66 SCIENTIFIC AMERICAN November 2009In 2004 a team of Australian and Indonesian scientists who had been excavating a cave called Liang Bua on the Indonesian island of Flores announced that they had unearthed something extraordinary: a partial skeleton of an adult human female who would have stood just over a meter tall and who had a brain a third as large as our own. The specimen, known to scientists as LB1, quickly received a fanciful nickname—the hobbit, after writer J.R.R. Tol-kien’s fi ctional creatures. The team proposed that LB1 and the other fragmentary remains they recovered represent a previously unknown human species, Homo fl oresiensis. Their best guess was that H. fl oresiensis was a descendant of H. erectus—the fi rst species known to have colonized outside of Africa. The creature evolved its small size, they surmised, as a response to the limited resources available on its island home—a phenomenon that had previously been docu-KEY CONCEPTSIn 2004 researchers working on ■the island of Flores in Indonesia found bones of a miniature hu-man species—formally named Homo fl oresiensis and nick-named the hobbit—that lived as recently as 17,000 years ago. Scientists initially postulated ■that H. fl oresiensis descended from H. erectus, a human ancestor with body proportions similar to our own.New investigations show that ■the hobbits were more primitive than researchers thought, however—a fi nding that could overturn key assumptions about human evolution. —The EditorsHUMAN EVOLUTIONNew analyses reveal the mini human species to be even stranger than previously thought and hint that major tenets of human evolution need revision BY KATE WONGPHOTOGRAPHS BY DJUNA IVEREIGHHobbitsRethinkingthe Indonesiaof mented in other mammals, but never humans. The fi nding jolted the paleoanthropological community. Not only was H. fl oresiensis being held up as the fi rst example of a human following the so-called island rule, but it also seemed to re-verse a trend toward ever larger brain size over the course of human evolution. Furthermore, the same deposits in which the small-bodied, small-brained individuals were found also yielded stone tools for hunting and butchering animals, as well as remainders of fi res for cooking them—rather advanced behaviors for a creature with a brain the size of a chimpanzee’s. And astonishingly, LB1 lived just 18,000 years ago—thousands of years after our other late-surviving relatives, the Neandertals and H. erectus, disappeared [see “T he Lit t lest Human,” by Kate Wong; S cie n ti f-ic American, February 2005].Skeptics were quick to dismiss LB1 as nothing more than a modern human with a disease thatwww.ScientificAmerican.com SCIENTIFIC AMERICAN 67 Perhaps the most startling realization to emerge from the latest studies is how very primi-tive LB1’s body is in many respects. (To date, ex-cavators have recovered the bones of an estimat-ed 14 individuals from the site, but LB1 remains the most complete specimen by far.) From the outset, the specimen has invited comparisons to the 3.2-million-year-old Lucy—the best-known representative of a human ancestor called Aus-tralopithecus afarensis—because they were about the same height and had similarly small brains. But it turns out LB1 has much more than size in common with Lucy and other pre-erectus hominins. And a number of her features are downright apelike.A particularly striking example of the bizarre morphology of the hobbits surfaced this past May, when researchers led by William L. Jungers of Stony Brook University published their analy-sis of LB1’s foot. The foot has a few modern fea-stunted her growth. And since the announce-ment of the discovery, they have proposed a number of possible conditions to explain the specimen’s peculiar features, from cretinism to Laron syndrome, a genetic disease that causes insensitivity to growth hormone. Their argu-ments have failed to convince the hobbit propo-nents, however, who have countered each diag-nosis with evidence to the contrary.A Perplexing PasticheNevertheless, new analyses are causing even the proponents to rethink important aspects of the original interpretation of the discovery. The recent fi ndings are also forcing paleoanthropol-ogists to reconsider established views of such watershed moments in human evolution as the initial migration out of Africa by hominins (the group that includes all the creatures in the human line since it branched away from chimps). STRANGE SKELETON from Flores, Indonesia, calls into question which human ancestor was the fi rst to leave Africa—and when. Archaeologist Thomas Sutikna (lef t ) is one of the leaders of the excavation of the cave that yielded the skeleton.[THE EVIDENCE]A Mysterious MosaicTo date, excavators have recovered the remains of about 14 individuals from Liang Bua, a cave site on Flores. The most complete specimen is a nearly com-plete skeleton called LB1 that dates to 18,000 years ago. Some of its characteris-tics call to mind those of apes and of australopithecines such as the 3.2-million-year-old Lucy. Other traits, however, are in keeping with those of our own genus, Homo. This mélange of primitive features (yellow) and modern ones (blue) has made it diffi cult to fi gure out where on the human family tree the hobbits belong. Thick brain caseSmall teethShort faceRobust lower jawHomo traits Ape and australopithecine traitsBroad, fl aring pelvis ShortshinboneWILLIAM L. JUNGERS Stony Brook University (skeleton); COURTESY OF KIRK E. SMITH Mallinckrodt Institute of Radiology, Washington University School of Medicine (skull)68 SCIENTIFIC AMERICAN November 2009BRAIN is the size of a chimpan-zee’s. But a virtual reconstruc-tion—generated from CT scans of the interior of the braincase—indicates that despite its small size, the organ had a number of advanced features, including an enlarged Broadmann area 10, a part of the brain that has been theorized to play a role in complex cognitive activities. Such features may help explain how a creature with a brain the size of a chimp’s was able to make stone tools.WRIST resembles that of an African ape. Of particular interest is a bone called the trapezoid (shown) , which has a pyramidal form. Modern humans, in contrast, have a trapezoid shaped like a boot, which facili-tates tool manufacture and use by better distributing forces across the hand. tures—for instance, the big toe is aligned with the other toes,
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