First of all, thanks to all for a spirited discussion. As cynndara said, this was an honest, open discussion on a subject that is seldom overtly raised. There were, however, some points that I feel need some clarification, at least from my perspective.
The word race itself.
Prevalence of genetic disorders in ethnic groups -- role of founder effect versus selection.
When my children were much younger than they are now, they once had a heated discussion about whether a tomato is a fruit or vegetable. I explained to them that those two words (fruit and vegetable) come from two very different intellectual domains and therefore not directly comparable. The word fruit has a very precise meaning in botany. Fruits are derived from the ovary of a female (or hermaphrodite) flower after fertilization has taken place. At the same time, it has a far less precise usage in common language, where it is something of plant origin, ripe, usually sweet and can be eaten without cooking, often as dessert. In contrast, the word vegetable comes only from common everyday English language, and does not have a very precise meaning. A vegetable can be a fruit, a root, a stem, a leaf or a flower. In this particular instance, a tomato is a fruit by botanical terminology, and either a fruit or a vegetable in common parlance.
In the same context, I suspect that the word race means different things to different people, in part because it used imprecisely in every day speech. Deoliver47 says, in effect, "I am an anthropologist and I say there is no such thing as race and that is the end of the discussion." With all due respect to him or her, this is the kind of dogmatic, authoritarian statement that gives all of us scientists a bad name. Why is the viewpoint of an anthropologist any more valid than the viewpoint, for instance, of a physician such as myself? I would be doing my patients a disservice if I did not ask them what race they belong to, because I am aware that the incidence, course of disease and response to treatment of many diseases are different among different "racial" groups. When I address a volunteer group of (let us say) Indians, I make it a point to inform them that East Asian Indians are more prone to osteoporosis and osteoporotic bone fractures and that this increased propensity is seen even among men, even though osteoporosis is seen primarily as a problem for elderly females among "White Caucasians". A purist might argue that that is no such thing as White Caucasians, because allele frequencies among the Irish could be very different from, say the Bosnians. The same purist might even argue that there is no such thing as "Indians", because individuals from different parts of India exhibit very different genetic backgrounds. However, imprecise though the terminology may be, it is of enormous, current usefulness in the practice of public health.
Similarly, if I were addressing a group of African-American men about health issues, I would be remiss if I were not to point out to them that the course of hypertension is more malignant among them or that prostate cancer arises at a lower mean age and tends to be of higher histological grade than among white Caucasians or "Asian men". (Parenthetically, as an Indian, I often find the last phrase (Asian men) quite annoying because most of the data come from Chinese and Japanese studies, and there are little if any data that suggest that the incidence, age of onset or histological grade of prostate cancer is any different among Indian men then among white Caucasian men (though it might well be)). Even as I say this, I am not unaware of the fact that the term "African-American" is imprecise for a number of reasons. First, as someone pointed out in the discussion, there is a tremendous amount of genetic variability in the African continent and surely the location from which the ancestors of the African-American men arrived here has an impact on disease susceptibility. Secondly, the degree of African genetic contribution to individual African-American is highly variable. However, when one is discussing an issue of public health importance, the relevance of these two realities is overridden by the more immediate public health concern. If we can persuade African-American men to be screened for hypertension or prostate specific antigen (PSA) at an early age, we would be performing a useful service. Similarly, the gene for hemochromatosis is prevalent among people of Irish ancestry (the level of heterozygosity is about 12% among Irish-Americans!). Would it not be important to screen people of this group to make sure that they do not get liver cirrhosis? Do theoretical discussions about the precise terms use to categorize ethnic groups really matter? Deoliver47 seems to suggest that we should avoid the word race altogether. What else should we call these groups that manifest well documented differences in disease incidence and progression? Ethnic groups? Geographically isolated clusters? I can tell you that all the medical history taking forms I have seen in this country simply refer to the race of the patient. I suspect that is the way it is going to be for the foreseeable future.
- There was some discussion of Tay-Sachs and sickle cell diseases. In the context of the discussion it may be important to point out that the high frequency of Tay-Sachs among Ashkenazic Jews, French-Canadians in Québec and Cajuns in New Orleans is because of founder effects and not, as far as we know, due to selective advantages. The best-known instance of a strong founder effect is the case of the extraordinarily high prevalence of Huntington's Chorea in the village known as Barranquitas on the shores of Lake Maracaibo in Venezuela. Here it has been documented that a single woman ancestor with Huntington's Chorea settled in the village and had 10 children. Many of the current residents of Barranquitas are descendants from this woman and therefore manifest the disease. Many diseases due to founder effects tend to be restricted to ethnic groups or to geographically isolated populations. This is quite different from the case of sickle cell anemia and other hemoglobinopathies, which are widespread geographically due to selection by the malaria parasite.