Australopithecines

The Pleistocene

(1.8 ma-11,500years ago): Climatic fluctuations that culminated in widespread continental glaciers. Glaciation cycles resulted in the evolution of cold adapted mammals, as well as fragmentation and geographic shifts of existing ecosystems. Many species of vertebrates, esp. large mammals, went extinct. However, much of the modern flora and fauna are survivors from this epoch.

A. Afarensis and Kenyanthropus sites

A. Afarensis, Kenyanthropus in South America

Evolutionary Relationships: Australopithecus africanus

A. Africanus occurs at the right time period to be a transitional hominin. Descendent of A. Afarensis. Ancestor of the genus homo? Other scientists suggest it is another extinct branch of hominin evolution.

Evolutionary relationships: autralopithecus africanus

A. Africanus occurs at the right time period to be transitional hominid. Descendent of A. Afarensis. Ancestor of the genus homo? Other scientists suggest it is another extinct branch of hominin evolution. A. Afarensis to A. Africanus to ? Homo spp.

climates, hominin diets and survivors

Admidst fluctuating climate, two major shifts toward open grassland: - coincides with extinction of gracile australopiths and Kenyanthropus -expansion of H. erectus and loss of robust austrlopiths and others. Success of Homo linked to diverse diet

evolutionary relationships: australopithecus garhi

At the right place, at the right time. Fossil records show earliest evidence of Homo isn East Africa at 2.5 Ma. Possible that A. garhi descended from A. afarensis and was ancestral to Homo. Further, what we know of its anatomy fits this hypothesis.

possible tool use by australopithecus robustus

Bone tools recovered at site of A. robust us. May have been used to open termite nests or dig tubers.

Australopithecus garhi: stone tool use? meat eating?

Butchered animal bones with stone tool cut marks have been found near site. 2.5 ma hominin begin adding meat to diet.

Australopithecus afarensis: teeth

Canines larger than modern humans, smaller than living apes. Teeth of A. afarensis more primitive than Homo. Intermediate canines, small diastema, relatively big molars, curved tooth row. Dental features are transitional from ape like to human like.

Australopithecus afarensis: locomotion

Considerable evidence that A. Afarensis was a biped.

seeking: hominid ancestor to fill the gap between A. Afarensis and Homo

Desirable qualities: biped, small brain (with future evolutionary potential), small canines, small molars, preferably residing in East Africa, 2 to 3 ma. Would be nice if had interest in stone tool use. Candidates: A. Africansus, A. Garhi, A. Sediba

Did both of the later robust australopithecines have the same or different ancestors?

Did both A. boisei and A. robust us evolve from A. aethiopicus.? Or did A. robust us evolve from A. africanus?

First appearance of stone tool use?

Discovery of cut marks made by stone tools on animal bones in Ethiopia, pushes back appearance of lithic technology to 3.4 million years ago. This behavior attributed to Austrloptihecus afarensis. Did hominins use tools before 3.4 mya?

gracile australopithecine: australopithecus anamensis

FIRST DISCOVERED: 1965 (single arm bone) 1994 species name assigned now 100 fossils (~20 individuals) WHERE: Ethiopia, Kenya HOW OLD: 4.2-3.9 ma KEY FEATURES: bipedal, small canines

Robust Austrlopithecine: Austrlopithecus aethiopicus

FIRST DISCOVERED: 1967 partial mandible 1985 black skull WHERE: Kenya HOW OLD: 2.5 ma KEY FEATURES: brain size (410 cc), robust, huge molars, thick zygomatic, sagital crest. "The black skull."

Gracile Austrolopithecine: Australopithecus africanus

FIRST DISCOVERED: 1924 WHERE: South Africa HOW OLD: 3.3 to 2.5 ma KEY FEATURES: bipedal, brain size (451cc), big molars, small canines, post crania--similar to A. afarensis NICKNAMES: Taung Child, Mrs. Ples

Robust Austrlopithecine: Australopithecus robustus

FIRST DISCOVERED: 1938 WHERE: South Africa HOW OLD: 1.4-2 ma KEY FEATURES: brain size (476 cc), robust face and dentition, sexual dimorphism in body size (male 119 lb, female 88 lb)

Robust Autrlopithecine: Australopithecus boisei

FIRST DISCOVERED: 1959 WHERE: Kenya, Ethiopia, Tanzania HOW OLD: 3.4-1.4 ma KEY FEATURES: brain size (465 cc), huge molars, thick zygomatic arch, sagittal crest, sexual dimorphism in body size (male 108 lbs, female 75 lbs) NICKNAMES: Zing and Nutcracker man

Gracile Australopithecine: Australopithecus Afarensis

FIRST DISCOVERED: 1974 WHERE: Ethiopia, Kenya, Tanzania, Chad HOW OLD: 3.7 -3.0 Ma KEY FEATURES: -bipedal, but still also arboreal? - sexual dimorphism? -brain size: 433 cc -large canines -big molars NICKNAME: "Lucy"--because Beatles song Lucy in the Sky with Diamonds was playing at camp

Gracile Australopithecine: Australopithecus garhi

FIRST DISCOVERED: 1990 WHERE: Ethiopia HOW OLD: 2.5 Ma KEY FEATURES: brain size 450 cc, large molars, but different from A. Afarensis, meat eating with stone tools? "Garhi means surprise in the local afar language

Gracile Australopithecine: Kenyanthropus platyops

FIRST DISCOVERED: 2001 WHERE: KENYA, Africa HOW OLD: 3.5-3.2 Ma KEY FEATURES: small brain, jutting lower, face, small molars NICKNAME: "flat faced man o f kenya" Where does this hominid fit into our family tree?

robust australopithecines

Features unique to the robust austrlopithecines...-sagittal crest, adaptation for heavy chewing: huge molars, large cheekbones, large face. Some suggest that they should be assigned to their own genus. Paranthropus."Robust" refers to the very large back teeth, jaws, and face. Body size was not that different from that of gracile Australopithecines. Lived in Africa from 1-3 ma and then became extinct. Closely related to humans, but not our ancestors.

Lucy

Fossil is about 3.2 million years old. Adult female of about 25 years. She was 3'6'' tall and weighed about 62 lbs. About 40% of her skeleton was found. Her pelvis, femur,and tibia show her to have been bipedal.

current explanations: "variability selection"

Human qualities emerged in diverse and changeable settings. Thus our evolutionary adaptations offer a dynamic capacity to adjust to new environmental challenges. Which of these hominids could cope better with climate change? 1) ate grasses or related food: paranthropus boisei 2) more varied diet : homo erectus

Australopithecus boisei "nutcracker man"

In 1959, Mary Leakey found their first significant hominid fossil. Robust skull with huge teeth, in deposits that also contained stone told. Louis claimed it was a human ancestor (zinjanthropus boisei). To everyone else, it seemed markedly inhuman, similar to robust austrlopithecines. Regardless, it was a major find that gave them tremendous publicity.

Living primate model: tool sets used to harvest termites

In central Africa, chimps use a tool set comprised of puncturing sticks and fishing probes to extract termites from their nests.

Robust austrlopithecines: teeth

Large back teeth compared to small front teeth. Back teeth (premolars and molars) are more than 4x larger than modern humans.

another gracile australopithecine

Lee Berger reported on the partial skeletons of Austrlopithecus sediba. The fossils were originally discovered three years ago in an ancient cave. Lee Berger's son, Matthew, found one of the fossils while chasing his dog.

Overview: gracile austrlopithecines

Lived in Africa 3-4 Ma: Characteristics...bipedal, with ability to climb, large teeth, large face, small brains

evolutionary relationships: how do we get to the genus homo?

Look @ chart. Debate remains about how to classify Kenyanthropus.

Australopithecus anamensis: evolutionary relationships

Morphological features and timing...possibly and direct descendent of a species of Ardipithecus. Direct ancestor of Austrlopithecus afarensis.

baboon feeding ecology informs the dietary niche paranthropus boisei

Paranthropus boisei dervied 75%-80% of their diet from mainly low quality foods like grasses and sedges. In the same geographical area, East African Homo has diet that is 78% broader than Paranthropus. Studied yellow baboon populations who have a similar diet. Energetic requirements of Paranthropus could have met within a 6 hr feeding / foraging day. Tensile stresses on Paranthropus teeth look similar to wear patterns on baboon teeth

Discovery of australopithecus africanus

Raymond Dart (1858-1940), "Taung Child", Robert Broom (1866-1951), Mrs. Ples

Australopithecus africanus : ancestral to homo?

Reasons why scientists hesitate to adopt A. Africanus as ancestral to homo...A. Africanus may be too specialized. Lived in South Africa, whereas earliest homo is in east africa. Reasons why scientists hesitate to adopt A. Africanus as ancestral to Homo...A. Africanus may be too specialized, lived in south africa whereas earliest homo is in East Africa.

Australopithecus afarensis: sexual dimorphism?

Recent research shows that sexual dimorphism in A. afarensis was similar to that in modern humans. Early hominid demographic success may have derived from a reproductive strategy that involved pari bonding and male provisioning.

Meave Leakey and Louise Leakey

Richard Leakey's wife, MEave, is a paleothropologist. His daughter, Louise, is also following in the family's legacy.

Robust Austrlopithecines : skull

Sagittal crest anchors chewing muscles on sides and top of the skull. In humans, Cheekbone anchors chewing muscle; other muscles run in arch. Both have zygomatic arch: temporalis muscle runs from the jaw up under the zygomatic arch. Larger the temporal is muscle, the more the zygomatic arch must flare out.

Australopithecus anamensis: teeth

Shows a number of primitive, ape like characteristics in the teeth. Canines are fairly large. Back teeth are in parallel rows, unlike the more parabolic shape of human jaw.

debates over how to classify this fossil

Some classify it as...1)austrlopithecus afarensis: individual of Lucy's species 2) Australopithecus platypus: new species of Australopithecine 3) Kenyanthropus platypus, new genus and species. Disputes: Lump with identified taxa. Could be split into new taxa. Type specimen is very fragmented and distorted; clear designation will require more fossils.

Australopithecus anamensis: lifestyle

This hominid was bipedal and may have shown some male-male competition. Bipedal, with climbing, Fruits and tough foods such as nuts. Some degree of male male competition.

Australopithecus africanus: lifestyle

This hominid was bipedal, dentition indicate plant bsed diet, but speculated to have been "bloodthirsty killer". Bipedal, but also climbing. Plant based diet, with some seeds or nuts. Dart suggested they were killer apes, savage hunters?

Australopithecus afarensis: lifestyle

This hominin was bipedal, possibly living in male female pairs, ate mostly seeds, but also some tougher foods and possibly used tools in butchery. Bipedal, but also climbing? Plant based diet, with some seeds or nuts? Pair bonding? Tools?

Robust austrlopithecines: lifestyle

This hominin was bipedal, showed sexual dimorphism in body size, ate tough foods when other foods were scarce, and may have used bone tools.

paleoanthropology: current views

Timing of important transitions occurred at different time in our past.

Which hominin gave rise to the genus homo?

Was it A. Africanus or A. gar hi that gave rise to Homo? and now, there is a new candidate-A. sediba!

What are the relationships of the earliest hominids to each other and later hominins?

Were the earlier hominins directly ancestral to Australopithecus?

Australopithecus afarensis: skull

brain size: 433 cc Projecting face Overall, austrlopithecus afarensis skull looks like that of a small ape.

A. Anamensis fossil sites

look @ map

gracile australopithecines

look @fossil chart: 1) A. Anamenesis B) A. Afarensis 3) A. afrricanus D) garhi

human like characteristics

short fingers and long thumb, brain that is beginning to reorganize like a human. A sediba lived 2 million years ago, near the emergence of our genus, homo.

robust austrlopithecines: chewing muscles

temporals muscle: two muscles are responsible for closing the jaw during chewing: temporal is muscle, masseter muscle. In both robust austrlopithecines and humans, two muscles are responsible for closing the jaw during chewing: temporal is, muscle, masseter muscle.

ape like characteristics of Australopithecus sediba

tiny brain, long arms, chimp body size, narrow birth canal

comparing brain size among hominids (graph)

x axis = millions of years ago (mya decending from 3.5) y axis = cranial capacity In positive linear line goes 1) australopithecines 2) homo erectus 3) modern humans