Unit 7: Primate Ecology: Living Primates

Primatology

is a relatively new discipline that emerged in the 1950s when a number of paleoanthropologists realized that observations made among living apes might shed light on the lifeways of the fossil species that they were discovering.

What do primatologists study?

study living non-human primates in their natural habitats by conducting fieldwork and experiments that seek to determine different aspects of their behaviour.

Primates

are mammals that range in size from gorillas to marmosets to tiny tree shrews, and can live in habitats as different as rainforests and savannahs.

Comparative method

researchers compare the adaptations of related primates and look to see how they have evolved under similar or different circumstances—and extrapolate that to how early humans may have adapted due to the same stimuli.

Most relevant physical features defining mammals and primates:

• Mothers breastfeed their babies.

• They have a big brain.

• They possess specialized dentition.

• They eat a wide variety of food.

• They are diurnal

British anatomist Sir Wilfred E. Le Gros Clark determined primates to possess three main “tendencies.” He asserts that primates:

• They are adapted to live in trees.

• They eat a diverse diet.

• They spend a long time (relative to other species) raising and taking care of their young

Arboreal

living in trees

Primate body traits:

• Primates’ body plan

• grips and opposable thumbs

• opposable big toes

• primates’ sense of touch

• stereoscopic vision

• primates’ sense of scent

• primates’ dental formula

• extended juvenile period

Primates’ body plan

a skeletal system that is flexible, and designed to allow primates to move from branch to branch by gripping effectively with their hands and feet

Grips and opposable thumbs

One of the most important characteristics of primates is their grip; the ability of the fingers and opposable thumb to delicately pick up small objects and firmly grasp large ones fundamentally sets primates apart.

Opposable big toes

assist further in an arboreal environment. Human beings no longer have opposable toes, due to our evolutionary adaptation of bipedalism (walking upright) which requires all toes contacting the ground to provide forward movement when walking or running.

Primates’ sense of touch

• supports their “precision grips” and assists in climbing as well.

• In addition to identifying texture and aiding in grip, our fingers have nails in lieu of claws, another adaptation that supports the ability to pick up tiny objects. Nails have another function as well though: they also support the ends of the fingers by “spreading out the forces generated in the digits by gripping

Stereoscopic vision

rimates have their eyes in the front of their faces to allow a sense of depth to be created in the field of vision.

Nocturnal

Active during night

Diurnal

Active during the day

Primates’ sense of scent

Primates have a reduced snout length, due to a loss of internal surface area in their nasal passages, resulting in a poorer sense of smell.⁵ Some primates do have longer snouts, but this is an adaptation stemming from having larger canines, leading us into a discussion about dentition

Primates’ dental formula

The four types of teeth that all primates possess (in different ratios) are: incisors, canines, premolars, and molars. These teeth occur in a symmetrical fashion, reflecting even numbers between upper and lower jaws, and on both the right and left sides of the mouth.

The dental formula:

is the number of each tooth type (incisors, canines, premolars, and molars) on one half of the jaw.

In the case of humans, this is written as ‘2/1/2/3’ and means two incisors, one canine, two premolars, and three molars, (per quadrant) respectively.

Primate taxonomy

used by anthropologists and primatologists, are flexible categories that are used to organize primates

Two major exist in the discussion of primates:

taxonomy by physical characteristics (Linnaean) and taxonomy by genetic analysis.

Anthropoidea

(anthropoid) suborders

Prosimii (prosimian) suborder includes

Lemurs, lorises, and tarsiers

Anthropoidea contains

monkeys, apes, and humans

Prosimians

Lower primates

Anthropoids

Higher primates

Hominidae family includes subfamilies

• Hominiae

• Hominini (or hominins)

Homininae subfamily

Chimps, bonobos, and humans

Hominini (or hominins)

Includes humans and their fossil ancestors