neandertal mtdna evidence: reported 1997

Neandertal mtDNA evidence: reported 1997

• Dr. Svante Pääbo (Max Planck Institute for Evolutionary Anthropology).

• mtDNA sequence from type specimen of “neanderthalensis”

• 379 base sequence compared to 994 human lineages

• 1) mtDNA difference among human lineages: mean of 8 base substitutions

• 2) Mean differences (base-pair substitutions) between Neandertal sequence and– European lineages: 28.2

– African lineages: 27.1

– Asian lineages: 27.7

– North American lineages: 27.4

– Australian/Oceanic lineages: 28.3

• Conclusion?

mtDNA research (2008)

• 1) Max Planck Institute for Evolutionary Anthropology +

• 2) 454 Life Sciences Corporation

• 38,000 ybp Croatian Neandertal

• New techniques (< 0.5 g of bone used)

• Sequenced > 1 billion mtDNA fragments

• Sequences of 3 billion bases obtained

• Complete mtDNA has been sequenced (16,000 bp)

• Compared to 53 living humans

– Modern human and modern humans (2-188 differences)

– Modern humans and Neandertals (201-234 differences)

• Neandertal mtDNA is not found in modern humans

• Evidence for validity of Homo neanderthalensis?

• Estimate of divergence date between the two mtDNA lineages:

• 660,000 ± 140,000 ybp

Anatomically modern humans

Anatomically modern humans

Intermediacy between H. heidelbergensis and H. sapiensHerto, Ethiopia, Africa160,000-154,000 ybp (argon-argon dating)

Multiregionalmodel

Out-of-Africa or African Replacement model

Predictions from each model

1. the extinct archaic and extant modern humans in each region will be each other’s closest relatives

Lieberman (1995)

Predictions from each model

1. all groups of modern humans will bemore closely related to eachother than to any archaic species.2. among archaic species, those from Africa will be the most closely relatedto modern humans

53 individualscomplete sequence of mtDNA

Common ancestor of all modernmtDNAs lived in Africa

A

B

A. Most recent commonancestor of all modern mtDNA

B. Most recent common ancestor of Africans andnon-Africans

Consistent with AfricanReplacement Model

Comparison of genetic variation (mtDNA)

Chimpanzee subspecies are more genetically variable than any two human populations

Orange: within groupBlue: between groups

Variation in one gene in chromosome 12 among people of 7 geographic regions

12 different alleles

• Each plot shows the frequencies of the various alleles for people of a particular region.

• Vertical arrangement by travel distance between areas.

• If non-African populations were founded by small bands of people migrating out of Africa, then non-African populations should have reduced genetic diversity.

– 1. African populations show much greater allelic diversity than non-African populations

– 2. Progressive reduction in allelic diversity with distance from Africa.

– 3. Consistent with African replacement model.

Paleontological evidence

Milford WolpoffPhillip Rightmire

Richard Klein

Competing hypotheses