What ethnic groups are most likely to be lactose tolerant? As I wrote in my book, Milk Is Not for Every Body: Living with Lactose Intolerance, northern and western Europeans and various African tribal groups who live along the fringes of the Sahara and the Sahel deserts are the groups least likely to get symptoms from drinking milk. They - or their ancestors, who are also likely to be ancestors of many people in the U.S. - grew up in milk-drinking cultures, where the ability to digest milk as an adult gave people a slightly better change to survive and bear more children.
One thing most people would quickly notice is that northern Europeans are among the lightest-skinned ethnic groups and the African tribal peoples are among the darkest. They're of two different races in the usual cultural sorting of race.
Genetically, however, they share a mutated gene that puts them both in the minority of humanity.
There's a real problem with using skin color as a separator of peoples. The extremes may be instantly noticeable, but the fringes overlap in many ways. And skin color is just another product of your genetic underpinnings, one of many, possibly thousands. So what sense can it possibly make to divide race by this particular set of genes rather than a different set of genes, like the one that controls lactase production?
That's a question Sharon Begley asks in her Newsweek blog.
She also uses the lactase gene as an example, among others:
But how you group people depends on which traits you focus on: sorting people according to one set of traits produces different groupings than sorting them by different but equally valid traits.
Say you decide that the distinguishing trait is the gene for hemoglobin. If you divide humankind by which of two forms of the gene each person has, then equatorial Africans, Italians and Greeks fall into the “sickle-cell race;” Swedes and South Africa’s Xhosas (Nelson Mandela’s ethnic group) are in the healthy-hemoglobin race. Or how about dividing humanity by who has epicanthic eye folds, which produce the "Asian" eye? Then the !Kung San (Bushmen) belong with the Japanese and Chinese. Or say you sort humanity by the presence of the lactase gene. Then Norwegians, Arabians, north Indians and the Fulani of northern Nigeria are in one race, while everyone else—other Africans, Japanese, Native Americans—forms the no-lactase race. Depending on which trait you choose to demarcate races, “you won't get anything that remotely tracks conventional [race]categories,” anthropologist Alan Goodman told me back then.
That’s why Venter and colleagues conclude that race is too crude a proxy for what genetic group—ethnicity or, as biologists say, population—someone belongs to. It is imperative to “go beyond simplistic ethnic categorization,” they write, since that can be seriously—and perhaps fatally—misleading. (In the U.S., some 100,000 people a year die of adverse drug reactions, many caused by an inability to properly metabolize the medication because of a particular CYP2D6 variation.) “Race/ethnicity should be considered only a makeshift solution for personalized genomics because it is too approximate,” they write.
It's way too simple and simplistic to say that your are your genes (although that's about a million times as sensible as saying that you are your blood type.) Being lactose intolerant doesn't need to cut you off from all dairy and many people perfectly capable of having dairy without symptoms choose to be vegans.
The opposite of that - saying that you are nothing but what you genes make most visible - is equally simplistic, if not downright moronic.
The next time you hear someone make a case for judging people by the color of their skin, think of lactose intolerance. And tell the racist to shut it.