Human Evolution VSI

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Out of Africa or multiregional?
Author

Stephen J. Mildenhall

Published

2024-04-12

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homoplasy

a phenomenon in evolution where traits are similar due to convergent evolution or parallel evolution, not because of a common ancestry. It occurs when different species develop similar traits independently, often as a result of facing similar environmental challenges and evolutionary pressures, rather than inheriting the traits from a common ancestor.

pleiotropy

a situation in genetics where a single gene influences two or more seemingly unrelated phenotypic traits. This means that one gene can affect multiple characteristics or functions in an organism.

Here’s a GPT-generated summary of the main theories of human evolution, followed by a table depicting the “tree of life” focusing on the lineage descending from great apes, including conjectured hominins.

Main Theories of Human Evolution

  1. Out of Africa Theory: This is the most widely accepted theory, proposing that Homo sapiens evolved in Africa and then dispersed to other continents. The theory suggests a single, African origin for all modern humans.

  2. Multiregional Theory: This theory suggests that early humans evolved in several places around the world simultaneously. According to this theory, different populations of Homo erectus evolved into Homo sapiens independently while maintaining gene flow between populations.

  3. Assimilation (or Hybridization and Replacement) Theory: This is a blend of the first two theories. It suggests that modern humans originated in Africa but interbred with local populations of Homo erectus as they spread throughout the world, leading to the species we see today.

Tree of Life: Descent from Great Apes

Ancestor Descendants Details
Great Apes (Hominidae) Homininae This family includes humans, chimpanzees, gorillas, and orangutans.
Homininae Homo (Humans) and Pan (Chimpanzees) The split from the common ancestor occurred around 5-7 million years ago.
Homo H. habilis, H. erectus, H. neanderthalensis, H. sapiens Homo habilis is considered one of the earliest members of the genus Homo. H. erectus was very successful and spread across continents. Neanderthals and modern humans diverged from a common ancestor about 600,000 years ago.
H. sapiens Modern Humans Anatomically modern humans, Homo sapiens sapiens, emerged around 300,000 years ago in Africa.

Conjectured Hominins

  • Ardipithecus: Dated to about 4.4 million years ago, this genus is one of the earliest known hominins, showing a mix of ape-like and human-like characteristics.

  • Australopithecus: Includes several species like A. afarensis (famous for the Lucy skeleton) and A. africanus, showing a mix of bipedal locomotion and tree-climbing abilities.

  • Homo habilis: Known as “handy man,” this species is thought to be one of the first to use stone tools.

  • Homo erectus: One of the longest-living hominin species, known for its adaptability and migration out of Africa.

  • Homo neanderthalensis (Neanderthals): Close relatives of modern humans, they lived in Europe and Asia before going extinct around 40,000 years ago.

  • Denisovans: A relatively recently discovered group, known only from a few fossils, but genetic evidence suggests they once ranged widely across Asia.

These conjectured hominins showcase the complexity and diversity of human evolution, indicating not a linear progression but a tree with many branches, some of which have gone extinct while others have flourished.

Deets

  • Bernard Wood
  • Volume 142
  • Published 2019