Antiquity of HumanityAntiquity of Humanity

Later Human Evolution:Later Human Evolution:

Homo habilisHomo habilis

Evolution of HumansEvolution of Humans

H omo sapiens sapiens

Archaic H omo sapiens H omo sapiens neanderta lensis

H omo erectus

H omo habilis

Homo habilisHomo habilis (ca. 2.5-1.6 mya) (ca. 2.5-1.6 mya)

Homo habilisHomo habilis was first discovered in 1959 in the was first discovered in 1959 in the Olduvai Gorge in Tanzania. Olduvai Gorge in Tanzania. A nearly complete skull of A nearly complete skull of H. habilisH. habilis was discovered in was discovered in 1972 at Koobi Fora on the shores of Lake Turkana in 1972 at Koobi Fora on the shores of Lake Turkana in Kenya. Its age is estimated at 1.8 million years and its Kenya. Its age is estimated at 1.8 million years and its brain capacity at 800 cc. brain capacity at 800 cc. Other Other H. habilisH. habilis remains have since been discovered at remains have since been discovered at Olduvai Gorge. There is considerable variation among Olduvai Gorge. There is considerable variation among the specimens from this era found thus far. the specimens from this era found thus far. Some anthropologists argue that the variations appear to Some anthropologists argue that the variations appear to indicate that several separate species of humans existed indicate that several separate species of humans existed and competed at the same time in east Africa; other and competed at the same time in east Africa; other scientists lump all the individuals together in a single scientists lump all the individuals together in a single species. species.

H. habilisH. habilis finds finds

Homo habilisHomo habilis

Homo habilisHomo habilis is the earliest known is the earliest known species of the genus species of the genus HomoHomo; that is, the ; that is, the first human species. first human species. – It existed from approximately 2.5 to 1.6 million It existed from approximately 2.5 to 1.6 million

years ago in east Africa.years ago in east Africa.– Only a few fossil remains have been Only a few fossil remains have been

discovered so far, but these specimens discovered so far, but these specimens exhibit a clear trend toward larger brain size. exhibit a clear trend toward larger brain size.

– H. habilisH. habilis brains are about 30% larger than brains are about 30% larger than those of those of A. africanusA. africanus..

Homo habilisHomo habilis

Brain size much bigger than Aus. (500-800)Brain size much bigger than Aus. (500-800)

Teeth smaller, thinner enamel, more parabolic Teeth smaller, thinner enamel, more parabolic dental arcade.dental arcade.

Skulls rounder, less prognathic, jaw muscles Skulls rounder, less prognathic, jaw muscles reduced.reduced.

East and South Africa, same time as robusts.East and South Africa, same time as robusts.

Handyman, associated with Pebble choppers Handyman, associated with Pebble choppers (more later).(more later).

This reconstructed This reconstructed skull was found in skull was found in 1972 on the shores of 1972 on the shores of Lake Turkana.Lake Turkana.

Represents the oldest Represents the oldest individual human yet individual human yet discovered.discovered.

Homo habilisHomo habilisAge:ca. 1.8 million yearsAge:ca. 1.8 million yearsDate of Discovery:October 1968Date of Discovery:October 1968Location:Olduvai Gorge, TanzaniaLocation:Olduvai Gorge, Tanzania

Sexual DimorphismSexual Dimorphism

Males were much larger Males were much larger than females, as shown than females, as shown by the two skulls at far by the two skulls at far right. right.

The male is pictured on The male is pictured on the left. the left.

Sexual dimorphism in Sexual dimorphism in habilis is expressed in habilis is expressed in significant size significant size differences.differences.

First Stone Tools:First Stone Tools:Oldowan Pebble ChoppersOldowan Pebble Choppers

Tool TechnologyTool Technology

Oldowan Pebble ChoppersOldowan Pebble Choppers

rounded pebblesrounded pebbles

portions broken to form sharp edgeportions broken to form sharp edge

flakes used for butcheringflakes used for butchering

These crude hand axes and stone flakes could have been manufactured as needed or as opportunity arose. The fracture lines of stones create a sharp cutting surface capable of butchering fairly large animals. The photo above right shows a modern anthropologist skinning a calf with a stone tool made just as ancient Homo habilis would have done.

EnvironmentEnvironment

The background of the The background of the photo shows the kind of photo shows the kind of environment in which this environment in which this earliest-known human earliest-known human species lived--open bush species lived--open bush and savannah country in and savannah country in east Africa. east Africa. This must must have This must must have been a very challenging been a very challenging environment, filled with environment, filled with large predators. large predators.

?

BehaviorBehavior

Meat eatingMeat eating

Home base, food sharing, sexual division Home base, food sharing, sexual division of labor.of labor.

Archaeological evidenceArchaeological evidence– Animal bones and stone tools at sites Animal bones and stone tools at sites

(Olduvai)(Olduvai)– Hunting or Scavenging?Hunting or Scavenging?

"Hunting Hypothesis""Hunting Hypothesis"

One widely held view of human development has held One widely held view of human development has held that hunting as an activity was the chief driver of that hunting as an activity was the chief driver of evolutionary change in early humans, as it would have evolutionary change in early humans, as it would have selected for for certain kinds of intelligence, coordination, selected for for certain kinds of intelligence, coordination, and aggressive behavior and aggressive behavior Was Was Homo habilisHomo habilis a hunter of large game and a a hunter of large game and a successful competitor with the great predators of Africa--successful competitor with the great predators of Africa--lions, leopards, hyenas? Or was this species an lions, leopards, hyenas? Or was this species an opportunistic taker of small game and a scavenger?opportunistic taker of small game and a scavenger?Present evidence cannot answer the question, but a Present evidence cannot answer the question, but a scavenging role seems more likely.scavenging role seems more likely.

The The Homo habilisHomo habilis Debate Debate

It was once thought that the evolution of the It was once thought that the evolution of the genus genus HomoHomo was an example of was an example of anagenesisanagenesis, the , the continual and gradual change of one parent continual and gradual change of one parent species into its daughter species in a linear species into its daughter species in a linear fashion. fashion. As the fossil record began to expand and more As the fossil record began to expand and more early human fossils were found dating to the early human fossils were found dating to the period between 2 million and 1 million years ago, period between 2 million and 1 million years ago, some questions as to the validity of this some questions as to the validity of this hypothesis were raised. hypothesis were raised.

Below are two fossils, shown to scale. KNM ER Below are two fossils, shown to scale. KNM ER 1813 is to the left, and KNM ER 1470 is to the right. 1813 is to the left, and KNM ER 1470 is to the right. Originally, both were assigned to the species Originally, both were assigned to the species Homo Homo habilishabilis, with ER 1470 thought of as male and the , with ER 1470 thought of as male and the smaller ER 1813 a female in a strongly dimorphic smaller ER 1813 a female in a strongly dimorphic species. However, the anatomies of the two skulls species. However, the anatomies of the two skulls

differ considerably.differ considerably.

DifferencesDifferences

Note that there is a strong supraorbital torus Note that there is a strong supraorbital torus (horizontal bar of bone above the eye sockets) (horizontal bar of bone above the eye sockets) on 1813, whereas the supraorbital torus of 1470 on 1813, whereas the supraorbital torus of 1470 is slight at best, and does not have the is slight at best, and does not have the depression behind it that is seen in 1813. depression behind it that is seen in 1813. The face of 1470 is longer than 1813's and The face of 1470 is longer than 1813's and 1470's upper jaw is square instead of rounded-1470's upper jaw is square instead of rounded-off. off. There is a great discrepancy between the cranial There is a great discrepancy between the cranial capacities of the two individuals as well. capacities of the two individuals as well. – ER 1470 has a cranial capacity of 775cc, where ER ER 1470 has a cranial capacity of 775cc, where ER

1813 has a cranial capacity of only 510cc (which is 1813 has a cranial capacity of only 510cc (which is above the australopith average, but well below the above the australopith average, but well below the accepted 600cc cutoff for accepted 600cc cutoff for HomoHomo))

DebateDebate

One debate in paleoanthropology today is whether or not One debate in paleoanthropology today is whether or not ER 1470, and several other fossils previously identified as ER 1470, and several other fossils previously identified as H. habilis,H. habilis, should be grouped into a new species, should be grouped into a new species, Homo Homo rudolfensisrudolfensis. . This classification would acknowledge that ER 1470 and This classification would acknowledge that ER 1470 and the other members of the other members of Homo rudolfensisHomo rudolfensis differ more from differ more from Homo habilisHomo habilis, , sensu strictosensu stricto ("in the strict sense," meaning: ("in the strict sense," meaning: as originally defined), than could possibly be accounted for as originally defined), than could possibly be accounted for by variation within a population or between sexes. by variation within a population or between sexes. This would place two species of the genus This would place two species of the genus HomoHomo in Africa in Africa during the same time period in addition to two members of during the same time period in addition to two members of the genus the genus ParanthropusParanthropus, and, possibly, late surviving , and, possibly, late surviving members of the species members of the species Australopithecus africanusAustralopithecus africanus. . Far more complicated than the original neat, linear model. Far more complicated than the original neat, linear model.

Homo rudolphensis (KNM-ER 1813) Homo habilis (KNM-ER 1470)

DifferencesDifferencesHomo habilis Homo habilis HeightHeight1.0 metres1.0 metresPhysique Physique Relatively long armsRelatively long armsCranial Volume Cranial Volume 500 – 650500 – 650Known DateKnown Date2.0 – 1.6 million 2.0 – 1.6 million years ago years ago Distribution Distribution Eastern & S? Africa Eastern & S? Africa Skull form Skull form Relatively small face; Relatively small face; nose developednose developedJaws/Teeth Jaws/Teeth Thinner jaw; Thinner jaw; smaller, narrow molarssmaller, narrow molars

Homo rudolfensisHomo rudolfensisCa. 1.5 metres Ca. 1.5 metres RobustRobustcc600 – 800 cc cc600 – 800 cc 2.4 – 1.6 million years 2.4 – 1.6 million years ago ago Eastern Africa Eastern Africa Larger, flatter faceLarger, flatter faceRobust jaw; large Robust jaw; large narrow molarsnarrow molars