ARTICLE ON Homo Sapiens Dispersal: Out of Africa Theory

• The understanding of how Homo sapiens dispersed globally has changed over time.
• Modern humans inhabit every continent except Antarctica. This wasn't always the case.
• H. sapiens emerged in Africa >300,000 years ago, eventually trekking and voyaging across the world.

Out of Africa Theory

• Accepted theories about human evolution today are the "Out of Africa" theories.
• The "Out of Africa" theories propose that H. sapiens evolved in Africa, spreading to other continents.
• As they spread, H. sapiens displaced or mated with other members of the Homo genus (hominins).
• The "multiregional" hypothesis (or "candelabra" hypothesis) once suggested H. sapiens also evolved in places other than Africa, like Europe and Asia.
• The "multiregional" hypothesis is now rejected.
• Evidence points to the origin and movement of Homo sapiens out of Africa.
• Recent studies indicate H. sapiens evolved from earlier hominins in Africa ~300,000 years ago.
• H. sapiens first dispersed from Africa ~200,000 years ago (100,000 years after evolving).

Into Asia

• H. sapiens first spread from Africa into the eastern Mediterranean region, likely through the Sinai.
• The Sinai region (between Egypt, Jordan, and Israel) is now a desert, but was greener when humans first traveled there.
• Another hypothesis supposed early modern humans migrated from Africa via a land bridge at the southern end of the Red Sea, across the Bab el Mandeb, into the Arabian Peninsula.
• A 2006 study established there had been no such land bridge.
• The Bab el Mandeb was always only a few miles wide, so people may have floated or paddled across.
• H. sapiens quickly spread east into Asia from the eastern Mediterranean.
• Multiple waves of early humans may have settled along Asian coastlines >100,000 years ago, then moving inland.
• Between 54,000 and 44,000 years ago, some H. sapiens bred with Denisovans (another early human species).
• Gene variants from Denisovans appear in the genomes of many Asians today.

Into Europe

• The earliest evidence of H. sapiens in Europe is from Apidima Cave in southern Greece, dating to ~210,000 years ago.
• That dating may be from a very early wave of migrating H. sapiens who later died off or retreated during a glaciation.
• Our species arrived in Europe permanently between 50,000 and 60,000 years ago.
• During this time, they bred with and replaced the existing population of Neanderthals.

Into Oceania

• Mitochondrial DNA dating indicates H. sapiens arrived in Southeast Asia ~60,000 years ago.
• From there, they spread into the prehistoric Sunda and Sahul regions (which later became Southeast Asia and Australia and were mostly dry land then).
• Archaeological evidence suggests modern humans were in the New Guinea region up to 50,000 years ago.
• From there, they spread throughout the Pacific Islands in migration waves:
  • Lapita expansion (~3,000 years ago)
  • Polynesian expansion (~1,500 years ago)

Into North America

• The leading theory once stated Paleo-Indian people arrived ~13,000 years ago from Siberia via Beringia (a land bridge to Alaska).
• Evidence of pre-Clovis settlements and human footprints from New Mexico suggest the first North Americans arrived by that route (and along the Pacific coast) ≥23,000 years ago.

Into South America

• Archaeological and genetic evidence indicates early modern humans spread from North America through Central America to South America.
• Fossils/artifacts suggest they arrived in South America ~15,000 years ago.
• The site of Monte Verde II in southern Chile dates to ~14,550 years ago.
• The date of the first human arrival in South America is still debated.

Into Antarctica

• The first person in Antarctica may have been John Davis (American sealer and explorer), reportedly in 1821, though his claim is disputed.
• It might have been Henrik Bull (Norwegian businessman) or Carsten Borchgrevink (Norwegian explorer), both claiming arrival in 1895.
• There is a suggestion that early Māori sailed to Antarctica from New Zealand as early as the 7th century, which is not widely accepted.