She stood barely more than a meter tall and had a brain the size of a chimpanzee’s. That is about all scientists can agree on in the case of the adult human skeleton known as LB1—popularly dubbed the hobbit. Unveiled in 2004, the diminutive bones hail from a cave called Liang Bua on the Indonesian island of Flores. Based on analyses of LB1 and some other, more fragmentary remains, the discovery team concluded that the specimens belonged to a previously unknown human species, Homo floresiensis, that lived as recently as 12,000 years ago [see “The Littlest Human,” by Kate Wong; Scientific American, February 2005]. But within days skeptics emerged, countering that the tiny remains instead belonged to a small-bodied population of modern humans and that LB1—with her tiny brain and other odd features—was a diseased member of the group.
In recent months researchers have published several papers favoring the minority view of the skeptics. Hobbit proponents, however, think that the evidence for the hobbit as a separate human species is stronger than ever. The stakes are high. Proponents now believe the finds suggest that the first human ancestors to leave Africa may have been far more anatomically primitive—and may have left far earlier—than previously thought. If they are right, the Flores remains rank among the most important paleoanthropological discoveries of all time, one that will revolutionize our understanding of human evolution. If they are wrong, “it will be worse than Piltdown” in terms of its effect on the field, as one anonymous observer put it, referring to the 1912 hoax that combined modern human and orangutan fragments.
Detractors have long argued that LB1 exhibits a number of skeletal and dental anomalies in addition to her minuscule brain case, including various asymmetries in the skull and skeleton. But finding a disorder that can account for those traits has proved challenging. To that end, last June a team of scientists determined that LB1 may have had Laron syndrome, a genetic disease that causes insensitivity to growth hormone. Then, in February, a second research group concluded that she might have suffered from another genetic condition known as microcephalic osteodysplastic primordial dwarfism type II (MOPD II), which produces individuals with small bodies and small brains who nonetheless are of near-normal intelligence. And in March a third team reported that, based on photographs, LB1’s skull seems to have an abnormally large cavity for the pituitary gland. This, the researchers said, was evidence of myxoedematous endemic cretinism; the disorder arises from prenatal nutritional deficiencies that render the thyroid gland unable to function, which in turn supersizes the pituitary.
Within days of the publication of the cretinism paper, investigators led by Lee Berger of the University of the Witwatersrand in Johannesburg announced that they had discovered small modern human bones ranging in age from 1,400 to 2,900 years old in two caves in Palau, Micronesia. In addition to being tiny, the bones display traits that are typically associated with earlier members of our genus, including pronounced browridges and a nonprojecting chin. These characteristics also occur in the hobbits and have been used to help make the case that they represent a new species. But Berger and his colleagues argue that these features may simply arise as a side effect of evolving a small size. And that, they say, supports the possibility that LB1 is a diseased member of a small-bodied modern human population.
Experts dispute all these hypotheses. Dean Falk of Florida State University and Ralph L. Holloway of Columbia University, who have studied CT scans and casts of the interior of LB1’s skull, both note that LB1’s pituitary was much smaller than the cretinism theorists claim. And in a presentation given to the American Association of Physical Anthropologists in April, Falk rejected the diagnosis of Laron syndrome, noting that many of the 33 traits said to characterize the disease are not present in LB1.
Meanwhile humans around the globe have bones just as small or smaller than these fragments from Palau, says William L. Jungers of Stony Brook University, who has been studying the postcranial skeleton of LB1. “But none of them anywhere in the world are as short as the various individuals of Homo floresiensis.” Furthermore, he adds, none of them share LB1’s suite of primitive skeletal characteristics, such as her apelike wrist bones and her flaring pelvis, which bears an uncanny resemblance to the pelvis of the 3.2-million-year-old fossil from Ethiopia known as Lucy.
Even hobbit deniers, such as Robert B. Eckhardt of Pennsylvania State University, concede that “it’s easy to rule out cretinism and MOPD II.” Still, he and others maintain that Laron syndrome is a viable diagnosis. The problem, they say, is that pathologies are complex and the way they manifest varies from person to person. “If you have to match all 33 symptoms, you’re not going to find anything,” remarks John Hawks of the University of Wisconsin–Madison. “You have to go based on the preponderance of evidence.”