Passage II

Passage A is adapted from the article “The Other Humans: Neanderthals Revealed” by Stephen S. Hall (©2008 by The National Geographic Society). Passage B is adapted from the editorial “Fossils for All” by the editors of the journal Scientific American (©2009 by Scientific American, Inc.).

Passage A by Stephen S. Hall

One of the longest and most heated controversies in human evolution rages around the genetic relationship between Neanderthals and their European successors. Did the modern humans sweeping out of Africa beginning some 60,000 years ago completely replace the Neanderthals, or did they interbreed with them? In 1997 the latter hypothesis was dealt a powerful blow by geneticist Svante Paabo—then at the University of Munich—who used an arm bone from the original Neanderthal man to deliver it. Paabo and his colleagues were able to extract a tiny 378-letter snippet of mitochondrial DNA (a kind of short genetic appendix to the main text in each cell) from the 40,000-year-old specimen. When they read out the letters of the code, they found that the specimen’s DNA differed from living humans to a degree suggesting that the Neanderthal and modern human lineages had begun to diverge long before the modern human migration out of Africa. Thus the two represent separate geographic and evolutionary branches splitting from a common ancestor. If there was any interbreeding when they encountered each other later, it was too rare to leave a trace of Neanderthal mitochondrial DNA in the cells of living people.

Paabo’s genetic bombshell seemed to confirm that Neanderthals were a separate species.

However, "During this time of the biological transition," says Erik Trinkaus, a paleoanthropologist at Washington University in St. Louis, “the basic behavior [of the two groups] is pretty much the same, and any differences are likely to have been subtle.” Trinkaus believes they indeed may have mated occasionally. He sees evidence of admixture between Neanderthals and modern humans in certain fossils, such as a 24,500-year-old skeleton of a child discovered at the Portuguese site of Lagar Velho, and a 32,000-year-old skull from a cave called Muierii in Romania.

Katerina Harvati, a researcher at the Max Planck Institute in Leipzig, has used detailed 3-D measurements of Neanderthal and early modern human fossils to predict exactly what hybrids between the two would have looked like. None of the fossils examined so far matches her predictions.

The disagreement between Trinkaus and Harvati is hardly the first time that two respected paleoanthropologists have looked at the same set of bones and come up with mutually contradictory interpretations. Pondering—and debating—the meaning of fossil anatomy will always play a role in understanding Neanderthals.

Passage B by the editors of Scientific American

In June of 2009 the famed Lucy fossil arrived in New York City. The 3.2-million-year-old partial skeleton of Australopithecus afarensis could attract hundreds of thousands of visitors over the course of her fourmonth engagement—part of a six-year tour.

Before this tour, Lucy had never been on public display outside of Ethiopia. One might expect scholars of human evolution to be delighted by the opportunity to share the discipline’s crown jewel with so many members of the science-interested public. But news reports announcing her New York debut included the same objections that aired when she first landed in the U.S.: namely, that the bones could sustain damage and that the tour takes a key specimen out of scientific circulation for too long. Indeed, some major museums turned the exhibit away in part for those reasons.

The objections reflect a larger problem of possessiveness in the field of human origins. Indeed, fossil hunters often block other scientists from studying their treasures, fearing assessments that could scoop or disagree with their own. In so doing, they are taking the science out of paleoanthropology.

Critics of such secrecy commonly point to the case of Ardipithecus ramidus, a 4.4-million-year-old human ancestor discovered by Tim White of the University of California, Berkeley. Fifteen years after White announced the first fossils of A. ramidus and touted the importance of this species for understanding human origins, access to the specimens remains highly restricted.

White, for his part, has said that he published only an initial report and that normal practice is to limit access until publication of a full assessment. And he has noted that the condition of a key specimen—a badly crushed skeleton—has slowed the release of the team’s detailed report.

The scientists who unearth the remnants of humanity’s past deserve first crack at describing and analyzing them. But there should be clear limits on this period of exclusivity. Otherwise, the self-correcting aspect of science is impeded: outside researchers can neither reproduce the discovery team’s findings nor test new hypotheses.