recent genetic evidence on the neandertal/modern human relationship

Recent genetic evidence on the Neandertal/modern human relationship

The Neandertal Genome• Reported in journal: Science, May 2010• Modern human/Neandertal divergence c. 440,000 ybp.• Modern humans arrived in the Middle East c. 100,000 ybp

and there were Neandertals there until c. 60,000 ybp.• Last of the Neandertals in Europe c. 30,000 ybp.• Vindija Cave site, Croatia (close to Shanidar Cave)• Bone fragments from three different Neandertal females

provided nuclear DNA fragments for sequencing.• Bone dates: 38,000 ybp and 44,000 ybp.

• Challenges:• 97% of the DNA in the bones was fungal & bacterial.

– Had to be identified and removed.

• Many Neandertal DNA fragments were only 40-50 base pairs in length.– Had to be aligned

• > 4 billion nucleotides sequenced from fragmentary DNA – (c. 60% of the genome).

• Compared to the genomeS of five contemporary humans• South Africa (San), West Africa (Yoruba) , China (Han), New

Guinea (Papuan), and France (European).• Of these five individuals, non-Africans had 1-4% Neandertal

DNA markers.• None of the two Africans had Neandertal DNA.

• An enigma! Not only was Neandertal DNA in the European, it was in the individuals from China and New Guinea as well.

• Therefore, Chinese and Papuans are as closely related to Neandertals as Europeans.

• Neandertal fossils have never been found in either eastern Asia or New Guinea.

• Therefore, interbreeding must have taken place in the Middle-East region before modern humans expanded their range and diverged in other areas.

• None of the three Neandertals had genetic markers of modern humans.

• Gene flow was unidirectional: from Neandertals into modern humans.

• Follows a general pattern of colonization between closely related populations.

• Gene flow movement most often from the resident population into the colonizing population, not the reverse.

• Resident population: Neandertals• Colonizing population: anatomically modern humans

Sophistication of recent stone tool manufacture

Discovered in 1957Two amateur archeologistsOlsen-Chubbuck siteC. 140 mi. SE Denver

Wind erosion had exposedA bone bed in an ancientArroyo.

c. 1/3 excavated by Olsen and Chubbuck, then theyNotified C.U. archeologistsExcavation in 1958 and 1959.

Cross-section of the arroyoBuried by wind-borne deposits.

A bison trap.

Part of the excavated arroyo.

Arroyo was 170 feet longRemains of 193 bisonBison occidentalisnot Bison bisonBones in three layers:Bottom: complete skeletons of 13 individualsMiddle: bones of partially butchered individualsTop layer: individual bones and partially articulated bones in similar piles.Dated at 6,500 ybp

A few of theprojectile pointsassociated withthe bison bones.

Material culture

Scottsbluff points:Scottsbluff tradition

Eden points: Eden tradition

Milnesand points:Milnesand tradition

Dispelling the idea1. that stone toolswere easily manufactured.

2. that tool typesdefined differentgroups of people(typology)

Reconstruction of events

1. Time of year.2. Wind direction3. The stampede.

Social structure

75% of the bison were completely butchered.Based on numbers in various age classes, the number of butchered bison would have produced56,640 pounds of fresh meat4,000 pounds of edible internal organs5,400 pounds of fat.

100 people could have completed the butchering in half a day.

Enough meat, internal organs, and fat to feed a group of 150 for 23 days.