Are Human Beings Alike Or Different? The Evidence Is In, But It's Hard To Talk About

The human sciences are in a paradoxical situation. Vast quantities of new data are pouring in, particularly from the exponential improvements in genome sequencing. Yet theorizing about what the new data imply has seldom been more career-threatening—as the fates of James Watson and Larry Summers show.

Perhaps not surprisingly, the May 10, scientific conference on "Evolution, Culture, and Human Behavior" at UC Irvine, which brought together leading theorists for a day of presentations centered around the debate over human uniformity vs. human biodiversity, flew under the radar. It needed only a single normal-sized classroom.

Still, the few dozen spectators included an honor roll of prominent figures in the human sciences.

For example, Leda Cosmides, the co-developer of the field of evolutionary psychology. Also: John Hawks, the young anthropologist from the University of Wisconsin, whose remarkably broad range of expertise, from the oldest bones to the latest statistical techniques for genetic analysis, has quickly made him a star science blogger.

Hawks is already a strong prose stylist. If he continues to improve, he could someday fill the job of the human sciences' Public Sage—a role for which such luminaries as Stephen Jay Gould, Edward O. Wilson, Richard Dawkins, and Steven Pinker have competed.

And in attendance: Gregory Cochran. In evolutionary theory over the last decade, Cochran has been the straw that stirs the drink—as slugger Reggie Jackson described his function on the tumultuous 1970s Yankees baseball team. (Here's the unofficial Cochran Fan Site.)

There were four main speakers:

  • Shinobu Kitayama, director of the Culture and Cognition Program at the University of Michigan.

Kitayama discussed the sizable differences in personality between Americans and Japanese. Just as the stereotype would suggest, Americans are more independent; the Japanese more interdependent. Americans like to feel individually in control of the situation; the Japanese are happiest when their group is cohesive.

Interestingly, the Japanese on the northernmost island of Hokkaido generally fall midway between the Japanese and American norms. Kitayama speculates that this is related to Hokkaido having been a wilderness frontier, not settled until the late 19th Century, rather like the United States.

Bouchard explained that the state of the art in twin and adoption studies shows that IQ is highly heritable. Remarkably, the heritability of IQ goes up as we age. Identical twins who grew up together tend to become more alike in IQ when they are adults living apart than when they were children in the same home.

The conference was organized and emceed by UCI professors


  • Robert Moyzis, one of the co-authors of the late 2005 paper "Global landscape of recent inferred Darwinian selection for Homo sapiens" [PDF], which listed 1,800 genes that have been under varying selection pressure in Africa, Europe, or East Asia over the last 50,000 or so years. This shattered the conventional wisdom that Darwinian selection had somehow ceased to operate on the human species when our ancestors first left Africa. The data now suggests what common sense always implied—that when humans dispersed out of the tropics, the new environments they encountered, such as cold weather, led to important degrees of racial diversification.

The central argument of the conference turned out to be between the other two speakers, the prominent anthropologists, Henry Harpending of the University of Utah and John Tooby of UC Santa Barbara over, in effect, whether diversity or uniformity best characterizes humanity.

Harpending spoke first on the accumulating evidence that human evolution has actually accelerated since we came out of Africa, especially after the invention of agriculture. This was proposed by Harpending, with Cochran, Moyzis, Hawks, and Eric T. Wang, in their important December 2007 paper "Recent acceleration of human adaptive evolution", [PDF] which appeared in the Proceedings of the National Academy of Sciences

For example, Harpending suggested that the prehistoric spread of Indo-European languages across a huge swath of Eurasia from India to Ireland might have been made possible by a beneficial genetic mutation for "lactose tolerance." This allows many adults in this region to drink milk without gastro-intestinal discomfort. In the right terrain for dairying, a tribe whose adults can get much of their nourishment from the milk of cattle or goats has a big competitive advantage over tribes that can't—perhaps allowing the Proto-Indo-European-speaking milk drinkers to impose their language and spread their useful gene.

By the way, a "lactose tolerance-centric" theory of world history was put forward by the Irish dairy farmer-turned-economist Raymond D. Crotty in his ambitious but little known 2001 book When Histories Collide: The Development and Impact of Individualistic Capitalism. (It hasn't been published in the U.S., but you can read part of it on Google Books. And here is a brief summary.) Crotty attributed the medieval rise of property rights and the rule of law in Northwestern Europe to deep roots going back to the type of European agricultural society made possible by the evolution of lactose tolerance.

In contrast, John Tooby, co-founder of evolutionary psychology with Leda Cosmides, who is his wife, countered Harpending's emphasis on human biodiversity with their Gray's Anatomy Test. Open that 1918 book of medical charts at random, close your eyes, and poke a drawing. In all likelihood, whatever tiny anatomical detail you're touching can be found in virtually everybody on Earth. (Or at least everybody of one sex).

Although the parts differ in size from person to person, the basic human blueprint is extremely uniform in terms of which parts are used.

This uniformity is what allows sexual reproduction. Imagine that you want to assemble a working Toyota Camry from the parts of two other cars, Tooby suggests. You'll see that you'd better start with two other Toyota Camrys.

As cognitive scientist Steven Pinker wrote in his 1994 bestseller The Language Instinct, produced after a sabbatical year spent in Santa Barbara with Tooby and Cosmides, "To a scientist interested in how complex biological systems work, differences between individuals are so boring!"

Well, that's one way of looking at it …

Tooby also suggested that human nature is reasonably uniform in many behavioral areas as well. For instance, in virtually every society currently in existence, incest within the nuclear family is unusual and socially disapproved.

Sigmund Freud famously theorized that humans desperately want to commit incest with their nearest and dearest relatives, and that makes necessary the convoluted apparatus of Freudianism. But Finnish anthropologist Edvard Westermarck offered a simpler idea way back in 1891: that humans have evolved an instinct to find incest repugnant because it leads to birth defects. (In a 2007 paper in Nature, "The Architecture of Human Kin Detection," [PDF] Tooby, Cosmides, and Debra Lieberman offer what they believe are the two rules for recognizing siblings—seeing your sibling being nursed by your mother, or being raised together--that make Westermarck's instinct feasible.)

So who is right? Is the human race uniform or diverse?

Well, they're both right. It all depends upon what you're interested in at the moment.

That's usually how it goes—the things that interest us the most, that get us most worked up, are those that are on the knife edge, that look different when viewed from different angles.

Let's consider a similar question that's remote enough that we can think about without political biases getting in the way: Is the universe empty or full?

Outer space is famously empty. You can't get much emptier than space. By one account, the universe is about 0.00000000000000000000000000001 as dense as water.

And yet, outer space is also famously full of "billions and billions" of stars, as Johnny Carson used to say when parodying astronomer Carl Sagan. In 2003, a team of Australian astronomers estimated that there are 70 sextillion stars in the known universe. That's 70,000,000,000,000,000,000,000 stars.

Now, it's perfectly reasonable to conceive of the universe both ways, depending upon what you need to think about at the time. The incredible emptiness of space is terribly important to understand if you are, say, contemplating an interstellar voyage. Nevertheless, to be frank, once you grasp that fact, it gets kind of boring to think about. So, astronomers spend more time thinking about the tiny fraction of space that isn't empty, those 70 sextillion stars.

Similarly, the Wikipedia article on Human Genetic Variation reports DATE, "Two random humans are expected to differ at approximately 1 in 1000 nucleotides"

Well, that's not a very big number.

But Wikipedia goes on to say, "However, with a genome of approximate 3 billion nucleotides, on average two humans differ at approximately 3 million nucleotides."

Well, three million is a pretty big number. (It's not as big as 70 sextillion, but still …)

So, now we can see why, no matter what Pinker says, the African-American 7'-1" basketball player Shaquille O'Neal and the Lebanese-Colombian 5'-1" singer Shakira seem interestingly different.

Of course, probably they would not at all be very different at all compared to space aliens possibly living on a planet going around one of those 70 sextillion stars.

And if those aliens showed up in hostile flying saucers to conquer the human race, no doubt Shaq and Shakira and everybody else would team up to fight them off. Ronald Reagan said exactly this to the United Nations back in 1987:

"I occasionally think how quickly our differences worldwide would vanish if we were facing an alien threat from outside this world."[Address to the 42d Session of the United Nations General Assembly in New York, New York]

But, we're not facing space aliens. So the differences between humans are interesting—and important.

When it comes to thinking about race,—which is all about who your relatives are—it's all, well, relative.

[Steve Sailer (email him) is founder of the Human Biodiversity Institute and movie critic for The American Conservative. His website www.iSteve.blogspot.com features his daily blog.]