HUMAN EVOLUTION Rethinking the Hobbits of Indonesia New 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 WONG PHOTOGRAPHS BY DJUNA IVEREIGH KEY CONCEPTS In 2004 researchers working on the island of Flores in Indonesia found bones of a miniature human species formally named Homo floresiensis and nicknamed the hobbit that lived as recently as 17 000 years ago Scientists initially postulated that H floresiensis 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 finding that could overturn key assumptions about human evolution The 66 Editors SCIENTIFIC AMERICAN I n 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 Tolkien s fictional 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 mented in other mammals but never humans The fi nding jolted the paleoanthropological community Not only was H floresiensis being held up as the first example of a human following the so called island rule but it also seemed to reverse a trend toward ever larger brain size over the course of human evolution Furthermore the same deposits in which the small bodied smallbrained individuals were found also yielded stone tools for hunting and butchering animals as well as remainders of fires 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 The Littlest Human by Kate Wong Scientific American February 2005 Skeptics were quick to dismiss LB1 as nothing more than a modern human with a disease that November 20 09 stunted her growth And since the announcement 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 arguments have failed to convince the hobbit proponents however who have countered each diagnosis with evidence to the contrary A Perplexing Pastiche Nevertheless new analyses are causing even the proponents to rethink important aspects of the original interpretation of the discovery The recent findings are also forcing paleoanthropologists 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 w w w S c i e n t i f i c A m e r i c a n c o m Perhaps the most startling realization to emerge from the latest studies is how very primitive LB1 s body is in many respects To date excavators have recovered the bones of an estimated 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 Australopithecus 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 analysis of LB1 s foot The foot has a few modern fea STRANGE SKELETON from Flores Indonesia calls into question which human ancestor was the first to leave Africa and when Archaeologist Thomas Sutikna left is one of the leaders of the excavation of the cave that yielded the skeleton SCIENTIFIC AMERICAN 67 A Mysterious Mosaic To 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 complete skeleton called LB1 that dates to 18 000 years ago Some of its characteristics call to mind those of apes and of australopithecines such as the 3 2 millionyear old Lucy Other traits however are in keeping with those of our own genus Homo This m lange of primitive features yellow and modern ones blue has made it difficult to figure out where on the human family tree the hobbits belong Brodmann area 10 Homo traits Ape and australopithecine traits Thick braincase Small teeth Short face Robust lower jaw Broad flaring pelvis Short thighbone Short shinbone 68 SCIENTIFIC AMERICAN BRAIN is the size of a chimpanzee s But a virtual reconstruction 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 facilitates tool manufacture and use by better distributing forces across the hand FOOT is exceptionally long compared with the short leg This relative foot length is comparable to that seen in bonobos and it suggests the hobbits were inefficient runners Other apelike traits include long curved toes and the absence of an arch Yet the big toe aligns with the rest of the toes among other modern characteristics tures for instance the big toe is aligned with the other toes as
View Full Document
Unlocking...