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An estimate on the "total number of people who have ever lived" as of 1995 was calculated by Haub (1995) at "about 105 billion births since the dawn of the human race" with a cut-off date at 50,000 BC (beginning of the Upper Paleolithic), and inclusion of a high infant mortality rate throughout pre-modern history. [13]
The controversial Toba catastrophe theory, presented in the late 1990s to early 2000s, suggested that a bottleneck of the human population occurred approximately 75,000 years ago, proposing that the human population was reduced to perhaps 10,000–30,000 individuals [14] when the Toba supervolcano in Indonesia erupted and triggered a major ...
Demographic history is the reconstructed record of human population in the past. Given the lack of population records prior to the 1950s, there are many gaps in our record of demographic history. Historical demographers must make do with estimates, models and extrapolations.
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 km 2 and a median density of 0.0444 humans per km 2, 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.
This suggests that heavy smokers—who were common in Britain during the 1950s but not in Northern California—were selected against. A set of alleles linked to later menarche was more common among women who lived for longer. An allele called ApoE4, linked to Alzheimer's disease, fell in frequency as carriers tended to not live for very long. [22]
That was associated with a 1.5 °C fall in temperature, as determined from oxygen-isotope analysis, and an observed increase in the frequency of El Niño. [117] Tropical Pacific coral records indicate the most frequent and intense El Niño–Southern Oscillation activity was in the mid-17th century. [118]
The map shows the probable extent of land and water at the time of the last glacial maximum, 20,000 yrs ago and when the sea level was probably more than 110m lower than today. During this time sea level was much lower and most of Maritime Southeast Asia formed one land mass known as Sunda .
Map of early human migrations based on the Out of Africa theory; figures are in thousands of years ago (kya). [1]The peopling of the Americas began when Paleolithic hunter-gatherers (Paleo-Indians) entered North America from the North Asian Mammoth steppe via the Beringia land bridge, which had formed between northeastern Siberia and western Alaska due to the lowering of sea level during the ...