BROOKLYN — A 2023 study published in Science Advances estimated the average human generation interval over the past 250,000 years as 26.9 years. The research, led by population geneticist Matthew Hahn of Indiana University Bloomington, provides a long-term estimate based on genetic data and modeling of human demographic history.
The generation interval is typically defined as the average age at which humans have children. This metric is central to calculating the total number of human generations since the emergence of Homo sapiens. Using fossil evidence, scientists place the origin of Homo sapiens at approximately 300,000 years ago. Dividing this time span by the 26.9-year interval yields an estimate of roughly 11,152 generations of humans over the species’ existence.
The 2023 finding contrasts with earlier, more limited estimates. A 2003 study of Icelandic genealogical records published in the American Journal of Human Genetics calculated an average generation interval of 30.3 years over the past 300 years in that population. Similarly, a 2005 study focusing on European women between 1960 and 2000 reported an average generation interval of 29.1 years. Both of these earlier studies relied on recent demographic data from specific populations, whereas the 2023 analysis aimed to capture variation across a much longer timescale and broader human groups through genetic inference.
Hahn’s study represents one of the first attempts to estimate a species-wide generation interval across tens of thousands of years. Such estimates are critical for interpreting patterns in genetic variation, dating evolutionary events, and calibrating molecular clocks used in population genetics. The shorter interval of 26.9 years suggests that, over deep time, humans may have reproduced at younger ages on average than modern demographic data imply.
The calculation of human generations remains dependent on the chosen interval. If future studies revise this figure upward or downward, corresponding estimates of total generations since the origin of Homo sapiens would shift accordingly. For now, the 26.9-year benchmark offers a reference point grounded in genomic evidence spanning much of human evolutionary history.