Unit 4: Primates — part 1 Physical Traits

Primates: Embers p. 51

The goal of primatology is to understand how different primates have adapted anatomically and behaviorally to their environments. These studies may help us understand the behavior and evolution of humans.

The similarities and differences between different primates may give us a window into the how and why humans diverged from their primate ancestors and relatives.

Using fossil evidence and comparative anatomy we may know more about early primates, their physical and social structures. Variation in adaptations may explain the divergence of primate evolution. If we can identify the traits that belong to humans alone it may suggest why we branched away from our closest living primate relatives—bonobos, chimps and gorillas.

To do this we are going to look at the common features of living primates first, then examine the different animals of the order Primates, looking at the distinctive characteristics of each major type. Last we will look at the traits we believe belong to humans alone – we are trying to identify the features of primate anatomy and behavior that have bearing on human evolution.

Common Primate Traits

All Primates belong to the class Mammalia – fur covered bodies, usually for insulation. They are warm blooded, give birth to live young that develop to a considerable size within their mother and are nourished via her mammary glands. The young have a relatively long dependency period after birth – this gives them the opportunity to learn from their parents. This may mean that a great deal of mammal behavior is learned, rather than instinctive. Play is an important part of the learning process for mammals.

Physical features –

Primate physical features are not unique to primates but the combination of these traits (complex) is!!

1. Each limb has one bone in the upper portion for strength and two bones in the lower portion for rotation and flexibility

2. The collarbone or clavicle allows for great freedom of movement at the shoulder, up and down, back and forth – a remnant of an arboreal past where lower limbs were used for support and upper limbs needed to tolerate pushing and pulling forces that allowed for travel through the tree canopy-

3. We use this combination of abilities to manipulate objects with ease – throwing balls, spears, and turning doorknobs, using our rotational abilities for optimal survival skills.

4. dental array supports our omnivorous diet – we can eat almost anything., unspecialized molars for processing vegetable matter, highly specialized incisors and canines allow for the eating of meat. Lower primates have even more specialized dental arrays

5. primate hands are extremely flexible – all primates have prehensile grasping hands that can be wrapped around an object. They generally have five digits on their hands and feet (not all are the same length) and their nails are generally broad and flat rather than clawlike. They have hairless sensitive pads on their fingers, toes, heels, and palms that help them to grip and hold objects more efficiently. Most have opposable thumbs for an even more powerful and precise gripping ability.

6. Primate brains have a larger section devoted to vision than other senses such as smell.

Primate brains have stereoscopic or depth vision – with their eyes directed forward rather than sideways like some other animals. This allows them to focus on an object with both eyes at once. Most primates also have color vision which would aid in identifying useful plant foods – e.g. when fruit is ripe, etc.

7. Primate brains are large in proportion to their body size. Animals with large brains tend to mature slower and live longer than most other animals with smaller brains, giving primates a longer time to accumulate knowledge and adaptive skills s and behaviors.

8. Primate reproductive systems set us apart from other animals as well.

Male primates have a pendulous penis un attached to the abdomen as in other species – a trait shared by bats and bears

Female primates usually only have two nipples on the chest and a uterus that is able to hold only a few offspring at a time – not a litter as with most other animals. Stress is quality over quantity for offspring.

Infant primates tend to be relatively well developed at birth, although humans and other apes, and some monkeys have helpless infants. Most infant primates can cling to their mothers from birth.

Primates take a long time to mature. Rhesus monkeys are not sexually mature until 3, chimpanzees at 9, humans and gorillas don’t reach sexual or physical maturity until even later.