The evolution of separate sexes is not inevitable across lineages.
Is it true that the evolution of separate sexes is not inevitable across lineages?
Yes. The evolution of separate sexes (dioecy) is not an inevitable outcome across all lineages, as evidenced by numerous plant and animal clades that maintain hermaphroditism or exhibit labile transitions driven by specific ecological contexts and trade-offs.
Verdict: SUPPORTED · 9 sources for, 0 against · Last checked
The retrieved papers consistently show that the transition from hermaphroditism to separate sexes (dioecy) is contingent upon specific ecological conditions, genetic trade-offs, and ancestral mating systems. Multiple studies document independent origins, reversions, and alternative reproductive strategies across diverse lineages, confirming that separate sexes are not inevitable.
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Ashman, T. (2006). The evolution of separate sexes: a focus on the ecological context. doi.org. https://doi.org/10.1093/oso/9780198570851.003.0011
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T, L., JR, P., & C, M. (2024). An explanation for the prevalence of XY over ZW sex determination in species derived from hermaphroditism.. doi.org. https://doi.org/10.1073/pnas.2406305121
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Fu, Y., Zhang, X., Zhang, T., Sun, W., Yang, W., Shi, Y., Zhang, J., He, Q., Charlesworth, D., Jiao, Y., Chen, Z., & Xu, B. (2025). Evidence for evolution of a new sex chromosome within the haploid‐dominant Marchantiales plant lineage. doi.org. https://doi.org/10.1111/jipb.13867
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Bentz, P. C., Burrows, J. E., Burrows, S. M., Mizrachi, E., Liu, Z., Yang, J., Mao, Z., Popecki, M., Seberg, O., Petersen, G., & Leebens-Mack, J. (2024). Bursts of Rapid Diversification, Dispersals Out of Southern Africa, and Two Origins of Dioecy Punctuate the Evolution of Asparagus. doi.org. https://doi.org/10.1093/gbe/evae200
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Lesaffre, T., Pannell, J. R., & Mullon, C. (2024). The joint evolution of separate sexes and sexual dimorphism. doi.org. https://doi.org/10.1101/2024.05.31.596835
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PC, B., SB, C., F, M., H, H., V, R., F, S., A, H., & JH, L. (2026). Two independent origins of XY sex chromosomes in Asparagus.. doi.org. https://doi.org/10.1093/molbev/msag003
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Lesaffre, T., Pannell, J., & Mullon, C. (2024). A model for the gradual evolution of dioecy and heterogametic sex determination. doi.org. https://doi.org/10.1101/2023.03.24.534076
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S, K., V, B., AE, B., I, D. C., T, G., FE, H., R, H., V, H., GAB, M., JR, M., B, O., AST, P., DB, S., JC, S., H, Š., P, T., & F, V. R. (2026). Silene, a versatile model system: from sex and genome evolution to ecology and speciation.. doi.org. https://doi.org/10.1111/nph.71153
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JT, H., N, D., & Y, Y. (2026). Reproduction and Sex in the Androdioecious Barnacle <i>Scalpellum scalpellum</i>: Darwin's Model for Studying Reproductive System Evolution.. doi.org. https://doi.org/10.6620/zs.2026.65-10
What does the evidence say?
The retrieved papers consistently show that the transition from hermaphroditism to separate sexes (dioecy) is contingent upon specific ecological conditions, genetic trade-offs, and ancestral mating systems. Multiple studies document independent origins, reversions, and alternative reproductive strategies across diverse lineages, confirming that separate sexes are not inevitable.
- Is the evolution of separate sexes inevitable across lineages?
- Does every lineage eventually evolve separate sexes?
- Is it true that separate sexes are not bound to evolve in every lineage?
- Do all lineages necessarily evolve separate sexes over time?
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