BIOL 3445 Lecture Notes - Lecture 28: Foramen Magnum, Homo Habilis, Turkana Boy
BIOL 3445.001 | Lecture #28 | 4/26/2018
Human Evolution
OVJECTIVES
― What are some of the synapomorphies that define the clade hominin?
― What are synapomorphies that define the clade Homo?
― What factors may have led to the evolution of bipedalism? Our big brains?
― What parts of our brains have been slow to evolve? Why?
HOMININ EVOLUTION
― Hominin: a taxonomic group that includes humans and closely related species
o Chimpanzees and bonobos are the outgroup
― First hominins appeared over 6 mya
― Some species are represented by only a single
fossil
o Different species?
o Or just weird individuals?
― Lots of homoplasy
― We can make a phylogeny using only well-
supported relationships
o Excludes many potential species that are
less well studied
Bipedalism
― Bipedalism: walking upright on two legs
― Sahelanthropus had a vertical foramen magnum
o In chimps and other non-bipedal primates
have a foramen magnum in a different
orientation
― Ardipithecus had muscle anchors on leg bones
that are present in humans but not in other apes
o Also lacked some of the adaptations for tree-swinging present in chimps
o Suggests they probably spent a lot of time on the ground
― Australopithecines had many more adaptations for walking upright
o Double-curved spine that held the body straight over the hips
o Knees and legs tend to be straighter
o Feet have arches
o Still small-brained though
Perks of Being Bipedal
― Environmental changes probably led to the evolution of bipedalism in hominins
o Climate change led to decreased rainfall
o Habitat shift to more open grasslands and less forests
o Hominins adapted to life in open areas by traveling across the ground
― Frees up your arms to carry young and food across greater distances
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BIOL 3445.001 | Lecture #28 | 4/26/2018
― Decreases surface area exposed to sun (helps with thermoregulation)
Toolmakers
― Hominins are the first primates to make and use stone tools
o Oldest stone tools date to around 3mya
― Homo habilis (2.4 mya) was a known tool-maker
o Shaped rocks used for butchering meat
THE RISE OF HOMO
― Homo: genus that includes our species and our closest relatives
o First fossil of H. erectus is a 12yo Turkana boy
o Tall with slender ribcage
o Long legs and narrow hips
o Relatively large brain
― Homo synapomorphies
o No tree-climbing adaptations
o Completely bipedal
o Larger brain case with smaller jaw and teeth
― First genus to leave Africa
o Phylogenetic relationships between most of
the species are confusing
― Homo also show advances in cognition
o More sophisticated stone tools
o Shells modified into beads
o Smaller intestines (suggesting a change in diet)
― These changes took hundreds of thousands of years
o Suggesting no huge leaps in technology
o Still limited cognition compared to modern humans
PARALLEL HUMANS
― H. heidelbergensis
o Diverged from H. erectus around 800,000 years ago
o Spread to Europe and Asia alongside H. erectus
o Diet specialized on meat
▪ Advanced hunting using cooperation
▪ Spear use
▪ Creation of fire
o Did not produce art
― H. neanderthalensis
o Diverged about 300,000 years ago
o Adapted to a colder climate
o Brains are large like ours
o Made colored beads and buried their dead
o Went extinct about 40,000 years ago
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