Natural History Highlight
Walking, but not running, with the real 'Hobbits'
By Stephanie Guzik, (Volunteer Science Writer)
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Matt Tocheri laser scanning the skull of LB1. Photo by Djuna Ivereigh (indonesiawild.com).
Scientists are a big step closer to understanding the evolution of walking in humans. Bipedalism—or walking upright on two feet—has long been considered one of the hallmarks of human evolution, signaling the transition from an ape-like reliance on arms and hands for locomotion to an upright gait using the legs and feet.
In the cover story of the May 7, 2009 issue of the scientific journal Nature, a global team of scientific collaborators, led by William L. Jungers of Stony Brook University Medical Center and co-authored by Smithsonian’s Matt Tocheri of the Department of Anthropology’s Human Origins Program, investigates the foot anatomy and bipedalism in a primitive human species called Homo floresiensis—more commonly referred to as the “hobbit.”
Since the discovery of the first hobbit skeleton in 2003 on the Indonesian island Flores, researchers have marveled over the scientifically intriguing hominin (human-like) species. The first and most complete hobbit skeleton is exceedingly small for an adult human—only 3 ½ feet tall with a brain size similar to that of a chimpanzee. Similarly, the anatomy of the hobbit skull, shoulder, and wrist is highly reminiscent of other earlier hominin species that predate the origin of modern humans roughly 200 thousand years ago. The current research conducted by Jungers and colleagues focused on the hobbit’s relatively complete feet—a rare find in hominin fossil discoveries—and their analyses uncover an intriguing mix of both human- and ape-like features. Jungers notes, "A foot like this one has never been seen before in the human fossil record," and it "offers the most complete glimpse to date of how a primitive bipedal foot was designed and differed from that of later hominins and modern humans."
The assembly. Photo by Djuna Ivereigh / ARKENAS.
The hobbit's big toe--or hallux-- illustrates this dichotomy: it is adducted, meaning that like in modern humans, the big toe points in the same direction as the other (lateral) toes; but it is considerably shorter than the lateral toes which is a characteristic reminiscent of chimpanzees and other apes. Meanwhile, the hobbit's lateral toes (the forefoot) are proportionally long compared with the ankle bones (the hindfoot) in a manner that, again, is similar to apes.
Furthermore, the relative proportions of the hobbit’s foot in comparison to its leg bones intriguingly also share similarities with chimpanzees. The length of the hobbit foot from the heel to the longest toe is exceedingly long compared to the rest of the leg— almost 70% of the femur (thigh bone) length—in contrast to modern human feet which are approximately half the length of the femur, regardless of whether you are short or tall.
The reconstructed left foot of the hobbit, Homo floresiensis, is 70% as long as its leg bones. Here, the foot length is contrasted with the length of its right tibia.
Photo by William Jungers.
Combining an overall flat-footed bone structure in the hobbit’s foot with a relatively short big toe and long lateral toes, as well as a relatively long foot and short legs, hobbits were definitely bipeds (walked upright) but they would not have moved with the same gait that we have today. Hobbits would have required a different leg motion to compensate for these large differences in leg and foot proportions and they likely would not have been able to run as efficiently as modern humans do.
Since the hobbit was first unearthed, its skeleton has been the focus of both scientific intrigue and controversy. Some scientists have provided data that suggest the hobbits are a different species of human that are closely related to, but distinct from, our own species, Homo sapiens, and other hominins like Neandertals (Homo neanderthalensis). Others believe the hobbits are simply modern humans with a disease resulting in small stature.
The results reported by Jungers and colleagues add more evidence that the hobbits are a distinct human species, Homo floresiensis, noting that there are no known diseases that cause alterations in limb proportions as seen in the hobbit. Moreover, the authors argue that the many primitive features seen in the hobbit skeleton suggest this novel species may not owe its recent ancestry to Homo erectus, the hominin species credited with the first migration out of Africa roughly 1.8 million years ago, but rather to another more primitive species of the genus Homo.
Although more fossil discoveries and analyses are needed to fully elucidate the interwoven evolutionary stories of Homo floresiensis and bipedalism in hominins, the striking combination of human- and ape-like traits of the hobbit foot adds important pieces to both puzzles.
This report by Jungers and colleagues presents conclusive data that the primitive human nicknamed the hobbit—named after the diminutive human-like creatures of JRR Tolkien’s fictional writings—has officially walked out of fictional literature and into the real story of human evolution. Co-author Matt Tocheri remarks, “These particular 'hobbit' feet may never have walked into Mordor, but they certainly remind us how little we know about which other hominin species walked out of Africa and the many possible places their feet helped take them."
May 2009
Reference:
'Hobbit' was a dwarf with large feet Article in NatureNews
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