Lecture 35—Primates

This lecture emphasizes the characteristics of primates and how they fit into the evolutionary scheme. We do so by following the discovery of a key fossil primate, Ardipithecus, who lived 4.4 MYA as the scientists unravel what she looked like and behaved. She is just one of the hundreds of our fossil ancestors that have been found in eastern Africa, the origin of the human species. The phylogeny of primates is important to know; chimpanzees and Bonobos are our nearest relatives.

Some of the characteristics are fundamental to human evolution.

Development of the primate hand with an opposable thumb allows manipulation of objects and is essential for tool creation and use.

Development of bipedalism frees the hands for manipulation and visibility.Necessitates change in foot with loss of opposable toe, shift in spine and pelvic girdle and change in foramen magnum (hole for spinal cord in the back of the skull).

Brain enlarges and change in skull from fox-like face to flat face with reduced snout and a rounding of the forehead into a bun. Shape of jaw changes to be more rounded.

Body size increases as we go from prosimians to monkeys to apes. This necessitates a longer gestation and longer growth period for young. Allows greater passing of information between parents and young.

Evolution scheme for humans based on best evidence:

Ardipithecus appears to have an anatomy intermediate between chimpanzees and humans based upon her bipedal nature, and pelvic girdle, opposable toe, reduction of canine teeth, but she is more human than chimp.

Terms/Concepts to Define:ArdipithecusProsimianAnthropoidsHominidsForamen magnumSimiansBipedal

Can you answer these questions?

1. There are many different “races” of humans with different physical and physiological features. Using what you know about evolution how could these differences have developed?

2. How could scientists have determined that Ardi lived 4.4 MYA?3. Draw a diagram of the phylogeny of the great apes.4. List 3 characteristics that humans share with the prosimians.5. Name 3 anatomical changes that occurred when humans became bipedal.

6. Why should we expect that the position of the foramen magnum will tell us if a mammal is 4-legged or 2-legged?

7. Draw a graph showing the relationship between brain size and body weight in primates and indicate where humans fall on this scale.

8. Draw a cladogram showing the relationships of these organisms: H. neanderthalensis, H. habilis, H. sapiens, H. erectus, A. afarensis and Ard.