Comparative Primate Anatomy

1. Comparative Primate Anatomy The Hardware of Human Culture

2. 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

3. 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.

4. 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

5. 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

6. 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

7. 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

8. 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

9. 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.

10. 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

11. 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

12. 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.

13. 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

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

15. 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

16. 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

17. 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?

18. 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

19. 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 andthe 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.

20. 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

21. 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

22. 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

23. 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

24. 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

25. 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

26. 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

27. 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

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

29. 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

30. 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

31. 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.

32. 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

33. 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.

34. 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.

35. Chimp and Human Locomotion Compared

36. 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

37. 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

38. 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

39. 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

40. 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