Back in 1997 I was spent Easter Sunday with a good friend. His brother, who lived in the La Jolla area of San Diego, hosted us for dinner. On the drive up the La Jolla ridge overlooking the Pacific, my friend pointed over to the right side of the road and said, "That's Junior Seau's house." I caught a glimpse of number 55, along with what looked like a dozen family members filing out of a couple vans in front of the house. They were the largest human beings I had ever seen. The women were large, the men were unimaginably large, and even the children seemed enormous. Junior somehow appeared to be the runt of the family. I got the impression Samoans were all giants.
Last season there were 30 NFL players of Somoan descent, and 200 more playing Division IA college football. (Here's a list from 2008.) That's a lot of players from a group of people whose entire population could easily fit into an NFL stadium. Earlier this year 60 Minutes aired a profile on Samoan football, and if you missed it it's a great story. (I've embedded the clip at the end of this article. Edit--CBS has killed the link.)
Undoubtedly, the culture and character of the Samoan people are factors in their disproportionate level of success in football. But, as my drive through La Jolla suggested, hereditary traits may also play a role. Still, how can a single small island produce so many top players?
Like almost all human traits, the things that make a great football player great, like size, strength, speed or aggressiveness, conform to a normal distribution, also known as the bell curve. Normal distributions all share a certain shape in which there are lots of people near the average and steadily fewer people toward each extreme, known as the "tails" of the distribution.
Suppose there are two different populations of people, and they had nearly identical distributions of a certain characteristic. Their only difference was that each population's average differs by a relatively small amount. If one population is, on average, only slightly larger, stronger, or faster than the other, there will be nearly the same number of people from each population around their average values. The graph below plots the distributions of such a scenario. The x-axis represents the level of any characteristic of interest, and the y-axis represents the proportion of a population that possesses that characteristic at that level.
You'd think that there would be a correspondingly slight difference among each population's elite, but that's not the case. A slight difference in the average value of a characteristic means there will be extreme differences in the tails. Notice that as we zoom in on the right tails of the distributions, the further out the tail we go, the more drastic the difference:
For example, men and women have different average heights. In the US, the average man is about 8% taller than the average woman. But at 5'10" there are 30 men for every woman, and at 6'0" there are 2,000 men for every woman. In other words, a just 1.08 : 1 ratio of averages translates into a 2000 : 1 ratio of men to woman at 6-feet. The point is, a relatively small difference in the average value of a characteristic can result in drastic differences in the proportions of populations toward the tails.
If, on average, Samoans are only slightly stronger, faster, or anything else considered good for football than the rest of us are, we'll see vastly disproportionate outcomes in the right tails. And the right tails are where NFL players come from.
Further, even if two populations share the same average value of some characteristic, a difference in variance would cause the large disproportions in the tails. In other words, the more "spread out" a distribution is, the fatter the tail will be and the more likely there will be outliers.
As we zoom in on the right tails again, we see a disparity in the number of outliers within the respective populations.
When there is a combination of both effects, a difference in averages and a difference in variances, the effects are multiplied and the resulting disparities can become extreme. I suspect that's part of the story of Football Island, and there's a broader lesson here too.
Samoans probably aren't much different than the rest of us, and in fact, no particular group of people are really that different from another group. There may truly be slight differences among groups, but they are probably quite small. When we focus on the extremes of the distributions, either in the right tail, where we get our superstars in athletics or any other field, or in the left tail, where we see the less successful elements of society, we're likely to form misleading impressions. Not to sound too preachy, but perhaps some part of our prejudices are largely the result of a mathematical property of nature.