Human evolutionAditi Pai
"Hominid" refers to members of the human family, Hominidae, which consist of all species from the point where the human line splits from apes towards present day humans.
Habitual bipedal locomotion (movement on two legs), an upright position, and a large brain that has lead to: tool use, language, and culture characterize hominids.
Human evolution
A. History
B. Important stages in human evolution
C. Theories of human evolution
D. ‘Human Characteristics’
E. Are we still evolving?
History
• 1856-Neander Valley– Discovery of a skull that was not quite human
• 1859 – Darwin publishes ‘The Origin of Species’
• 1871- Darwin predicts that ancestors of humans would be found in Africa
• Up till 1930s– Humanity evolved
in Europe
• 1950s--1960s– Many significant
fossils discovered
ABC D
ABCD
Bush model
Linear model
• 1970s – present– more fossils – molecular
techniques– ‘tree model’ of
human evolution
Current Controversy
6-7 m y old fossil
Earliest bipedal hominid?
Sahelanthropus tchadensis
Important stages in human evolution
1. 3.2 million years ago2. 3 million years ago3. 2 million years ago4. 1 million years ago5. 200, 000 years ago6. 150, 000 years ago
"Hominid" refers to members of the human family, Hominidae, which consist of all species from the point where the human line splits from apes towards present day humans.
Habitual bipedal locomotion (movement on two legs), an upright position, and a large brain that has lead to: tool use, language, and culture characterize hominids.
3.2 mya: The southern ape of afar
• Fossil: – “Lucy” (discovered
1974, Ethiopia)– Australopithecus
afarensis
Male
Fossil of “Lucy”
Female
Australopithecus afarensis
• Habitat: savannah and woodland
• Food: leaves, fruit, seeds, nuts, termites and eggs, grasses (?)
• Physical characteristics: – low forehead, flat nose, no chin– small brain– long dangly arms, short legs– facultative bipedal (upright on ground but could
dangle from branches)– sexually dimorphic
Paranthropus boisei Homo habilis
3 mya: Paranthropus boisei
• Habitat: open terrain
• Food: nuts, roots and tubers
• Physical characteristics: – enormous jaw with chewing muscles, – large back teeth, small front teeth– specialized as vegetarians
• Not direct human ancestors
3 mya: Homo habilis-the ‘handy man’
• Habitat: open terrain• Food: Scavenged for meat• Physical characteristics:
– small jaw and teeth – shorter arms– increase in brain size (because of carnivorous
diet and mode of feeding)– capable of speech
Oldowan Tools
Made tools
Human migration
• 1.9 mya humans began to leave Africa to other continents
Homo ergaster
2 mya: Homo ergaster• Habitat: dry -hot habitat
• Food: scavenger for meat
• Physical characteristics: – Tall with long limbs– Smooth and dark skin
• Temperature regulation through sweating– Narrow pelvis (lead to narrow birth canal)
• Mothers needed support of partner and group to raise babies
Acheulean bifaces
Homo erectus
• brain, almost human size • stocky, human-like body (larger than Homo habilis) • Java, China, and Africa • use of fire • increased but infrequent group hunting • language • crude shelters and some migration to colder areas • used tools
Homo erectus
Homo heidelbergensis
1mya: Homo heidelbergensis
• Food: hunted for meat
• Physical characteristics: – Large brain – Tall
• Direct ancestors of Homo sapiens
Boxgrove tools
H.heidelbergensis made Hand axes, wooden spears etc.
200,000 ya: Homo neanderthalensis
male female
200,000 ya: Neanderthal man
• Habitat: cold • Food: hunted for meat• Physical characteristics:
– Large face with massive ridges– No chin– Short stocky body (conserve heat)– Muscular
• Language• Social relationships important
What happened to the Neanderthals?
• Extinct 28, 000 ya• Competition from Homo sapiens?
• 120, 000 ya • Physical characteristics:
– Eyebrow ridge small or absent– Prominent chin
• Tools --antler, bone, stone• Clothing, jewelry, artwork, musical
instruments
Homo sapiens
Theories of human evolution
• Humans evolved in sub-Saharan Africa and spread from there
or• Humans evolved independently in
several places around the globe
Out of Africa hypothesis
• Homo sapiens evolved in a single speciation event in Africa ~ 250, 000 ya
• Migrated to other regions, replaced Homo erectus
Multi-regional hypothesis
• Local populations of Homo erectus evolved into Homo sapiens
• Mixed genes
• Retained local characteristics
Support for multi-regional hypothesis
• No break in culture in S.E Asia
• Can explain the occurrence of regional characters
Races• Original skin color- black
• Divergence from original black color to many different colors
How different are the races?
• No genetic discontinuities between races
• Genetic differences between races only 10% of genetic diversity among humans
• No evidence for major biological differences
Support for ‘out of Africa’ hypothesis
1. Level of diversity in maternally inherited mitochondrial DNA of humans from around the world highest among Africans
2. Based on genetic diversity all non-Africans descended from a small band of humans that left Africa ~ 100, 000 ya
Support for ‘out of Africa’ hypothesis
3. The Y-chromosome too shows no sign of any non-African DNA
Support for ‘out of Africa’ hypothesis
• Australia --- ~60,000 ya• Europe --- ~70,000 ya• Near East --- ~90,000 ya• Africa --- ~130, 000 ya
Human migration
Who were the first Americans?
• 13,000 ya• Crossed Bering Strait
Human characteristics
• Bipedal gait • Big brain• Tool making• Social relationships• Art • Culture
Bipedalism• When?
– Before Australopithecines• Advantages:
– Freed hands to carry objects – See predators better in grasslands– Access to foods not previously available– Carry children– Protection from sun in grasslands
Evolution of bipedalism
1. Carrying objects2. See predators3. Aquatic environment (?)
Evolution of big brain• Meat eating from Homo habilis onwards
– Did not require large intestines– Energy freed up for other organs including
brainor
• Cooked tuber eating in Homo erectus– Hunter-gatherers rely less on meat than
tubers– Reliance on scavenged meat is difficult.
Tool making• Homo habilis onwards• Tool-making was considered a
‘human trait’– Discovery of tool-making in
chimpanzees– Tool making in Australopithecines?
Homo sapiens survived extinction in late Pleistocene– ‘bottlenecks’ (drastic reduction in
population size )– cultural explosion– Societies became co-operative (‘troop-to-
tribe transition’)
Social relationships, art, and culture
Are we still evolving?