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3: Pliocene Epoch
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- 3.1: Introduction to the Pliocene Epoch
- The Pliocene Epoch (~5.3–2.6 mya) was characterized by global cooling and weather disruptions due to the formation of the Panama land bridge and resultant changes in ocean currents. The polar ice caps were expanding and sea levels had already begun to drop, as the Pleistocene Epoch (~2.6 mya–11.7 kya) approached. The geologic record shows us that Africa was subject to cooling and drying trends, with seasons becoming more pronounced.
- 3.2: Australopithecus anamensis
- Australopithecus anamensis is the earliest known australopith. We do not know nearly as much about the species as about other australopiths due to a paucity of fossil material.
- 3.3: Gracile Australopiths
- Genus Australopithecus (“southern ape”) was first used in 1924 by Raymond Dart for the “Taung Child,” a juvenile Au. africanus specimen from the quarry site of Taung, in South Africa. Au. anamensis, afarensis, africanus, and sediba (depending on the evolutionary schema of individual paleoanthropologists) are popularly known as gracile australopiths, due to their more gracile masticatory apparatus relative to the robust paranthropines.
- 3.4: Australopithecus afarensis
- Australopithecus afarensis, or the “southern ape from Afar,” is a well-known species due to the famous “Lucy” specimen. It has been extensively studied by numerous famous paleoanthropologists. As mentioned, it is categorized as a gracile form of australopith. The species survived for over a million years in the changing East African landscape, covering a broad geographic range.
- 3.5: Australopithecus bahrelghazali
- While it is possible that Au. bahrelghazali was a distinct species, the majority view is that it was a geographic variant of Au. afarensis.
- 3.6: Kenyanthropus platyops
- A surprisingly “flat-faced” hominin came to light with Meave Leakey’s discovery and naming of Kenyanthropus platyops (“flat-faced human from Kenya”) in 1999. The degree of orthognathism was surprising for such an early hominin.
- 3.7: Australopithecus prometheus or africanus
- The controversial material that has come to be known as “Little Foot” is an almost complete skeleton from the site of Sterkfontein. The story is remarkable in that the skeletal components were discovered at two different times. The earlier material was cataloged and stored as “cercopithecoid” (Old World monkey) remains. Fifteen years later, the rest of the skeleton was found at the same location at Sterkfontein (Silberburg Grotto) and matched to the previous material.
- 3.8: Australopithecus africanus
- Australopithecus africanus was the first fossil hominin discovered in Africa. In 1924, Raymond Dart identified the face, mandible, and endocast as being that of a juvenile bipedal ape. Eugène Dubois’s discovery of the Javanese Homo erectus fossils in 1891 refuted the reigning belief that “we got smart before we stood up.” Once Dart’s claims were accepted, the world realized the extent to which that idea was false. Early hominins were bipedal apes as opposed to quadrupedal humans.