Lecture 24 Human Evolution 1 Flashcards
Every independent morphological and molecular study places
Humans among apes
Synapomorphies for Hominoidea include (among others)
Changes in the arm, shoulder, wrist, thumb, and tail (we lost it) some of which are associated with brachiation
Apes are split into
Hylobatidae (gibbons) and Hominidae (great apes and humans)
Humans form a clade with the other
African apes, excluding the South-east Asian Orangutan and gibbons
Our closest relative is the
Chimp with an estimated divergence around 5-6 mya, based on a molecular clock
Bipedalism evolved
Early, Fossil footprints at Laetoli, Tanzania demonstrate modern gait at 3.6 mya
Australopithicus
Gracile australopithicines (Lucy)
Brain slightly larger than chimps
Loss of opposable thumb (on foot) (halux)
Efficient long-distance walkers
Washburn’s feedback hypothesis
Probably had about 5 species bipedal, large-brained organisms in Africa coexisting
Testing adaptive hypotheses of bipedalism
Evident around 6 mys
Thumb in Homo and Paranthropus is modified for
More control, associated with tools (about 2.5 mya)
We have 3 extra muscles to help with fine grip (caused wider metacarpals as well)
Enlarged brains gradual with acceleration only in
Homo
Two clades are supported
Robust Australopithicines (Paranthropus) and Homo
Paranthropus
The robust, vegetarian australopithicines (chewing specialists, enlarged molars and sagittal crest)
Jaw muscles attached to top of head rather than temples because they were basically the cow version of ourselves
Homo
Adaptation to long distance running, enlarges brain, reduced canine- was it a key event in the evolution of Homo from Australopithecus?
Homo erectus
Was the first hominid to disperse out of Africa, around 1 mya
Long distance running as key adaptation?
Change in brain allometry (grows faster than in non-human hominids)
Long distance running as a key adaptation?
Caused us to lose our body hair and expand our sweat glands
