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 organisms- their 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

3-year-old Australopithecus afarensis Knees of a Biped, Shoulders of a climber II. Why Study Human Evolution? Dinkenesh,” meaning “You are beautiful” or "you are wonderful"

Larger brains, no tail, more erect, hips/ankles more flexible, changes in structure of arms/ shoulder Elongated skull, brow ridge enlarged shorter and stouter canines, front of upper jaw, fusion of certain bones in wrist, larger ovaries, mammaries, reduced hairiness Phylogeny based on anatomy III. Phylogenetic Evidence

Molecular markers Antibody response Mitochondrial cytochrome oxidase II alleles

Timing divergence from the molecular clock and fossils

Human chromosome 2 and its homologues in chimpanzees & gorillas IV. Genetic and other differences

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 Knucklewalker (our ancestors, since divergence with chimps) Broad fruit based diet Lived in a range of habitats Tools Hunted Dominated by Males/Females Violent aggression/war? Homosexuality, recreational sex? Differ between Chimps and Bonobos

V. Fossil Evidence Hominin or hominid: species more closely related to human than chimp

Human and Chimp Lucy

"The Laetoli Footprints" Note position of big toe And heel strike See also: Natl Geographic Soc.

Summary of fossil evidence on the recent ancestry of humans

Very hypothetical Phylogeny of Homo sapiens and recent ancestors and extinct relatives 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. = H. erectus

VI. Origin of Species Homo sapiens Oldest fossils of ergaster/erectus appear simultaneously in Africa,Europe and Asia about mya, all ancestors > 2mya from Africa

Genetic (mtDNA) diversity in humans versus African great apes Genetic Evidence: 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 < 300,000 ya 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

Making complex tools VII. Human Attributes

Thumb metacarpal bones in a variety of hominins

Hyoid bones from Homo neanderthalensis and a common chimpanzee Language? Brain Body Mass bonobo, common chimpanzee, orangutan, and gorilla A.afarensis, A. africanus, P. boisei, and P. robustus; H. habilis, H. ergaster/erectus, and H. sapiens Chimp Neandertal

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