Breadcrumbs

• Home »
• News

Story Posted: 23 June 2006

Their interpretation was widely accepted by the scientific community and heralded by press around the world...

When scientists found the 18,000-year-old bones of a small, humanlike creature on the Indonesian island of Flores in 2003, they concluded that the bones represented a new species in the human family tree they named Homo floresiensis. Their interpretation was widely accepted by the scientific community and heralded by press around the world. Because of its very short stature, H. floresiensis was dubbed the ‘Hobbit’.

But a team of multidisciplinary team of scientists, including Roehampton University’s Professor of Evolutionary Anthropology, Ann MacLarnon, with colleagues from Chicago has found that the bones in question do not represent a new species at all.

Their results, to be published in the May 19 issue of prestigious journal Science, found that a far more likely explanation is that the bones belonged to a modern human who suffered from microcephaly, a pathological condition that causes small brain size, often associated with short stature.

“The proposed new hominid species is based primarily on a specimen known as LB1 consisting of a diminutive adult skull and partial skeleton about three feet tall. Initially, H. floresiensis was claimed to be a dwarf derived from Homo erectus, a human ancestor that lived as far back as 1.8 million years ago. This seemed like an appealing explanation because islands are known to play tricks on the evolution of animals, sometimes causing them to shrink due to limited food supplies and the reduced presence of predators.

“The evidence used by some scientists to rule out the possibility that LB1 could have been microcephalic is flawed. In research published last year that attempted to exclude this possibility, a team led by Dean Falk studied a virtual brain cast from a single microcephalic skull, even though microcephaly can take dozens of different forms,” said Prof. MacLarnon.

“Furthermore, the skull from which the brain cast was made was that of a 10-year-old child, whereas LB1 was an adult and should have been compared with human microcephalics with a relatively mild condition that would have permitted survival into adulthood. Finally, the skull from which the virtual brain cast was generated is a poor-quality, plaster copy comprised of two parts that do not match up!

“But all mammals that shrink because of an island’s resources, or any other reason, such as selective breeding, do so within certain parameters: body size can shrink considerably, but brain size always shrinks moderately. At 400 cubic centimetres LB1’s brain is simply too small to follow this universal law,” she said.

“In fact, for LB1 to be a dwarfed form of H. erectus, it would have to have been just one foot tall with a body weight of only four pounds to explain such a diminutive brain. The tiny cranial capacity of LB1, which is smaller than in any other known hominid younger than 3.0 million years old, is demonstrably far too small to have been derived from Homo erectus by normal dwarfing.”

She also said the defective plaster copy of a microcephalic skull used in the study by Falk et al. was inappropriate for any scientific study: “Quite simply, it was the worst possible choice for this study. The cranial capacity turned out to be only 260 cc, just over half of that recorded for the LB1 skull, and is one of the smallest that I have so far found in a survey.”

Small brain size is just one of several problems with the science behind claims that LB1 represents a new species, according to the authors. The primary problem, clashing directly with the tiny brain size, is the sophisticated nature of the stone tools found in the same cave deposits where the fossils were discovered. Based on their size, style, and workmanship, these tools belong to types that are consistently associated with modern humans, or Homo sapiens. Such tools have never been associated with H. erectus or any other early hominid. They are so advanced that is highly improbable they were made by anyone other than Homo sapiens. Another problem with the science surrounding the interpretation of the Flores fossils is that a distinct species of hominid so closely resembling modern humans but living only 18,000 years ago is virtually inconceivable given that H. sapiens had almost certainly reached Flores by that time.

The plaster copy of the microcephalic skull, which was made more than 100 years ago, is housed at the American Museum of Natural History in New York. It took some detective work on the part of Prof. Martin, from the Field Museum, Chicago, to track down the original skull (from which the plaster copy had been made). It is held in the collections at the Natural History Museum in Stuttgart, Germany.

This leaves the theory that LB1 was a microcephalic modern human as the only plausible explanation for the Flores fossils, according to the authors. They believe there has been too much media hype and too little critical scientific evaluation surrounding this discovery.