Human
Evolution
I. Darwin
• "light will be thrown on the origin of man and his history".
from On the Origins of Species, 1859
• … the weighty arguments derived from the nature of the
affinities which connect together whole groups of organismstheir geographical distribution in past and present times, and
their geological succession. The homological structure,
embryological development, and rudimentary organs of a
species remain to be considered, whether it be man or any
other animal, to which our attention may be directed; but
these great classes of facts afford, as it appears to me,
ample and conclusive evidence in favour of the principle of
gradual evolution. The strong support derived from the other
arguments should, however, always be kept before the mind.
from The Descent of Man, 1871
II. Why Study Human Evolution?
3-year-old Australopithecus afarensis
Knees of a Biped,
Shoulders of a
climber
Dinkenesh,” meaning “You are beautiful” or "you are wonderful"
III. Phylogenetic Evidence
Phylogeny based on
anatomy
Elongated skull,
brow ridge enlarged
shorter and stouter
canines, front of upper
jaw, fusion of certain
bones in wrist, larger
ovaries, mammaries,
reduced hairiness
Larger brains, no tail,
more erect, hips/ankles
more flexible, changes
in structure of arms/
shoulder
Molecular markers
Antibody response
Mitochondrial
cytochrome
oxidase II alleles
Timing divergence from the molecular clock and fossils
IV. Genetic and other differences
Human chromosome 2 and its homologues
in chimpanzees & gorillas
Other data: 1.4% nucleotide subst., 3.4% in/del = 5%
What makes a human?
Differences in gene expression patterns in different tissues
of humans, chimps, and rhesus macaques
Enard et al., Science, 2002
Stellar’s Jay
Blue Jay
Behavioral traits we inherited from
Chimp-Human Common Ancestor
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Knucklewalker (our ancestors, since divergence with chimps)
Broad fruit based diet
Lived in a range of habitats
Tools
Hunted
Differ between
Dominated by Males/Females
Chimps and
Violent aggression/war?
Bonobos
Homosexuality, recreational sex?
V. Fossil Evidence
Hominin or hominid:
species more closely related to human than chimp
Lucy
Human and Chimp
"The Laetoli Footprints"
Note position of big toe
And heel strike
Natl Geographic Soc.
See also:
http://www.pbs.org/wgbh/evolution/library/07/1/l_071_03.html
Summary of fossil evidence on the
recent ancestry of humans
Phylogeny of Homo sapiens and recent ancestors and extinct
relatives
= H. erectus
Very hypothetical
Evidence for hominid radiation
Paranthropus boisei, left and Homo ergaster both lived in what is now
Koobi Fora, Kenya, about 1.7 million years ago.
VI. Origin of Species Homo sapiens
Oldest fossils of ergaster/erectus appear simultaneously
in Africa,Europe and Asia about 1.6-1.9 mya, all
ancestors > 2mya from Africa
Genetic Evidence:
Genetic (mtDNA) diversity in humans versus African great apes
Single origin?
All pairwise differences between individuals within a species
Evidence of geographic structure in living human populations
Multiorigin?
Phylogeny of Neandertals & modern humans (mtDNA)
Single origin?
An evolutionary tree
of complete
mitochondrial DNAs
of 53 humans
Single origin?
Phylogenetic tree for 14 human populations based on allele
frequencies at 30 microsatellite loci
Single origin < 300,000 ya
Genetic diversity at a single locus among people of 7 geographic regions
Single origin < 300,000 ya
VII. Human Attributes
Making complex tools
Thumb metacarpal bones in a variety of hominins
Language?
Neandertal
Chimp
Hyoid bones from
Homo neanderthalensis
and a common chimpanzee
H. habilis,
H. ergaster/erectus, and
H. sapiens
A. afarensis, A. africanus,
P. boisei, and P. robustus;
bonobo, common chimpanzee,
orangutan, and gorilla
Brain Body Mass
VIII. Summary
1. Relationships among Humans and Extant Apes
2. Divergence time about 5 mya
3. Hominid radiation
4. African Replacement or independent evolution of
H. sapiens in Africa, Europe and Asia?
5. Evolution of uniquely human traits