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Early Hominid Origins And Evolution

Chapter 10 - Clark Spenser Lawson
What Is a Hominid?
Bipedal Locomotion: Getting Around on Two Feet

i. Evolved before large brain size

ii. Walking on two limbs (with associated skeletal changes)
What Is a Hominid?
Nonhoning Chewing: No Slicing, Mainly Grinding

i. Refers to the way the mouth processes food

ii. Lack of projecting canine, diastema

iii. More pressure on front portion of chewing muscles
2 obligate behaviors of hominids
bipedal locomotion
nonhoning chewing
Material Culture date
2.6 mya
Evidence of hominid behaviors
bipedal locomotion
nonhoning teeth
material culture
Increased Brain Size contributes to:
reflecting advanced (human) intelligence
- yeilding to language, tool use
Five Characteristics in the skeleton
1) the foramen magnum is positioned at the bottom of the skull
2) the pelvis is shorter from front to back
3) the legs are long relative to the body trunk and arms
4) the foot has a double arch
5) the bog toe (hallux) is not opposable
the foramen magnum reflects:
that the bipedal hominid carries it's head atop it's body
the shortened pelvis reflects:
anatomical changes that coincide with the shift from quadrupedal to bipedal
long legs reflect:
gluteal muscles for stabilizing the hip in walking, ability to stride, and do so with minimal energy
-double-arched foot
loss of opposability reflects:
the use of this digit (big toe) in helping propel the body forward during walking and running
Nonhoning Chewing:
1) have small, blunt, and nonprojecting canines and no diastema
2) canines wear on the tips intead of the backs
3) the cusps on both sides are similar in size
4) hominids do not hone their canines as they chew
Human Dentition
1) the third and fourth premolars, upper and lower have 2 cusps each
2) upper molars have 4 cusps
3) lower molars have 5 cusps
Masticatory Muscles
temporalis, masseter, and pterygoid muscles

provide greater vertical force in crushing food
Charles Darwin's Hunting Hypothesis
i. Bipedalism had freed the hands for carrying weapons.

ii. Intelligence increased; size of canines diminished.

iii. Tool production and use essential for development of human intelligence.

iv. New evidence shows this not to be the case.
Rodman & McHenry's Patchy Forest Hypothesis
as the forests became patchy, fragmented, toward the Miocene period, food became more dispersed, hominids used walking energy and it allowed them to pick up food, they could have fed in trees or on the ground depending the resources
S. African Hominids
Australopithecus africanus

Paranthropus robustus
E. African Hominids
Australopithecus afrensis
Paranthropus boisei
Paranthropus aethiopcus
Homo habilis
Homo erectus
Asian Hominids
Homo erectus
European Hominids
Homo neanderthalensis
Davidson Black
1884- 1934
student of G. Elliot Smith
1917 - goes to China/ Peking Univ
1927 - finds tooth/ zhoukoudien
Sinanthropus pekinenis (specimen type)
--Homo erectus
tooth - 500 - 250 kya "Peking Man"
1929 - 1931 perfect skulls
Ralph von Koenigswald
1920- 1982
1936 Java Man 2/ followed Java Man 1
meets Franz Weidenreich 1873-1948
- compared Java Man & Peking Man
- same paleo species/ Java fossils older
-fossils get lost at sea
Eugene Dubois
Between 1887 and 1895, Dubois searched at potential sites near rivers and in caves, first on the island of Sumatra, then on the Indonesian island of Java.
In 1891, Dubois discovered remains of what he described as "a species in between humans and apes". He called his finds Pithecanthropus erectus ("ape-human that stands upright") or Java Man. Today, they are classified as Homo erectus
Fossils of Australopithecus
1) a series of limestone caves in S. Africa
2) in sedimentary basins and associated river drainages in the E. Rift Valley (Ethiopia, Kenya, and Tanzania)
Louis Leakey
1903-1972 - missionary parents
13 yro finds stone tools
Cambridge Univ/ Mary Nichol illustrator
-later marries Mary (Leakey)
Olduvai Gorge (site)
Tanzania, Africa- side branch of Rift Valley
15 mile - 500 ft cliff
Mary Leakey
July 17, 1959 finds part of skull, near where Louis found stone tools
-first fossil find outside of S. Africa
-hyper robust - "Zinj" Paranthropus boisei
"Zinj" Zinjanthropus boisei
1.75 mya (radiometric dating)
"nut cracker man"
NOW-> Paranthropus boisei
sagittal keel - zygomatic arches, jaw
Specimen numbering
5th find
Who Made Stone Tools? L. Leaky
National Geographic sponsored
1959-1964 Olduvai Gorge
"handy man" " "waste basket" taxonomy
Homo habilis
Homo habilis
same age at Homo erectus
"discoverer's bias"
Emperor Haile Selassie
1966 visits Kenya meets Leaky, asks him to hire a team to dig Ethiopia. Leaky sends his 2nd son Robert Leaky
Robert Leaky
b. 1944 - Maeve Leaky - wife
Louise Leaky - daughter
did not go to college
safari business/ pilot - E. Lake Rudolf
terminal kidney disease/ transplant
1993 - plane crash/ broken legs
Eastside of Lake Rudolf, Kenya
Koobi Fora Foundation
1968- work begins
1969-1975 amazing discoveries
Westside of Lake Rudolf, Kenya
Koobi Fora Foundation
1980's - Lake Turkana
Robert Leakey's finds
E. Rudolf Lake (Turkana)
Paranthropus boisei and Homo Erectus
-found in the same deposit
1984 - Turkana Boy (H. Erectus)
- KNM - WT
H.erectus (Asia) H. ergarta (Africa)
Turkana Boy - 1984
1984 - Turkana Boy (H. Erectus)
- KNM - WT
H. erectus
age 11-12 yro
-no hands or feet
adaptive radiation of bipedal hominids
KNM - WT 17000
"The Black Skull" - Paranthropus aethiopcus
~ 1.6 mya - one of the oldest specimens
"Black Skull" - magnesium sediment
-sagittal keel
-brain size 400 cc
Laetoli Footprints - Tanzania
E. Africa 1976-1978
Andrew Hill finds
volcanic tuff (walkway)
-fully bipedal ~ 3.6 mya
- Australopithecus afrensis
-pathway in ash footprints, baby prints too
"Lucy", with and adult male, and child 3 yr
1974 -Australopithecus afrensis - Laetoli
~ 3.2 mya
Lucy -3'5" tall
70 lbs.
Male - 5'-5'.5" tall
430 cc
Christmas - Don Johansen
Lucy in the sky with diamonds
- only species that could have left prints at Laetoli
- Hadar, Africa
Specimin numbering
AL 288-1
288th find, part 1
Laetoli Footprints
-geological evidence indicates the eruption of a nearby volcano, which spewed a thin layer of very fine ash across the landscape.
- after eruption a light rain fell, causing the ash to turn into a thin gooey mud, the 3 hominids walked through it ~ 3.6 mya
- preserved in wet carbonatite
Andrew Hill
E. Africa 1976-1978
volcanic tuff (walkway)
-fully bipedal ~ 3.6 mya
- Australopithecus afrensis
-pathway in ash footprints, baby prints too
Australopithecus afrensis - Sites
from the 1970's
3.6 - 3.0 mya
- Laetoli, Tanzania
- Hadar, Ethiopia
- Korsi Dora, Ethiopia
- Dikika, Ethiopia
Afar is the name of the tribe- fossils found
Australopithecus afrensis - Laetoli
1974 - Don Johansen
- finds 40% complete skeleton
Miocene epoch
period where hominids' first appeared
5-10 mya
Owen Lovejoy's Provisioning Hypothesis
If the father could provide more food, the mother could have more than on child, time in between is reduced.
monogamy/ paired bonding, of food provisioning, of cooperation, and bipedalism
Aramis, Ethiopia (village)
1980's Tim White & colleagues
-fossil- rich Middle Awash Valley of Ethiopia's Afar Depression
- geologic and tectonic activity
- site of transition from pongid to hominid
- a cool, wet forest
Ardipithecus kadabba
canines worn from the tips
- perihoning complex
Ardipithecus ramidus
bipedal and arboreal
- no perihoning complex
Awash River
fossil- rich Middle Awash Valley of Eithiopia's Afar Depression - arid region
- geologic and tectonic activity
-river flows thru the depression
-creating rich plant and animal life
- Afar's floor is volcanic rock = radiometric dating thru geological strata
National Museum in Addis Abada, Ethiopia
109 hominid fossils = 36 individuals
- partial skeleton, "Ardi" ARA-VP-6/500, predates "Lucy" by a million years
Ardi - female adult, 110 lbs, 4 ft. tall
300-350 cc, highly projecting face
- big incisors/canines & sectorial complex
- omnivorous, eating nonabrasive foods, hard foods
closest to chimps and human ancestor
Ardi and ramid
Ardi = ground or floor
ramid = root
Australopithecus anamensis
Allia Bay (east lake) and Kanapoi (south end)
of Lake Turkana, Kenya
4 mya - anam = "lake" in Turkana lingo
likely ancestor of A. afaransis
-woodland environments
studied by: Mave Leakey, Carol Ward, Alan Walker
Sexual Dimorphism and Human Behavior
i. Many primate species are highly sexually dimorphic, with males larger than females.

ii. Some scientists see little sexual dimorphism in early hominids; therefore males would have been more cooperative and less competitive.
Bipedality Had Its Benefits and Costs: An Evolutionary Tradeoff
i. Bipedalism was a clear advantage to early humans.

ii. It allows for a better view of the horizon, but also exposes the individual to predators.

iii. Walking along with lifting or carrying heavy loads can cause back injury.

iv. The circulatory system also faces a greater burden.
The Pre-AustralopithecinesThe Pre-AustralopithecinesThe Pre-Australopithecines
Sahelanthropus tchadensis
(1) Found by Michel Brunet in 2001

(2) Located in central Africa and dated to 7-6 mya

(3) Brain size (cranial capacity) of 350 cc

(4) Foramen magnum indicative of likely bipedality

(5) Nonhoning chewing complex

(6) Close to pongid/hominid divergence
Sahelanthropus tchadensis
Central Africa - Toros - Menalla
named so meaning "genus named for the region of the southern Sahara desert known as the Sahel" dated 7-6 mya
- human originated in Africa during the late Miocene and early Pliocene
-brain size of 350cc
- massive browridge
Orrorin tugenensis
(1) Found by Brigitte Senet and Martin Pickford

(2) Located near Lake Turkana and dated to 6 mya

(3) Femurs indicative of bipedalism

(4) Curved hand phalanx, suggesting time spent in trees

(5) Nonhoning chewing complex

(6) Lived in a forest
Orrorin tugenensis
6 mya
Tugen Hills - W. Lake Turkana
- Brigitte Senut & Martin Pickford
- Femurs found, missing the knee (bipedal)
-phalanx - curved - spent time in trees
- canines worn on the tips, nonhoning
- animal bones + Orrorin = lived in forest
Ardipithecus kadabba and Ardipithecus ramidus
(1) Found by Tim White and Yohannes Haile-Selassie

(2) Located at Aramis and dated to 5.8-4.4 mya

(3) Partial skeleton, other bones, and teeth

(4) Variation in tooth wear; possessed thin enamel

(5) Lived in a forest

(6) Time spent on ground and in trees
The Australopithecines (4-1 mya)
Australopithecus anamensis (4 mya)
(1) Found by Maeve Leakey, Carol Ward, and Alan Walker; other remains studied by Tim White

(2) Located at Lake Turkana and Ethiopia and dated to 4 mya

(3) Physically somewhat similar to Ardipithecus

(4) Large canines, parallel tooth rows, different cusp pattern on lower first premolar
Australopithecus afarensis (3.6-3.0 mya)
(1) Found by Donald Johanson, Maurice Taib, and Tim White

(2) Located in Laetoli, Tanzania and Hadar, Korsi Dora, and Dikika, Ethiopia and dated to 3.6-3.0 mya

(3) Lucy (type specimen) is very complete for the age, 40% of skeleton found in Hadar

(4) Bipedal, may have had stride similar to modern humans

(5) Long arms, curved finger bones, suggesting tree use

(6) Cranial capacity of 430 cc

(7) At Laetoli, assemblages include hominids as well as footprints of three hominids

(8) Lived in varied habitats
Australopithecus (Kenyanthropus) platyops (3.5 mya)
(1) Found by Maeve Leakey and colleagues

(2) Found at Lake Turkana and dated to 3.5 mya

(3) Woodland habitat

(4) Flat face with some primitive characteristics
Diversification of the Hominidae: Emergence of Two Evolutionary Lineages from One (3-1 mya)
Australopithecus garhi (2.5 mya)
The First Maker, and User, of Tools(1) Found by Berhane Asfaw and colleagues

(2) Located in Ethiopia and dated to 2.5 mya

(3) Bones, teeth, partial skeleton, and a skull

(4) Larger teeth than earlier australopithecines

(5) More humanlike humerus-to-femur ratio

(6) Cranial capacity of 450 cc

(7) Probable ancestor of Homo

(8) Associated mammal bones with cutmarks, leading to conclusion that A. garhi made Oldowan tools, the earliest stone tools

(9) Stone tools were long associated with meat consumption; some wear may indicate tools were also used for digging in the ground.
Evolution and Extinction of the Australopithecines
v. Evolution of earliest hominids resulted in a diverse group of species.

vi. Change in facial structure reflected dietary specialization.

vii. No large change found in brain size.

viii. A. garhi may have been ancestor of H. habilis.
Australopithecus aethiopicus
(1) Found in Lake Turkana (A. aethiopicus), Olduvai Gorge (A. boisei), and other locations in Africa

(2) A. aethiopicus dates to 2.5 mya and had a cranial capacity of 410 cc

(3) A. boisei dates to 2.3-1.2 mya and had a cranial capacity of 510cc

(4) Smaller front teeth, larger back teeth

(5) Sagittal crest for attachment of chewing muscles

(6) Dietary focus on harder foods
Australopithecus boisei
(1) Found in Lake Turkana (A. aethiopicus), Olduvai Gorge (A. boisei), and other locations in Africa

(2) A. aethiopicus dates to 2.5 mya and had a cranial capacity of 410 cc

(3) A. boisei dates to 2.3-1.2 mya and had a cranial capacity of 510cc

(4) Smaller front teeth, larger back teeth

(5) Sagittal crest for attachment of chewing muscles

(6) Dietary focus on harder foods
Australopithecus africanus
(1) Found by Raymond Dart

(2) Found at Taung, South Africa and other sites, dating to 3-2mya

(3) Larger teeth than A. afarensis

(4) Brain size of 450 cc
Australopithecus robustus
(1) Found in South Africa and dated to 2 mya

(2) Large premolars and molars, with a large face and sagittal crest

(3) Similar to East African forms

(4) Brain size of 530 cc
Australopithecus sediba
(1) Found in Malapa, South Africa, and dated to 2.0-1.5 mya

(2) Had relatively small face, jaws, and teeth and a more homo-like pelvis

(3) Had small body and long arms like those of australopithecines

(4) Brain size of 420 cc

(5) Presence of homo-like features suggests a place in the ancestry of genus Homo