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Part IV: Pleistocene Epoch

[ "article:topic-guide", "authorname:bwelker" ]
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  • The Pleistocene epoch is often colloquially referred to as the Ice Age and lasted from about 2,588,000 to 11,700 years ago, spanning the world's most recent period of repeated glaciations.

    • Introduction to the Pleistocene Epoch
      The Pleistocene Epoch is commonly known as the Ice Age. The climate of Africa continued on the trajectory that began in the late Miocene and continued throughout the Pliocene. While the Pleistocene was characterized as a period of global cooling, glacial advances, and dropping sea levels, the cold periods were interspersed with interglacial periods when the ice retreated and sea levels rose.
    • 16: Paranthropines
      The paranthropines are three species of fossil hominins that exhibited hyper-robust masticatory apparatus, as evidenced by their heavy faces and mandibles, huge molars, and muscle insertions. They were included in the genus Australopithecus for many years, but the original genus invented by Robert Broom for the South African form, Paranthropus robustus, has been revived for at least two of the species.
    • 17: Australopithecus/Paranthropus aethiopicus
      Australopithecus aethiopicus is the most primitive of the robust species. I use genus Australopithecus because it is thought to be descended from Au. afarensis. In addition, Paranthropus was the genus name assigned to the South African robust form, P. robustus, and questions remain as to whether the two species are related.
    • 18: Paranthropus boisei
      Fossils from more than 100 individuals have been recovered in the last 55 years. Over time, the genus has changed from Zinjanthropus to Australopithecus to Paranthropus, but some researchers are still using genus: Australopithecus.
    • 19: Paranthropus robustus
      In 1938, Robert Broom discovered the first Paranthropus robustus material at the site of Swartkrans, South Africa. He later found material at Kromdraai, and because the molar teeth were more primitive at that site, he changed the species name at Swartkrans to P. crassidens but used P. robustus for the Kromdraai material.
    • 20: Australopithecus garhi
      In 1996, researchers recovered portions of the frontal and parietal bones as well as a maxilla that contained teeth. These materials were attributed to Australopithecus garhi. While nearby limb bones could not be attributed to the species with absolute certainty, they have been used by some paleoanthropologists to describe the species’ characteristics. Thus there is very little useful material to “reconstruct” this species.
    • 21: Australopithecus sediba
      Six well-preserved individuals of a new species of Australopithecus were discovered, beginning in 2008, at the cave site of Malapa, South Africa. Lee Berger’s crew is credited with the discovery after Berger’s nine-year-old son Matthew happened upon the fossils of a juvenile male (MH1) that became the holotype for the species. The other five individuals were an adult male, an adult female (MH2) and, remarkably, an infant.
    • 22: Genus Homo
      It is generally thought that by 2.5 mya, there were at least two species of Homo in East Africa, Homo habilis and Homo rudolfensis. The inclusion of those fossils in our genus is not accepted by all and is somewhat arbitrary. Some argue that H. habilis does not differ enough from australopiths to warrant different genus designation. Its inclusion in Homo was prompted by the fact that they are thought to have made and used tools and thus to have been cognitively advanced.
    • 23: Homo habilis
      Louis and Mary Leakey discovered the first fossil material in 1960 at their site in Olduvai Gorge, Tanzania. Louis had been recovering stone tools from the site for years, but the manufacturer of those tools had previously eluded him. He named the species Homo habilis or “handy-man.” Fossils attributed to H. habilis have also been found at Hadar (and possibly Omo), Ethiopia; Koobi Fora, Kenya; and the South African sites of Swartkrans and Sterkfontein.
    • 24: Homo rudolfensis
      The second species of Early Homo to be discovered is now known as Homo rudolfensis, since it was discovered at the site of Koobi Fora on the east side of Lake Turkana, which was formerly known as Lake Rudolf.
    • 25: Homo species indeterminate
      A possible new species of Early Homo was recently discovered. Villmoare et al. (2015) reported on what they are calling Homo species indet. (“indeterminate”).
    • 26: Homo naledi
      This newest member of our genus has once again confounded the evolutionary history of the Homo lineage. The most exciting aspect is the nature of the remains suggests that they were intentionally deposited in the deep cavern where they were discovered. H. heidelbergensis was heretofore the earliest species thought to have practiced intentional body disposal. Attempts at dating the remains have not been successful.
    • 27: The “erectus Grade”
      The species that are collectively known as the erectus grade are believed to be descendants of the African “erectus” form, Homo ergaster, which in turn is thought to be descended from one of the two species of early Homo, H. habilis or H. rudolfensis. They lived in one form or another from 1.8 mya to as recently as 25–17 kya. H. erectus was first discovered by Eugène Dubois in 1891, at the Trinil site on the Solo River in Java.
    • 28: Homo ergaster
      H. ergaster is thought to have evolved from either H. habilis or H. rudolfensis in East Africa. However, it is possible that H. habilis may have been the first to leave Africa, after which it may have evolved into a pre-ergaster/erectus form that then moved into Africa and Asia. If H. habilis was in our ancestry, the latter scenario might explain how the more modernly proportioned H. ergaster appeared in the fossil record contemporary with H. habilis in East Africa.
    • 29: Homo erectus
      Homo erectus is the genus and species combination that was retained for all mainland Asian, Taiwanese, and Javanese fossil material.
    • 30: Homo georgicus
      Located in the southern Caucasus region of the Republic of Georgia, Dmanisi is the only known site for the geographic species Homo georgicus, of the erectus grade. Some treat it as a subspecies of Homo erectus, H. erectus georgicus, while others attribute it to H. erectus.
    • 31: Homo antecessor
      Until the recent discovery of hominin fossils dating to over 1.2 mya in the Atapuerca Mountains of Spain, the earliest known fossil material from the area was no more than 800 kya. The 800 kya material was assigned the taxonomic designation of Homo antecessor, or “Pioneer Man,” as the first hominins to have ranged into Western Europe.
    • 32: Homo floresiensis
      The material assigned to the species Homo floresiensis comes only from the cave site of Liang Bua  on the island of Flores in Indonesia. Because of its diminutive size, the new species took the world by storm when it was discovered in 2003 by Mike Morwood and his team. While tools attributed to the species have been dated to almost 100 kya, skeletal remains are dated to as young as 18 kya and as old as 95–74 kya.
    • 33: Homo heidelbergensis
      Fossil material from Europe and Africa that was formerly assigned to “Early Archaic” Homo sapiens is now termed Homo heidelbergensis, with some researchers using Homo rhodesiensis for some of the African material. It is now well accepted that H. heidelbergensis was ancestral to both humans and neandertals.
    • 34: The Denisovans
      In 2008, Russian scientists Michael Shunkov (paleontologist) and Anatoly Derevianko (archaeologist) discovered a terminal finger phalanx from a young girl, dubbed “X-woman,” in the Denisova Cave in the Altai Mountains of Russia. The Denisovans, as they have come to be called, inhabited the cave by 50 kya.
    • 35: Homo neanderthalensis
      Although Homo neanderthalensis was originally included in our own genus and species but distinguished by subspecies status, i.e. Homo sapiens neanderthalensis, increasing evidence from DNA analysis suggests that the two lineages split sometime prior to 300 kya and, if new DNA evidence is correct, possibly prior to 800 kya. However, DNA evidence shows that they interbred.
    • 36: Homo sapiens
      The origin of our species is thought to have occurred in Africa sometime prior to 200 kya, based on fossil and genetic evidence. We may be descended from an African population of Homo heidelbergensis (sometimes referred to as Homo rhodesiensis) or an earlier common ancestor of heidelbergensis, based on recent genetic evidence. Fossils characteristic of a transitional form, termed Homo helmei, are found at the South African site of Florisbad and dated to 260 kya.

    Thumbnail: Pleistocene of South America showing Megatherium and two Glyptodon. Image used with permission CC BY-sa 3.0; DiBgd).