AN 102, SPRING 2013

LAB 7 – LATE AUSTRALOPITHECUS TO EARLY HOMO

Today’s class:

Quiz

Lecture

Lab

The genus Australopithecus

Gracile FormsA. anamensis (EAST)

A. afarensis (EAST)

A. africanus (SOUTH)

A. garhi (EAST)

A. sediba (SOUTH)

A. robustus (SOUTH)

A. aethiopicus (EAST)

A. boisei (EAST)* Sometimes placed in genus Paranthropus

Robust Forms*

For each species, we will learn:The taxonomic nameIts chronological ageThe site where it was foundThe traits it manifests

Australopithecus africanus

“Taung Child”

The first Australopithecus specimen was discovered by Raymond Dart in South Africa in 1924.

It was a 4-year-old child.

Dates from 3-2.0 mya

Foramen magnum anterior

Flatter face, bigger brain, smaller canines, non-sectorial P3

400-500cc cranial capacity

Australopithecus garhi Discovered in Ethiopia in 1999

Dates to 2.5mya

450cc brain and very prognathic face

Bigger teeth than A. afarensis and A. africanus

Proportionally longer lower limb bones

At nearby localities, antelope bones exhibited cut marks and damage from hammerstones

Important because it was previously thought that no Australopithecine made tools

Australopithecus sediba Discovered in South

Africa in 2008

Dates to 1.977 mya

420cc brain

Small cheek teeth (Homo-like!)

Human-like hand and pelvis

More ape-like foot.

Otherwise like A. africanus

Demonstrates that there were different ways to be bipedal

Robust AustralopithecinesA. anamensis, A. afarensis, A. africanus, A. garhi, and A. sediba are all gracile Australopithecine forms.

Around 2.5 mya, a new group of Australopithecines evolves: the robusts.

•They are found in East and South Africa

•Dental and jaw morphology differ from those of gracile forms

•Specialized diet

Robust

Gracile

Robust Australopithecus species have:

Larger cheek teeth/ very reduced anterior teeth

Larger attachment sites for muscles involved in chewing Sagittal crest in males Broad, flaring cheek bones

Large temporal fossa Post-orbital constriction

Face

Postorbital constriction

In other words, robust species are highly adapted “chewing machines”

View looking down on the skull

Robust Australopithecines

Temporal fossa

The attachment area of the temporalis muscle was larger in robust Australopithecine forms than in modern humans

Robust Australopithecines

Australopithecus aethiopicus

“the black skull”

•Found in Ethiopia

•Dates to approx. 2.5mya

•No postcranial bones identified for sure in this and other E. African robusts

A. aethiopicus exhibits a mix of traits:

• Small brain and prognathic face (like A. afarensis)

• Sagittal crest and large molar teeth (like other robust forms)

Sagittal crest

Large molar teeth

TemporalFossa

Australopithecus robustus

Flaring cheek bones

South African form

Dates from 2.0-1.5 mya

500-530cc brain size

Sagittal crest and other heavy chewing adaptations

Australopithecus boisei East African form: First

found by Mary Leakey at Olduvai Gorge in 1959

Dates from 2.2-1.4 mya

“Hyper-robust”

Sagittal crest and other heavy chewing adaptations

Very sexually dimorphic in body size

475-545cc brain size

Very reducedanterior teeth

Very large molarswith thick enamel

•The genus Kenyanthropus has only one species and was named by Meave Leakey, who discovered it in northern Kenya in 1999.

•Dates to approx. 3.5mya

•Less prognathic face (like later humans)

•Small brain (400-500cc), like Australopithecines

•No definitive post-cranial fossils

•Relationship to Australopithecines not entirely clear (could be a regional variant)

Kenyanthropus platyops

Australopithecine behavioral patterns

LocomotionAll have bipedal adaptations, but some also retain adaptations for climbing

Sexual DimorphismModerate canine dimorphismModerate to high body size dimorphism

DevelopmentFaster to reach sexual maturity, less infant dependency than humans; more than apes

Tool UseSome Australopithecines may have used stone tools (e.g., A. garhi)

Suggests polygynous or multi-male/multi-female social system

Brain Size

On average, 20% larger brain than chimpanzees. But, still considerably smaller than humans.

Diet

Herbivory and hard seeds in robust forms

A bit more omnivory in gracile forms

Pitted = hard food items (seeds, tubers)

Scratches = grainy food items (leaves)

Magnified tooth-enamel surface of two australopithecines

A. africanus A. robustus

Australopithecine behavioral patterns

Status and Body Size in Australopithecines

Estimates show large differences in body mass and height between male and female

Australopithecines.

Past

Present

Miocene Hominoids

Ardipithecines (Sahelanthropus, etc.)

Gracile Australopithecines (extinct)

Robust Australopithecines (extinct)

Early Homo (extinct)

Later Homo (extinct)

Modern humans

Modern chimps

What are the phylogenetic relationships

of all these species?

Can we be more specific?

early Homo

A. anamensis

A. afarensis

A. africanusKenyanthropus

A. boiseiA. robustus

A. aethiopicus

A. ghari

Pre-Australopithecine

time

One possible scenario….

Why do we have such difficulty determining this kind of phylogeny?

time

Actual history of species relationships

Recovered fossils (if we’re lucky)

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?

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The Recovery Problem

R

R

R

G

G

G

G

A recap of pre-Homo hominid evolution

**A. sediba - G

early Homo

A. anamensis

A. afarensis

A. africanusKenyanthropus

A. boiseiA. robustus

A. aethiopicus

A. garhi

Pre-Australopithecine

time

MOVING TO THE GENUS HOMO

•The oldest known species of the genus Homo

•Louis Leakey discovered the first specimen at Olduvai Gorge in Tanzania (where A. boisei was also found) in 1960.

OH 7 mandible

OH 7 hand

Homo habilis

Leakey was convinced this fossil was not A. boisei because:

•It had no sagittal crest

•It had smaller teeth

•It was found in close association with tools

Leakey named the new fossil Homo habilis, meaning “handy man,” in reference to its presumed tool-making abilities.

-Leakey also emphasized the fact that his specimen had a had a larger brain than any Australopithecine.

Homo habilis

Richard and Louis Leakey

Many paleoanthropologists rejected Leakey’s new classification.

-They said the new fossil material was too fragmentary to accurately conclude it belonged in a new genus.

-They did not like the idea of “tool use” being a criterion for naming a new genus.

Subsequently, Louis’s son Richard set up a new site at Koobi Fora in Kenya, where he also found A. boisei and H. habilis.

-At the time, his finding solidified the taxonomy of H. habilis

-Today, some people argue that the name should be changed to A. habilis due to post-cranial and developmental features.

HOMO HABILIS

•H. habilis is found at sites in East Africa

•Dates from 2.4-1.5mya

Post-cranial features:

•Long, strong thumb

•Short, straight fingers

•Broader fingertips Post-cranial materialsFound at Olduvai

Gorge in 1986

Features associated with increased manual dexterity

Homo habilis

Homo habilisA. africanus

Skull less rounded Skull more roundedSmaller brain (<500cc) Larger brain (600-700cc)Prognathic face Less prognathicLarger molars Smaller molarsMore postorbital constriction Less postorbital constriction

Homo habilis

•Recently, some people have argued that based on the variation seen in the cranial fossils, Homo habilis should be divided into 2 species:

-Homo habilis (smaller brains, less robust)

-Homo rudolfensis (more robust with larger brains)

•Not yet agreed upon whether variation is more likely within a single species or between 2, but we will refer only to Homo habilis in this lab.

Homo habilis taxonomy

•Eugene DuBois discovered the first H. erectus fossils in Java in 1891.

•2 key specimens were recovered: a skullcap and a femur

DuBois

Homo erectus

•In the 1930s, Davidson Black, Franz Weidenreich, and Pei Wenshong began to excavate at Zhoukoudian (China)

•They uncovered over 100 fossils attributed to H. erectus

•Over time this has been a very well-studied site

Homo erectus

H. erectus shows up in the fossil record about 1.8mya

It is unequivocally different from any prior hominid:

•It is bigger, and has a bigger brain•It is found in sites outside of Africa•It has more advanced tools•Many of its features approximate modern human traits

Homo erectus

•Significant increase in brain size

-Range of 750-1250cc-Average of 900cc

•More encephalized than H. habilis, less encephalized than H. sapiens

Homo erectus: Cranial Traits

Cranium

•Large browridges

•Low forehead

•Broad at skull base

•Nuchal or Occipital torus

•Thick cranial bones

•Shovel shaped incisors (also found in some modern populations)

Homo erectus: Cranial Traits

A. africanus A. robustus

H. erectus H. sapiens

H. erectus A. afarensis H. sapiens

•As tall as modern humans

•More sexually dimorphic than modern humans

•Thicker long bones

Homo erectus: Post Cranial Traits

H. sapiens H. neanderthalensis

H. heidelbergensis

H. ergaster H. erectus

H. habilis

Homo erectus and Homo ergaster

•Researchers often distinguish between H. erectus (Asian form) and H. ergaster (African form.) For simplicity, I will refer to both as H. erectus, although they do exhibit a few differences.

% of resting energy allocated to brain

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Increase in brain size and EQ in H. erectus

•Site occupied intermittently for over 250,000 years

•Over 100,000 artifacts have been collected

•Debates continue over how to interpret some of these artifacts

Homo erectus at Zhoukoudian

Homo erectus in Africa (H. ergaster)

KNM-ER 3733

KNM-ER 3883

Paleoanthropologists have found several nearly complete H. erectus crania in East Africa.

•KNM-ER 3733: Dates to 1.8mya.

•KNM-ER 3883: Dates to 1.6mya

Homo erectus in AfricaA particularly famous H. erectus fossil was discovered by Lake Turkana in 1984. It is commonly known as Turkana Boy or Nariokotome Boy

•Is over 90% complete•Dates to 1.6mya•Was 8-12 years old when he died (younger if he grew in a more chimp-like way)•Was 1.6m tall (5’ 3”), and likely to have reached 1.85m (6’1”)•Had a long, linear body shape like modern humans •Had a cranial capacity of ≈ 900cc

Homo erectus: World Traveler•Since 1999, several H. erectus* crania

were unearthed at Dmanisi in the Republic of Georgia

•These crania date to 1.77 mya, making them the oldest known hominins outside of Africa

•They are associated with Oldowan tools, showing that H. erectus migrated out of Africa with their toolmaking skills.

*Some have suggested a new species, H. georgicus, for these specimens

Early andLater migrations

Homo erectus

•Homo erectus is found in the fossil record from 1.8mya to 200,000 years ago (possibly hung around longer in East Asia)

•Toward the end of this time period, another species of hominid appears in the fossil record, at 800 kya

•This species takes on an even more modern appearance

H. sapiens H. neanderthalensis

H. heidelbergensis

H. ergaster H. erectus

H. habilis

Next time… Later Homo Evolution &

Tools