This paper by economist Joni Hersch has been getting a lot of play in the blogosphere (e.g. here and here). for apparently proving that, among immigrants to the United States, those with the lightest skin color earn 8 to 15 percent higher pay than those with the darkest possible skin, even after controlling for many other variables such as English proficiency, education, and years since arrival in the US. The skin color effects found in the study go beyond black vs. white differences, since they extend also to other nonwhite immigrant groups such as Indians and East Asians.
Hersch's study is well-designed and has some impressive data. But I nonetheless have reservations about it. In particular, it fails to control for two key variables that are highly correlated with skin color among immigrants: cultural similarity of the immigrant's country of origin with the United States and quality of education. These shortcomings do NOT prove that there is no skin color discrimination against nonwhite immigrants. But they do suggest that its effects may not be as large as the study claims.
I. Cultural Similarity.
Immigrants from majority white nations (primarily Canada, Australia, New Zealand, and various European countries) generally come from societies that are much more similar culturally to the United States than those from which most non-white immigrants originate. Cultural similarity makes it easier for immigrants to assimilate (which is surely a strong predictor of economic opportunity), and also to function effectively within US businesses. This point applies even to different immigrant groups of the same race. For example, immigrants from Western Europe or Canada have higher incomes, on average, than my fellow Russian immigrants, despite the fact that both groups are mostly white (even more so in the case of Russians than Western Europeans). This is in part because those countries' cultures and business practices are closer to those of the US than Russia's, so Western Europeans and Canadians can assimilate faster and more completely.
The author of the study could have partially controlled for this variable by, for example, checking to see if the results hold up if immigrants from Europe, Canada, and Australia/NZ are excluded. Note that controlling for English proficiency (as the author does) does not fully address this issue, because schools in many countries culturally very dissimilar to the US teach English as the primary foreign language covered in school curricula.
II. Quality of Education.
The study controls for quantity of education (years of schooling), but not for quality. Unfortunately, however, the majority-white nations that send immigrants to the US have, on average, much better education systems than most of the majority-nonwhite ones. An immigrant who got 12 years of schooling in Germany is probably much better educated than one who got 12 years in a third world nation. Moreover, even within particular countries, it is often the case that whites get better quality schooling than non-whites, in part because of historical discrimination against non-whites . This is certainly true, for example, in South Africa and many Latin American countries. Even employers completely indifferent to skin color could still rationally choose to take these quality differences into account. The author does note that part of the effect she observes may be due to discrimination in immigrants' home countries, but does not consider the ways in which this affects quality of education.
This effect is much harder to control for than cultural similarity. But it might be possible to take a stab at it by, for example, controlling for how well students from the immigrant's country of origin do on international comparisons of basic educational skills.
As noted above, these points do not prove that there is a complete absence of skin color discrimination against either nonwhite immigrants or other nonwhites. They do, however, suggest that the study's findings may be overstated.
I would be impressed if I saw a study showing that an average white immigrant from Russia with an IQ of 105 makes $x more than a black immigrant from Jamaica with an IQ of 105. Education is only a limited proxy for intelligence.
That said, if I had to guess, I would say that dark-skinned people, on average, are discriminated against in the workplace, still. It's just that this study fails to adequately narrow the gap to that portion of it which is accounted for by discrimination, and discrimination only.
There are many other characteristics that one would expect to lead to high wages: networking skills, work ethic, ambition, the list goes on and on. It would be almost impossible to control for them all.
Luckily, like intelligence, what they all have in common is there is no reason to think that they correlated to skin color. This is not like Ilya Somin's criticisms, where there is a logical case the uncontroled variables would cause a systematic bias.
I suggest that unless there is a plausible argument an uncontrolled variable would systematically bias a study in one direction one cannot complain that failure to control for it is a flaw casting doubt on the study's conclusion.
Average IQ correlates with economic level of nations; why not of immigrant groups?
It's not hard to believe that "racial" bias plays a role in the average income of new immigrants. What makes me skeptical of any study that "proves" this is the fact that immigrants from different regions tend to come with different skills. More South Asian immigrants are MDs and engineers than their peers from Latin America or Africa. Has anyone looked at average income differentials /within/ occupations?
"The Mismeasure of Man has been highly controversial. The popular and literary press have mostly praised the book, while most scientific journals have been critical.[4] Among psychologists, the reaction has been largely negative. Hans Eysenck's[5] review called the book "a paleontologist's distorted view of what psychologists think, untutored in even the most elementary facts of the science.""
Actually, here is the whole "criticisms" section from the wikipedia entry. Sorry, but it's pretty long:
http://en.wikipedia.org/wiki/
The_Mismeasure_of_Man#Criticisms
My impression is that we are getting very few immigrants from Europe and very many from Mexico and regions South. I know that the vast majority of those who come here from Mexico and other Latin American countries have as their primary skill a strong back and a willingness to work hard.
Luckily, like intelligence, what they all have in common is there is no reason to think that they correlated to skin color.
Don't be silly. Ignoring intelligence, it seems obvious that the other traits are correlated to skin color, because they're correlated to culture and *that* is correlated to skin color.
The theory of the post is that we'd expect Indians to have done better than those from the former Soviet Union, or at least to have been only marginally disadvantaged by racial difference. I'd be curious to see whether the numbers bore that out.
As an aside, my wife, a Russian Jew, recently interviewed for a position that she was more than qualified for. The first three interviewers all agreed she had the experience and qualifications. The last interviewer was an Islamic Middle Easterner that did not ask any pertinent questions to the position being applied for. My wife did not get the position and was told she was not qualified and what they were looking for. Possible discrimination or just bad interviewing practices? Who knows?
This means that it's not enough to say that majority-white countries are more similar to the US or have better education systems. In order to explain Hersch's result based on country of origin, we have to say that within majority-white countries, the darker ones are less attuned to the US culture and have worse schooling. The same has to be true for majority-Asian and majority-black and majority-Hispanic countries as well. (Right? Is there something I'm missing?)
Now I don't think is an implausible story. It might help to explain the "somewhat surprisingly" pronounced association between skin color and race for non-Hispanic whites (page. 13). I would guess that "paleness" is really picking up "Northern-Europeaness."
Criticism by opponents doesn't, per se, make something "suspect" or "discredited". It just makes it "controversial", which is, in fact, the term Wikipedia uses.
Apparently whites and blacks have pretty much the same preferences in skin color. They both prefer a skin color something like that of Hale (sp?) Berry.
Of course this is a statistical generality and was the result of a survey about people in the US. However, I believe it is also well documented that their is considerable discrimination in africa against those who have darker skin. Not to mention the serious colorism in places like India.
The upshot of all this is that I don't find this result surprising in the slightest. We know that taller people and more attractive people earn more money when we control for everything else. If you are attractive and appealing you are going to make a better impression in the interview. Given that at least a large fraction of the world views lighter colored skin as more attractive, including people in the states it is totally unsurprising that people with lighter colored skin end up doing better.
It's of course unfortunate but I can't think of anything you can do about it. I'm also not sure if it is particularly worse than the income benefit taller people get.
If the criticism were, in fact, from the entire scientific community, or even a strong majority, I'd certainly agree with you (global warming, anyone?). But the Wiki article included criticism from people like Jensen and Eyseneck, which is somewhat like asking Bill O'Reilly what he thinks of Keith Olberman (or vice versa).
To be clear, I'm not insisting that Gould was right, just that this area of research is not at the stage where people can make definitive claims (his included).
I certainly hope it did, but I'm never surprised anymore if a study overlooks a simple factor.
Nick
Just to be clear, in case you dont want to click the link, we are talking about "meta-analysis of 127 studies involving 20,352 participants."
I read the link. I wasn't impressed with it as science. It did have some interesting political views, though.
Nick
markm -- That makes sense. But do note that I said "associated with" and not "caused by."
The nonwhite sending countries with strong educational systems (South Korea, Japan, Taiwan), also tend to have citizens with relatively light skin (although not as light as whites). So they will tend to reinforce the study's finding that lighter-skinned immigrants do better.
Further, some nonwhite immigrant populations, such as those from India, are heavily weighted with the highly educated, while those from Eastern Europe are not.
I am skeptical that this is more true for India than for Eastern Europe (to say nothing of Canada and Western Europe). A high proportion of the Eastern European immigrants are Russian Jews who are, on average, the most highly educated group in their country of origin.
Yes, but she found no such within-race effect among blacks, only among Hispanics and Asians.
This means that it's not enough to say that majority-white countries are more similar to the US or have better education systems. In order to explain Hersch's result based on country of origin, we have to say that within majority-white countries, the darker ones are less attuned to the US culture and have worse schooling. The same has to be true for majority-Asian and majority-black and majority-Hispanic countries as well.
As I pointed out in the post, it is often the case that darker-skinned people within a given country have worse schooling than lighter-skinned ones do because of discrimination, and may also be more culturally divergent from the US. THis is certainly true in Latin America. In Asia, the countries with mostly lighter-skinned people (Japan, Korea, Taiwan), tend to have better educational systems.
Finally, as Hersch notes, the effect does not hold up for black immigrants.
Sorry, I worded my last post poorly. What I meant was that I didn't consider the study cited to be determinative of a consensus scientific viewpoint. One study is just one study.
Again, I'm not contending that the study is wrong or that Gould is right. I'm only asserting that our scientific understanding of this issue is still at an early stage, and that it's too early to claim that either side is "debunked" or "discredited".
It's true that there was no statistically significant relationship between darkness and wages for black immigrants, but it's also true that her point estimate for blacks is of a similar magnitude as those for Asian and Hispanic immigrants.
For me, the most interesting part of her results is that the group with the largest association between skin color and decreased wages is white immigrants. Can anyone think of a plausible story for why that would be true? I would guess that it's a functional form issue. Assuming that there is some sort of discrimination at work here, maybe the first few gradations of skin tone are more important for wage outcomes (i.e. the dropoff between "white" and "almost white" is steeper than the drop off between "really dark" and "really really dark"). If this is true, then I think the coefficient on skin color should be higher for whites, since their variation in skin color is measured from the lowest baseline and their skin tones are therefore more likely to fall in the range where the effect is larger.
I am tentatively impressed with Professor Somin's suggestion that what might be called 'cultural readiness' is important.
That might explain the well-known higher success rate of West Indian black immigrants to the US compared with US-born blacks.
The skin colors are indistinguishable, and -- whatever the ravings of some of the racists here -- the native intelligence must be the same. It is even arguable, I'd say, that West Indians, though foreigners, come in with cultural values closer to those of the (mostly white) people who make employment decisions than the native-born blacks have.
It is more the case of the character and professional assasination of scientist who was controversial, really pissed off the religious right, and was able to communicate effectively to lay audiences. Because his theories were unorthodox and he wrote bestsellers and was the go-to guys for television interviews and newspaper and magazine articles, he engendered both professional criticism and jealousy. He also was also willing to take on the religious right on the issue of creationism, so was hardly popular with them. He was also a socialist.
So since his death, the villification of everything he ever said or did has reached a fever pitch and is largely unfair. The Mismeasure of Man recounted the sloppy science that justified the eugenics movement. As for IQ, it is a ridiculous assertion that one number from one test can measure something as complex as human intelligence.
The median salary of recent russian immigrant family is $59,000, the median family salary of every other immigrant group, (including Indians) is $35,000.
Source here
The source is in russian, and it is a translation of a French study
Anne de Tinguy. «La grande migration. La Russie et les Russes depuis l'ouverture du rideau de fer» — Paris: Plon, 2004, 662 pp
This is the paragraph Vovan relies on. Indeed, seems to check out, (and also seems to confirm my intuition).
According to these statistics the median family income of indian-americans is $61,322.
However, unlike the previously cited study, these statistics apparently do not distinguish between recent, and мultiple-generation immigrants.
Однако, индусы умнее нас будут...нехорошо...
Do you mean that the median income of an Indian immigrant family is $25000?
Other information relevant is this study from the NY fed of immigrants to NYC in the 90's. Immigrants from the Indian subcontinent made $21,900/year and immigrants from the former Soviet Union made $25,000/year despite the fact that immigrants from the Indian subcontinent were more likely to be fluent in English. Although the immigrants from the former Soviet Union were more likely to have graduated from college, education level was controlled for in the skin color study. So, despite being more culturally similar, immigrants from the Indian subcontinent were paid less.
While the Fed report did not test the skin color- income link or control for a host of confounding variables, it is consistent with the conclusion that darker skin, all things being equal, will result in lower earnings for immigrants. It is also in conflict with Prof. Somin's alternative hypothesis.
http://www.newyorkfed.org/research/current_issues/ci11-6.pdf
Mike, I would assume that the majority of the Russian immigrants surveyed were at least partially Jewish, so unless you are looking for regional distinctions (Buharian versus Ukrainian), that's probably as best a study as you can get.
As far as Steven Jay Gould is concerned, both he and his critics have their own agendas but here the question is a very narrow one. We already know IQ differences start appearing between individuals at early ages and tend to persist and diverge over time. In other words, IQ emerges long before individuals enter the labor force. To the extent there is a correlation between IQ and earnings (and it is not accounted for by controlling for education or socioeconomic status), IQ is in fact capturing useful information about the ability of someone to succeed in a modern, capitalist economy. Socialists like Gould may not think that the ability to succeed in a capitalist economy is important, but that is exactly what this paper is trying to measure.
People who think that IQ is "mismeasuring" ability are welcome to come up with alternative measures of ability that are better predictors of economic outcomes. Until then, IQ belongs in these regressions and not including it is sloppy.
In fact, a paper came out a while ago showing that much of the evidence of height discrimination goes away when you control for IQ. The reason is that as a statisical matter, IQ and height are positively correlated so when you omit IQ from your regression, you wind up with spurious correlation between height and earnings.
The paper I referred to is Case and Paxson which you can download at http://www.nber.org/papers/w12466 if you have academic access to NBER's website.
Here's the abstract:
It has long been recognized that taller adults hold jobs of higher status and, on average, earn more than other workers. A large number of hypotheses have been put forward to explain the association between height and earnings. In developed countries, researchers have emphasized factors such as self esteem, social dominance, and discrimination. In this paper, we offer a simpler explanation: On average, taller people earn more because they are smarter. As early as age 3 — before schooling has had a chance to play a role — and throughout childhood, taller children perform significantly better on cognitive tests. The correlation between height in childhood and adulthood is approximately 0.7 for both men and women, so that tall children are much more likely to become tall adults. As adults, taller individuals are more likely to select into higher paying occupations that require more advanced verbal and numerical skills and greater intelligence, for which they earn handsome returns. Using four data sets from the US and the UK, we find that the height premium in adult earnings can be explained by childhood scores on cognitive tests. Furthermore, we show that taller adults select into occupations that have higher cognitive skill requirements and lower physical skill demands.
The study does control for level of English proficiency.
Yes, education level was controlled for in the skin color study, but not in the figures from NY fed study that is cited to demonstrate relative incomes as between Indian and Russian immigrants. Once the higher education levels of the latter are controlled for, the income differences between them might disappear.
But I await your explanation of the overplus of dark athletes in elite competition.
To state that IQ is correlated to race is to state a fact. To state that inherent congative potential is correlated to race is to make a statement that is by definition racist, whether it is true or not.
Regardless of whether you mean "intelligence" to convey this meaning, it is likely to be read this way.
This is disingenuous. We both know very well that that is not the definition typically meant when people are accused of racism in the context of politics.
Belief that another race is mentally inferior is not racism? I quite genuinely disagree.
The Hypothetical:
While IQ may be highly predictive of economic performance, my understanding is that it is still somewhat ambiguous what it measures and why it is so predictive. Critics of IQ tests will often claim that one of the things the tests measure is distance from and knowledge of a particular social or cultural milieu. This milieu is invariably claimed to be a white one, so the argument continues that this aspect of the test will correlate well with race.
Now presume that employers do not care about the cultural milieu factors that affect the test, but they do discriminate by race. Because the two are corelated, the test would still be predictive of economic performance (moreso than a test that somehow measured only the other aspects of IQ), but it would be predictive partly for the reason that it aproximates the results of racial discrimination.
Now if all of this is true, wouldn't controlling for IQ then factor out some of the discrimination that the researcher is trying to find?
Back to why WHITE immigrants earn more if they are whiter and less if they are slightly tan... Isn't country of origin a good explanation? The palest white people come from some of the richest countries on the planet, which also happen to be culturally similar to the US, and the white people with the best tans come from the Middle East and North Africa.
The exception seems to be Eastern Europeans, who can be very pale but may also come from impoverished rural societies. But I would bet that the poorest Eastern Europeans don't have the resources to make it all the way to the United States. They probably get to the richer European Union countries at most (and why not?), so that Eastern Europeans in the US may be from more elite backgrounds than Eastern European emigrants generally.
To state that ANYTHING is correlated by race is, by definition, racist. ANYTHING. "Racism" meaning, "to discriminate by race", and "discriminate" is lacking it's negative connotations.
To state that "inherent cognative potential" is correlated to race is only BIGOTED (a common meaning of "racism") if is it UNTRUE.
In short, the above quote makes no sense whatsoever. They are either BOTH racist statements, or the second is only racist is UNtrue, depending on which definition of "racist" you are using (discriminating by race, which ALL race studies inherently do, or BIGOTED by race, which I think we all agree is a bad thing).
Some people want to have their cake and eat it, too, on this topic. It just doesn't work that way.
One more point: it seems highly likely that, as a group, "races" would have at least slightly varying "inherent cognative potential"; a "race" is nothing more than a shared genetic ancestry, and to think that that would only affect physical appearance is, well, stupid.
Each INDIVIDUAL should be judged as an individual, but "racial" groups will likely have measurable differences in MANY areas, from physical talents to mental ones. To think it would only affect physical traits is scintifically unsound.
Yet another reason why I wish these RACIST studis would just not be done. The sooner we STOP grouping people by "race", the sooner people will stop being bigoted by race. That is to say, I think focusing on the problem provides some minor short term gains, but is, in the long run, HIGHLY counterproductive.
A.C. -- this makes sense, but does it explain why the coefficient on skin color is larger for whites than it is for other races? The interesting question for me isn't why there is an association between color and earnings for whites--it's why this association is stronger for whites than it is for other race.
You know what else correlates with height--better nutrition. You know what else correlates with better nitrition, higher intelligence. Who'd a thunk.
As for all of you who thinks that the correlation between high IQ and higher earnings think this proves that IQ actually does measure intelligence (and I am sure you are all certain that you think that you are much smarter than most people and have the IQ test scores to prove it), apparently IQ doesn't measure the ability to think logically or to recognize circular reasoning. So let me spell it out for you.
There is no doubt that IQ tests do measure some aspects of human intelligence. Those aspects that they measure are pretty good indicators of how well you will do in our system of education. Success in our system of education is a pretty good indicator of financial success. Therefore a high IQ would correspond with success in school and a good job. But it doesn't prove a thing other than it is a good test for measuring what it was designed to measure.
Although deoxy is on the side of the angels, the statement 'to think that [purported race differences] would only affect physical appearance is, well, stupid.'
This reflects a common misunderstanding. Even if it is more likely that a random male in Holland or Uganda will be more than 7 feet tall, the genetic capacity to be 7 feet tall is the same in all populations. Same for any other trait.
In Hawaii, before there were any European immigrants, there was a word, ehu, (red) to describe people who were not dark-skinned and black-haired.
More Americans are named Smith than anything else, but we do not speak of a racial tendency to be named Smith.
IQ tests measure how well you do on IQ tests. Nothing more.
Now who is being naive? Are you saying that all populations, whether black, white or asian, have the same genetic tendency to possess, say, brown skin, or suffer from tay sachs disease, or develop relatively better immunity to malariia? Grow up.
I'm agnostic, and don't take offense on behalf of Jesus, Buddha, Mohammed, etc., but the lack of consistency really reveals a hypocrisy.
I'm not a psychologist and so cannot comment on whether there is "proof" that IQ measures intelligence without a rigorous definition of intelligence. I am an economist and I can tell you that IQ does correlate to earnings when we control for lots of other things. The correlation is imperfect but it is definitely there.
There is no doubt that IQ tests do measure some aspects of human intelligence. Those aspects that they measure are pretty good indicators of how well you will do in our system of education. Success in our system of education is a pretty good indicator of financial success. Therefore a high IQ would correspond with success in school and a good job. But it doesn't prove a thing other than it is a good test for measuring what it was designed to measure.
Since you've already conceded the point that IQ does measure intelligence, even if it is an error-prone and imperfect measure, what's the point you are trying to make in this paragraph? If success in school leads to job market success for reasons entirely unrelated to intelligence then you are right that the correlation between IQ and earnings doesn't tell us anything. However, I don't find that a plausible assertion at all. Note there are lots of reasons why some poeple make more money than others: your implicit claim is that intelligence -- or at least that part of intelligence measured by IQ -- is not one of them. That's a pretty strong assertion.
When you control for intellectual ability, a Harvard graduate does not make much more money than a state university graduate. Additionally, we know that IQ explains some amount of earnings differentials between people with the same years of schooling.
But if you learned genetics from wikipedia, I can see why you would not know the difference.
But I await your explanation of the overplus of dark athletes in elite competition...if you learned genetics from wikipedia, I can see why you would not know the difference.
It may be useful to learn genetics from a journal, say Science.
http://www.sciencemag.org/cgi/content/full/305/5684/637
Peering Under the Hood of Africa's Runners
Constance Holden
Kenyans dominate endurance running, and West Africans excel as sprinters. With a physiological explanation in hand, researchers are now probing the genetics of this geographic mastery
In 1968, a Kenyan runner named Kip Keino emerged as a shining star of the Mexico City summer Olympics, setting a world record in the 1500-meter race. Year after year Keino's success has been followed by equally dazzling feats by his compatriots: Kenyan men now hold world records in the 3000-meter track race, the 15-, 20-, and 25-kilometer road races, the half-marathon, and the marathon. Kenyan men have won 13 of the last 14 Boston marathons. Kenyan women are also rising fast: They hold half of the top 10 marathon times and world records in 20-, 25-, and 30-km track races. What is even more remarkable is that most of these athletes come from a small area in Kenya's Rift Valley, from a group of tribes called the Kalenjin who number little more than 3 million people.
Figure 1
Running revolutionary. Kenya's Kip Keino in 1972.
CREDIT: BETTMANN/CORBIS
Theories abound about what Kenya-born writer and runner John Manners calls "the greatest geographical concentration of achievement in the annals of sport." Is it the high altitude that fosters big lungs and efficient oxygen use? Is it their maize-based diet? Or the fact that many children run to school? A grueling training regimen, perhaps?
Such questions have inspired a handful of researchers to try to define the Kenyan magic. Meanwhile, scientists are unraveling why athletes whose ancestors come from the other side of the continent--West Africa--have emerged as the world's fastest sprinters.
Fuel economy
Leading the charge in penetrating the Kenyan mystique has been Bengt Saltin, a Swedish physiologist who heads the Copenhagen Muscle Research Centre in Denmark. In the 1990s, Saltin's group began comparing Kenyan and Scandinavian runners by scrutinizing their physiological makeups and assessing the "trainability" of novice runners in both countries.
A decade later, the scientists have ruled out most of the popular explanations for Kenyans' domination of running. Altitude is not the key to the riddle, they have found, because there's no difference between Kenyans and Scandinavians in their capacity to consume oxygen. And the Kenyan diet is on the low side for essential amino acids and some vitamins as well as fat, says Dirk Christensen of the Copenhagen center: "In spite of the diet, they perform at high level." The running-to-school hypothesis was demolished as well: Kenyan children aren't any more physically active than their Danish peers. Do Kenyans try harder? The researchers found that the Danes actually pushed themselves harder on a treadmill test, reaching higher maximum heart rates.
An important clue is the ability of Kenyans to resist fatigue longer. Lactate, generated by tired, oxygen- deprived muscles, accumulates more slowly in their blood. Comparisons of lactate levels have suggested to Saltin's group that Kenyan runners squeeze about 10% more mileage from the same oxygen intake than Europeans can.
Just as more aerodynamic cars get better gas mileage, the Kenyan build helps explain their fuel efficiency. A recent British TV documentary described the Kalenjin as possessing "birdlike legs, very long levers that are very, very thin [on which they] bounce and skip" along.
Saltin's group has quantified this observation. Compared with Danes, the thinner calves of Kenyans have, on average, 400 grams less flesh in each lower leg. The farther a weight is from the center of gravity, the more energy it takes to move it. Fifty grams added to the ankle will increase oxygen consumption by 1%, Saltin's team calculates. For the Kenyans, that translates into an 8% energy savings to run a kilometer. "We have solved the main problem," declares Henrik Larsen of the Copenhagen center. "Kenyans are more efficient because it takes less energy to swing their limbs." Other scientists say the jury is still out on the Kenyan question. But "I think Saltin is probably the most correct that anyone is at the moment," says physiologist Kathryn Myburgh of the University of Stellenbosch in South Africa, who is exploring the role of Kenyans' training.
Figure 2 Triumph of fast twitch. Carl Lewis, a U.S. sprinter with West African roots, winning the 400-meter race at the 1992 Olympics in Barcelona.
CREDIT: JEAN-YVES RUSZNIEWSKI/TEMPSPO
However, slim lower legs are not the whole story. Kenyan runners also have a higher concentration of an enzyme in skeletal muscle that spurs high lactate turnover and low lactate production. Saltin says that this results in an "extraordinarily high" capacity for fatty acid oxidation, which helps wring more energy out of the muscles' biochemical reactions. Because intense training alters the body's biochemistry, Saltin says that he can't say for sure whether the ezyme levels are due to genes or training. But he adds, "Ithink it's genetic."
Research in South Africa jibes with the Copenhagen group's findings. A team led by exercise physiologist Adele Weston of the University of Sydney, Australia, compared black South Africans, whose running strengths are similar to those of Kenyans, with white runners. The two groups had similar VO2 max values--that is, when putting out maximum effort, they used up the same amount of oxygen per kilogram of body weight per minute. But the black runners were more efficient in their oxygen consumption, lasting on a treadmill at maximum speed for twice as long as the whites. As with the Kenyans, the black South African runners accumulated less lactate and had higher levels of key muscle enzymes.
A little more twitchy
Whereas East Africans dominate long- distance running, West Africans have surged to the fore in short-distance events. Little research has been done on West Africans, but there's powerful circumstantial evidence for some physical advantages, as presented by Jon Entine in his book Taboo: Why Black Athletes Dominate Sports and Why We're Afraid to Talk About It. Athletes of primarily West African descent--which includes the majority of U.S. blacks--hold all but six of the 500 best times in the 100-meter race, "the purest measure of running speed," says Entine, whose book set off a broad debate on the subject.
Various studies have shown that West African athletes have denser bones, less body fat, narrower hips, thicker thighs, longer legs, and lighter calves than whites. But the differences between East and West Africans are even more striking. The fabled Kenyan runners are small, thin, and tend to weigh between 50 and 60 kilograms, whereas West African athletes are taller and a good 30 kilograms heavier, says Timothy Noakes, a prominent exercise physiologist and researcher at the University of Cape Town.
Figure 3 Out of East Africa. In less than 2 decades, Kenyans came to dominate the top 20 performances in six races ranging from 800 meters to the marathon.
CREDIT: HENRIK B. LARSEN, J. COMP. BIOCHEM. PHYSIOL.
The differences don't stop with body shape; there is also evidence of a difference in the types of muscle fibers that predominate. Scientists have divided skeletal muscles into two basic groups depending on their contractile speed: type I, or slow-twitch muscles, and type II, fast-twitch muscles. There are two kinds of the latter: type IIa, intermediate between fast and slow; and type IIb, which are superfast-twitch. Endurance runners tend to have mostly type I fibers, which have denser capillary networks and are packed with more mitochondria. Sprinters, on the other hand, have mostly type II fibers, which hold lots of sugar as well as enzymes that burn fuel in the absence of oxygen. In the 1980s, Claude Bouchard's team at Quebec's Laval University took needle biopsies from the thigh muscles of white French Canadian and black West African students. They found that the Africans averaged significantly more fast-twitch muscle fibers--67.5%--than the French Canadians, who averaged 59%. Endurance runners have up to 90% or more slow-twitch fibers, Saltin reports.
Bouchard, now at Louisiana State University in Baton Rouge, says his team looked at two enzymes that are markers for oxidative metabolism and found higher activity of both in the West Africans, meaning they could generate more ATP, the energy currency of the cell, in the absence of oxygen. The study suggests that in West Africa there may be a larger pool of people "with elevated levels of what it takes to perform anaerobically at very high power output," says Bouchard.
Although training can transform superfast-twitch type IIb fibers into the hybrid type IIa, it is unlikely to cause slow- and fast-twitch fibers to exchange identities. Myburgh says there is evidence that, with extremely intensive long-distance training, fast IIa fibers can change to slow type I fibers. So far, however, there is no evidence that slow-twitch fibers can be turned into fast-twitch ones. As an athlete puts on muscle mass through training, new fibers are not created, but existing fibers become bigger.
Figure 4 Road Test. Masks monitored Kenyans' oxygen use.
CREDIT: THOMAS NOLAN
Running ACEs
The differences in physique and muscle makeup that underlie the dominance of Kenyan endurance runners and West African sprinters doubtless have a strong genetic component. But researchers are only just getting off the starting mark in the search for genes that influence running performance. Bouchard's group, for example, is collecting DNA samples from 400 runners and other top endurance athletes from the United States and Europe, but he says they haven't spotted any running genes yet.
There are a couple of intriguing possibilities, though. In 1999, a team headed by Kathryn North of the Children's Hospital at Westmead in Australia described two versions of a gene that affects production of name-actinin-3, a protein found only in fast-twitch muscles. They found the less efficient version of the gene--which results in poorer energy conversion--in 18% of the members of a group of Caucasians. In 2003, North's group reported in the American Journal of Human Genetics that only 6% of a group of sprinters had the gene defect; 26% of endurance runners had it. The authors surmise that name-actinin-3 helps muscles generate "forceful contractions at high velocity."
Alejandro Lucia Mulas of the European University in Madrid is taking DNA samples from Eritrean runners to explore another candidate: different versions of the gene for angiotensin-converting enzyme (ACE). Lucia says the less active version, or I allele, of this gene is associated with less muscle, less fluid retention, and more relaxed blood vessels--which would enhance oxygen uptake--and appears to be more prevalent in endurance runners.
And in Scotland, sports physiologist Yannis Pitsiladis has launched a major onslaught on the Kenyans' secrets with the International Centre for East African Running Science. Headquartered at the University of Glasgow, the virtual center will bring together research on demography, diet, and socioeconomic factors as well as genes. Pitsiladis says he has spent the last 3 years in East Africa collecting DNA samples from their "living legends" and now has DNA from 404 Kenyan and 113 Ethiopian athletes. His team has found a higher prevalence of the I allele for the ACE enzyme in male marathoners compared with men from the general Ethiopian population. But Pitsiladis thinks his numbers may lack significance given the variability of the trait in African populations. "At the moment there is no evidence" that East Africans have a genetic advantage in running, he says.
None of the data negate the importance of cultural habits and training. But as Entine quotes anthropologist and sports science expert Robert Malina, who is retired from Michigan State University, "Differences among athletes of elite caliber are so small that if you have an advantage that might be genetically based ... it might be very, very significant."
Next month's Olympic games in Athens should demonstrate yet again that West African runners are built for speed and Kenyans built to endure.
Not only is there a meaningful difference between capability and tendency, but also between range and average. Sheesh.
No, it is NOT the same for "any other trait" - there are traits NEVER witnessed outside of certain populations.
Not to mntion that this ENTIRE THREAD is about group tendency, SPECIFICALLY not "genetic capacity".
Sveral commenters (myself included) have spcifically said that each individual should be judged individually, but IF you group by "race", each group will have strnegths and weaknesses compared to the others.
In other words, "capacity" is entirely irrelevant to this conversation.
Hey, you do whatever make syou happy, eh? But please, if it's completely irrelevant, go do it somewhere else.
If you can find one, it won't be under genetic control.
Anyhow, I have two words for random geneticist: Lasse Viren
If you do, it may or may not be expressed.
You and random geneticist are badly confused about what genes do and how they work.
There is no trait found in Kenya that is not found in Sweden and vice versa.