Paleodemography: Difference between revisions
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==Genetic analysis== |
==Genetic analysis== |
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In the [[Upper Paleolithic]], human populations consisted entirely of non-sedentary [[hunter-gatherer]] populations, which fall into a number of [[archaic Homo sapiens|archaic species or sub-species]], some but not all of which may be ancestral to the modern human population due to possible [[archaic human admixture with modern humans]] taking place during the Upper Paleolithic. Estimates of the size of these populations are a topic of [[paleoanthropology]]. |
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A late human [[population bottleneck]] is postulated by some scholars at approximately 70,000 years ago, during the [[Toba catastrophe theory|Toba catastrophe]], when the ''[[Homo sapiens]]'' population may have dropped to as low as between 1,000 and 10,000 individuals.<ref name=ambrose1998>{{cite journal |
A late human [[population bottleneck]] is postulated by some scholars at approximately 70,000 years ago, during the [[Toba catastrophe theory|Toba catastrophe]], when the ''[[Homo sapiens]]'' population may have dropped to as low as between 1,000 and 10,000 individuals.<ref name=ambrose1998>{{cite journal |
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| author=Stanley H. Ambrose |
| author=Stanley H. Ambrose |
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Revision as of 11:11, 22 February 2016
 | This article includes a list of general references, but it lacks sufficient corresponding inline citations. (August 2010) |
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Paleodemography is the study of human demography in antiquity and prehistory. More specifically, paleodemography looks at the changes in pre-modern populations in order to determine something about the influences on the lifespan and health of earlier peoples.
Reconstruction of ancient population sizes and dynamics are based on bioarchaeology, ancient DNA as well as inference from modern population genetics.
Skeletal analysis
Skeletal analysis can also yield information such as an estimation of age at time of death. There are numerous methods that can be used,[1] and it is best to field questions of further interest to an osteologist or bioarchaeologist. In addition to age estimation and sex estimation, someone versed in basic osteology can ascertain a minimum number of individuals (or MNI) in cluttered contexts—such as in mass graves or an ossuary. This is important, as it is not always obvious how many bodies compose the bones sitting in a heap as they are excavated.
Occasionally, disease history for things like leprosy can also be determined from bone restructuring and deterioration. While that tends to fall more under paleopathology, it is important to keep such things in mind in how they affect mortality rates.
Genetic analysis
In the Upper Paleolithic, human populations consisted entirely of non-sedentary hunter-gatherer populations, which fall into a number of archaic species or sub-species, some but not all of which may be ancestral to the modern human population due to possible archaic human admixture with modern humans taking place during the Upper Paleolithic. Estimates of the size of these populations are a topic of paleoanthropology. A late human population bottleneck is postulated by some scholars at approximately 70,000 years ago, during the Toba catastrophe, when the Homo sapiens population may have dropped to as low as between 1,000 and 10,000 individuals.[2][3][4]
With the increasing availability of DNA sequencing since the late 1990s, it has become possible to place estimates on Paleolithic effective population sizes.[5] Such models suggest a human effective population size of the order of 10,000 individuals for the Late Pleistocene. This includes only the breeding population that produced descendants over the long term, and the actual population may have been substantially larger (in the six digits).[6] Sherry et al. (1997) based on Alu elements estimated a roughly constant effective population size of the order of 18,000 individuals for the population of Homo ancestral to modern humans over the past one to two million years.[7] For the time of speciation of Homo sapiens, ca. 130,000 years ago, Sjödin et al. (2012) estimate an effective population size of the order of 10,000 to 30,000 individuals, inferring an actual "census population" of early Homo sapiens of roughly 100,000 to 300,000 individuals.[8] The authors also note that their model disfavours the assumption of an early (pre-Out-of-Africa) population bottleneck affecting all of Homo sapiens.[9]
See also
References
- ^ Aggrawal, A (2009). "Estimation of age in the living: in matters civil and criminal" (PDF). J Anat. doi:10.1111/j.1469-7580.2009.01048.x. PMID 19470083.
- ^ Stanley H. Ambrose (1998). "Late Pleistocene human population bottlenecks, volcanic winter, and differentiation of modern humans". Journal of Human Evolution. 34 (6): 623–651. doi:10.1006/jhev.1998.0219. PMID 9650103.
- ^ Ambrose, Stanley H. (2005). "Volcanic Winter, and Differentiation of Modern Humans". Bradshaw Foundation. Retrieved 2006-04-08.
- ^ Robock, A., C.M. Ammann, L. Oman, D. Shindell, S. Levis, and G. Stenchikov (2009). "Did the Toba volcanic eruption of ~74k BP produce widespread glaciation?". Journal of Geophysical Research. 114 (D10): D10107. Bibcode:2009JGRD..11410107R. doi:10.1029/2008JD011652.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ^ A. J. Drummond, A. Rambaut, B. Shapiro, and O. G. Pybus , 'Bayesian Coalescent Inference of Past Population Dynamics from Molecular Sequences', Mol. Biol. Evol. 22(5):1185–1192. 2005, doi:10.1093/molbev/msi103. "The maximum preexpansion population size for the NorthCentral African population is 6,600, the lower bound for the postexpansion population size is 8,400, and the allowed dates are between 49,000 and 640,000 years ago" D. E. Reich and D. B. Goldstein, 'Evolution Genetic evidence for a Paleolithic human population expansion in Africa', Proc. Natl. Acad. Sci. USA, Vol. 95, pp. 8119–8123, July 1998. Natacha Nikolic and Claude Chevalet, 'Detecting past changes of effective population size', Evol Appl. 2014 Jun; 7(6): 663–681, doi: 10.1111/eva.12170.
- ^ "The relationship between census size and effective size is complex, but arguments based on an island model of migration show that if the effective population size reflects the number of breeding individuals and the effects of population subdivision, then an effective population size of 10,000 is inconsistent with the census size of 500,000 to 1,000,000 that has been suggested by archeological evidence. However, these models have ignored the effects of population extinction and recolonization, which increase the expected variance among demes and reduce the inbreeding effective population size. Using models developed for population extinction and recolonization, we show that a large census size consistent with the multiregional model can be reconciled with an effective population size of 10,000, but genetic variation among demes must be high, reflecting low interdeme migration rates and a colonization process that involves a small number of colonists or kin-structured colonization." Elise Eller, John Hawks and John H. Relethford, 'Local Extinction and Recolonization, Species Effective Population Size, and Modern Human Origins', Human Biology 81(5-6):805-824. 2009 doi: http://dx.doi.org/10.3378/027.081.0623.
- ^ Stephen T. Sherry, Henry C. Harpending, Mark A. Batzer, Mark Stoneking Alu Evolution in Human Populations: Using the Coalescent to Estimate Effective Population Size, GENETICS December 1, 1997 vol. 147 no. 4 1977-1982.
- ^ Per Sjödin, Agnès E Sjöstrand, Mattias Jakobsson and Michael G B Blum, "Resequencing data provide no evidence for a human bottleneck in Africa during the penultimate glacial period" Mol Biol Evol (2012) doi: 10.1093/molbev/mss061. "A small human effective population size, on the order of 10,000 individuals, which is smaller than the effective population size of most great apes, has been interpreted as a result of a very long history, starting ∼ 2 mya, of a small population size, coined as the long-necked bottle model (Harpending et al. 1998; Hawks et al. 2000). Our findings are consistent with this hypothesis, but, depending on the mutation rate, we find either an effective population size of NA = 12,000 (95% C.I. = 9,000−15,500 when averaging over all three demographic models) using the mutation rate calibrated with the human-chimp divergence or an effective population size of NA = 32,500 individuals (95% C.I. = 27,500−34,500) using the mutation rate given by whole-genome trio analysis (The 1000 Genomes Project Consortium 2010) (supplementary figure 4 and table 6, Supplementary Material online). Not surprisingly, the estimated effective mutation rates θ = 4NAµ are comparable for the two mutation rates we considered, and are equal to 1.4 × 10−3/bp/generation (95% C.I. = (1.1−1.7) × 10−3). Relating the estimated effective population size to the census population size during the Pleistocene is a difficult task because there are many factors affecting the effective population size (Charlesworth 2009). Nevertheless, based on published estimates of the ratio between effective and census population size, a comprehensive value on the order of 10% has been found by Frankham (1995). This 10% rule roughly predicts that 120,000−325,[0]00 individuals (depending on the assumed mutation rate)"
- ^ "In contrast to the bottleneck theory, we show that a simple model without any bottleneck during the penultimate ice age has the greatest statistical support compared to bottleneck models." Per Sjödin, Agnès E Sjöstrand, Mattias Jakobsson and Michael G B Blum, "Resequencing data provide no evidence for a human bottleneck in Africa during the penultimate glacial period" Mol Biol Evol (2012) doi: 10.1093/molbev/mss061.
Further reading
- C.S. Larsen, 1997. Bioarchaeology: interpreting behavior from the human skeleton. Cambridge University Press.
- M. Katzenberg and S. Saunders, eds., 2000. Biological anthropology of the human skeleton. Wiley.