Australopithecus garhi

Australopithecus garhi, the Hominin SurpriseJenna Wesley

Overview

Discovery

Fossils

Overview

Australopithecus garhi is a hominin species hailing from Middle Awash, Ethiopia, and is a unique link between the African Australopithecines. Its juxtaposition of ancestral and derived traits make this species an important, though modest, informant in the understanding the human lineage.

Discovery

The first evidence of Australopithecus garhi was discovered in 1997 by Yohannes Haile-Selassie while excavating in Bouri, Middle Awash, Ethiopia. Haile-Selassie, working with Berhane Asfaw, Tim White, and other notable paleoanthropologists, discovered that the morphologies recorded from this sample were unlike any other known species, and declared this find to be representative of a new one altogether: Australopithecus garhi.

Fossils

BOU-VP 12/130 with reconstruction (Asfaw, 1999)

BOU-VP 12/130

Australopithecus garhi is a species poorly represented in the fossil record. Its type specimen, BOU-VP 12/130, is the only confirmed fossil for this species, though several other fossils were found near and in potential association with BOU-VP 2/130 (Asfaw, 1999).

BOU-VP 12/130 is a set of cranio dental remains showing a mixture of ancestral and derived characteristics:

Ancestral:

Cranial capacity (450cc)
Prognathism
U-shaped dental arcade
Maxillary Diastema

Derived:

Megadont teeth
Thicker enamel

Overall, A. garhi boasts teeth larger than most other Australopithecines. Shown in the figure on the right, A. garhi also maintains the ancestral u-shaped dental arcade, more similar to A. afarensis as opposed to the more parabolic dental arcade of A. boisei. In addition to these two species, analyses by Asfaw et. al suggest that A. garhi presents traits found in both A. africanus and Early Homo.

Asfaw et. al have concluded that, based on sheer size, BOU-VP 12/130 is like a male. Because of the documented dimorphism in A. afarensis and A. boisei, projections for A. garhi would result in smaller craniodental traits. Therefore, the robusticity present in BOU-VP 12/130 suggests that this individual was male.

All A. garhi Fossils

Though not confirmed, other fossils associated with A. garhi are:

BOU-VP-11/1
- proximal portion of adult ulna
BOU-VP-12/1A-G
- proximal femur and associated forearm elements
BOU-VP-12/87
- crested cranial vault fragment
BOU-VP-17/1
- mostly complete mandible with dentition
BOU-VP-35/1
- humeral shaft

Comparison of palates between Australopithecus afarensis (A), Australopithecus boisei (B), and Australopithecus garhi (C & D) (Asfaaw, 1999).

"On biochronological grounds, these...specimens are about the same age as the more southerly cluster of hominid remains at Bouri localities 11 and 12" (Asfaw, 1999). This means that while the fossils listed to the left are not currently recognized as being classified as A. garhi, they are likely from the same time period. And, because no other hominin species have been found in this location, paleoanthropologists conjecture that these fossils are related to A. garhi (Australopithecus, 2025).

These associated fossils provide postcranial evidence that A. garhi may be an intermediate between A. africanus and Early Homo. BOU-VP-12/1A-G, the proximal femur, shows elongation relative to the humerus, similar to that of Homo. However, while the ratio of femur to humerus has increased, the humerus is still fairly long. This suggests that A. garhi may have retained arboreal capabilities while simulatneously engaging in bipedalism (Johanson, 2019).

Evolutionary Tree

"(A) Aladogram depicting relationships among widely recognized early hominid taxa...(B) the chronological relationships of early hominid taxa...(C to F) Alternative phylogenies depicting possible relationships among early hominid taxa" (Asfaw, 1999).

"Schematic temporal distribution of and relationships among Australopithecus species, putative ancestral and descendant taxa solely on the basis of FAD and LAD" (Alamseged, 2023).

While Australopithecis garhi is made of a small fossil sample, it plays a large role in the overall understanding of hominin ancestry. A. garhi exhibits a mixture of traits found in both preceding (such as A. afarensis) and succeeding (such as A. africanus, A. boisei, and Homo) species. As more fossils are recovered, A. garhi may play a larger role in understanding intermediaries between Australopithecines and Homos.

References

Alemseged, Zeresenay. “Reappraising the Palaeobiology of Australopithecus.” Nature, vol. 617, no. 7959, 3 May 2023, pp. 45–54, https://doi.org/10.1038/s41586-023-05957-1. Accessed 17 Dec. 2023.

Asfaw, B. “Australopithecus Garhi: A New Species of Early Hominid from Ethiopia.” Science, vol. 284, no. 5414, 23 Apr. 1999, pp. 629–635, https://doi.org/10.1126/science.284.5414.629.

“Australopithecus Garhi • Becoming Human.” Becoming Human, Institute of Human Origins, becominghuman.org/hominin-fossils/australopithecus-garhi/. Accessed 25 Feb. 2025.

Johanson, Donald, and Henry McHenry. “Australopithecus - Australopithecus Afarensis and Au. Garhi.” Encyclopædia Britannica, 2019, www.britannica.com/topic/Australopithecus/Australopithecus-afarensis-and-Au-garhi.

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