Apr 1 2007

Evolution Confusion

Newsweek’s muddled version of human origins

Given the many pressing public issues these days that hinge on questions of science, it’s critical that news outlets have the ability to interpret and explain scientific topics. Unfortunately, some of the journalists hired by major media to cover these issues instead garble them, with damaging consequences for the public debate.

Take a recent Newsweek cover story, “The Evolution Revolution: The New Science of the Brain and DNA Is Rewriting the Story of Human Origins” (3/19/07). Towards the end of the article, Newsweek’s Sharon Begley—a senior editor who specializes in science stories—describes researcher Peter Underhill’s technique of looking at the changes in the DNA code to see how long ago two populations separated:

Applying the molecular clock technique, he concludes that the most recent common ancestor of all men alive today lived 89,000 years ago in Africa. The first modern humans—and therefore, unlike the earlier wave of Homo erectus into Asia a million years ago, the ancestors of everyone today—departed Africa about 66,000 years ago.

These pilgrims were strikingly few…. The best estimate: 2,000 men. Assuming an equal number of women, only 4,000 brave souls ventured forth from Africa. We are their descendants.

Whoa—“We are their descendants”? Who’s “we,” exactly? Some of us people are descended from the modern humans who left Africa—and others of us are descended from the modern humans who stayed in Africa. (Many people, of course, are descended from both groups.)

One wants to believe that Begley does not mean to imply that no Newsweek readers (or writers?) are of modern African descent. Her sentence that begins “the first modern humans” could be read to mean that the ones who left Africa are “the ancestors of everyone today,” with some of them presumably doubling back at some point to repopulate Africa. This would be wrong, but less offensive than assuming that no one who is reading your article is black.

But Begley does acknowledge that the 4,000 people she says “we” are descended from are actually only the ancestors of non-Africans. In an online chat (Newsweek online, 3/10/07), Begley corrects a reader who had surmised from her article that “the modern human population is descended from only 4,000 adults 66,000 years ago”:

That figure of 4,000 refers to the hominids who left Africa for Eurasia (not that they knew they’d entered a new continent, of course); others like them remained in Africa and became ancestors of people living there today.

“Hominids” seems like an odd way to refer to members of our own species who are virtually identical, genetically speaking, to ourselves. But at least she’s clear (in the chat, anyway) that the descendants of the people who left Africa are not all the people.

This confusion persists, however, through the remainder of the article, where Begley suggests a series of fairly recent mutations may have played roles in the development of human culture. She suggests that one gene that plays a role in speech, FOXP2, may have arisen “as recently as 50,000” years ago, adding, “If so, then it is only humans as modern as those in the last diaspora out of Africa who developed advanced, spoken language.” Since, as Begley earlier noted, the latest common ancestor of humans lived an estimated 89,000 years ago, a mutation that happened 50,000 years ago could not be inherited by all people; if it were responsible for the speech ability, large swaths of humanity would be unable to speak.

She goes on to report that another gene, known as microcephalin, emerged 37,000 years ago, “when symbolic thinking was taking hold in our most recent ancestors,” and that a third gene, ASPM, is 5,800 years old, arising “just before people established the first cities in the Near East.” She concludes from this that “we are still evolving.”

Well, probably, but since these mutations are not universally distributed across humanity—they can’t be, since they occurred after humanity had split into African and non-African populations—they could only be responsible for symbolic thought and the ability to form cities if those traits were possessed by just some groups of modern humans. (Begley refers to microcephalin and ASPM as “genes” that recently emerged; actually, they’ve been around at least as long as humanity, but there are mutant variations in those genes that emerged more recently.)

Is Begley trying to make some crypto-eugenics argument for racial supremacy? Or does she not understand the implications of what she’s writing? Either way, the consequences for the intellectual development of Newsweek’s readers are not good.