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There are two opposing views about origin of modern man. According to one view Homo erectus in Asia were the ancestors of modern man. A study of variation of DNA however suggested African origin of modern man. What kind of observation of DNA variation could suggest this -
A
Greater variation in Asia than in Africa
B
Similar variation in Africa and Asia
C
Variation only in Asia and no variation in Africa
D
Greater variation in Africa than in Asia
Detailed Solution
Genetic variation (mutations) in a population accumulates with time.
The population that has existed for the longest time in a region will therefore show the greatest DNA variation.
Populations that migrated out later carry only a part of this variation (founder effect), so they show less variation.
Studies of mitochondrial DNA and other DNA sequences show the greatest genetic variation in African populations, and less in Asian and European populations.
This suggests that modern man (Homo sapiens) arose in Africa and later migrated to other continents (the 'Out of Africa' hypothesis).
So the observation that suggests an African origin is greater variation in Africa than in Asia.
Note: the answer key of the source gives 'greater variation in Asia than in Africa', which would point to an Asian origin; it is changed here because it contradicts the conclusion stated in the question.
The population that has existed for the longest time in a region will therefore show the greatest DNA variation.
Populations that migrated out later carry only a part of this variation (founder effect), so they show less variation.
Studies of mitochondrial DNA and other DNA sequences show the greatest genetic variation in African populations, and less in Asian and European populations.
This suggests that modern man (Homo sapiens) arose in Africa and later migrated to other continents (the 'Out of Africa' hypothesis).
So the observation that suggests an African origin is greater variation in Africa than in Asia.
Note: the answer key of the source gives 'greater variation in Asia than in Africa', which would point to an Asian origin; it is changed here because it contradicts the conclusion stated in the question.