lec9.pdf

Early Hominins Pre- Australopithecines ( 7 - 4.4 mya) Sahelanthropus tchadensis, Ororin tugensis Ardipithecus kadaba, ramidis Early Australopithecines (4.2 - 1.2 mya) anamensis afarensis Later More Derived Australopiths (2.5-1.2mya) Paranthropus aethiopicus Paranthropus boisei Australopithecus africanus Paranthropus robustus The Path to Humanes: Biger Brains, Tol Use, and Adaptive Flexibility Homo habilis OH-24 KNM-ER 1470 -1.8mya, 80c Richard Leakey KNM-ER 1813 Change tok place 3.0?2.5 mya Homo habilis and Australopithecus Homo erectus and the early Pleistocene record The earliest hominid ancestors, the preaustralopithecines, (S. tchadensis, O. tugensis, A. kadaba, A. ramidus) lived in a forested seting, although it might have had a discontinuous tre cover. Found by Maeve Leakey, Carol Ward, and Alan Walker; other remains studied by Tim White Located at Lake Turkana and Ethiopia and dated to 4 mya Physically somewhat similar to Ardipithecus Primitive dentition - large canines, parallel tooth rows, different cusp pattern on lower first premolar (sectoral first premolar - shearing surface) Australopiths Australopithecus anamensis (4 mya) U shaped versus parabolic shaped mandible Found by Donald Johanson, Maurice Taib, and Tim White Located in Laetoli and Hadar (found first in Hadar) and dated to 3.6?3.0 mya Lucy (type specimen) is very complete for the age, 40 percent of skeleton found Bipedal but with shorter legs, resulting in a slightly diferent stride Long arms, curved finger bones, sugesting tre use Cranial capacity of 430 c At Laetoli, asemblages include hominids as wel as fotprints of thre hominids Lived in varied habitats Australopiths Australpithecus afarensis(3.6-3.0 mya) fosil remains of a thre-year-old child Evolution and Extinction of the Australopiths - East Africa Paranthropus aethiopicus and Paranthropus boisei Found in Lake Turkana (P. aethiopicus), Olduvai Gorge (P. boisei), and other locations in Africa P. aethiopicus dates to 2.5 mya and had a cranial capacity of 410 c P. boisei dates to 2.3?1.2 mya and had a cranial capacity of 510 c Smaler front teth, larger back teth Sagital crest for atachment of chewing muscles Dietary focus on harder fods Evolution and Extinction of the Australopiths South Africa Australopithecus africanus Found by Raymond Dart Found at Taung, South Africa and other sites, dating to 3?2 mya Larger teth than A. afarensis Brain size of 450 c Evolution and Extinction of the Australopiths - South Africa Paranthropus robustus Found in South Africa and dated to 2 mya Large premolars and molars, with a large face and sagital crest Similar to East African forms Brain size of 530 c Evolution of earliest hominins resulted in a diverse group of species. The earliest hominids can be grouped as folows: ? Pre- Australopithecines ( 7 - 4.4 mya) Sahelanthropus tchadensis, Ororin tugensis Ardipithecus kadaba, ramidis ? Early Australopithecines (4.2 - 1.2 mya) anamensis Afarensis ? Later More Derived Australopiths (2.5-1.2mya) Paranthropus aethiopicus Paranthropus boisei Australopithecus africanus Paranthropus robustus Change in facial structure reflected dietary specialization. No large change found in brain size. The ?robust? lineage is present in both East (P. aethiopicus, P. boisei) and South Africa (). robustus), but the ?gracile? lineage (A. africanus) is only in South Africa. Sumary of Early Hominins ?Gracile? australopithecines are smal-brained but not as large-tothed as the ?robust? varieties. There sem to be no significant diferences in body size betwen the ?robust? and ?gracile? varieties. Dietary specialization, might have led to the eventual extinction of both P. robustus and the East African robust species, as they were not able to adapt to vegetation changes caused by climate change. Sumary of Early Hominins con?t Time Line of Plio-pleistocene hominins The Path to Humanes: Biger Brains, Tol Use, and Adaptive Flexibility During the 1960s, Mary and Louis Leakey(Paranthropus boisei) continued work at Olduvai Fragmentary fosils dating to 2 mya Larger cranial capacity OH-24 KNM-ER 1470 -1.8mya, 80c Richard Leakey KNM-ER 1813 Change tok place 3.0?2.5 mya Homo habilis and Australopithecus: Similar in Body Plan Immediate ancestor unconfirmed Bigger brain, smaller chewing complex Body plan similar to that of australopithecines Homo habilis OH24 Tanzania 1.8mya KNM ER 1470 Kenya 1.8mya Distinctive features of Homo habilis Larger brain case (80c) Larger and narower face Canines and incisors larger than A. robustus Molars and premolars smaller No sagital crest Oldowan Tols Homo habilis?s Adaptation: Inteligence and Tol Use Become Important Archaeological sites Stone tols - most widespread and persistent type of tol industry 2.5 mya Olduvai, Lake Turkana, Omo, Swartkrans Core and flake tols - simple, relatively efective tols Anatomical evidence from the hand bones sugests precision grip. Tols becoming fundamental to survival, unlike australopiths Habitat Changes and Increasing Adaptive Flexibility Spread of warm season grasses and increasing habitat diversity. Skull and tooth morphology suggest dietary variability in Homo habilis. Stone tools important for obtaining food resources as well as for processing foods. Homo erectus and the early Pleistocene record The Pleistocene 1.8 mya to 10,00 ya (lasted 1.75 my - encompased the emergence and disapearance of Homo erectus) known as the ice age major fluctuations in climate Niche Diferentiation H. erectus, A. boisie, H. habilis co-exisiting in east Africa 1.6mya each exploiting a diferent niche While both of these genera were contemporaneous for a period of time in Africa, there are important differences in their cranial and dental morphologies. ?Homo erectus 1.8 mya- 20,00 ya Homo erectus was the first hominid to expand into new regions of the Old World. As a species, H. erectus existed over 1 million years. The behavioral capacities of H. erectus, along with the morphological changes, help us understand its suces as a hominid species. ?Homo erectus left Africa about 1.8 mya. ?From Kenya they headed north, where we find them first in the Republic of Georgia, at a site named Dmanisi, in the Caucasus region. ?The next earliest fossil sites are found on the island of Java, Indonesia. ?About 1.6 mya H. erectus was living in three geographically divided regions: East Africa, eastern Europe, and Southeast Asia. Homo erectus In the last few decades, discoveries from East Africa established Homo erectus by 1.8 m.y.a. Some researchers see anatomical differences between these African discoveries and the Asian discoveries. They place the African fosils into a species, they cal Homo ergaster. Analyses show that H. erectus/ergaster represents a different grade of evolution than their African predecessors. Morphology of Homo erectus Brain size as related to overall body size increased. Body size dramatically increased compared to earlier hoinins. Cranium had a distinctive shape with a thick cranial bone and large brow ridges. Shovel-shaped incisors sugest an adaptation in hunter-gatherers. The Dmanisi hominins The discovery of the Dmanisi materials began in the early 190s. The most informative specimens are four wel-preserved crania, with one recently discovered being almost complete. These remains are the best-preserved hominins of this age found anywhere outside of Africa -1.8 mya They exhibit a mixed set of characteristics, some quite unexpected. The Dmanisi hominins The Dmanisi crania have some similarities to H. erectus, while some characteristics are different from other hominid finds outside of Africa. The most complete specimen has a les robust and thiner browridge, a projecting lower face, and a large uper canine. Al thre Dmanisi crania have smal cranial capacities. A number of stone tols, similar to early ones from Africa, have ben recovered at Dmanisi. Questions Raised by the Dmanisi Discoveries Was Homo erectus the first hominid to leave Africa?or was it an earlier form of Homo? Did hominins require a large brain and sophisticated stone tool culture to disperse out of Africa? Was the large, robust body build of H. erectus a necessary adaptation for the initial occupation of Eurasia? Patricia Richards lec9austr,homospr10.ppt