26 - Ancient DNA & Archaic Introgression

African genetic diversity

African populations have the most and oldest genetic variation

Out of Africa genetic pattern

All non African diversity is a subset of African diversity

Genetic diversity and distance

Genetic variation decreases the farther populations migrated from Africa

Ancient DNA definition

Genetic material recovered from degraded ancient remains

Modern vs ancient DNA

Modern DNA is intact while ancient DNA is fragmented contaminated and low quantity

Ancient DNA sources

Found in bone teeth plaque coprolites sediments ice and preserved tissues

Ancient DNA preservation

Best preserved in cold dry cave or permafrost environments

Ancient DNA challenges

Degradation damage contamination and tiny target DNA amounts

Clean room labs

PPE and sterile labs prevent contamination during ancient DNA extraction

First Neanderthal DNA

Recovered in 1997 from Feldhofer Cave mtDNA

Neanderthal genome

First full genome sequenced in 2010 from Vindija Cave

Neanderthal diversity

Neanderthals had low genetic diversity suggesting small populations

Neanderthal social structure

Eastern Neanderthals show signs of patrilocality

Denisovan discovery

Found in Denisova Cave in Siberia based solely on ancient DNA

Denisovan Neanderthal relation

Denisovans are a sister group sharing a common ancestor about 250 thousand years ago

Denisovan range

Occupied Siberia Tibet Central Asia and Southeast Asia

Paleoproteomics definition

Study of ancient proteins allowing identification when DNA is too degraded

Xiahe mandible significance

160 thousand year old Tibetan mandible identified as Denisovan through proteins

Harbin cranium result

Paleoproteomics and DNA show the Dragon Man skull is Denisovan

Archaic introgression

Interbreeding between modern humans Neanderthals and Denisovans

Neanderthal Denisovan hybrid

A first generation hybrid discovered in 2018

Archaic population size

Neanderthals and Denisovans had small inbred populations

Modern human introgression

Most humans today have about zero point five to five percent archaic ancestry

African archaic ancestry

Africans also carry some Neanderthal DNA through back migration

Adaptive introgression definition

Archaic genes that improved survival in modern humans

EPAS1 adaptation

Tibetans inherited high altitude adaptation from Denisovans

Introgression and health

Archaic alleles influence immunity metabolism and disease risk

COVID 19 example

A Neanderthal derived haplotype is associated with higher severe COVID risk in some Eurasians

Species concept challenge

Archaic interbreeding blurs boundaries of what defines a species