BILD 3 Lecture Notes - Lecture 18: Foramen Magnum, Ardi, Flat Feet
13 Jun 2018
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BILD 3 Lecture 18
5/14/2018
• About 1.2% of our genome differs from chimpanzees
• About 0.1% of our genome differs from one another
• Rodents are closest relatives to primates (lemurs, non-human primates like chimps and
bonobos)
• Monkeys have tails, apes do not
• We separated from a common ancestor of chimps and bonobos about 4-6 MYA
• Species that share the most recent common ancestor with human head lice:
chimpanzees
o Pubic lice= gorilla lice
• Bipedalism
o We are uniquely weight-bearing columns of all animals
• Fossilized remains of more than 6,000 early hominid individuals have been found
• Ardipithecus ramidus (Ardi)
o Found along the Awash river in Ethiopia
o 4.4 million years old
o Had an opposable toe like our ape-like relatives
o Thought she stood more upright than our more ape-like ancestor
▪ Evidence for this is in the shape of her pelvis
▪ Chimps have a long, narrow ilium, compared to our broad and shortened
ilia
▪ Shape of ilium had changed in Ardi and Lucy to be more human-like and
support more upright characteristics by inferring what the muscles would
have looked like from the skeletons
▪ Shorter, more spread out muscles make for less power, but increased
stability; gives us more parasagittal movement and allows us to stand on
one foot
• Lucy (Australopithecus afarensis)
o Few prominent features of her skeleton that indicate she would be upright:
▪ Position of her foramen magnum: shows a transition from the spinal cord
exiting near the back of the head to the human condition where it exists
beneath the head (Lucy was in between the position of a human and that
of a gorilla)
▪ Midfoot break of the bonobo compared to human foot stabilized by the
arch. Non-human primates today have very flat feet (the midfoot break is
that the heel is the only thing to lift when walking, with humans, the arch
lifts up). What gave humans this adaptation is the pronounced arch
across the metatarsals. Lucy already had this stabilizing arch that would
allow her to walk on her feet for long distances with reduced injury. They
found one of her fourth metatarsals, and could infer from that she had an
arch like ours due to the shapes and angles of the proximal and distal
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