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Reconstructing generation intervals over time

Nature Reviews Genetics (2024)Cite this article

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Evolutionary success relies on life history traits that influence our capacity to grow, reproduce and survive. One critical trait is the generation interval, defined as the average time between two consecutive generations. Small-sized and short-lived species, such as rodents, reproduce and die early, facilitating rapid recovery from previous population declines, as well as quick adaptation to sudden environmental changes. This life history strategy often, but not always, correlates with larger population sizes, and thus entails lower extinction risks in comparison with long-lived megafauna. However, as any other phenotype, generation intervals can vary within each species owing to behavioural plasticity or evolutionary adaptations. In periods or regions of abundance, individuals may mate earlier, indirectly promoting genetic variants that facilitate this behaviour. Conversely, habitat fragmentation and resource scarcity may compromise newborn survival if parents are inexperienced, effectively delaying their reproduction age.

Reconstructing generation intervals over time is paramount for characterizing the past and predicting the future of biodiversity in the face of current environmental crises. Studying life history traits has traditionally involved time-consuming experiments on model species that do not represent the entire tree of life1. In humans, only one study has attempted to estimate generation intervals from genomic data to date2. However, this method relied solely on the evolution of the mutation spectrum over time, which — inconveniently — is affected by confounding factors in addition to age at conception3.

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Fig. 1: Reconstructing generation intervals over time.

References

  1. Flatt, T. & Heyland, A. (eds) Mechanisms of Life History Evolution: The Genetics and Physiology of Life History Traits and Trade-Offs. (Oxford Univ. Press, 2011).

  2. Wang, R. J., Al-Saffar, S. I., Rogers, J. & Hahn, M. W. Human generation times across the past 250,000 years. Sci. Adv. 9, eabm7047 (2023).

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  3. Gao, Z., Zhang, Y., Cramer, N., Przeworski, M. & Moorjani, P. Limited role of generation time changes in driving the evolution of the mutation spectrum in humans. eLife 12, e81188 (2023).

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  4. Librado, P. et al. Widespread horse-based mobility arose around 2,200 bce in Eurasia. Nature 631, 819–825 (2024).

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  1. Pablo Librado

    Present address: Institut de Biologia Evolutiva (CSIC – Universitat Pompeu Fabra), Barcelona, Spain

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  1. Centre d’Anthropobiologie et de Génomique de Toulouse, CNRS UMR 5288, Université Paul Sabatier, Faculté de Médecine Purpan, Toulouse, France

    Pablo Librado

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  1. Pablo Librado
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Correspondence to Pablo Librado.

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Librado, P. Reconstructing generation intervals over time. Nat Rev Genet (2024). https://doi.org/10.1038/s41576-024-00766-2

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