Random Samples

Science  02 Mar 2001:
Vol. 291, Issue 5509, pp. 1699
  1. Natural Inspiration?

    The sudden rise of Egyptian civilization about 5000 years ago is the result of a confluence of two cultures, scholars say—farmers living on the Nile, and nomads from the desert who moved to the Nile Valley in response to an increasingly dry climate. Boston University (BU) geologist Farouk El-Baz says the people from the west brought not only “desert wisdom” but an intimate knowledge of arid landforms that may well have inspired designs of the pyramids and the sphinx.

    Writing in the March-April issue of Archaeology magazine, El-Baz, head of BU's Center for Remote Sensing, notes that solid rocks are hewn by desert winds into pyramid shapes that are uniquely able to withstand wind erosion. Similarly, the winds also carve sphinxlike forms, called yardangs, which are sculpted to resemble overturned boat hulls. El-Baz says the headlike protrusion always faces the prevailing winds and is formed by vortices created when the wind loops up from the base.

  2. Engineering Honor Roll

    The National Academy of Engineering (NAE) has elected 74 U.S. engineers and eight foreign associates to membership. The U.S. total is now 2061 and the foreign total 154. New members include a record seven women, who now make up 2.8% of NAE membership. For names, go to http://www.nae.edu./

  3. A House Divided

    Of all the uses of the U.S. census, the most important—to politicians—is the apportionment of congressional seats. Since 1941, Congress has assigned seats by a complicated formula that replaced a simpler approach designed in 1832 by the American statesman Daniel Webster.

    But Peyton Young, a senior fellow at the Brookings Institution in Washington, D.C., says Webster's system was actually better. The current method is biased, giving less populous states 3% to 4% more seats than they deserve, Young reported at the AAAS (publisher of Science) meeting in San Francisco last month.

    Assigning House seats might seem simple: Calculate each state's fraction of the population, multiply by 435, round up the largest fractions to achieve 435, and round down the rest. But this can cause states to lose a seat when they gain population or vice versa.

    Webster's method avoided these paradoxes with a formula that scales up fractions, then rounds them to the nearest whole number. Its successor was supposed to be even better, because it minimized differences in states' per capita representation. But it also introduced a bias, says Young, because small numbers are rounded up more often than large numbers are: 1.45 gets rounded up, for example, whereas 54.45 gets rounded down.

    Because every state gets two senators regardless of population, “the whole system is now rigged toward small states,” Young says. He thinks it's time for Congress to switch back to Webster's method. Steven Brams, an expert on voting systems at New York University, doesn't foresee any surge of support for a change. But he agrees that Webster's scheme—or even the older method—”would be superior” to what's in place today.

  4. Of the Genome We Sing

    After an intense day of press conferences and scientific symposia surrounding the announcement on 12 February of the publication of the human genome sequence, members of the publicly funded project let loose at Nature's party at the National Building Museum in Washington, D.C. Entertainment was provided by The Directors, including lead guitarists (left to right) National Institutes of Health genome chief Francis Collins, arthritis institute head Steve Katz, and cancer institute honcho Rick Klausner.

    Several songs to commemorate the accomplishment (and to chide Celera Genomics for not depositing its version in GenBank) made their debut. Sample lyrics (set to the tune of “You've Really Got a Hold on Me”):

    We Really Got the Code on You,

    Mendel had all his wrinkled peas, And Darwin had all his finches' beaks.

    Watson, Crick, and Franklin too, Figured out just how you groove.

    I love you and all I want to do Is just read you, read you, read you, read you.

    They didn't know you, but now we know you, Just wanna know you, don't wanna own you.

    Sulston, Waterston, Branscomb, Gibbs, and Lander, Then Craig Venter got up their dander.

    Chorus:

    Oh, oh, oh, we really got you now, you can't stop us now,

    We really got the code on you, really got the code on you,

    We really got the code on you, we really got the code on you, baby.

  5. But Did They Mate?

    1. Ann Gibbons

    If Neandertals and modern humans lived in close proximity for thousands of years (see main text), the obvious question is, did they mate· Novelists like Jean Auel, with steamy sagas of brute Neandertals and lissome moderns, have tended to answer with a resounding yes. And some scientists agree: “I think that one thing that was going on was sex,” says Fred Smith, a paleoanthropologist at Northern Illinois University in DeKalb. But there's no way to track these Paleolithic trysts—unless they created offspring. Thus, for scientists, the possibility of children is the key issue. Successful reproduction would imply that Neandertals and humans were part of the same species and shared a recent evolutionary history. “I'm not interested in whether Neandertals and modern humans had sex, but whether Neandertals contributed genes to modern humans,” says geneticist Svante Pääbo of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany.

    But even this seemingly more tractable question is hard to answer. Indeed, the species question is so tricky—and the field of paleoanthropology so divided (see sidebar on p. 1728)—that most researchers avoid it, thus creating some nomenclatural chaos. Paleoanthropologist Milford Wolpoff of the University of Michigan, Ann Arbor, who believes that Neandertals and moderns were members of the same species, advises against using those names (although most anthropologists do), because it “makes them separate.” Others, such as Harvard University paleoanthropologist David Pilbeam, suggest simply calling them separate populations.

    Whatever you call them, those who think the two groups did indeed mate and bear children cite as evidence a 4-year-old child buried in Lagar Velho, Portugal, about 24,500 years ago. The skeleton, says Joao Zilhão of the Portuguese Institute of Archaeology in Lisbon, is anatomically modern but has features inherited from Neandertal ancestors. The mix of inherited features—short arms and a broad trunk like a Neandertal, but a modern-looking chin and pubic bone—implies that this child was not the result of a chance affair and that Neandertals and moderns interbred extensively for many generations, according to a 1999 report in the Proceedings of the National Academy of Sciences (PNAS). Or, as Time magazine quoted co-author Erik Trinkaus of Washington University in St. Louis: “This is not one Neandertal and one modern human making whoopee in the bushes.” If Trinkaus is right, Neandertals disappeared because most of their traits were swamped out when they interbred with modern humans, whose population size was much greater. But other paleoanthropologists doubt that the Portuguese boy is a hybrid. Ian Tattersall of the American Museum of Natural History in New York City and Jeffrey Schwartz of the University of Pittsburgh argued in a commentary in the same issue of PNAS that he looks simply like a “chunky” modern human child, “lacking any suggestion of Neandertal morphology.”

    In the “replacement” view, Neandertals became extinct without fertile offspring. But this debate may never be settled by morphology, partly because there is little consensus on the criteria used to classify Neandertal and early modern human skulls. There is some genetic evidence, however: Studies of the maternally inherited mitochondrial DNA (mtDNA) from three Neandertals show it to be distinctly different from that of living humans, suggesting that Neandertal genes do not survive today and supporting a replacement view (Cell, 11 July 1997, p. 19; Science, 11 July 1997, p. 176).

    But a new genetic study of an anatomically modern man who died 62,000 years ago at Lake Mungo, Australia, raises another possibility, according to a report in January in PNAS (Science, 12 January, p. 230). The Lake Mungo man apparently possessed a now- extinct lineage of mtDNA, although this has not yet been confirmed in an independent lab, a step most ancient DNA researchers say is essential. But all researchers agree that the man is anatomically modern and therefore might have contributed genes to living people. If a mtDNA sequence present in an ancient modern human could simply become extinct, then something similar could have happened to the mtDNA of Neandertals. “Then the absence of Neandertal mtDNA in living humans does not reject the possibility of some genetic continuity with modern humans,” John Relethford of the State University of New York College at Oneonta wrote in PNAS.

    Further complicating the debate is the lack of any genetic yardstick for species definition and the fact that the variation between Neandertals and modern humans falls within the range of mtDNA variation between subspecies of chimpanzees, says Pääbo, whose lab sequenced the Neandertal mtDNA. Another genetic tack is to examine Cro-Magnon mtDNA to see if these modern humans who lived in Europe in the past 40,000 years are ancestral to living Eurasians. mtDNA has been extracted from two late Cro-Magnons from Gough's Cave in England, but analyses that tie them to recent Europeans have yet to be published in detail, says paleoanthropologist Christopher Stringer of the Natural History Museum in London. In the meantime, barring the discovery of a cave artist's depiction of the event, there is no consensus on whether Neandertals and modern humans mixed it up.

  6. Anthropologists Duel Over Modern Human Origins

    1. Michael Balter

    LONDON—Chris Stringer carefully lays the wooden box on a long table cluttered with scientific journals. He unfastens the latch, opens the top, and gingerly lifts out a human skull that is perhaps 400,000 years old. As Stringer gently turns the cranium in his hands, its appearance is startling. The flat, nearly vertical midface and large brain cavity could almost be mistaken for those of a modern human. Yet above the eyes, heavy browridges and a sharply receding forehead distinctly recall Homo erectus, a long-extinct early human. “It's modern, and yet not modern,” Stringer tells a visitor to his office at London's Natural History Museum.

    The paradox of fossils like this one from Broken Hill, Zambia, with its mixture of ancient and modern traits, has sparked one of the most bitter and longest running battles in paleoanthropology. Stringer is a leading proponent of what many consider the dominant theory—that humans with such transitional features belonged to transitional species, in this case one often called Homo heidelbergensis. According to how Stringer reads the fossil record, an unbroken evolutionary chain in Africa may link this species to modern humans, who then swept around the globe, replacing already-settled human populations such as the Neandertals in Europe (see main text) and perhaps even H. erectus in Asia.

    But although this “Out of Africa” scenario is established in many media and textbook accounts, a staunch band of skeptics, led by paleoanthropologist Milford Wolpoff of the University of Michigan, Ann Arbor, holds to an opposing theory called multiregional evolution. In this view, the evolution of modern humans has been occurring across the globe since early humans left Africa nearly 2 million years ago. Thanks to continuous exchanges of genes among populations in different regions, humans have always belonged to one species and have evolved together into today's modern form. For Wolpoff, there is no such thing as “H. heidelbergensis”: Such a mix of modern and ancient features reflects normal variation within a species. Nor does Wolpoff concede that his view is in the minority. “I think paleoanthropologists are split right down the middle on this,” he says.

    As leaders of two irreconcilable scientific camps, Stringer, 53, and Wolpoff, 58, have come to personify this bitter debate. And indeed, the argument has often become personal. “Milford and I have had some nasty exchanges,” Stringer admits. In one 1989 article, Wolpoff ridiculed the idea that modern humans had replaced Neandertals as a “scientific rendering of the story of Cain,” adding that this scenario's “violent” implications were “not pleasant.” And Stringer, in his 1996 book African Exodus, co-written with Robin McKie of the London-based Observer newspaper, countered that “attention to inconvenient details has never been part of the Wolpoff style of rhetoric.” The last straw, Wolpoff says, was a 1997 opinion piece in The New York Times cosigned by Stringer and McKie. The article contended that a recent African origin implies that racial differences are superficial and that “we are indeed all Africans under the skin.” On the other hand, it concluded, “some scientists and those with narrow political agendas have put forward arguments to sustain the idea that races exist with fundamental biological differences.” Wolpoff believes the article implied that his views make him a racist and says he has “not been on speaking terms with Stringer” ever since. (Stringer says the article was aimed at right-wing organizations, not Wolpoff.)

    Yet despite their acrimonious disagreements, there are interesting parallels in the routes the men took to opposite conclusions. Both trace their interest in fossils to early childhood. As a youngster, Stringer often visited London's Natural History Museum, and Wolpoff says he was “astounded” to learn in college that “there was actually a profession” devoted to this hobby. While a graduate student at the University of Bristol in the early 1970s, Stringer spent 4 months traveling through Europe in an old Morris Minor, examining fossil skulls in museums across the continent. The data he gathered, including measurements of a nearly modern skull from North Africa, led him to question then-popular notions that Neandertals were our ancestors. Meanwhile, after receiving his Ph.D. from the University of Illinois, Urbana- Champaign, in 1969, Wolpoff took off on his own series of fossil tours, visiting Africa, Asia, and Australia. He began to develop his ideas about multiregional evolution, he says, when he realized that humans from Asia and Australia had retained some traits over several hundred thousand years, even as other features changed. “Asian features are found at all time periods,” he says. For example, skulls from China always have small, forward-facing cheeks, flat noses, and very little facial projection, whereas ancient skulls from Australia are “robust and prognathic” with “huge cheeks” that he says are reflected in the features of some living Australian Aborigines.

    Despite the sometimes heated argument, admirers of both Stringer and Wolpoff insist that each man bases his views on science. Stringer “has always tried to convince by scientific results,” says paleoanthropologist Günter Bräuer of the University of Hamburg in Germany, an early proponent of the Out of Africa theory. And biological anthropologist John Relethford of the State University of New York College at Oneonta, who has often questioned the Out of Africa camp's genetic evidence, says that Wolpoff “has studied virtually every [fossil]. … He has a keen sense of variation across time and space.”

    Yet it seems unlikely that either side will convince the other anytime soon. Two months ago, the multiregionalists mustered both genetic and fossil evidence that they say bolsters the case for continuous evolution (Science, 12 January, pp. 230 and 231). Wolpoff says he thinks the argument will go on until he, Stringer, and other members of the opposing camps retire. “Then you will know how the debate turned out, by seeing what the new generation thinks.” As for why the debate has become so emotional, Stringer says: “Scientists show the same frailties as the rest of the human species, especially when talking about our own origins.”