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Hominid Evolution
Hominid Evolution
• Humans did not evolve from monkeys but from apelike
ancestors that evolved independently of the pro-simians
• 25 million years ago, the environment cooled, glaciers
advanced and rainforest changed to the African savanna.
• As trees and fruits became scarce many apes came down to
the Savanna floor to take advantage of the abundance of
food there.
• On the ground there were different natural selective forces
at work. The hominids of the savanna began to evolve
differently than the apes of the trees and forest.
Differences between Apes and
Hominids
• Relative brain size
– Corresponds with higher intelligences and speech
centers
• Pelvis shape
– Humans have wider bowl shaped pelvis
– In Humans the Joints attaching the legs to the pelvis are
at the base of the pelvis. This is contrasted to apes
which have hind legs attached to the front of the pelvis
Differences between Apes and
Hominids cont.
• Skull feature
– Humans have high forehead and no brow ridge
– In humans, vertebrae and spinal cord attach and enter
at the base of the skull. The spinal cord of apes enter at
the back of the skull
– The human jaw is thinner and curved compared to the
longer rectangular shape of apes.
– Teeth are smaller especially the canines
Similarities between apes and humans
• Monkeys share 93 percent
of their DNA structure
with humans.
• Gorillas differ by about
2.3 percent, from us or
from the chimps.
• Humans differ from
chimps in about 1.23
percent of their DNA, and
share 98.8 percent
Australopithecus afarensis (Lucy)
3.7million years ago
– .3' to 3.5' feet tall 50
lbs
– .Bipedal skeleton and
footprints
– .400 cc brain capacity
Australopithecus africanus
– .2.8 million years ago
– .4.5' feet tall 80 lbs,
more robust body
– .Bipedal skeleton
– .450 cc brain capacity
Homo habilis (Handy man)
• 1 million years ago
• Made stone tools
• 660 cc brain
• Sexual dimorphism
(males larger)
• Scavengers and
omnivorous
Homo erectus
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200,000 years ago
1200 cc brain capacity
Used fire and clothes
Smaller jaw and teeth
Migrated out of Africa to
Europe and Asia
Mostly hunter gathers
Sexual dimorphism (males
larger)
Lived in small family
groups
Homo sapian-neanderthal
• 125,000 - 35000 years ago
• .Very modern looking facial
features
• .Built stronger and stockier
than modern man
• .Made advanced tools
• .1500 cc brain
• .Able to think in the
abstract, comprehending
religion and spiritual maters
• .Buried and mourned their
dead
• .Hunters
• .Strong family groups
Homo Sapians-sapians
•
40,000 years ago
Cultural revolution
– Domestication of animals and agriculture
– .Technology
– .Larger social orders that go beyond the family (politics)
Pseudogenes
• Are vestigial genes that no longer function
due to mutation.
– A single mutation in the promoter region is
enough to inhibit a gene from being expressed
• It is possible for a back mutation to occur
which reactivate these ancient genes.
– reversions to ancient forms.