Demic Expansions and Human Evolution

• Published in: Science (American Association for the Advancement of Science) Vol. 259; no. 5095; pp. 639 - 646
• Main Authors: Cavalli-Sforza, Luigi L., Menozzi, Paolo, Piazza, Alberto
• Format: Journal Article
• Language: English
• Published: Washington, DC American Society for the Advancement of Science 29.01.1993; American Association for the Advancement of Science; The American Association for the Advancement of Science
• Subjects: Agriculture; Animals; Biological and medical sciences; Biological Evolution; Brain; Chromosome Mapping; City squares; Demographics; Evidence; Evolution; Evolutionary genetics; Fundamental and applied biological sciences. Psychology; Genetic mapping; Genetic variation; Genetics; Genetics of eukaryotes. Biological and molecular evolution; Geography; growth; Hominidae - genetics; Human; Human evolution; Human genetics; Human population genetics; Humans; Individualized Instruction; man; Migration; Paleontology; Population; Population Density; Population genetics; Population genetics, reproduction patterns; Population Growth; Robustness (Statistics); Steppes; Verbal Communication; Human; Biological evolution; World population; Anthropology; Population structure; Population genetics; Population density; Geographical variation
• ISSN: 0036-8075; 1095-9203
• DOI: 10.1126/science.8430313

Geographic expansions are caused by successful innovations, biological or cultural, that favor local growth and movement. They have had a powerful effect in determining the present patterns of human genetic geography. Modern human populations expanded rapidly across the Earth in the last 100,000 years. At the end of the Paleolithic (10,000 years ago) only a few islands and other areas were unoccupied. The number of inhabitants was then about one thousand times smaller than it is now. Population densities were low throughout the Paleolithic, and random genetic drift was therefore especially effective. Major genetic differences between living human groups must have evolved at that time. Population growths that began afterward, especially with the spread of agriculture, progressively reduced the drift in population and the resulting genetic differentiation. Genetic traces of the expansions that these growths determined are still recognizable.