Cryptic genetic variation can make "irreducible complexity" a common mode of adaptation in sexual populations

article Cryptic genetic variation can make "irreducible complexity" a common mode of adaptation in sexual populations published yes Meredith Trotter author Daniel Weissman author 2D0CE020-F248-11E8-B48F-1D18A9856A87 Grant Peterson author Kayla Peck author Joanna Masel author NiBa department Limits to selection in biology and in evolutionary computation project The existence of complex (multiple-step) genetic adaptations that are "irreducible" (i.e., all partial combinations are less fit than the original genotype) is one of the longest standing problems in evolutionary biology. In standard genetics parlance, these adaptations require the crossing of a wide adaptive valley of deleterious intermediate stages. Here, we demonstrate, using a simple model, that evolution can cross wide valleys to produce "irreducibly complex" adaptations by making use of previously cryptic mutations. When revealed by an evolutionary capacitor, previously cryptic mutants have higher initial frequencies than do new mutations, bringing them closer to a valley-crossing saddle in allele frequency space. Moreover, simple combinatorics implies an enormous number of candidate combinations exist within available cryptic genetic variation. We model the dynamics of crossing of a wide adaptive valley after a capacitance event using both numerical simulations and analytical approximations. Although individual valley crossing events become less likely as valleys widen, by taking the combinatorics of genotype space into account, we see that revealing cryptic variation can cause the frequent evolution of complex adaptations. Wiley-Blackwell2014 eng Evolution 1310.6077 00034607560000110.1111/evo.12517 68123357 - 3367 Trotter, M., Weissman, D., Peterson, G., Peck, K., & Masel, J. (2014). Cryptic genetic variation can make &quot;irreducible complexity&quot; a common mode of adaptation in sexual populations. Evolution. Wiley-Blackwell. <a href="https://doi.org/10.1111/evo.12517">https://doi.org/10.1111/evo.12517</a> Trotter, Meredith, Daniel Weissman, Grant Peterson, Kayla Peck, and Joanna Masel. “Cryptic Genetic Variation Can Make &quot;Irreducible Complexity&quot; a Common Mode of Adaptation in Sexual Populations.” Evolution. Wiley-Blackwell, 2014. <a href="https://doi.org/10.1111/evo.12517">https://doi.org/10.1111/evo.12517</a>. Trotter, Meredith, et al. “Cryptic Genetic Variation Can Make &quot;Irreducible Complexity&quot; a Common Mode of Adaptation in Sexual Populations.” Evolution, vol. 68, no. 12, Wiley-Blackwell, 2014, pp. 3357–67, doi:<a href="https://doi.org/10.1111/evo.12517">10.1111/evo.12517</a>. Trotter M, Weissman D, Peterson G, Peck K, Masel J. Cryptic genetic variation can make &quot;irreducible complexity&quot; a common mode of adaptation in sexual populations. Evolution. 2014;68(12):3357-3367. doi:<a href="https://doi.org/10.1111/evo.12517">10.1111/evo.12517</a> Trotter M, Weissman D, Peterson G, Peck K, Masel J. 2014. Cryptic genetic variation can make &quot;irreducible complexity&quot; a common mode of adaptation in sexual populations. Evolution. 68(12), 3357–3367. M. Trotter, D. Weissman, G. Peterson, K. Peck, and J. Masel, “Cryptic genetic variation can make &quot;irreducible complexity&quot; a common mode of adaptation in sexual populations,” Evolution, vol. 68, no. 12. Wiley-Blackwell, pp. 3357–3367, 2014. M. Trotter, D. Weissman, G. Peterson, K. Peck, J. Masel, Evolution 68 (2014) 3357–3367. 19322018-12-11T11:54:47Z2025-09-29T12:10:43Z