and “human” is a very useful one! The point, though, is that we tend to underestimate the variability within a category and overestimate the boundaries between categories. If you want to read more about essentialism as an obstacle to understanding evolutionary theory, I highly recommend Ernst Mayr, Elliot Sober, and Andrew Shtulman.
I’m reminded of the persistence of the idea of the great chain of being in which organisms are ranked from highest to lowest. I personally remember how upset I was to learn that octopi are more intelligent than many mammals. Octopi—they’re invertebrates, for crissake! What next—an amoeba who can beat me in chess??
Thank you very much for the authors you’ve suggested. I’ve only had a chance to look at some of their work, but it appears to me that they do not address the issues I was rising.
I think that the claim that belonging to some category is a “matter of a degree” is not very enlightening unless we are also told how to decide what the degree in question is. It seems, that To do the latter one would have to specify what constitutes “being a human”, “being a woman” etc. to the degree 1, as well as provide some guidelines for determining the threshold value. Saying (as many do) that the answers to these questions will “depend on the context” (or “practical considerations”) would be just passing the buck. The real question then becomes how in a given context (or given specific “practical” consideration) we should determine the membership in a category under consideration.