Celebrating human genetic diversity
sara abdulla
Wednesday, 30 September 2009 13:43 UTC
Credit: Atlantide Phototravel/Corbis
Is genetic diversity, including group diversity, among humanity’s greatest assets?
Society is ill-prepared for results from genetic research showing group variation in biologically important traits according to Bruce Lahn and Lanny Ebenstein in Nature this week.
Studies of human genetic diversity are increasingly finding evidence of biological variation among groups of people, not just among individuals. Some of these traits are superficial, such as skin colour, or non-controversial, such as lactose intolerance, but to ignore the possibility of group diversity is to do poor science and poor medicine, the Opinion authors say.
Scientists are naturally wary of making claims that may be interpreted as favouring one population group over another, especially when it comes to important biological traits such as brain biology. Some have even called for a halt to such studies of genetic diversity to prevent any misuse of the information. See previous forum discussion on Untouchable Science here.
In recent decades, ‘biological egalitarianism’ − the view that human groups have no, or very few, meaningful genetically based biological differences − has emerged as the dominant moral position say Lahn and Ebenstein. The authors argue that this position is dangerous. Instead, they urge the science community to embrace genetic diversity, including at the group level, as one of humanity’s chief assets.
What do you think?
- Are the fears of scientists who don’t wish to engage in this research natural and understandable?
- Will genetic information be misused however the debate is framed by scientists and ethicists?
- Do you steer away from controversial areas for these reasons?
- Have you ever had your work misused or misrepresented?
Please share your views and experiences with the rest of the forum. The Opinion authors will also be joining in the discussion.
Updated 07 October 2009 17:08 UTC
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Lahn and Ebenstein mention the 2008 Olympic Games as “a beautiful showcase of human diversity” and even go on and state “should genetic variation contribute in any way to regional athletic ability, it would be hard not to see group diversity as a great asset of our species.” This is an ugly statement since the diversity differences in Olympics exists purely due to how they are organized. Olympic weight-lifting for example does not show regional differences in its medal awards.
Olympic weight lifting is organized with divisions (eight for men and seven for women) determined by body mass. Awards are then based on Sinclair Coefficients which calculate strength-to-weight ratio of the lifters. As result, athletes of diverse inherited body builds can compete on equal terms. Also, and critically, it ensures that Olympic weight lifting is race-neutral since variations in body build across the world do not effect who gets on the podium.
Track and field events could, but are not, organized with similar divisions and correction coefficients for inherited physique and physiological differences that vary geographically. The result is that such events are not race-neutral: no Indian has ever won a track or field event Olympic medal and the Chinese at Beijing won only two bronze (out of a potential 141 medals). Thus in effect nearly half the world’s potential track and field athletes are excluded from international competition awards—a situation which would not exist if such competition was organized so that inherited body differences were controlled for and thus did not play a role in determining who won.
The science community can play an important role in ensuring the Olympics is beautiful because it is race-neutral.
First, researching the physique and physiological factors that are inherited and how they scale with athletic performance so they can be controlled for. This would ensure that all athletes (as in weight-lifting) compete on an equal “start line”. We would not expect an athlete that is 1.50 m (the average height of the Aka, Efé and Mbuti of central Africa) to have the same potential running speed as an athlete who is 1.96 m (such as Usain Bolt). We need a new well funded science that can provide the data for creating event specific divisions and correction coefficients so that athletes irrespective of inheritance can compete on equal and fair terms. Scientists already play a key role in researching the effects and detection of performance enhancing drugs, a similar need exists for researching the effects and correction of inherited performance factors.
Second, the scientific community needs to identify and make more public research upon the relationship between athletic competition (from the international level down to that done in schools) and the individual uptake of exercise. A major factor in the prevention and treatment of diverse conditions such as heart disease, cancer, diabetes and depression is vigorous exercise. Both India and China face major a public health crisis in such diseases particularly diabetes. Limited research shows that an individual’s engagement in exercise as an adult links to their experience of success in school athletes. It is also not unreasonable to suggest that the presence or lack of ethnic athletic “heroes” is also another important factor. More research is needed upon these links since they suggest the lack of race-neutrality in athletes at all levels (international to school) might have a major impact upon public health. This is important since it argues that the organizing of athlete competition in a race-neutral way is an issue of urgent general public concern not merely one for athletic organizations.
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Following John Skoyles’ suggestions above to their natural conclusion, I propose that we also devise handicapping systems correcting for differences in muscle strength, cardiovascular performance, general physical activity levels and motivation, since these also differ between human groups.
Obviously we will only achieve true parity when every participant in every Olympic event – regardless of their race, gender, age or athletic ability – crosses the finish line at precisely the same moment. Gold medals for everyone!
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The article “Let’s celebrate human genetic diversity” by Bruce T. Lahn and Lanny Ebenstein seriously misrepresents the current situation of research in human genetic diversity. The article is a rhetorical piece filled with half-truths and misquotations.
For instance, right in the first paragraph they state that “It is now recognized that despite the high degree of genetic similarities that bind humanity together as a species, considerable diversity exists at both individual and group levels”. That is a very biased assessment of the state of the science.
First of all they introduce a term “group level” that is completely undefined. Are these different populations within a continent, different continents?
Second, they so not provide any reference for their statement simply because there are no good studies that support a strong non-individual diversity in the human species. Rather, most studies consistently show that the interindividual component represents more than 90% of human genomic diversity.
They then build a straw man by stating that “the current moral position is a sort of biological egalitarianism” and proceed to demolish it. The fact is that very few molecular population geneticists would in fact support such a view. The prevailing paradigm is not that we are all equal, but that we are equally different. They would have no arguments against that!
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Anonymous
To Sergio D.J. Pena:
The box of the article clearly describes what the authors mean by “diversity at the group level”. Reference 5 (and numerous references therein) provides irrefutable evidence of genetic differentiation among major human geographic groups. Exactly how much human diversity resides within as opposed to among groups is a matter of ongoing research (and the article indeed acknowledges the likelihood that most diversity may be within human groups), but this does not detract from the article’s central thesis, namely, it is not beyond the realm of possibilities that there may be a nontrivial amount of genetically determined biological differentiation among human groups, and the society should have a positive moral attitude toward this possibility. -
Dear anonymous,
Sorry to disagree, but the Box does not provide a satisfactory definition of what is meant by a group. It states that “it is possible to group humans on the basis of their genetic make-up”. That it is possible is self-evident. The question is whether it is warranted.
To decide on that one has to consider both ascertainment and sampling strategy of the “human groups”. For instance, Serre and Paabo (Genome Res 14, 1679–1685, 2004) argue that most of the differentiation observed in the several studies done using the CEPH-HGDP panel is due to the peculiar geographical arrangement of the individuals tested. This point was further discussed extensively by Handley et al. (Trends Genet 23, 432-439, 2007).
In a recent study of worldwide human diversity Long and Hunley (Am J Phys Anthropol 139, 23-34, 2009) conclude: “In summary, we find for our own data and for a large published data set, that human populations have much diversity when DNA sequences are considered. We show that simple partitions of diversity are biased and that they hide the true extent of diversity. “
Also, in my view, reference 5 does not provide “irrefutable evidence of genetic differentiation among major human geographic groups”. First of all, they conclude that “Together, these results reaffirm that within-population variation accounts for most of the genetic diversity in humans”.
They do observe a small component of population structure (unexplainably they do not address the adequacy of the sampling method), and state “The observed population structure can be largely explained by random drift at neutral loci”. This last conclusion differs frontally from the strong selectionist bias of the paper by Lahn and Ebenstein.
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Anonymous
To Sergio D.J. Pena:
My take of the article is that, it is not making any claim about EXACTLY how much genetic diversity is within versus among groups or EXACTLY what fraction of that genetic diversity is functional. In fact, the article said explicitly in a few places that most diversity may lie within groups and that the question of what fraction of genetic diversity is functional remains a subject of ongoing research. So, it seems that, as far as what is currently known about human genetic diversity, the article’s brief summary is not so inconsistent with what you are saying.
What the article IS about, in my take, is that emerging research is revealing the POSSIBILITY of a nontrivial amount of genetically determined group differentiation in traits beyond just skin color (by the way, this can be the case even if most genetic diversity resides within as opposed to among groups), and that given this POSSIBILITY, scientists and society should adopt a moral position that would not fall apart if this possibility (or just some part of it) turns out to be true. So, I think the article is more about arguing for a new moral position that would withstand whatever facts are revealed by science regarding human diversity, and much less about just exactly how much genetic diversity there is in humans or how that diversity is apportioned among groups or how it relates to function. If you can’t definitely rule out, at this stage of research, the POSSIBILITY that nontrivial differentiation among groups can exist for some important traits (and the example of group difference in chemo drug response given in the article seems pretty reasonable to me after I read some of the references), then it is hard not to see the need for a new moral position that makes misuse of that information less palatable. The call of the article to adopt a positive attitude toward diversity seems like a sensible step toward that goal. As the article suggests, if people really come to appreciate that genetic diversity is mostly a good thing, even if some of that is manifested at the group level, then it seems that people would be less inclined to think negatively every time they hear that some genetic difference is found between some groups. Hardcore racists probably cannot be brought around. But they will be further marginalized in an environment that cherishes human diversity. The article suggests that this is analogous to cultural diversity: it is much more effective to defend against oppression of people based on culture by stressing that cultural diversity is a great thing rather than by stressing that people throughout the world are culturally indistinguishable at the group level.
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John Skoyles’s comment that “diversity differences in [the] Olympics exist purely due to how they are organized” strikes me as inaccurate. He says that different body types and characteristics are more or less likely to result in different performance in different athletic areas. Quite plausibly, some of these body types and characteristics are more or less likely to be in found than average for all of humanity in individuals from some geographic areas than in individuals from others, as suggested in the reply. To be sure, it might be possible to devise an “individualistic Olympics” in which group characteristics would be largely factored out, but this doesn’t mean the relative uniformity that then would result would thereby be natural. It would be as much a result of how the Olympics were organized as the current results.
Sergio D. J. Pena says the article “seriously misrepresents the current situation of research in human genetic diversity.” I don’t believe this is the case. Good evidence exists to support the following views:
1) there is more genetic diversity at individual and group levels than thought a few years ago,
2) some of this diversity is functional,
3) human evolution, rather than having stopped in the past 50,000 to 40,000 years, may have increased.
In addition to footnote 5, see footnote 2, with respect to global variation in copy number in the human genome, and footnote 6 for signals of recent positive selection in a worldwide sample of human populations, among other articles.
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Regarding the big (and natural) varieties of individual bodies and genomes, I think that the much more important distinction to be made may be the old philosophical (and quite mocked upon) distinction between bodies or genomes (here, e.g, the genome of “my own” body: XY-hsp.aab-70Syadde-eph345_BDNF45axx_R) and Selves (“minds” or “social interaction partners”, e.g. here: Oliver P. Elbs).
However, this distinction has never been made consistently throughout some “human history”, nor has it been told to pupils in the class-room — instead, most “humans” (!) seem to have permanently mistaken and confounded the one medical thing (i.e., genomes & bodies like XY-hsp.aab-70Syadde-eph345_BDNF45axx_R) with the other, socially and linguistically constructed one (here: Oliver P. Elbs).
Besides, ambiguous terms like “humans” (“bodies” OR “Selves”?) should be replaced by much more precise terms, e.g., “members of H. sapiens” or even better: “XY-hsp.aab-70Syadde-eph345_BDNF45axx_R” OR “Oliver P. Elbs”.But alas, I certainly will still have to wait for a “much more subtle and delicate time & society than mine”, where everybody (or more correct: every one) will be able to separate and distinguish CLEARLY between these two both things (bodies/genomes vs. Selves).
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Lanny Ebenstein in his response to me acknowledges that track and field events could be organized in a manner similar to that of weight-lifting and that as a result “group characteristics would be largely factored out”. But he questions whether the “relative uniformity that then would result would thereby be natural”.
Naturalness however is not the issue which instead must be the overwhelming public health interest that athletics is fair to ensure maximum uptake of vigorous life-long exercise.
Take for example diabetes in China and India. Diabetes prevalence in India in 2000 was 31.7 million and is predicted to increase to 79.4 million by 2030 while in China the figures are 20.8 million and 42.3 million1. This represents not only a vast cost in human suffering but also a large financial one: the direct medical costs of type 2 diabetes and its complications in China are estimated to have been in 2007 26.0 billion USD and will rise to 47.2 billion USD by 20302. An urgent public health research and policy issue is how such epidemic levels can be reduced. Identifying why so few people participate in exercise is a major issue since exercise plays a major role in reducing type 2 diabetes 3,4 and indeed has been described as “a cornerstone in prevention” 5.
Central to this is how athletics is organized since this can either link success to genetic factors (as at present) or not (when organized as with weight-lifting with divisions and correction Sinclair coefficients). These have very different implications for exercise participation because sport and athletic participation by people at school and college links to perceived athletic competence 6,7 self-efficacy, 8 and a person’s belief that athletic competence is “something that can be learned” rather than innate fixed trait.7
Young people in India and China first lack a strong sense of athletic competence due to the present organization of athletics as they do not see people like themselves winning track and field event medals as there are geographical inequalities. No Indian has ever won a track and field Olympic event and only two Chinese athletes won medals out of a potential 141 at Beijing (Zhou Chunxiu, Bronze, Marathon; Zhang Wenxiu, Bronze, Hammer throw). However this situation contrasts with Olympic weight-lifting: for example Indians have won medals in this event (for example, Karnam Malleswari, the first Indian woman to win an Olympic medal) and the Chinese at Beijing won nine out of a potential 45 medals (proportionate to its 20% of the world’s population).
Second and equally importantly at a local and school level athletics is organized without regard to inherited physiological and physique differences. Since perceptions of athletic competence are shaped by how it is rewarded, the failure to adopt weight-lifting type divisions and correction coefficients could be a factor in limiting the uptake of exercise in India and China in young people. Promoting participation at an early age is critical in reducing diabetes rates since it predicts later adult exercise 9. Failure to factor out genetic variation could as a result be leading to an avoidable prevalence in these countries of exercise linked diseases such as diabetes.
Creating suitable divisions and using appropriate correction coefficients to do this however requires that scientists identify the genetic factors that affect track and field performance and calculate how they might be scaled to allow for them to be factored out. Such research is presently unfunded but it is possible. Limited research already shows for example that speed in the 100m dash scales with height 10. However this has been only shown with data involving elite athletes using world speed records10. This makes it only preliminary to creating the scaling coefficients needed for genetic-factor-natural and race-neutral athletics. However in principle given funding there is no reason why the physiological and physique factors involved cannot be identified and done so in the context of the full range of human variation and in regard to all athletic activities.
This is an unresearched area and one would hope that scientists across the world might collaborate in researching. If investigated such factors could allow athletes from the Olympics down to the school level to gain a positive and fair experience of their sporting potential that is unaffected by genetic differences—particularly that linked to geography.
1. Wild, S., Roglic, G., Green, A., Sicree, R. & King, H. Global prevalence of diabetes: estimates for the year 2000 and projections for 2030. Diabetes Care 27, 1047-53 (2004).
2. Wang, W. et al. Type 2 diabetes mellitus in China: a preventable economic burden. Am J Manag Care 15, 593-601 (2009).
3. Colberg, S. R. & Grieco, C. R. Exercise in the treatment and prevention of diabetes. Curr Sports Med Rep 8, 169-75 (2009).
4. Boule, N. G., Haddad, E., Kenny, G. P., Wells, G. A. & Sigal, R. J. Effects of exercise on glycemic control and body mass in type 2 diabetes mellitus: a meta-analysis of controlled clinical trials. Jama 286, 1218-27 (2001).
5. Gaesser, G. A. Exercise for prevention and treatment of cardiovascular disease, type 2 diabetes, and metabolic syndrome. Curr Diab Rep 7, 14-9 (2007).
6. Papaioannou, A., Bebetsos, E., Theodorakis, Y., Christodoulidis, T. & Kouli, O. Causal relationships of sport and exercise involvement with goal orientations, perceived competence and intrinsic motivation in physical education: a longitudinal study. J Sports Sci 24, 367-82 (2006).
7. Lintunen, T., Valkonen, A., Leskinen, E. & Biddle, S. J. Predicting physical activity intentions using a goal perspectives approach: a study of Finnish youth. Scand J Med Sci Sports 9, 344-52 (1999).
8. Shen, B. & Xu, C. Effects of self-efficacy, body mass, and cardiorespiratory fitness on exercise motives in Chinese college students. J Phys Act Health 5, 706-18 (2008).
9. Telama, R., Yang, X., Laakso, L. & Viikari, J. Physical activity in childhood and adolescence as predictor of physical activity in young adulthood. Am J Prev Med 13, 317-23 (1997).
10. Charles, J. D. & Bejan, A. The evolution of speed, size and shape in modern athletics. J Exp Biol 212, 2419-25 (2009).
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I agree with John Skoyles that it is valuable to encourage life-long exercise. He apparently agrees that there may be some group genetic differentiation that accounts for some of the outcome variation by groups in some athletic areas. To the extent that human diversity is good—which it is—group diversity, to the extent it adds to human diversity, is a good thing.
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