Comparative Primate Anatomy

Comparative Primate Anatomy The Hardware of Human Culture

The Hardware of Human Culture
We could not be us without. . .
A language to communicate with and to use for learning
An ability to make and use tools
All the abilities that standing and walking on two feet allow us
So without understanding our anatomy, we cannot understand our culture

Comparative Hominid Anatomy
Anatomically, we are very similar to apes and even to monkeys
But we are not identical: Humans are fully bipedal, for example, while chimps are not.
We have two arches in our foot; chimps do not.
Therefore we need to compare our own anatomy with (a) other living primates and (b) fossil hominin forms.

Overview: The Human Skeleton
You do need to know some of the parts of the human skeleton
Use the online graphics (such as this) or your printed handouts
We make a detailed comparison of skeletal parts later

The Roots of Culture: The Brain
If culture is symbolic, then it is founded on language
The source of language is located in parts of the brain
Our ability to make and use tools is also begins in the brain
Therefore, we start by examining the parts of the brain

Structure of the Brain: Description I
You may want to switch back and forth between the description in the next two slides and the diagram that follows them in the third slide
Frontal Lobe: The lobe that allows us to think and plan ahead
Motor Cortex: The strip along the edge of the motor cortex that moves the facial muscles (lips, tongue, vocalization) and the arm, hand, and finger muscles
Parietal Lobe: The lobe that enables us to touch and taste

Structure of the Brain: Description II
Occipital Lobe: The lobe of the brain that enables us to see
Temporal Lobe: The lobe that enables us to hear
Olfactory Bulb: The part of the brain that enables us to smell
Supplementary Motor Cortex : The part that provides sensory feedback from an action involving the motor cortex

Structure of the Brain: Diagram
Frontal Lobe and Motor Cortex :
Cognition: Thinking Ability
Motor Abilities
Parietal Lobe: Touch and Taste
Temporal Lobe: Hearing
Occipital Lobe: Vision
Olfactory Bulb : Smell

The Motor Cortex
The next diagram gives a schematic view of the functions of the motor cortex or strip
Lower part : The strip regulates the facial and oral muscles
They include the tongue, the lips, the organs for vocalization, and the jaws
These are related to the language function
Upper part : The strip regulates the arm, the hand, and their fingers
These are related to the tool manufacture and use functions.

Parts of the Brain: Motor Cortex
Related to Language : Lower Part
Lips
Tongue
Vocalization
Related to Tool Making and Use: Upper part
Fingers and Thumb
Hand
Arm

Language Functions of the Brain: Description I
Again, you may want to move back and forth between the descriptions and the diagram that follows the descriptions
The language functions all occur on the left hemisphere of the brain in most humans
Broca’s Area functions to process the generating of speech
Notice that it is located at the base of the motor cortex, which handles the tongue, vocalization, and lip movements
Wernicke’s Area functions to process the reception of speech
Notice its location in the temporal lobe, which processes hearing

Language Functions of the Brain: Description II
The angular gyrus is the part that coordinates all the sense functions housed in the brain
They coordinate the senses of sight from the occipital lobe, of the touch and taste of the parietal lobe, of the smell from the olfactory lobe, and of hearing from the temporal lobe
If you smell the scent of a rose and visualize a rose in the mind’s eye
Its function for language is to translate all the sensory information into the sense of hearing so we can assign meaning to speech.

Parts of the Brain: Language Centers
Parts of Cerebrum
Frontal Lobe
Motor Cortex
Broca’s Area
Temporal Lobe
Auditory Cortex
Wernicke’s Area
Arcuate Fasciculus
Parietal Lobe
Occipital Lobe
Angular Gyrus

Comic Relief, Anyone? (Courtesy of Geico)
So easy a caveman can do it. . . .?

So Why Do We Pick on the Bones?
With few exceptions bones are all we have to reconstruct past human and humanlike life forms
Therefore we have to coordinate what we know about anatomy—human and nonhuman primate—to reconstruct what our ancestors might have been like.
Bottom Line: We rely heavily on inference to trace our ancestry

Human Skill: A Description
The forehead is high, making room for the frontal lobe
The skull is rounded, allowing a greater volume for the entire brain
There is no brow ridge or supraorbital torus
The jaw does not jut forward; it is not prognathous

Human Skull: Bones that Cover the Lobes
The bones of the skull are named after the lobes they cover
The frontal bone covers the frontal lobe
The parietal bone covers the parietal lobe
The occipital bone covers the occipital lobe
The temporal bone covers the temporal lobe
Refresh your memory: what are each of these lobes for?

Human Skull: The Diagram
Note the following:
High forehead
Rounded skull
No brow ridge
Chin is present
Teeth are small
The bones are named after the lobes of the brain they cover

Comparative Primate Anatomy: Human and Chimpanzee
In the next diagrams, the differences are significant to biological capacity for culture
The area for brain of a chimp is more limited than human brain because of its sloping forehead and the heavy supraorbital torus that covers much of the forehead
The chimp jaw has a prognathism absent in humans
Chimps have larger canine teeth than humans; so much so that there is a diastema (gap) for the opposite canine to fit.

Skull Morphology: Chimp and Human
Note the following
Larger brow ridge (supraorbital torus) of chimp compared to human
Sloping forehead of chimp compared to human
More prognathous (jutting) jaw of chimp compared to human
Larger canine and gap (diastema) of chimp compared to human

Comparative Brain Structure: Human and Chimpanzee
In the next diagram, the human brain has a Broca’s area for processing speech.
The chimp brain has a Brodman’s area, where calls may originate, but no speech
Our Wernicke’s area, which receives speech, is at the same place as the planum temporale among the chimps
The chimp brain is much smaller than humans’—400 cubic centimeters compared with our 1400 cc.
The frontal lobe of the chimp is smaller than the human’s, partly owing to the sloping forehead

Human and Chimp Skulls Compared: Brain Structure
Compare the following
Chimp’s brain is much smaller (400cc vs. 1400cc)
It has reduced frontal lobe
It has no Broca’s or Wernicke’s area
It does have Brodmann’s area 10, where calls may originate—but no speech
It does have planum temporale, where calls are received—but not processed as language

What This All Means
Our brains are larger than the chimps’
We have a well-developed frontal lobe
We have well developed language areas: Broca’s and Wernicke’s area
The motor strip is more well developed among humans than among chimps

Comparative Primate Anatomy: Chewing Mechanism
The next diagrams compare human dentition (structure of teeth) with that of the chimps
Our overall dental arcade (arrangement of teeth) is more rounded (arc-like) than the chimps
Chimpanzee have a more rectangular dental arcade, with the back teeth more parallel
Our teeth are much smaller than the chimps’
We have small canines (jagged teeth)
Chimps have large canines, so large that they need a gap (diastema) in the opposite jaw for them to fit

Human Dentition: Diagram
For each jaw (upper or maxilla or lower or mandible:
Incisors (4) in the front for cutting food)
Canines (cuspid) (2) for piercing
Premolars (4) for light grinding of food
Molars (6) in back for heavy grinding of food

Chimp and Human Dentition
Note the following:
Dental Arcade: Humans’ are arc-like; apes, parallel back teeth
Canines and Diastema (gap): Apes have larger canines and gaps in opposite jaw to fit them; humans do not

Comparative Primate Anatomy: Hand Structure
Our fingers are straight; that of the chimps and other apes are curved
We have a much longer thumb than do the apes
Importance: we are capable of a more precise grip than the apes
This implies that we can make finer tools than those apes who can make and use tools

Human Hand Structure: Diagram
Note The Following:
Our digits are straight
Our thumb is opposable
The thumb is long

Ape and Human Hands: Diagram
Hands of orangutan, chimpanzee, gorilla and human
Note the following:
Our thumbs are longer than the others’
We can make a finer grip than the others can
Less visible: apes’ digits are curved, ours are straight

Power and Precision Grip
Note the Following:
Power grip: Fingers and thumbs wrap around the object
Precision grip: Forefingers and thumb hold the object
Importance: We can do finer work compared to nonhuman primates

Comparative Primate Anatomy: Bipedalism vs. Quadrupedalism
Homo sapiens is the only mammal capable of bipedalism, or the ability to stand and walk entirely on two feet.
Kangaroos stand on two feet, but they hop rather than walk and their forepaws are too small for any function.
Chimpanzees can walk on two feet, but not very efficiently; they are closer to quadrupedalism, or the ability to move around on four feet.
What are the advantages of bipedalism over quadrupedalism. Answer the question and then look at the next slide.

Advantages of Bipedalism
Efficient locomotion
Freeing of hands for many proposes :
Foraging and hunting/scavenging
Tool making and use
Care and provisioning of offspring
Increased height for viewing across landscape :
Tracking migrating herds
Predator avoidance

Bipedalism: Diagram
We are the only mammals that can stand and walk on two feet
Apes are semi-bipedal, but use their knuckles to get around (top photo)
The bottom photo compares the “quadrupedalism” of a human with that of a chimp
Notice the human is on his knees, not just his feet
The chimp is using its hind feet, not its knees.

Comparative Human Anatomy: Locomotion
You will need to make a close comparison of human and chimp anatomy in the next diagram
Pelvis: Compare the length of the ilium of the chimp with that of the human
Compare the arm length of the chimp with the human
Compare the leg bones of the chimp with the human
Compare the foot structure of the chimp with the human
What are the differences between each set of characteristics? Write your answers, then look at each of these characteristics in detail.

Chimp and Human Locomotion Compared

Vertebral Column and Pelvis
Note the following:
Human vertebral column is S-shaped, supporting the upper torso
Chimp vertebral column is bow-shaped
Human pelvis, with ilium, is bowl-shaped; muscles from the thigh keep him upright
Chimp pelvis is long, with flat ilium

Pelvis and Femur
Note the following:
Longer ilium of chimp
Shorter, more curved ilium of human
Straight vertical orientation of chimp femurs, which do not support the upper body well
Inward angle of human femurs, which support the upper body more efficiently

Foot Structure
Note the following:
Large toe of chimp foot (right) is opposable to other digits
Large toe of human foot (left) is aligned with other digits
Ankle bones (tarsals) of human food are larger and more rigid than the chimps

Foot Arch: Longitudinal and Transverse
Note the following:
Longitudinal arch that runs from the first metatarsal to the calcaneus (heel bone)
Large tarsals to the rear contribute to the rigid structure of the foot and its arch
Transverse arch can be inferred from lower placement of outside foot to the instep

What We Have Learned
We have learned the hardware essential to culture
They include our brain, where language and tool use originate
We have learned about our ability to stand and walk on two feet and the importance of this ability
We have also learned about the characteristics of ape anatomy
This comparison gives us a clue on the next phase of this unit, human biological evolution

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Comparative Primate Anatomy

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