Lecture+25+notes.pdf

Introduction to Human Evolution Lecture 25 notes th Wednesday, November 8 • Today: o Introduction to Australopiths ▪ Gracile Group • Australopiths (4.2-1.2 mya) o Have an established time range of over 3 million years o The best known, most widely distributed, and most diverse of the early Africa...

Introduction to Human Evolution Lecture 25 notes th Wednesday, November 8 • Today: o Introduction to Australopiths ▪ Gracile Group • Australopiths (4.2-1.2 mya) o Have an established time range of over 3 million years o The best known, most widely distributed, and most diverse of the early African Hominins o Made up of two closely related genera: ▪ Australopithecus and Paranthropus • Gracile and Robust groups • Australopiths (4.2-1.2 mya) o Major features ▪ They are all bipedal (although not necessarily identical to Homo in this regard) ▪ They all have relatively small brains (i.e., compared to Homo) ▪ They all have large teeth, particularly back teeth, with thick to very thick enamel on the molars • “Gracile” Australopiths o Key Species: Australopithecus afarensis, Australopithecus africanus o Pliocene – early Pleistocene (4.2-2.0 mya) o Eastern Africa, Southern Africa, and North-Central Africa o Size: Large (30-60 kg or 66-132 lbs) o Terrestrial bipedalism, some arboreal suspension/climbing • “Gracile Australopiths” o A. Africanus was discovered in S. Africa ▪ Lived in wooded or savannah-woodland mosaic habitats ▪ Brain slightly larger than apes (400 – 550 cc) ▪ Large molars & premolars with blunt cusps and thick enamel, thick jaws, further reduced canines ▪ Many traits indicating terrestrial bipedalism, although unlike bipedalism in modern humans ▪ Several traits indicating arboreal behaviors ▪ Considerable sexual dimorphism in body size ▪ Possibly made stone tools • Australopithecus afarensis o Lived in wooded or savannah-woodland mosaic habitats o Brain slightly larger than apes (400 – 550 cc) o Large molars & premolars with blunt cusps and thick enamel, thick jaws, further reduced canines o o o o Many traits indicating terrestrial bipedalism, although unlike bipedalism in modern humans Several traits indicating arboreal behaviors Considerable sexual dimorphism in body size Possibly made stone tools • Australopiths o The most famous fossil is that of “Lucy” ▪ Named for the Beatles song, “Lucy in the Sky with Diamonds” ▪ Nearly 40% complete skeleton of A. afarensis ▪ Bipedal ▪ Evidence for tree-climbing adaptation in long arms and curved fingers and tows ▪ Small-brained and otherwise similar to a chimpanzee o • Changes in Hominin Dentition o Teeth showed an evolutionary trend toward smaller front teeth and very large back teeth o o Dental arch becomes parabolic unlike apes with a “U” shaped arch Viewed as an adaptation to diet • Dental Changes o Chimp: Parallel and prognathic o A. africanus: Less parallel, more parabolic and Less prognathic o Homo sapiens: Parabolic and orthognathic Parallel use parallels more parabolic Parabolic Prognathic prgnathic • How big was Lucy? o Lucy in comparison to a modern human o orthognathic