Australopithecus garhi


Introduction

The naming of a new species is almost always controversial, and Australopithecus garhi is no exception. Named in the April 23, 1999, issue of Science, the large research group that discovered the finds made some broad claims and supposition that is definitely not accepted by all, though any real acceptance of these claims and/or hypotheses will have to come later on, as time enough passes for the information has been fully disseminated, others have had a chance to examine the remains, and the dust has settled.

The remains that are directly attributed to the new species come from the Hatayae Member of the Bouri Formation, Ethiopia, and have been dated to approximately 2.5 myr. The type specimen of the species is BOU-VP-12/130, an associated set of cranial fragments comprising the frontal, parietals, and maxilla with dentition. The specimen was discovered by Y. Haile-Selassie on November 20, 1997, and the word garhi means “surprise” in the local Afar language. These specimens are important no matter what the eventual final attribution, due to the fact that the remains are from East Africa at a time when there is very little remains (2.0–3.0 myr).


Diagnostic Features

One of the more striking features of the A. garhi remains is the size of the postcanine dentition, which is at or beyond the nonrobust australopithecine or A. robustus extremes. This is the only feature that suggests any link to the robusts, and as such it is very unlikely that the specimen is in any way derived from or is a sister species to robustus. This is seen especially in the large size of the anterior teeth, exceeding those of the largest australopithecines and far exceeding the robusts, who are marked by anterior tooth reduction or stasis. Based on tooth size, the garhi material seems to fit well with schemes that see either one or both of africanusand afarensis as a direct human descendent, as the canine-to-premolar/molar size ratios are comparable to both species and early Homo.

The cranial attributes do not seem to directly make an attribution or negate the possibility of attribution to a specific phylogeny, but this may be due to the sparse nature of the remains and the small sample size (the sample size must be kept in mind of any phylogenetic discussion based on the described traits). Specific cranial attributes include:

  • The lower face is prognathic with procumbent incisors.
  • Canine roots are placed quite laterally to the nasal aperture margin.
  • The premaxillary surface is separated from the nasal floor by a blunt ridge and is transversely and sagittally convex.
  • The palate is vertically thin.
  • The zygomatic roots originate above P4/M1.
  • The dental arcade is U-shaped, with slightly divergent dental rows.
  • The temporal lines encroach deeply on the frontal, past the midsupraorbital position and likely met anterior to bregma.
  • The postglabellar frontal squama is depressed in a frontal trigon. The localized frontal sinus is limited to the medial one-third of the supraorbital surface.
  • There is marked postorbital constriction.
  • The parietal bones have a well-formed, bipartite, anteriorly positioned sagittal crest that divides above lambda.
  • Cranial capacity of approximately 450 cc (reconstructed).


Conclusions

There is not much to conclude at this point, merely to explain what the researchers hypothesize as the possible phylogenetic relationship of A. garhi. The researchers discuss the idea that garhi represents a direct ancestor of modern humans that is derived from africanus which is likely derived itself from afarensis. This does fit in with Wolpoff’s idea of an unidentified late africanus group with many robust features, but know one can say with any certainty at this point. The specimens may even be attributed to Homo rather than Australopithecus. All that can be done now is to watch what unfolds.

 

Bibliography

Aiello, L., and C. Dean. 1990. An Introduction to Human Evolutionary Anatomy. London: Academic Press.
Asfaw, B., T.D. White, O. Lovejoy, B. Latimer, S. Simpson, and G. Suwa. 1999. “Australopithecus garhi: A new species of early hominid from Ethiopia.” In Science, vol. 284, pp. 629–635.
Culotta, E. 1999. “A new human ancestor?” In Science, vol. 284, pp. 572–573.
de Heinzelin, J., J.D. Clark, T.D. White, W. Hart, P. Renne, G. WoldeGabriel, Y. Beyene, and E. Vrba. 1999. “Environment and behavior of 2.5-million-year-old Bouri Hominids.” In Science, vol. 284, pp. 625–629.
Wolpoff, M. 1999. Paleoanthropology. second edition. Boston: McGraw-Hill.