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Population bottleneck followed by recovery or extinction. A population bottleneck or genetic bottleneck is a sharp reduction in the size of a population due to environmental events such as famines, earthquakes, floods, fires, disease, and droughts; or human activities such as genocide, speciocide, widespread violence or intentional culling.
Population Bottlenecks and Volcanic Winter "Toba Volcano by George Weber". Archived from the original on April 22, 2011 "The proper study of mankind" – Article in The Economist; Homepage of Professor Stanley H. Ambrose, including bibliographic information on the two papers he has published on the Toba catastrophe theory
The impact of a population bottleneck can be sustained, even when the bottleneck is caused by a one-time event such as a natural catastrophe. An interesting example of a bottleneck causing unusual genetic distribution is the relatively high proportion of individuals with total rod cell color blindness ( achromatopsia ) on Pingelap atoll in ...
A 2022 study by an independent group presents genomic evidence that a previously unidentified pre-18,000 BP South American population suffered a major disruption at the Younger Dryas onset, resulting in a significant loss of lineages and a Y chromosome bottleneck.
The environment can directly affect the survival of a small population. Some detrimental effects include stochastic variation in the environment (year to year variation in rainfall, temperature), which can produce temporally correlated birth and death rates (i.e. 'good' years when birth rates are high and death rates are low and 'bad' years when birth rates are low and death rates are high ...
The population warning comes as countries struggle to encourage more people to have kids, while the likes of Elon Musk and others in the tech sector have warned on shrinking populations.
A population bottleneck may also cause a founder effect, though it is not strictly a new population. The founder effect occurs when a small group of migrants—not genetically representative of the population from which they came—establish in a new area.
Neutral events can radically reduce genetic variation through population bottlenecks. [108] which among other things can cause the founder effect in initially small new populations. [109] When genetic variation does not result in differences in fitness, selection cannot directly affect the frequency of such variation.