Bio Anthro Exam 3

Australopiths& Hominins

Raymond Dart

found the first fossil of Australopithecus africanus

natural endocast

you can see how big the brain is and what shape it was

Taung Child

Australopithecus africanus from Taung, South Africa
Dart claimed endocast was more human than ape-like and foramen magnum placed forward = evidence for bipedalism

basic idea about bipeds

they need to balance their heads atop an upright torso, quadrupeds don't

Dart's conclusion

Australopithecus africanus is a biped and early fossil relative of humans

Scientific community response

Not true and that taung child was a young fossil chimp

3 main reasons they didn't believe that

-racism
-brain before bipedalism
-piltdown man (sealed the deal)

Mauer Mandible

-1907, found in sand quarry near Heidelberg 600 KYA

Piltdown Gravel Pit

Charles Dawson digs a pit and found fossils (Eonanthropus dawsoni) in sussex England 1912
-convinced experts that "ape men" lived in England long ago.

Was piltdown real?

No... it was a chimera of modern human bits and modern orangutan bits.

Robert Broom

-Scottish MD + Paleontologist
-1934 started work @ Transvaal Museum
-met dart and got permission to return to Taung where he found nothing left

Sterkfontein

Broom found adult Australopithecus africanus cranium (Mrs. Ples-1947)
-2.5 MYA

similarities to chimpanzee

-small brain (chimp has 400 cc and Mrs. Ples has 485 cc)
-prognathic (projecting jaws)

Orthagnathic

a non prognathic cranium with jaws and lower face that doesn't project very far forward in front of face

Evidence for bipedalism in australopithecus africanus

postcranial specimens
pelvis and lumbar spine show clear functionality

similarities to modern human

lumbar lordosis, short illium, laterally-directed illium

problem with bipedalism

-only one leg on ground
-tendency to fall toward side with leg up

lesser gluteal muscles

-gluteus medius -gluteus minimus
-counteracts pelvic tilt in Au. africanus and modern humans

Who has dorso-ventrally oriented illia

Quadropeds like Pan

facts about lesser gluteal muscles

-they extend at leg and hip joint
-hip extension generates forward motion during walking
with reorientation of illia, lesser gluteal muscles become abductors
-stabilize hip joint during bipedalism

general idea

change anatomy of a site where a muscle attaches to a bone

lesser gluteal muscles for apes

primitive function to extend leg at hip during quadrupedalism
-modified in Au. africanus and modern humans to maintain balance during bipedalism-derived

standard anatomical position

head forward, feet forward, hands forward

superior

feature going up toward head
ex. shoulder joint is superior to hip join

inferior

feature going down toward feet

medial

toward mid-line axis of bilateral symmetry
ex. nose is medial to ear

lateral

away from midline axis of bilateral symmetry
ex. thumb is lateral to pinkie

Anterior (ventral)

toward front

Posterior (dorsal)

toward back

skeleton separated into two parts

axial skeleton and appendicular skeleton

axial skeleton

medial part of skeleton
ribcage, breast bone, etc

appendicular skeleton

forearms, calves, thighs

proximal

toward axial skeleton
ex. knee joint proximal to ankle joint

distal

away from axial skeleton
ex.wrist is distal to elbow

two parts of skull

mandible & cranium

mandible

lower jaw and all area underneath
holds all lower teeth, chin, and important attachment for joints

cranium

starting from teeth up

orbit

eye socket

piriform aperture

nose

two main parts in lateral view

neurocranium and splanchocranium

neurocranium

surrounds and protects the face
frontal and temporal (side of braincase)

splanchocranium

face

parietal

superior and posterior

occipital

anterior and inferior

what's underneath the cranium

maxilla, temporal, occipital bone

basicranium

floor of braincase, numerous foramina (holes) that transmit nerves and vessels

clavicle + scapula

collar bone + shoulder blade

humerus

proximal end- shoulder joint
distal side- forms side of elbow joint

radius

lateral side

ulna

medial side

carpals

bunch of irregularly shape joints that make up wrist

metacarpals

5 of them- forms fleshy part of hand

phalanges

fingers (singular: phalanx)

femur

thigh bone- proximal end has big round bone that articulates pelvis to form hip joint

tibia

biggest of lower leg, most important on medial side

fibula

lateral to tibia, skinnier and doesn't bear as much weight

tarsals

proximal end of foot, contributes to ankle joint (heel to hind foot)

metatarsals

long skinny bones-fleshy part

phalanges

bones of toes

ribs sternum

ribs meet breastbone-term for the end is sternum

vertebral column

spine, term for magnum

pelvis

connects vertebral column to hind limbs

human vertebral column

cervical-7
thoracx- 12
lumber- 5
sacrum- 5
coccyx - 4 (anchors muscle that holds pelvis in place)

kyphosis

dorsal curvature

lordosis

ventral curvature - feature of bipedal relatives

right innominate
left innominate

(os coxa) femur articulates at the deep concavity
(acetabulum) to form hip joint
has three parts - illium, ischium, pubis
they separate bones early in development

specimens from sterkfontein show what?

convincing evidence for bipedalism in australopithecus africanus

pelvis + lumbar spine show that?

clear functionally significant synapomorphies with Homo

Australopithecus africanus features

primitive, ape-like
bipedal like modern humans
all from africa

what is the first major adaptive shift in becoming human?

bipedalism

newer specimens support previous findings that

primitive cranium biped (have short legs)

ECV mean is...

458 cc
pantroglodytes: 400 cc
homosapiens: 1400 cc

Australopithecus africanus has a what sized brain?

ape-sized brain

Little Foot

3.6 MYA
Au. prometheus

Taxonomy of Australopithecus africanus

is an australopithecine
subfamily homininae

tribe australopithecini

early fossil hominins

tribe homini

humans + all fossil relatives
-living + fossil Homo

A.A. similarity to homo

-bipedal
-most have thick enamel
-varying degrees of canine reduction

A.A. differences to homo

small brain (ape-sized)
most have larger cheek teeth -dead giveaway to finding A.A.

when are hominin species from?

last 7 MYA

Sahelanthropus tchadensis

from Tororos-Menala, Chad
7-6 mya
ancient lake margin

Michael Brunet

worked in Lake Chad area in 2002
discovered bones (hominin skull with other parts)

Sahelanthropus tchadensis

-massive thick supraorbital bones (like gorilla)
-very small ECV :320 cc
-small molars
-not like most australopithecines...

why possible hominin?

-intermediate enamel thickness (

Chimps (& other apes) teeth

-projecting canines
-upper hones against lower

Modern Humans teeth

-canines incisiform
-have apical rather than honing wear (like incisor)

most catarrhines have ...

projecting canines
honing relationship between upper canine and lower third premolar

modern human canines are...

incisiform

after sahel... cranium was digitally reconstructed, what was figured out?

no longer compares with gorilla
-a wee bit less prognathic
-supraorbital torus morphology differs from apes
-forward placement of foramen magnum

REMEMBER

forward shift of foramen magnum on cranial base distinguished humans from other hominoids

forward shift of foramen magnum is also evident in...

other bipedal mammals

FM position can be quantified using...

a Basioccipital ratio- humans + close fossil relatives on left of scale (bipeds)
living apes on right of scale (quadropeds)

most bipedal mammals have what compared to close relatives, no matter the posture?

forward shifted foramen magnum

earliest known hominin ancestor

sahelanthropus tchadensis- small brained biped with slightly reduced canines and increased molar enamel thickness

Great Rift Valley

East Africa- system of interconnected valleys
(some have deep rift valley lakes)
-east coast splitting away from rest of continent

rifting

diverging boundary between 2 adjacent tectonic plates; forms rift valleys where new crust is formed

Rio Grande Rift

happening between west texas + new mexico

tripartheid rifting system

rift valleys that have already formed seaways between africa and arabia

what is great for collecting and exposing fossils + dating fossils

great rift valley

igneous (volcanic) rocks

contain radioactive elements or isotopes
-over time, decay into stable elements/isotopes
(lava over time will transform to lead)
-radiometric dating based on knowledge of rate of decay