The origin and dispersal of modern humans

Oct. 21, 2008

http://upload.wikimedia.org/wikipedia/commons/f/f8/Hominintree4.gif

Introduction

• ~200-150 Ka the first modern Homo sapiens evolved in Africa; most likely from some African Homo heidelbergensis population

• When did they first appear?• Where did the transition take place?• What was the pace of evolutionary change?• How did the dispersal of modern humans take

place?• Why so successful?

Approaches to understanding Modern Human Origins

• Complete replacement model

• Regional continuity, or multiregional evolution

• Partial Replacement

Complete Replacement Model

• Recent African Evolution

• Stringer & Andrews, 1988

• Anatomically modern humans arose in Africa within the last 200 Ka as a result of a biological speciation event.

• As such, interbreeding with archaic hominids was not possible

mtDNA and Y-chromosomal evidence on Modern Human Origins

• Neither is significantly altered during recombination or sexual reproduction

• African populations are the most genetically diverse• Powerful direct evidence of a genetic discontinuity

between Neanderthals and Modern Humans• Problem – Contamination, lost lineages and

population bottlenecks related to Pleistocene climatic fluctuations, volcano eruptions & differences in sex dispersal?

Partial Replacement (or Assimilation) Model

• Some interbreeding occurred between modern humans and archaic hominids

• No speciation event occur, all hominids (from the Middle Pleistocene onwards) should be considered members of Homo sapiens

• Although, African populations probably have made the most contributions to modern populations; ‘mostly out of Africa’

The Regional Continuity Model (or Multiregional Evolution)

• M. Wolpoff & A. Thorne• Local populations in Europe, Asia and Africa

continued their evolutionary development from premodern Middle Pleistocene forms to anatomically modern humans

• Assumptions – H. sapiens did not exclusively originate in Africa; Gene flow between regional populations; single, though polytypic species

Seeing the big picture

• Disagreements are overstated and overdramatized

• High congruence between genetics and fossil evidence

• “strong” multiregional model highly unlikely

• Interbreeding between hominid species most likely was possible, but didn’t happen very often

The Earliest discoveries of Modern humans

• Africa: Omo-Kibish (195 Ka), Herto (154-160 Ka), Border (60-80 Ka?), Blombos (73-140 Ka) and Klasies River Mouth (120 Ka) Caves

• The Near East: Skhul (100-130 Ka) and Qafzeh (92-120 Ka), Israel

The Earliest discoveries of Modern humans

• Central Europe: Mladec, Czech Republic (31 Ka) and Oase Cave (35 Ka), Romania

• Western Europe: Cro-Magnon, France (30 Ka) and the Aurignacian (Upper Paleolithic stone tool industry).

• Asia: Zhoukoudian Upper Cave (27 Ka) and Tianyuan (40 Ka), China

• Niah Cave (35-45 Ka), Borneo• Australia: Lake Mungo (25-60 Ka), Kow Swamp (9-

14 Ka)

Something new and different

• By 25 Ka modern humans occupy most major areas of the Old World and begin entering the New World ~15 Ka

• Remnant hominids in East Asia?: Homo erectus (>30-50 Ka) and Homo floresiensis (~18 Ka; 95-74 Ka to >12)

Homo floresiensis

• The island of Flores, Indonesia• ~18 Ka

Technology & Art in the Upper Paleolithic

• European Stone tool industries:

• Magdalenian, 17 Ka• Solutrean, 21 Ka• Gravettian, 27 Ka• Aurignacian and

Chatelperronian, 35-40 Ka• Africa – beads made from

ostrich egg shells ~38-50 Ka. Pinnacle point at 165 Ka with ocher, blades and exploitation of shellfish. Bone tools at Katanda, DRC, 80 Ka.

Summary of Upper Paleolithic Culture• Stone tool industries of Europe -• Magdalenian, 17 Ka; atlatal and bow

& arrow, cave art• Solutrean, 21 Ka; artistic parallel

flaked lance heads• Gravettian, 27 Ka; Portugal child

burial with ochre• Aurignacian (associated with the first

modern humans in Europe) and Chatelperronian (associated with some of the last Neanderthals), 35-40 Ka

• Burials and grave goods• Venus figurines• Engravings• Climatic Fluctuations

Abrigo do Lagar Velho, Portugal (Gravettian 24.5 Ka)

Images of early Modern humans

Cro-Magnon

Skhul

Characteristics of Modern Humans:

-Vertical forehead

- Canine fossa

- Relatively small brow ridges and face

- Pyramidal mastoid process

- Definite chin

Klasies River Mouth

Qafzeh