Anthro 101: Human Biological Evolution Lecture 8: Primate Comparative Anatomy Prof. Kenneth Feldmeier

feldmekj@lavc.edu

Comparative Anatomy & Behavior Assignment

• Due March 14th • This will be a short 2 page essay about the material covered

this week and next. I will upload the question onto the class website.

• Refers to Chapter 8 & 9, and Lecture 8 & 9 (tiny bit of 10) • These are likely to appear on the exam! !

Basic primate phylogeny

Lemurs, lorisesTarsiers

ProsimiiAnthropoideaNew World Monkeys

Old World MonkeysApes & humans

Haplorhines

Strepsirrhines

Primates

(Hominoidea)

Forms of Locomotion• Slow quadrupedal climbing • Vertical Clinging & Leaping • Arboreal & Terrestrial

Quadrupedalism • Semi-brachiation • Brachiation • Knuckle walking • Bipedalism

Horse Skeleton - specialized

Primate Skeleton - generalized

http://www.bristol.ac.uk/centenary/look/cabinet/monkey.html

Skeletal features to note as you do the in-class activity:

• Body position • Spine shape • Length & shape of trunk (torso) • Position of shoulder blade (scapula) • Limb length • Finger length (thumbs) • Length of tail

Slow quadrupedal climbing (prosimians)• Slow lorises of South Asia • Robust muscles & limb bones • Mobile ankle, wrist, hip • Short tails

Vertical clinging and leaping - prosimians

• Vertical body ◆ Orthograde

• Push off branch with hindlimbs • Turn midair and land vertically

again !

• Evolved two or three different times in prosimians !

• Bush babies • Sifakas • Lemurs

Sifaka

Lets Check Out Some Lemur Locomotion

• http://upuid-www-bbc-co-uk.tru-m.net/programmes/p00cn9fh

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Intermembral Index

• humerus + radius x 100 femur + tibia !• hindlimbs vs. forelimb

◆ longer in the part that does the most work !

• Bipeds & vertical clinging and leaping ◆ hindlimb longer than forelimb

• Quadrupeds ◆ Approx equal lengths

• Brachiators ◆ forelimbs longer than hindlimbs

Arboreal quadrupeds – monkeys• Arboreal - run & leap • Walk on palms on top of branches • Push off with hindlimbs • Stabilize with tail (long) • Pronograde (horizontal) posture • Longer fingers & toes to grab branch • Prehensile tails in NWM • No terrestrial species in NWM Owl Monkey

Squirrel MonkeyDiana Monkey

Monkey Time

• https://www.youtube.com/watch?v=YZM_5LAv9m8&index=18&list=PL6AE4226E1A528B69

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Semibrachiation

• New World ◆ Hands + prehensile tail !!!

• Old World ◆ Hands, no tail use

Semibrachiation (New World Monkey)

• This is a Red Howler Monkey— Check out how it uses its Prehensile tail.

• https://www.youtube.com/watch?v=YO2KHggo4oc&list=PL6AE4226E1A528B69&index=2

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Terrestrial quadrupeds - Old world monkeys• Lots of time on ground, but also in trees • Pronograde (horizontal) posture • Walks on palm/toes (shorter digits) • Move limbs in limited plane

◆ (baboons, dogs) • Rarely hang full weight from arms • Shorter tail – not balancing • Barrel shaped rib cage

baboon

Mandrill © Robert Young

Mandrills

• https://www.youtube.com/watch?v=qlAzwsTRzKU&index=12&list=PL6AE4226E1A528B69

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Brachiation - gibbons• Shoulder blade on the back

rather than top of torso ◆ Full range of arm motion

• Cone-shaped rib cage • Long, curved fingers • Small thumbs • Long arms • Ball and socket wrist • No tail

Siamang

Lets Check out a Gibbon Brachiating

• https://www.youtube.com/watch?v=mSLFHPd8LX0&list=PL6AE4226E1A528B69&index=7

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Slow quadrumanous climbing - orangutans• Grasp branches with hands and feet as

slowly move through trees • Females almost totally arboreal • males distance travel on the ground

◆ Fist walking rather than knuckles !

• Brachiating ancestor ◆ Longer arms than legs ◆ Cone shaped torso ◆ No tail ◆ Long fingers

The Man of the Forest (Orangoutangs)

• https://www.youtube.com/watch?v=HgZT5Xr3vkM

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Knuckle-walking - chimps & gorillas• Great apes too large to brachiate frequently

◆ Still use upper body & arms, suspend body when they do

• Stronger wrists bones than brachiators in order to support weight on arms !

• Brachiating ancestors ◆ Longer arms ◆ Longer fingers ◆ No tail ◆ Scapula on back ◆ Cone shaped torso

Chimpanzee

Knuckle Walkers

• https://www.youtube.com/watch?v=HDxA8-01cp4&index=26&list=PL6AE4226E1A528B69

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Hominoids: Homininae: Hominini Bipedalism

• Unique to humans (hominins) !

• Modifications to pelvis & feet

• Torque (twist and downward pull at hip) is opposed by abductor muscles !

• Abductors tighten during each stride and keep you upright !

• Abductors attach to ilium and to the neck femur !

• Wider, thicker ilium and longer neck of femur increase surface area for muscle attachment

One leg at a time: Why don’t we fall over?

Reminders

!!

• Questions about grades? Come see me!

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Changes in the pelvis

Human pelvis is a bowl ◆ Supports internal organs ◆ Short and broad ilium ◆ Shorter ischium ◆ abductor muscles attach to wide

surface of ilium ◆ Maintains the center of gravity

over one foot while walking • Chimp pelvis is longer and narrower

◆ Organs “hang” below ◆ Strong muscles on ischium

• “S-shaped” curves in spinal column keep trunk centered over pelvis

• Lumbar curve !

• C-shaped curve in chimps more

Changes in the Spine

To walk efficiently, knees must be close to center line of body

• Pelvis wider and shorter • Femur slants inward from wide

pelvis • Close-knee stance • Centers weight for balance and

efficiency (less muscle work to hold upright) !

• Longer leg bones ◆ Increased stride

chimp human

• Arched foot ◆ “spring”-like shock

absorbers ◆ Return energy to the next

push ◆ Heel-toe stride !

• Loss of opposable toe necessary to act as a platform for body - big toe in-line !

• Stiff foot makes better platform

Bipedality also causes changes in the feet

Changes to limbs: forelimbs

• Support the body in quadrupeds • Suspend the body in brachiators • Manipulate objects in bipeds – precision grip (vs. power grip)

Comparative anatomy of manipulation

• Apes long curved fingers & short thumb !

• Humans shorter fingers & longer thumb ◆ Allows precision grip and

greater opposability of hand ◆ Bones in palm rotate more

to allow finger tips to meet the thumb

Human hand

Changes in the skull: Foramen magnum• Hole in skull where spinal cord and brain connect • Position indicates body posture • Nuchal ridge on back of skull (occipital bone) show

where muscles attachHuman skull is balanced on top!

Brain Size

Lemur

Howler monkey (NWM) à

OWM

Features of the skullPrognathism Enclosed eye Orbits !Dental arcade Diastema Canine size