From trees to the ground: The significance of australopithecus anamensis in human evolution

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Abstract

Recent fossil discoveries of early human ancestors from paleoanthropological sites in Africa and elsewhere have demonstrated how various phases of human evolutionary history were much more complicated than previously thought. The fossil record is always far from complete, and in some time slices too scarce, to provide a very detailed picture of how we became who we are today. Inadequate sample size and unsampled time periods in the fossil record are major impediments to conducting comprehensive and more rigorous analyses to test new and existing hypotheses. However, there are also instances where a single specimen, such as the 3.8-million-year-old Australopithecus anamensis cranium (MRD-VP-1/1) from the Afar region of Ethiopia, can provide a wealth of information on the paleobiology, paleoecology, paleogeography, and phylogenetic relationships of a particular species. Such specimens are extremely rare in the fossil record, but when they are discovered, they can fundamentally increase our understanding of the anatomy of a species and clarify its relationships with other species. For example, MRD-VP-1/1 provides the first glimpse of the craniofacial anatomy of Australopithecus anamensis and demonstrates that this species retained a number of primitive features similar to those of its predecessors, while sharing derived features with its descendant, Australopithecus afarensis. This is new information that paleoanthropologists did not have until the discovery of MRD-VP-1/1. The mosaic nature of its morphology combined with its geological age places Au. anamensis at the root of the origin of the genus Australopithecus and as a possible ancestor of all later hominins. Although this species has been hypothesized as the linear ancestor of Au. afarensis, recent fossil discoveries from Woranso-Mille indicate that MRD-VP-1/1 probably represents a geographically isolated Au. anamensis population that may have followed an evolutionary trajectory different from its conspecific populations elsewhere. The contemporaneous presence of mid-Pliocene non-Australopithecus afarensis species at Woranso-Mille and in the Turkana Basin (Kenya) shows just how complex the earlier phases of human evolution were. These assumptions will require further investigation with increased sample sizes and better understanding of temporal and spatial distribution of different hominin species during the mid-Pliocene of eastern Africa.

Original languageEnglish (US)
Pages (from-to)457-482
Number of pages26
JournalJournal of Anthropological Research
Volume77
Issue number4
DOIs
StatePublished - Dec 1 2021

Keywords

  • Australopithecus anamensis
  • Hominin biogeography
  • Hominin diversity
  • Phylogenetic relationships
  • Woranso-Mille

ASJC Scopus subject areas

  • Anthropology
  • Arts and Humanities (miscellaneous)

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