New hominid species may be early version of Homo sapiens
In 2003, when fossil remains were uncovered in Liang Bua Cave on the Indonesian island of Flores, the discoverers dubbed the remains Homo floresiensis, a new hominid species. But in a new study, published online October 9, 2006 in The Anatomical Record, the official journal of the American Association of Anatomists, researchers suggest that the remains are, in fact, a Homo sapiens with microcephaly, an abnormally small head. The study is available via Wiley InterScience at http://www.interscience.wiley.com/journal/ar.
The main specimen of the remains, dated at about 18,000 years ago, consists of a skull and partial skeleton from a dentally adult individual (LB1). Using femur length to extrapolate height, the stature of the skeleton was estimated to be 106 cm. Other notable features were the absence of a chin in the jawbone and a very small cranial capacity. In addition to LB1, fragments of eight other individuals were found, along with advanced stone tools. The initial conclusion was that H. floresiensis was a new species, a dwarf derived from Home erectus.
In the current article, Professor Robert D. Martin of The Field Museum in Chicago, IL, and colleagues painstakingly analyze the anatomy of the remains in order to put forth the case that they are H. sapiens that had suffered from some kind of pathology. Although the original paper following the discovery dismissed the idea of microcephaly because the skeletal features did not seem to fit with this condition, the authors note that the skeleton displays many features of syndromes of microcephaly in modern man, of which there are more than 400 types often associated with severe short stature. They note that whatever condition afflicted the individual would not have prevented survival to adulthood, which is entirely possible with certain forms of microcephaly. According to their analysis, if the height, body mass, head circumference, and other anatomical anomalies attributed to H. floresiensis were compared to modern human standards, the result would be a believable, although malformed, individual. "All of these abnormalities taken together would lead to diagnosis of a severe short stature with microcephaly syndrome, although data are not sufficient to match this to a specific known syndrome," the authors state. They also point out that all microcephaly syndromes typically derive from an autosomal recessive gene and can easily recur in a small, inbred population, which would explain the presence of more than one specimen on an isolated island. In addition, they analyze several microcephalic syndromes that could be applied to the LB1 skull. "We find that this group of syndromes shares several features with the LB1 fossil, including very similar small stature and head size, a small and receding jaw, and dental anomalies," they write.
With regard to the stone tools found near the specimens, the authors note that they "clearly belong to types that are consistently associated with Homo sapiens and have not previously been associated with H. erectus or any other early hominid." In fact, they find it questionable whether H. erectus ever made his way to Flores, as the main evidence for his arrival, namely stone tools found in another location but dated much earlier, is equivocal. The authors conclude that "the features of LB1 best support the interpretation that it is a pathological, microcephalic specimen of Homo sapiens."
In an accompanying editorial, Associate Editor Jeffrey T. Laitman, and Editor-in-Chief Kurt H. Albertine cite numerous examples in which The Anatomical Record has published insightful studies on the analysis of material from prehistoric and early man, a tradition which is continued in the current issue. "Martin and colleagues present a detailed challenge to the species claim for Flores, advancing evidence to support their hypothesis that the brains of the little people were diminutive not due to distinctive evolution along a species line, but due to microcephaly," they write. "Are the Flores hominids really a new species or microcephalic dwarfs?" they ask. "Within the pages of this month's Anatomical Record the arguments will unfurl."
Article: "Flores Hominid: New Species or Microcephalic Dwarf?" Robert D. Martin, Ann M. MacLarnon, James L. Phillips, William B. Dobyns, The Anatomical Record Part A, Published Online: October 9, 2006 (DOI: 10.1002/ar.a.20389).
Editorial: "The Anatomical Record: A Tradition of Reporting What Is New About Things That Are Very, Very Old," Jeffrey T. Laitman, Kurt H. Albertine, The Anatomical Record Part A, Published Online: October 9, 2006 (DOI: 10.1002/ar.a.20394).
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