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BSC2011 Hominin evolution

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Hominin evolution
 Paleoanthropology is the study of
human origins and evolution, the brief
history since the divergence of human
and chimpanzee lineages.
Hominins (formerly called hominids)
are more closely related to humans
than to chimpanzees
Paleoanthropologists have discovered
fossils of about 20 species of extinct
hominin
Unlike chimpanzees, humans
• walk upright and
• have larger brains.
Human evolution
Human evolution is the
evolutionary process that led to
the emergence of anatomically
modern humans, beginning
with the evolutionary history of
primates – in particular genus
Homo – and leading to the
emergence of Homo sapiens as
a distinct species of the hominid
family, the great apes.
https://en.wikipedia.org https://en.wikipedia.org
Hominins originated in Africa about 6–7
million years ago
• Early hominins had a small brain but probably walked
upright
Two common misconceptions about early
hominins:
– Thinking of them as
chimpanzees
– Imagining human
evolution as a ladder
leading directly to
Homo sapiens
Humans are mammals that have a
large brain and bipedal locomotion
The species Homo sapiens is about 200,000
years old, which is very young, considering
that life has existed on Earth for at least 3.5
billion years.
Derived Characters of Humans
A number of characters distinguish humans from other apes:
 Upright posture and bipedal locomotion
 Larger brains
 Language capabilities and symbolic thought
 The manufacture and use of complex tools
 Shortened jaw
 Shorter digestive tract
Bipedalism arose millions of years before larger
brain size
Evidence of bipedalism includes
 3.6-million-year-old upright-walking hominin footprints
 fossil skeletons.
Evidence of bipedalism
Unlike chimpanzees, humans
– walk upright and
– have larger brains.
Skeletal implications of bipedalism
Location of foramen magnum
Tool Use
• The oldest
evidence of tool
use, cut marks
on animal
bones, is 2.5
million years old
• Tool use is
considered a
human trait
Rapid expansion of our species may have been
preceded by changes to the brain that made cognitive
innovations possible Art, a human hallmark
– For example, the FOXP2 gene is
essential for human language,
and underwent intense natural
selection during the last
200,000 years
– Homo sapiens were the first
group to show evidence of
symbolic and sophisticated
thought
Throughout evolution brains changed in:
 Size
 Complexity
 the ratio of brain
weight to overall
body weight
Human and Ape Brains
Humankind Emerging, 7th ed., p. 389
Hominid cranium comparison provides
evidence of evolution
Comparison of hominin skull structures
Larger brains mark the evolution of Homo
Cranial Capacity. Understanding Physical Anthropology
and Archaeology, 8th ed., p. 234
Australopiths had such small brains (400–450 cc) that they were too small to
be members of Homo.
Homo habilis (2.4–1.6 million years ago) had a brain size of 510–690 cc. Their
fossils are found with stone tools.
Homo ergaster (1.9–1.6 million years ago) had a brain size ranging from 750
to 850 cc.
Their fossils are found with more sophisticated stone tools and
- long, slender legs were adapted for long-distance walking.
Homo sapiens has a brain size of around 1,300 cc.
Comparison of hominin skull structures
Prognathism
“Muzzle” angles
(prognathism) of ape
and modern human
Sagittal crests and temporal muscle orientations.
Hominid compared to pongid.
(Line of greatest muscle force is shown in red.)
Sagittal
crest
Sagittal
crest
Understanding Physical Anthropology and Archaeology, 8th ed., p. 245
Comparison of hominin skull structures
Teeth / Dental Arcade
Teeth of a male patas
monkey.
Apes (and monkeys) still
possess conical, daggerlike canines which project
well beyond the surface
of the opposite teeth.
The gap is a diastema.
Monkey & Ape Canines
Understanding Physical Anthropology and Archaeology, 8th ed., p. 231
Homo sapiens
• Homo sapiens
appeared in
Africa by 195,000
A 160,000-yearyears ago
old fossil of
Homo sapiens
• All living humans
are descended
from these
African ancestors
• The oldest fossils of Homo sapiens outside Africa date back
about 115,000 years and are from the Middle East
• Humans first arrived in the New World sometime before
15,000 years ago
• In 2004, 18,000 year old fossils were found in Indonesia, and a
new small hominin was named: Homo floresiensis
Hominid cranium omparison provides
evidence of evolution
Modern
human
Common
ancestor
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