Lecture 25 Primates

Question 1

Describe primates

Answer 1

• Arboreal ancestor
• # of species: 230 - 270
• Grasping limbs with opposable thumb
• Forward-facing eyes
  – Depth perception
• Big Cerebrum
• Highly social
  – Reduced brood size and extended parental care

Question 2

Describe two major primate groups

Note: 48% of primate species are in danger of extinction within the next decade

Answer 2

Prosimians
- Mostly arboreal & noctural
- Once found on all continents, but now just Madagascar (lemurs) & Africa/SE Asia
- Lemurs in Madagascar have radiated, not all found in trees and some are diurnal
- many species are threatened/endangered
- this Loris was thought to be extinct since 1939, but recently seen
Ex: Tarsiers
- phylogenetic position uncertain
- Among the smallest primates
- only entirely carnivorous primate
-fossils found in Asia, Europe, and North America

Anthropoids: New World vs Old World Monkeys
* Prehensile tail = tail used to grasp/hold objects
– not present in Old world monkeys
– Present in most New world monkeys
* New World monkeys also have flat noses & tend to be arboreal

Gibbons, Orangutangs and African Apes
* Lack tails
* Gibbons: smaller than other apes, mostly arboreal
* Orangutangs: too large to cross from one tree to another by the branches and must go down to the ground and walk between them
* African Apes (incl. gorillas, chimpanzees, and hominids)

Question 3

Describe hominids evolution

Answer 3

• In 2009, fossils of Ardipithicine ancestor uncovered dating back 4.4 mya
• Fossils suggest it walked upright and didn’t use its arms for walking, as chimps do, yet it retains a primitive big toe that could grasp a tree like an ape

Question 4

Describe Australopithecus

Answer 4

Australopithecus (all extinct)
* Brains ~35% size of modern human brain
– Australopithecus afarensis
* “Lucy” 3.5 MYA from Ethiopia, most complete skeleton
- provided evidence that bipedalism evolved before brains fully evolved

Question 5

Describe Early Homo species

Answer 5

• Homo habilis “handy/skillful”
  – in Africa, 2.5-1.5 MYA
  – first tool use 2 MYA
  – Shorter jaw, bigger brain
• Homo erectus “standing”
  – Believe to be first hominid to leave Africa (spread to Eurasia)
  – 1.6 MYA – 250,000 YA
  – first fire use
  – As large as modern humans, but smaller brain, thick skull

Question 6

Describe mammalian nervous system

Answer 6

1. Central Nervous System (CNS)
   – dorsal, hollow tube of nervous tissue
   * large cephalic ganglion (brain)
   * long tube inferior to it (spinal cord)
   * Both brain and spinal cord protected by bone
2. Peripheral Nervous System (PNS)
   – system of lateral nerves
   * cranial nerves from the brain
   * spinal nerves from the spinal cord

Question 6

Describe recent Homo species

Answer 6

Homo neanderthalensis
* discovered in Neander valley, Germany
* coexisted w/ H. sapiens
* disappeared ~30,000 YA, possibly due to extermination by H. sapiens
* short, stalky but powerful build
* brains larger than H. sapiens

Homo sapiens
* ~0.2 MYA also arose in Africa
* also spread out of Africa across Eurasia and to rest of world
* Larger brains than earlier Homo species, favouring increasingly complex social life

Homo floresiensis another species that coexisted with Homo sapiens?
* Found on Flores, Indonesia
* survived until 17,000 YA*
* volcanic eruption likely caused its extinction

Question 7

Describe the brain

Answer 7

Question 8

Describe the cerebrum

Answer 8

Question 9

Describe Limbic system

Answer 9

Hippocampus may differ in size among groups

Amygdala encodes both the acoustic features of a stimulus and its valence (perceived unpleasantness)