Evidence for abnormality
"It turns out there's a huge forgotten body of literature on facial asymmetry, including many papers published nearly a century ago, based on studies at England's prestigious Galton Laboratory," Eckhardt says. "Everybody's face is asymmetrical to some extent. But when asymmetry exceeds about 1 percent, you're over the line into abnormality." In studying LB1, Eckhardt and Adam Kuperavage, a graduate student in kinesiology at Penn State, found that six of seven measurements taken on the skull's right side were larger than corresponding measurements on the left side by as much as 40 percent, while the seventh was 6 percent larger on the left side.
"Craniofacial asymmetry that extreme demonstrates that LB1 did not develop normally," Eckhardt says. "When we pointed out the asymmetry—which the Morwood group said in their original paper wasn't present—they backpedaled and said, sure, there's a small amount of asymmetry, but it was probably caused by pressure from sediments." Eckhardt cites a rebuttal of this explanation by the University of Wisconsin paleoanthropologist John Hawks, who writes in his weblog: "Yes, it is true that any archaeological specimen is likely to be distorted to some extent by reconstruction or postdepositional deformation. That might be true of this skull also. But in this case, the asymmetry clearly extends to morphological characters that should be relatively unaffected by such distortion."
Anthropologists frequently cite a unique shape or placement of teeth when describing a new species. According to Morwood's team, a CT scan had demonstrated the absence of a third molar for LB1. Etty Indriati had found the existing socket and a tooth fragment where the "missing" molar should have been. But LB1's teeth displayed other peculiarities, including enlarged wear surfaces, long roots, and an unusual rotated position of premolars in the upper jaw. "Those traits were characterized as unique," says Eckhardt. "But it turns out that the rotated premolars are shared by about 20 percent of the people still living in Rampasasa, a village near Liang Bua." This particular Australomelanesian population is short-statured enough to be known as the Rampasasa pygmies. Many individuals in the population show receding chins (another supposed species-distinguishing characteristic), leading Eckhardt and his colleagues to state in their PNAS paper: "Absence of a chin cannot be a valid taxonomic character for the Liang Bua mandibles." The Jacob team contends that Morwood and his research group should have compared LB1's teeth with those of other populations in the same region, such as the Rampasasa cohort, rather than with Homo sapiens from other geographic areas of the world, principally Europe and Africa.
Morwood's group had cited an unusual robustness of the leg bones of LB1. Eckhardt's team had CT scans done on the bones. "We paid for the scans with a few thousand dollars in traveler's checks that I was carrying," Eckhardt says. "Others in the group combined funds and paid the professional photographer. Our involvement in this project moved so rapidly that there wasn't time to apply for conventional grants."
The CT scans showed that the cortex, or outer solid bone, was actually quite thin: "Those femurs are not robust at all," says Eckhardt. On the bones, the location of attachment points for the muscles suggest at least some paralysis. The LB1 skeleton also showed a low degree of humeral torsion, the twisting of the upper arm bone between shoulder and elbow. Normal humeral torsion in Homo sapiens commonly is about 140 degrees; LB1's arms show 110 degrees of torsion. "When a limb develops with serious muscle weakness, torsion is usually only about 110 degrees," Eckhardt says. "Many points of evidence combine to suggest that this individual probably had severe movement disabilities."
How did humans evolve?
Was LB1 microcephalic? According to Eckhardt, around two hundred medically distinctive disease conditions can produce microcephaly. The malady can be genetic in origin, and it can be caused by various diseases and by infection. Asymmetries in the face and other bones often accompany microcephaly. Microcephaly exists in skeletons from the Upper Pleistocene and the Holocene periods. The ratio of LB1's small cranial capacity and short stature are similar to ratios found over several generations of microcephalics studied by physicians in the twentieth century. Scientists have also traced the condition through succeeding generations of humans.
Says Eckhardt, "The archaeologists who dug up LB1 made serious mistakes in characterizing what they found, and they drew conclusions that were not supported by the balance of evidence. Altogether, they have one complete skull, plus a second mandible, which is similarly small, and assorted other bones from perhaps eight individuals. You cannot designate a new species based largely on an abnormal individual.
Group photo in Yogjakarta. Left to right: Thorne, Indriati, Henneberg, Jacob, Soejono, Eckhardt. Courtesy C.D. Eckhardt
"In summary, the normal traits of LB1 were not unique but rather are characteristic of human populations in the region. The degree of humeral torsion, the structure of the long bones, the facial asymmetry, and the unusually small braincase all point to developmental abnormalities of the sort that often accompany microcephaly."
Continues Eckhardt: "We may be dealing with a population of individuals who went through a period of food shortages that made them smaller than they might otherwise have been. LB1 was about 1.25 meters tall, and abnormalities of the sort from which that individual suffered commonly reduce stature markedly. The Rampasasa pygmies living near Liang Bua average just under 1.5 meters. That's not a huge stature difference."
In an apparent reaction to the Jacob group's PNAS paper, "the proponents of Homo floresiensis have now switched to arguing that the small humans must have originated elsewhere," Eckhardt says. "It seems that whenever we test one hypothesis and disprove it, they reinterpret the hypothesis into a less readily testable form."
Since 1971, when Eckhardt earned his Ph.D. in anthropology and human genetics from the University of Michigan, many bones have passed through his hands. He has studied skeletal material in many of the major museums in the world, and spent five summers working with samples at the Institute of Anthropology and Human Genetics at the University of Frankfurt in Germany. In 1992 he published a comprehensive study of skeletal changes in native Peruvians, based on samples ranging in age from 10,000 years before present to living populations. He has studied variation in skeletons as it is affected by age at death; sex; pathologies and developmental abnormalities; and evolutionary changes over time. He has also worked with the bones of other mammals, including chimpanzees, gorillas, orangutans, macaques, and baboons.
"Most people in the fields of anthropology and archaeology believe the process of human evolution has been one of intense splitting over time," he concedes. "My belief, based on studying thousands of specimens during my career, is the opposite. Variation within any given species seems to be consistently underestimated."
The study of human evolution has always been a notably contentious field, and the Flores skeletons remain the focus of an intense and not always collegial debate. Currently scientists from different disciplines are studying the volume and shape of LB1's cranium, and trying—unsuccessfully, so far—to recover mitochondrial DNA from the skeletal material. (If found, this DNA might be compared to samples taken from both Neanderthal fossils and modern humans.) Morwood's team continues digging on Flores. The scientific press and mainstream media seem happy to keep the controversy alive.
Says Eckhardt, "My estimate is that 80 percent or so of paleoanthropologists want this new species to be real—so much so that they are willing to overlook glaring errors and inconsistencies in the studies and conclusions of the archaeologists who found the bones. This is not surprising, since LB1 was proclaimed to be our generation's critical test case of paleoanthropological theory. By disproving the validity of this new species, we have called a central dogma into question.
"Core beliefs are incredibly resistant to change. But testing and rejecting cherished hypotheses is how science moves forward." RPS
Robert B. Eckhardt, Ph.D., is professor of developmental genetics and evolutionary morphology in the Department of Kinesiology and the College of Health and Human Development. His email is eyl@psu.edu. His research interests include the interaction of genetic and environmental influences on growth and development in human populations, particularly in musculoskeletal structures.
