early hominins Flashcards
hominin ancestral traits
dental apes
arboreal and suspensory locomotion
hominin derived traits
bipedal locomotion
changes in canine honing complex
evolutionary theories on bipedalism
climate change between 8-6mya:
cooling in earth, causing less precipitation. trees dying out and savannah expanding in equatorial Africa. reduction of arboreal environments pressured for bipedalism
aridity hypothesis
forest hypothesis
bipedalism was present before expansion of grasslands
turnover pulse hypothesis
variability selection hypothesis
bipedal advantages over quadrupedalism
hands freed from locomotion
reduces thermal load on body
more energy efficient form of locomotion
osteology of bipedalism
shorter and wider pelvis, os coxa, vertebras in lumber spine; vulgus knee; wider distal femur and proximal tibia; forward foramen magnum.
habitual bipedalism
obligate bipedalism
artapithacus characteristics
opposable big toes, curved fingers, long arms
australopithacus
arched foot, big toe more parallel to toes
australopithacus africanus
possible early homo
australopithacus sediba
derived homo traits
long thumb (precision grip), smaller teeth, broad frontal bone, narrower pelvis
evidence for homoplasy of Australopithecus sediba
evidence of sympatric speciation of Australopithecus sediba
ancient & derived characteristics of Australopithecus sediba
transition to early homo
around 2.6mya, longer more intense cold periods leading to creation of glaciers and more land available
homo habilis
slight increase in brain size, smaller teeth, no grasping ability in foot, no canine honing complex, precision grip in hand. mainly females/juveniles identified
evidence for why homo rudolfensis should be treated as a dif. species
rudolfensis males have smaller brow ridges than Habilis females (should be the opposite as a secondary sex characteristic)
+ cranial capacity, brow ridges, face, posterior tooth size
homo rudolfensis
smaller brow ridges, less prognathic, large molars. mainly males identified
first dispersal out of Africa