Prehistoric demography, palaeodemography or archaeological demography is the study of

human Humans (''Homo sapiens'') are the most abundant and widespread species of primate, characterized by bipedalism and exceptional cognitive skills due to a large and complex brain. This has enabled the development of advanced tools, cultu ...

and hominid

demography Demography () is the statistical study of populations, especially human beings. Demographic analysis examines and measures the dimensions and dynamics of populations; it can cover whole societies or groups defined by criteria such as edu ...

prehistory Prehistory, also known as pre-literary history, is the period of human history between the use of the first stone tools by hominins 3.3 million years ago and the beginning of recorded history with the invention of writing systems. The use ...

. More specifically, palaeodemography looks at the changes in pre-modern populations in order to determine something about the influences on the lifespan and health of earlier peoples. Reconstructions of ancient population sizes and dynamics are based on bioarchaeology,

ancient DNA Ancient DNA (aDNA) is DNA isolated from ancient specimens. Due to degradation processes (including cross-linking, deamination and fragmentation) ancient DNA is more degraded in comparison with contemporary genetic material. Even under the bes ...

, and inference from modern

population genetics Population genetics is a subfield of genetics that deals with genetic differences within and between populations, and is a part of evolutionary biology. Studies in this branch of biology examine such phenomena as Adaptation (biology), adaptation, ...

Methods

Skeletal analysis

Skeletal analysis can yield information such as an estimation of age at time of death. There are numerous methods that can be used; 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 An ossuary is a chest, box, building, well, or site made to serve as the final resting place of human skeletal remains. They are frequently used where burial space is scarce. A body is first buried in a temporary grave, then after some years the ...

. This is important, as it is not always obvious how many bodies compose the bones sitting in a heap as they are excavated. Occasionally, historical disease prevalence for illnesses such as

leprosy Leprosy, also known as Hansen's disease (HD), is a long-term infection by the bacteria ''Mycobacterium leprae'' or ''Mycobacterium lepromatosis''. Infection can lead to damage of the nerves, respiratory tract, skin, and eyes. This nerve damag ...

can also be determined from bone restructuring and deterioration.

Paleopathology Paleopathology, also spelled palaeopathology, is the study of ancient diseases and injuries in organisms through the examination of fossils, mummified tissue, skeletal remains, and analysis of coprolites. Specific sources in the study of ancie ...

, as these investigations are called, can be useful in accurate estimation of

mortality rate Mortality rate, or death rate, is a measure of the number of deaths (in general, or due to a specific cause) in a particular population, scaled to the size of that population, per unit of time. Mortality rate is typically expressed in units of d ...

Genetic analysis

The increasing availability of DNA sequencing since the late 1990s has allowed estimates on Paleolithic

effective population size The effective population size (''N'e'') is a number that, in some simplified scenarios, corresponds to the number of breeding individuals in the population. More generally, ''N'e'' is the number of individuals that an idealised population w ...

s. 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). Sherry ''et al.'' (1997) based on

Alu element An Alu element is a short stretch of DNA originally characterized by the action of the ''Arthrobacter luteus (Alu)'' restriction endonuclease. ''Alu'' elements are the most abundant transposable elements, containing over one million copies disp ...

s estimated a roughly constant effective population size of the order of 18,000 individuals for the population of ''

Homo ''Homo'' () is the genus that emerged in the (otherwise extinct) genus '' Australopithecus'' that encompasses the extant species ''Homo sapiens'' ( modern humans), plus several extinct species classified as either ancestral to or closely relat ...

'' ancestral to modern humans over the past one to two million years. Huff ''et al.'' (2010) rejected all models with an ancient effective population size larger than 26,000. For ca. 130,000 years ago, Sjödin ''et al.'' (2012) estimate an effective population size of the order of 10,000 to 30,000 individuals, and infer an actual "census population" of early ''Homo sapiens'' of roughly 100,000 to 300,000 individuals. The authors also note that their model disfavours the assumption of an early (pre-'' Out-of-Africa'') population bottleneck affecting all of ''Homo sapiens''.

Estimates of habitable land area

According to a 2015 study, the total land area of

Africa Africa is the world's second-largest and second-most populous continent, after Asia in both cases. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 6% of Earth's total surface area ...

Eurasia Eurasia (, ) is the largest continental area on Earth, comprising all of Europe and Asia. Primarily in the Northern and Eastern Hemispheres, it spans from the British Isles and the Iberian Peninsula in the west to the Japanese archipelago ...

, and

Sahul __NOTOC__ Sahul (), also called Sahul-land, Meganesia, Papualand and Greater Australia, was a paleocontinent that encompassed the modern-day landmasses of mainland Australia, Tasmania, New Guinea, and the Aru Islands. Sahul was in the south- ...

that was habitable to humans during the Last Glacial Maximum (LGM) was around 76,959,712.4 km². Based on a dataset of average population density of hunter-gatherer groups collected by Lewis R. Binford, which indicate a mean density of 0.1223 humans per km² and a median density of 0.0444 humans per km², the combined human population of Africa and Eurasia at the time of the LGM would have been between 2,998,820 and 8,260,262 people. Alternatively, if a human population density based on that of modern medium to large-bodied carnivores, whose median density is 0.0275 individuals per km² and whose mean density is 0.0384 individuals per km², is used, a total Afro-Eurasian human population of 2,120,000 to 2,950,000 is obtained. Sahul's population density was significantly lower than that of Afro-Eurasia, being calculated as only 0.005 humans per km² during the time just prior to the LGM. As a consequence, assuming Sahul possessed an estimated total habitable land area of 9,418,730.8 km², its population was at most 47,000 at the time of the LGM, and probably less than that given that its population is believed to have declined by as much as 61% during the LGM, a demographic trend supported by archaeological evidence, and it thus would have possessed an even lower actual population density than the calculated density from just before the LGM.

Hominid population estimates

It is estimated by J. Lawrence Angel that the average life span of hominids on the

savanna A savanna or savannah is a mixed woodland- grassland (i.e. grassy woodland) ecosystem characterised by the trees being sufficiently widely spaced so that the canopy does not close. The open canopy allows sufficient light to reach the ground to ...

between 4,000,000 and 200,000 years ago was 20 years. This means that the population would be completely renewed about five times per century, assuming that infant mortality . It is further estimated that the population of hominids in Africa fluctuated between 10,000 and 100,000 individuals, thus averaging about . Multiplying 40,000 centuries by 50,000 to 500,000 individuals per century yields a total of 2 billion to 20 billion hominids that lived during that approximately 4,000,000-year time span.

Methods

Skeletal analysis

Genetic analysis

Estimates of habitable land area

Hominid population estimates

See also

References

Further reading