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

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.