Human Origins Exam 2

Problems with the search for the first human ancestors

• Fossils are old, not intentionally buried, and very fragmentary

• It is hard to tell if it is a hominid or not (human or ape side)

  • Because they are so close to the split, early hominids do not look much different from the ape side of the split

• Lumpers vs. splitters

Ramapithecus

• First discovered in 1932 by G.E. Lewis

• Originally believed to be the earliest ancestor

• In 1976, David Pilbeam discovered a complete Ramapithecus jaw in India that was clearly different from human-like jaws

• Current understanding says that it is actually an ancestor of orangutans

The Lothagam mandible

• uncertain dates

  • 5.6-5.8 mya

• Originally assigned to A. africanus

• could be Ardipithecus, a. anamensis, or afarensis

• KNM-LT 329

  • REMEMBER THIS

• Lower jawbone

• considered on of the earliest known hominin fossils

• Lothagam, Kenya

Sahelanthropus tchadensis

• Could be the earliest hominid ever found

• Found by Dr. Michel Brunet

• Toros-Menalla, Djurab Desert, Chad

• Tests the idea that east and west africa are the birth places of human evolution

• Features

  • Relatively complete skull

  • dates to 7 mya

  • tiny brain

  • Serious postorbital constriction

  • Short lower face

  • U-shaped dental arcade

  • BUT

    • Small canine

    • No diastema

    • Looks more like much later hominids than the early hominids they are closer to

• Skull was really distorted and when found

• Femur found near the skull

  • suggest bipedalism

Who found Sahelanthropus tchadensis?

Dr. Michel Brunet

Where was Sahelanthropus tchadensis found?

Toros-Menalla, Djurab Desert, Chad (TM)

What does Sahelanthropus tchadensis date to?

7 mya

What characteristics link Sahelanthropus tchadensis with apes?

• Small brain size

• Prominent brow ridge

• Sloping face

• Small post-canine teeth and U-shaped dental arcade

• Strong muscle attachments on the skull

• Foramen magnum not as far forward as later hominins, aligning a bit more with quadrupedal apes

What characteristics link Sahelanthropus tchadensis with humans?

• Reduced canine size

• Thicker enamel on teeth

  • Adapted for processing a varied diet

• Foreman magnum possibly indicating bipedalism

• Less prognathic (flatter) face than other apes

  • although it still slopes

• Intermediate facial structure

  • ex: reduced snout projection

Orrorin tugensis

• Could be earlier than Sahelanthropus tchadensis

• Features

  • Long demoral neck, flattened proximal shaft, small femoral head

    • Prob bipedal

    • The structure of the glute muscles and the wide pelvis increases the moment arm which increases the strength of the movement

    • Increased the moment arm and changed biomechanics as opposed to simply making the muscles bigger, which is harder

• “Millennium man”

Who found Orrorin tugensis and where?

• Martin Pickford and Briggitte Senut

• Tugen Hills, Kenya “Cradle of Humankind” or “Saimo”

What does Orrorin tugensis date to?

5.7-9.1 mya

Why do we think Orrorin tugensis might be a hominid?

• Femoral neck indicated bipedalism

• Thick enamel on teeth

• Small, human-like canines

Australopithecine hip and femur characteristics

• Bone mass is more concentrated on femoral neck because of where the weight goes

• Short, broad pelvis

• Ilium is curved and flared

• Anterior position of the iliac blades

• sacrum is broad

• Valgus angle

• Large femoral head

• Thick cortical bone on the inferior side of the femoral neck

• Long femoral neck

Biomechanics of Australopithecine hip and femur

• Increased moment arm and changed biomechanics instead of making the muscles bigger

• Bone is more concentrated on the femoral neck because of how weight is distributed in Australopithecines

Evidence that Sahelanthropus and Orrorin were bipedal

• Foreman magnum orientation

• Femur near the skull indicated bipedalism

• Femoral neck indicated bipedalism

Contrast of dental evidence for Sahelanthropus and Orrorin

• Both have small canines and thick enamel

• Sahelanthropus may show slightly smaller canines that Orrorin, with clearer apical wear

• Both lack the ape-like honing complex

• enamel thickness is similar, hinting at similar dietary adaptations

• Sahelanthropus have moderate molar size, while orrorin have relatively small molars

• We have fewer orrorin fossils than we do Sahelanthropus

What does the species Ardipithecus date to?

5.8-4.4 mya

Who found Ardipithecus and where?

Tim White in Aramis, Ethiopia

Why were the recent papers on Ardipithecus so exciting for the anthro community?

• Extremely delicate fossil

• May be different types of bipedalism

• Found in 1994, but not published till 2009

• Created a feeling of camaraderie in the anthropology community

• Helped describe the environment around ardi

• gave us massive insight into the last common ancestors

Ardipithecus cranium

• Reconstructed out of many pieces

• 300-350cc

• Reduced prognathism (still prognathic, just not as much as an ape)

• Foreman magnum shifted slightly forward from apes

Ardipithecus teeth

• Omnivorous

  • No big incisors like chimps have

  • Very generalized like us

• Canine size reduced

  • Little sexual dimorphism

  • Non-honing, wear on tip

  • Diamond shaped

  • Lower canine longer

• No post-canine megadontia

• Intermediate enamel thickness

  • Humans have thick enamel, apes have thin enamel

Ardipithecus hands

• Not knuckle-walking

• Phalanges are long, metacarpals are short

• Wrist adapted to dorsiflexion

• Moved palmigrade

Ardipithecus pelvis

• Ilium is short and broad, got standing on one leg

• Anterior inferior iliac spine is more pronounced, like a human

• But hamstrings/ischium primitive

  • climbs trees

Ardipithecus feet

• Fully abductable big toe

• foot is stiff

  • Apes highly mobile

  • Monkeys are stiff

Ardipithecus body proportions

• Low sexual dimorphism

• Apes have very long arms and short legs

• we have short arms and long legs

• Ardi looks like a monkey (arms and legs equal)

If Ardipithecus is a hominid, what does that tell us about the levels of convergence in the hominid family tree?

• We have always assumed that homoplasy doesn’t happen often, but if Ardipithecus is a hominin, a bunch of them have to happen

What is the evidence that Ardipithecus was bipedal?

• Short but broad upper pelvis blade

• Rigid midfoot

• Lateral foot structure

• Big toe used for pushing off

Australopithecus anamensis

• Over 50 cranial, dental, and postcranial fossils

• No full individual found

• Features

  • Prognathic

  • Parallele dental arcade

  • large canine roots with blade-like crowns

  • Diasthima

  • Canines

    • No change in size but a. anamensis is more blade-like than a. afarensis

Who found Australopithecus anamensis and where?

Meave Leakey in kanapoi and allia bay (kenya)

What does Australopithecus anamensis date to?

4.2-3.8 mya

Why do we think Australopithecus anamensis might be a hominid?

• bipedal

• human-like tibia

• Primitive features in jaws and teeth

Evidence that Australopithecus anamensis was bipedal

• Tibia indicates it

• Straight shaft

• Concave condyles

  • valgus angle???

Australopithecus anamensis teeth

• Parallel dental arcade

• Large canine roots with blade-like crowns

  • Diastema

• No change in size of canines, but a. anamensis is more blade-like than a. afarensis

How many Australopithecus afarensis individuals have been found?

Over 350 specimens, over 100 different individuals

What are the main sites associated with Australopithecus afarensis?

• Hadar Ethiopia

When does Australopithecus afarensis date to?

3.2 mya

Dikika baby

• found in 2006 in Ehtiopia

• 3.3. mya

• About three years old

• Female

• Partial skeleton (really complete comparatively)

  • Hyoid and patella

• Brain growth rates

  • Chimp 90% by 3

  • Dikika 63-88% by 3

  • Slow brain development in a. afarensis compared to chimps

What does the Dikka baby tell us about Australopithecus afarensis?

• tells us that their brains developed slower

• also dealt with the Bipedal Dilemma

Cranial characteristics that differentiate Australopithecus afarensis from apes and humans

• Birth was harder than apes but not as hard as in humans

• Pelvis is clearly bipedal

  • But is quite wide and flares over the femur more so than in modern humans

  • Increased quad moment arm

    • Ligaments stiff in full extension, large weight-baring surface

• Had both human and ape characteristics

How do we know Australopithecus afarensis was bipedal?

Evidence from hip: valgus angle, angle of pelvic flare

Evidence from knee:

• enlarged outer condyle

  • stability and weight distribution

Evidence from foot:

• Laetoli footprints

What can we say about birth in Australopithecus afarensis based on the shape of Lucy’s pelvis?

It was harder than an apes, but easier than a humans

They twisted during birth but not as much and as often as humans do

The Laetoli footprints

• Laetoli, Tanzania

• 3.6 mya

• Found by grad students having fun\

• Small A. afarensis foot fits well into these

• They show

  • Deep impression for heal strike

  • Well-developed longitudinal arch

  • Big toe in line

  • deep impression for big toe

What do the Laetoli footprints tell us about gait in Australopithecus afarensis?

• Heel strike

• stance

• Toe off

• All of these indicate bipedalism

• Also gives us the transfer of weight across the foot, which shows arches

Body proportions in Australopithecus afarensis

• The femur is short compared to humerus

• Upper limb proportions normal

• In afarensis, humerus is 84% of femoral length

• In chimps, humerus is 107% of femoral length

• In humans, humerus is 73% of femoral length

• Body proportions are still very much like an ape and not like a human

Sexual dimorphism in Australopithecus afarensis

• Very high

• 1.6 ratio for female vs male body size

• Social organization

• Suggests afarensis had male male competition

Evidence for Australopithecus afarensis climbing

• ape-like shoulder blades

• strong upper limbs

Evidence against Australopithecus afarensis climbing

• Rigid ankle and arched nongrasping feet

• Bipedal adaptations

• Hip joint loadings

• Forelimb adaptations

Australopithecus africanus

• Gracile vs robust

  • Almost identical body size

  • Robust = chewing adaptations NOT larger size

• One of the first species discovered

• Australopithecus = southern ape

• Pretty adaptable

• Probably all over Africa, and just geological accidents where we find them

• Not as hospitable environment as east Africa

  • Greater seasonality

Who found Australopithecus africanus and where?

Raymond Dart in Tuang

What does Australopithecus africanus date to?

3-2.3 mya

What are major sites associated with Australopithecus africanus

• Tuang

• Sterkfontain

• Makapansgat

• All South African

Features that differentiate Australopithecus africanus from Australopithecus afarensis

• Relatively bigger brain

  • EQ

    • Encephalization quotient

    • Actual brain size over expected brain size based on other mammals relative to body size

• Smaller canine

  • Larger molars that get bigger as they go back

  • Bigger jaws

• Anterior pillars

  • Buttress for forced through the face

  • nose pillars

• Everything is is similar to afarensis

Difficulties involved in aging juvenile hominids

• Need to know

  • Age of death

  • Height at death

  • Pattern of growth

• We can match juveniles to their adult counterparts, but if we don’t have adult counterparts or can’t determine what they are, it becomes much harder

What does the Taung endocast tell us about brain development in Australopithecus africanus?

• Ratio of cerebral to cerebellar higher than gorilla

• Brain reorganization towards a more human-like condition

• Potentially expanded parietal lobe

• More human-like sulcal organization

Why is speech difficult to reconstruct?

• Mostly soft tissue controls speech

• Position of vocal cords determine range of sounds available

How do the throats of apes and humans differ?

• Apes

  • Vocal cords high up

  • Tongue fills oral cavity

  • Supralayngeal vocal tract (SVT) small

• Humans

  • Vocal cords/larynx low

  • Tongue different position

  • Larger SVT

  • Air puffs over vocal cords in larynx and resonated in SVT

  • Permits speech but at the cost of creating risk of choking

• Apes and babies flow on each side of epiglottis

Evidence of morphological variation in A. africanus

• Differences in molar size

• Difference in facial structure

• Difference in sexual dimorphism

Possible hypotheses for why hominids became bipedal? What problems do they have?

• Hypotheses

  • Developed for open savannahs

  • Holding tools/weapons

    • Standing frees hands

  • Thermoregulation

    • Less sun exposure

  • Energy efficiency

    • Bipedalism is more efficient

    • Early bipeds were probably not efficient

• Problems: The obstetric dilemma

  • Heavy selection pressure against bipedalism

  • Bipedal pelvis is difficult to birth through

  • Babies are Altricial

    • Commpletely dependant on parents

    • Ex: Kittens, Birds, Humans

    • Humans born totally immature so head will fit

    • essentially fetal, rabid brain growth

    • Changes social system and care requirements

  • Back pain

    • Spine not designed to be weight bearing

    • Designed to be an arch

    • No other primates have back pain or slipped disks

  • Knee problems

    • Valgus angle makes us unstable

  • Feet

    • Relaxin and ligamnets

    • Support all body weight which makes them vulnerable

What does Owen Lovejoy’s Origin of Man hypothesis say about bipedality?

• It evolved as a result of monogamous mating systems and the need for males to provision females and offspring with food, freeing hands for carrying resources

Problems with Owen Lovejoy’s Origin of Man hypothesis in relation to bipedality

• Gender bias

• Simplistic view of human evolution

• Male centric

• Overemphasis on Provisioning

• Lack of evidence

• Fossil record shows hominins were still adapted to climbing

Selective pressure against bipedalism

• Problems: The obstetric dilemma

  • Heavy selection pressure against bipedalism

  • Bipedal pelvis is difficult to birth through

  • Babies are Altricial

    • Commpletely dependant on parents

    • Ex: Kittens, Birds, Humans

    • Humans born totally immature so head will fit

    • essentially fetal, rabid brain growth

    • Changes social system and care requirements

  • Back pain

    • Spine not designed to be weight bearing

    • Designed to be an arch

    • No other primates have back pain or slipped disks

  • Knee problems

    • Valgus angle makes us unstable

  • Feet

    • Relaxin and ligamnets

    • Support all body weight which makes them vulnerable

What does altricial mean?

• Completely dependent on parents upon birth

What does Precocious mean?

• Baby that is ready to go as soon as it is born

• Comes out in state of relative autonomy

The three types of robust australopithecines

• A. aethiopicus

  • A. boisei

  • Olduvai Gorge, Koobi

  • Most robust of the robust

  • Found by the leakies

  • OH 5

    • Zinj

• A. robustus

  • Kromdraai, Swartkans, Drimolen

  • Not as big, lives in a different space

Cranial characteristics that differentiate robust and gracile australopithecines

• 450-500cc

• Highly long and orthognathic face (flat)

• Sagittal Crest

  • small brain, large chewing apparatus

  • Temporalis and Masseter

• Large temporal fossae

  • Holes next to the temporal bones

  • Flared cheek bones

• Nuchal crest

• Wide zygomatics with concave face

• Good for resisting forces from chewing

• Large molars

  • Key difference

  • Major reason for being called robust

• Smaller anterior teeth

  • Not a frugivore

• Mandible deep and thick

• So much of their anatomy influenced by that adaptation to hard and gritty food

How does a sagittal crest form?

• Large chewing apparatus

• Creates less room for brain

• Sagittal crest is a muscle attachment

What unifies many of the features in robust australopithecines?

• adaptation for hard and gritty food

• Chewing aparatus

What is the primary adaptation of robust australopithecines?

Large molars

Australopithecus aethiopicus

• The black skull

• West Lake Turkana

• 2.5 mya

• Like afarensis

  • small brain

  • Prognathic face

  • large anterior teeth

When did Australopithecus aethiopicus exist?

2.5 mya

What features link Australopithecus aethiopicus with other robusts?

• Sagitall crest

• Wide zygomatics

• Space for huge back teeth

What features link Australopithecus aethiopicus to Australopithecus afarensis?

• Tiny brain

• Prognathic face

• Large anterior teeth

What australopithecine is the most robust (largest teeth)?

A. boisei

When and where did Australopithecus boisei live?

2.5-1.15 mya

eastern Africa

What sites are associated with Australopithecus boisei?

• Olduvai Gorge

• Koobi

When and where did Australopithecus robustus live?

2-1.2 mya

South Africa

What sites are associated with Australopithecus robustus?

• Kromdraai

• Swartkans

• Drimolen

How does the body size of robust Australopithecines compare with gracile Australopithecines?

• They are similar in body size

• robust refers to teeth and chewing apparatus, not body size

What is the evidence that Australopithecus robustus ate termites? What site is it from?

• Lots of grit that heavily wear-down teeth

• Worn teeth and large molars

• Bone tools found in Swartkrans South Africa

Evidence that Australopithecus robustus used tools

• bone tools used for termites

• Hands adapted for tool use

What sort of foods did robust australopithecines likely eat?

• Hard foods like nuts, termites

Where, when, and by whom was Australopithecus bahrelgazali found?

• Bahr el Ghazal, Chad

• 3.6 mya

• Discovered in 1993 by Michel Brunet

What is the interpretation of the specimen of Australopithecus bahrelgazli?

• Probably just A. afarensis

• Little less backwards sloping than afarensis

• 3 molars instead of one or two

Where, when, and by whom was Kenyanthopus platyops found?

• West Lake Turkana (Kenya)

• 3.5 mya

• Discovered in 1999 by the Leakeys

What is the interpretation of the Kenyanthopus platyops specimen?

• A “Leavithere”

  • Find it and leave it there because its useless

Where, when, and by whom was Australopithecus garhi found?

• Bouri Ethiopia

• 2.5 mya

• Discovered in 1999 by Tim White

What is the interpretation of the A. garhi specimen?

• Maybe sexual dimorphism of a. aethiopicus

What was found in loose association with the A. garhi specimen?

• Cut marked and hammer stone marked animal bones

• Earlyish tool use at 2.5 mya

Where, when, and by whom was Australopithecus sediba found?

• Malapa Cave south africa

• 1.78-1.95 mya

• Found by Lee Berger in 2008

What is the interpretation of the A. sedhiba specimen?

• Berger argues that this is the ancestor to later homo

• Mix of primitive and derived features

Where, when, and by whom was Homo naledi found?

• Lee Berger in the Dinaledi Chamber of the Rising Star cave system in 2013

What is the interpretation of the Homo naledi specimen?

• Possible climbing

• Claim of fire use and art

• 236,000 - 335,000 years old? Prob not tho

General criteria for inclusion in the genus homo

• Body 'proportions

  • Intermembral index lower (legs relative to arms)

• Increased body size

• Brain

  • Body size ratio (EQ) larger (erectus is around 900cc)

• Longer postnatal growth period

• Skull and dental morphology

  • Less heavily built (smaller teeth and less robust masticatory apparatus)

  • Less prognathism

• Technology

  • Stone tools manufacture (indicating a different adaptive strategy)

What is the type specimen of Homo habilis?

• OH-7 (Olduvai Hominid 7)

How did the type specimen for Homo habilis contribute to confusion surrounding what specimens should be included in that species?

• it is a Juvenile

What is the significance of the specimen KNM-ER 1470?

• East Turkana

• 1972

• Stuck in homo habilis

• Classified as an indeterminate species of homo originally, then placed in habilis or rudolfensis, which it is now the type specimen for

What species in KNM-ER 1470 considered?

• H. rudolfensis

How did KNM-ER 1470 contribute to the classification issues with early Homo?

• Louis Leakey believed the skull was a million years older than it was and classified it as an indeterminate species oh homo

Differences between Homo habilis and Homo rudolfensis

• Homo Habilis

  • Small teeth

  • Small orthognathic face

  • Well-developed brow ridges

  • small brains

• Homo rudolfensis

  • Big teeth

  • Giant, flat, australopith-like face

  • Small brow ridges

  • Bigger brain