1. Comparing Primate Anatomy
Chapter 8

2. Primate Locomotion Primates exhibit a wide range of locomotion:
vertical clinging and leaping
arboreal and terrestrial quadrupedalism
brachiation
semi-brachiation
knuckle walking
erect bipedalism

3. Anatomy, Limb Proportions and Locomotor Patterns
Skeleton of a vertical clinger and leaper (indri).

4. Anatomy, Limb Proportions and Locomotor Patterns
Skeleton of a terrestrial quadruped (savanna baboon.

5. Anatomy, Limb Proportions and Locomotor Patterns
Skeleton of an arboreal New World monkey (bearded saki).

6. Anatomy, Limb Proportions and Locomotor Patterns
Skeleton of a brachiator (gibbon).

7. Knuckle Walking
Note how the weight of the upper body is supported on the knuckles and not on the palm of the hand.

8. Suspensory Adaptation
Apes and humans share a number of anatomical features for suspensory behavior:
Spine contains fewer vertebrae than in the monkey
Spine is relatively inflexible
Scapula lies on the back
Humerus points inward into a shallow socket permitting a high degree of rotation of the shoulder
Hand can be rotated palms up and palms down
Unlike humans, apes have arms longer than legs with elongated, curved fingers and toes

9. Bipedalism Humans walk bipedally – on two feet
Adaptation to bipedalism has impacted human anatomy and physiology:
Position of the skull on top of the spine
The lumbar curve
Illium of the pelvis is short and broad
The leg is long and powerful
Thighs angle in towards the knee
Feet are inflexible, with an arch and a non-opposable big toe

10. The Primate Hand
Primates are characterized by pentadacytlism and palms and fingertips that are covered with epidermal ridges
Most primates have grasping hands and feet
In Old World monkeys, apes and humans, the thumb can be directly opposed to the other fingers permitting a precision grip

11. While raccoons are capable of considerable manual dexterity and can readily pick up small objects with one hand, they have no opposable thumb
Many monkeys are able to grasp objects with an opposable thumb, while others have very reduced thumbs
Humans are capable of a “precision grip”
Chimpanzees, with their reduced thumbs, are also capable of a precision grip, but they frequently use a modified form

12. Skull Anatomy The foramen magnum Eye sockets
Relative position is a reflection of locomotor pattern
Either side of the foramen magnum are the occipital condyles, which connect the occipital to the spine
Eye sockets
Zygomatic arch – cheek bones
Size may reflect diet
Postorbital bar – lateral bar behind the eye
Found only in prosimians
Postorbital septum - full enclosure at the rear of the eye socket
Found only in anthropoids

13. Evolution of the Brain
General increase in brain size relative to body size
Encephalization – ratio of brain size to body mass
Also includes brain usage
Encephalization quotient
Only used for mammals
Apes and Humans
Different areas associated with specific functions have become more clearly defined
Areas associated with hand coordination are three times larger in human brains compared to ape brains
Expansion of areas associated with language is larger for humans

14. Primate Dentition
Mammals are Heterodonts with four different kinds of teeth:
Incisors
Canines
Premolars
Molars
Dental Formula
in most humans
Different diets have different food processing needs and, therefore, different dental adaptations

15. Ape and Human Teeth Ape Humans
Canine is large and projecting
Canines interlock each fitting into the opposite jaw
Dental gallery is U-shaped, with parallel tooth rows
Great ape incisors are broad and spatula-like
Humans
The size of teeth has decreased
Canines
Do not show sexual dimorphism
Are relatively small
They do not project or interlock
Hominin teeth have relatively thick enamel

16. The Jaw
Large jaw muscles are also associated with a robust and flared zygomatic arch
Ape vs Human Jaw
Ape jaw is larger and longer
Small jaw results in smaller chin and jaw muscles
Apes mandibles are reinforced by a simian shelf
Sagittal crest for jaw muscle

17. Cytogenetics Human and chimpanzee karyotypes
Number and appearance of chromosomes in the nucleus of a eukaryotic cell
Easily pair up human chromosomes with a chimpanzee counterpart
Exception is human chromosome 2
Vestigial centromere
Genomes sequenced in 2003 and 2005, respectively
DNA sequence that can be directly compared between the two genomes are 98% identical
Including insertions and deletions, at least 96% identical
Ten times closer than rat and mouse