A new paper in the journal Science argues that there was a severe population bottleneck in the human lineage, with an average effective population size of around 1280 individuals, lasting for approximately 100,000 years.1 Previously, it had been widely assumed that the effective population size of humans did not dip below 10,000 individuals. However, this new paper uses software that can more accurately detect population bottlenecks.
No Room for Dogmatism
Evolutionary biologist Dr. Richard Buggs explains on his blog that,
The methods used in the study published in Science yesterday are similar to the older methods in that they also cannot detect short sharp bottlenecks. They rely on the assumption that the human population size was stable over time windows lasting many generations, in order to calculate an effective population size for that time window. Thus, a bottleneck of two is not ruled out by their methods. In some ways, the single-couple hypothesis becomes more plausible given the new evidence for a prolonged bottleneck with an average effective population size of about 1280.
These new developments underscore the fact that there is no room for dogmatism about claims concerning the smallest population size of humans. The once popular claim that humans cannot be descended from a primordial pair because the population size of early humans never dropped below 10,000 individuals has now, it seems, been shown to be incorrect. As Buggs explains, even the methods employed in this new study cannot exclude an abrupt bottleneck of two individuals, since their methods assume a stable population size over lots of generations. Science neither rules out, nor rules in, an historical Adam and Eve.
Though there is no direct evidence for Adam and Eve having existed, this does not necessarily make the belief irrational. In principle, it may be supported by indirect evidence (if one holds to a religious belief, itself well supported by evidence, that implies the historicity of Adam and Eve). Either way, current science tells us little about whether Adam and Eve plausibly existed.
- Hu W, Hao Z, Du P, Di Vincenzo F, Manzi G, Cui J, Fu YX, Pan YH, Li H. Genomic inference of a severe human bottleneck during the Early to Middle Pleistocene transition. Science. 2023 Sep;381(6661):979-984.