Lecture 7: Primates

Primates - Characteristic and Anatomical Adaptations

  • Generalized
  • The two most important adaptations for primates are their grasping hands and feet, (imposable thumbs and toes, nails and claws) and their vision. Most primates have developed colour vision, with eyes in the front of their head, and a bigger brain section focused on vision.
  • They have a longer childhood and greater dependency on behavioural flexibility. Ex. being on top of their parents back.
  • Primate Group Tendencies
  • Tend to live in social groups, where males are present most of the time.
  • Evolutionary Factors
  • These traits are favoured because primates ancestrally lived in the trees, so they needed good vision and grasping hands and feet.
  • Primates developed around the time flowering plants developed. So they ate the flowers, their seeds and also their fruits which were all coloured. Their vision was used to see the food and their grasping hands to pick it.
  • They were adapted to hunting small prey such as insects, having to see them clearly and catch them quickly. This depended on their vision instead of sound.
  • These are all complementary theories.
  • Diet and Teeth
  • Primates have generalized medium sized teeth.
  • There are only two differences. The new world monkeys have ancestral premolars while the old world monkeys like humans and apes have lost their premolars.
  • Lemurs have a dental column, which is a derived trait.
  • Dental structures tell us what part of the world the animal is from.

0606 dental formulas

  • Locomotion and Habitat
  • Primates have generalized locomotion, with the tendency to be upright.
  • Humans are bipedal.
  • Most primates have legs and arms which are the same size. It tells us about how they moved and what kind of environment they lived in.

Outline of Primate Groups

  • Strepsirhini - Lemurs (first picture), Lorises/ Galagoes (second picture)

0614 lemur ringtail 0617 galago-bush baby

  • Haplorhini - Tarsiers
  • Anthropoidea - Monkeys, apes, humans. Humans have bony eye plates.

Lemur & macaque skulls

primates eye plate

  • Platyrrhini - New world monkeys
  • Catarrhini - Old world monkeys, apes, humans

  • Cercopithecoidea - Old world monkeys, ex. baboons
  • Hominoidea - Apes, humans

Primate Behavioural Models for Human Evolution

  1. Comparative Approach to Evolution
  2. Biological continuum (both anatomy and behaviour). Humans are part of the continuum.
  3. Modern primates (monkeys) are not our ancestors.
  4. Evolution is not goal-directed. It is natural selection acting on environmental pressures. It does not lead to a perfect species. The only final species are the ones that went extinct because they cannot reproduce.
  5. Uniqueness of Humans
  6. Anthropocentrism is when a species thinks that it is the only important and best species out there. Ex. humans thinking it doesn't matter what happens to other species as long as humans survive.
  7. What does set us apart from other animals?
  8. Tool use? Other animals use tools as well.
  9. Cognitive abilities, especially language? Other animals show adaptations as well. Also show learned culture.
  10. Habitual bipedal locomotion?
  11. Lack of estrus?

Modern Non-Human Primate Behaviour - Biosocial Environment

  • How do we study Behavioural Evolution?
  • Ethology is the study of the behaviour of animals under natural conditions.
  • Kinds of Social Behaviour - Individual and Group Relations (page 151-158)
  1. Dominance: Ex. taking food and other items away from other individuals or enforcing territory against another group.
  2. Communication: Ex. hand and tail motions and facial gestures.
  3. Aggression: Ex. gorillas beating their chest to show power. Physical fighting and competition.
  4. Affiliation and altruism: Individuals of ranking, often about closeness. Ex. protecting, sharing food and objects with other members in the group who are close.
  • Social Role of Reproduction: Strategies, Group Structure and Learned Behaviour
  • Reproductive strategies and group structure
  • Sexual selection
  • Sexual dimorphism is the size difference of males vs. females in a group. Observed that in groups with high sexual dimorphism, where the males are much larger than the females, the group is associated with one dominant male, or just a few compared to the numerous number of females. The males are larger to fight off others.

Infanticide - If in a group with high sexual dimorphism a new male took over, it is likely for the male to kill off the young offspring of the group. This way it can produce new offspring which will carry out its genes over generations

2. Mother, father, infant and adult-child relations

  • Fathers are involved heavily in childcare, usually by carrying the babies or playing rough with them.
  • There is a long term relationship between parent and child.
  • Long term adult-child affiliation is when the parent takes care of and protects its young throughout its lifetime.

  • Cultural Behaviour and Language
  • Cultural behaviour is learned and passed on by observations and through teaching. Not biologically like by genetics. Ex. a monkey (Imo) learned that dunking rice covered in sand in the water would clean it much faster and more easily than by picking at it by hand. Or that dusting the sand off a potato before eating it made it taste better. The other members of the group followed the example.
  • Cognitive abilities for tool use: Ex. using a 'termite stick; which has a specific shape, size and colour for termites to crawl on to so they monkey doesn't have to pick at each one by hand. Or cracking nuts with stones which are a specific size and shape. This shows advanced preparation and forethought. The other members of the group usually follow the example.
  • Cognitive abilities for communication: Ex. vocalization. Animals have specific signals for specific predators. Ex. an ape using a computer keyboard to ask for certain things. It has memorized what each shape is for. Can learn sign language.

  • Primate Continuum
  • Differences of degree, not kind. This means humans differ from other animals because of their degree of ability to do these things.

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