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An Anthropological Application of Population Modeling Using Matrices. How Long Did It Take For Modern Humans To Migrate Out of Africa?. Rennie Ferguson Fall 2006. Homo sapiens. Originated in Africa 200-250,000 years ago Hunter-gatherers Nomads Agriculturists. Warfare?.
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An Anthropological Application of Population Modeling Using Matrices How Long Did It Take For Modern Humans To Migrate Out of Africa? Rennie Ferguson Fall 2006
Homo sapiens • Originated in Africa 200-250,000 years ago • Hunter-gatherers • Nomads • Agriculturists Warfare?
H. sapiens: Population • Ancestral population size • Ne=10,000-15,000 individuals • 45-240 individuals in a hunter-gatherer group • Average life span=35 years
But how did they get there? Out-of-Africa model Multiregional model Replaced Interbred
But how did they get there? Out-of-Africa model Multiregional model Replaced Interbred
Homo sapiens x1 x2 x7 x3 x6 x4 x5 x2 x3
Central Asia Alaska Europe Siberia Middle East China North America Africa A more comprehensive model… South America
The Model Leave Dates 130,000 years ago ? ? ? ? ? ? North America South America Middle East Siberia Africa Asia Alaska 60,000 years ago 25,000 years ago 130,000 years ago 100,000 years ago 15,000 years ago 13,500-13,000 years ago 12,000 (?) years ago Entry Dates
7 zones Became 1,000,000 km2 in my calculations
r=growth rate r=1.0015, or 0.15% per generation e=fraction of x1 that move to x2 = Average size of hunter-gatherer group/ Total people =142.5/ 10,000 =0.014 or 1.4% per generation (later had to be modified to 0.14% per generation)
Matrix Model n=time (measured in lifespans, where average lifespan=35 years)
AfricaMiddle East Population of x2 must reach 10,000, since area of Middle East ≈ area of Northern Africa When n=500, years=35x500=17,500 years
Middle EastAsia Population of x3 must reach 420,000, since area of Asia ≈ 42x the area Middle East When n=2500, years=35x2500=87,500 years
AsiaSiberia Population of x4 must reach 100,000, since area of Siberia ≈ 10x the area Middle East When n=155, years=35x155=5,425 years
SiberiaAlaska Population of x5 must reach 10,000, since area of Middle East ≈ area of Alaska When n=80, years=35x80=2,800 years
AlaskaNorth America We want the population of x6 to reach 245,000, since area of North America ≈ 24.5x area of Middle East. However, it takes 2000 generations for x6=241,787. So…something happens after arrival in Alaska that makes the model incorrect. More people moving out of Siberia? (so a larger e?) People living in larger groups? North America not populated evenly? Americas actually highly contested…
The Model Leave Dates (computed with the model) 112,500 years ago 25,000 years ago 19,575 years ago 16,775 years ago ? 130,000 years ago North America South America Middle East Siberia Africa Asia Alaska 60,000 years ago 25,000 years ago 130,000 years ago 100,000 years ago 15,000 years ago 12,000 (?) years ago 13,500-13,000 years ago Entry Dates
Conclusions • Considering level of detail, an accurate model for human population movement. • According to model, humans were entering North America (leaving Alaska) by 16,775 years ago. • Found that a mathematical model can aid in interpreting genetic and archaeological evidence. • Question of the Americas and entry into Alaska • Problems: • Doesn’t account for climate or geography • Assumes that entry of new zone only occurs when the population size is met • Doesn’t account for movement backwards • Doesn’t address movement from North America to South America
Sources Cohen, Mark Nathan. “Health and the Rise of Civilization” Review author: Henry Harpending. American Ethnologist, Vol. 17, No. 4. (Nov. 1990), pp. 799-800. Stable URL: http://links.jstor.org/sici?sici=00940496%28199011%2917 %3A4%3C799%3AHATROC%3E2.0.CO%3B2-Q (accessed 4 December 2006) “Homo sapiens.” http://www.answers.com/topic/human (3 December 2006) “Mitochondrial Eve”, http://en.wikipedia.org/wiki/Mitochondrial_Eve (30 October 2006) “Multiregional hypothesis.” http://en.wikipedia.org/wiki/Multiregional_hypothesis (3 December 2006) Nash, George. “Assessing rank and warfare-strategy in prehistoric hunter-gatherer society: A study of representational warrior figures on rock-art from the Spanish Levant, South-eastern Spain.” www.archaeologysafaris.co.uk/gn/violence.htm (3 December 2006) “Recent single-origin hypothesis.” http://en.wikipedia.org/wiki/Out_of_Africa_theory (3 December 2006) S. G. Webb. “The First Boat People”. From the series: Cambridge Studies in Biological and Evolutionary Anthropology. http://www.cambridge.org/catalogue/catalogue.asp?isbn=0521856566&ss=exc Stringer, Chris and Peter Andrews. The Complete World of Human Evolution. New York: Thames & Hudson, 2005. Wall, Jeffrey D. “Estimating Ancestral Population Sizes and Divergence Times.” Genetics 163: p. 395-404. January 2003. http://www.pubmedcentral.nih.gov/picrender.fcgi?artid=1462435&blobtype=pdf (3 December 2006)