Exam 3 Flashcards
(76 cards)
Distinguishing traits of hominins
larger brain size, bipedal, parabolic dental arch, reduction of facial projection, think molar enamel
Why move to bipedalism
climate change, bulky food, reduced exposure to sun,
What came first, Bipedalism or brain expansion?
bipedalism
how can we tell that the first hominins were upright?
innominate bones. illium is short and borad and flares out at the top, then twists to the side. toe bone, fragments of femur and tibia
3 reasons of bipedalism
upright provider, unright scavenger, aquatic ape
upright provider
walking frees the hands for carrying
upright scavenger
scavenger can scan territory and walk longer distances
aquatic ape
wetlands provide resources that are not usually eaten by primates, filling a niche
lumpers
approach of classification. tend to characterize similar fossils in the same species
splitters
approach of classification tends to create new species
Late Miocene Hominins
Sahelanthropus tchadensis, Orrorin Tugenensis, Ardipithecus kadabba
Sahelanthropus tchadensis
cranium similar to modern chimps, oldest known species in human family tree, ape like and human like features
Orrorin tugenensis
bipedal (femur), size of chimp, thick tooth enamel, possibly in Gorillini rather than Hominini
Ardipithecus Kadabba
known from very few specimens from six localities in Ethiopia
Early Pliocene Hominins
Australopithecus, widespread in Africa
Aridipithecus ramidus (Ardi)
Ethiopia, brain size of chimp, bipedal, arboreal and terrestrial
Genus Australopithecus
early bipeds, Eastern, Southern, and Central Africa, directly ancestral to humans
law of competitive exclusion
if two closely related species compete for a niche, one will win and the other will become extinct
Australopithecus afarensis
“Lucy”, Easter Africa, Ape and human like
ape: flat nose, projecting lower jaw, small brain case
human: bipedal, small canine teeth
Lucy
Australopithecus afarensis, 40% complete, flat feet
Laetoli footprints
oldest ichnological evidence of bipedalism, Olduvai Gorge, Tanzania
Burtele footprints
Ethiopia, contemporary of A.afarensis, retained divergent big toe
Australopithecus deyiremeda
Ethiopia, smallest teeth among australopithecines
Australopithecus africanus
South Africa, similar to A.afarensis, but rounder cranium with a larger brain and smaller teeth, bipedal but also adapted to the trees