THE “OUT OF AFRICA” THEORY
Vicky Lee
CHARLES DARWIN’S PREDICTION

The Descent of Man
“In each great region of the world the living
mammals are closely related to the extinct species
of the same region. It is therefore probable that
Africa was formerly inhabited by extinct apes
closely allied to the gorilla and chimpanzee; and
as these two species are now man's nearest allies,
it is somewhat more probable that our early
progenitors lived on the African continent than
elsewhere.”
BACKGROUND INFORMATION
Early species of Homo, Homo habilis, evolved in
Africa around 2 million years ago
 Later, Homo erectus evolved along with other
hominids and migrated out of Africa
 Homo erectus evolved to Homo sapiens around
100,000 to 200,000 years ago

WHAT IS THE THEORY?
A distinct group of sub-Saharan Homo sapiens
inhabited Africa for about 150,000 years
before migrating throughout other continents
 Homo sapiens completely replaced all earlier
human populations (Neanderthals and Homo
erectus)
 No interbreeding occurred

“OUT OF AFRICA”
FOUNDATION OF THE THEORY

Emerged in 1987 based on a study of
mitochondrial DNA (mtDNA)
 Rebecca

Cann
Genetic studies & fossil record
 Andrea
Manica
 Marcus Feldman
GENETIC STUDIES
Cann
 mtDNA is key
 Inherited
through mother, does not recombine, and
shows variation within gene pool from mutations
only

Restriction mapping
 Analyzed
mtDNA from 147 people living among five
different geographic populations
 All populations except African have multiple origins
implying each area was colonized repeatedly
GENETIC STUDIES
Cann
 Molecular clock
 Assumes
mtDNA sequence divergence
accumulates at a constant rate
 Timescale calculates age of hypothetical common
ancestor “Mitochondrial Eve” to be about 140,000225,000 years old

Evolutionary tree
 Diagram
of 133 types of mtDNA
 Inferred that Africa had the most diverse mtDNA
gene pool
EVOLUTIONARY TREE
GENETIC STUDIES
Manica
 Found that Africans have the highest genetic
variation
 The further humans migrated from Africa, the
more genetic diversity was lost within those
populations
GENETIC STUDIES
Feldman
 Studied genetic ancestry without identifying
where the population came from
 Interpreted that mixed ancestries caused by
 recent
intermixing
 shared common ancestry before the divergence of
two populations but without any additional gene
flow between them
GENETIC STUDIES
Feldman
 Found same conclusion as Manica study, less
variation the further humans go from Africa
 No single genetic marker can identify a
person’s race
 patterns
of thousands of genetic markers within the
group distinguishes one population from another
FOSSIL RECORD
Manica
 Analysis of skulls from populations on different
continents
 The further away from Africa the skulls came
from, the less variation found in physical
features compared with African skulls
Population bottleneck
 As more and more groups migrated further,
smaller parts of genetic variation were taken
THE RIVAL THEORY
Multiculturalism
 Created by anthropologist Franz Weidenreich
 Does not believe that there were two migrations
 Homo erectus migrated out of Africa and then
evolved into Homo sapiens in several
populations
 Interbreeding did occur
MULTIREGIONALISM
SUMMARY OF “OUT OF AFRICA” THEORY
Homo sapiens completely replaced all earlier
human populations (Neanderthals and Homo
erectus)
 No interbreeding occurred
 The further humans migrated from Africa, the
more genetic diversity was lost within those
populations
 Age of hypothetical common ancestor
“Mitochondrial Eve” is 140,000-225,000 years

REFERENCES
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Cann, Rebecca L., Mark Stoneking, and Allan C. Wilson. "Mitochondrial DNA and human
evolution." Nature 1 Jan. 1987: 31-36.
Connor, Steve. "How old is humanity, and where did 'Homo sapiens' come from?; The big
question." The Independent (London) 19 Jan. 2007: 1A.
Darwin, Charles. The Descent of Man. < http://www.literature.org/authors/darwin-charles/thedescent-of-man/chapter-06.html>.
Feldman, Marcus et al. "Worldwide Human Relationships Inferred from Genome-Wide Patterns
of Variation." Science 16 Nov. 2008.
Hua Liu, et al. A Geographically Explicit Genetic Model of Worldwide Human-Settlement History. The
American Journal of Human Genetics, volume 79 (2006), pages 230–237
Johanson, Donald. "Origins of Modern Humans: Multiregional or Out of Africa?" Action
Bioscience. May 2001. American Institute of Biological Science. 4 Nov. 2008
<http://www.actionbioscience.org/evolution/johanson.html>.
Pennisi, Elizabeth. "HUMAN EVOLUTION: Genetic Study Shakes Up Out of Africa Theory."
Science 19 Mar. 1999: 1828.
Roach, John. "Massive Genetic Study Supports "Out of Africa" Theory." National Geographic
21 Feb. 2008.
Templeton, Alan R. "GENETICS AND RECENT HUMAN EVOLUTION." The Society for the
Study of Evolution 2007: 1507-1519.
Wong, Kate. "Is Out-of-Africa Going Out The Door?" Scientific American Aug. 1999.