López Alonso Diego, Ortiz-Rodríguez Isabel M
Dept. Biología y Geología, Universidad de Almería, Spain.
Dept. Matemáticas, Universidad de Almería, Spain.
J Theor Biol. 2017 Apr 21;419:44-51. doi: 10.1016/j.jtbi.2017.01.043. Epub 2017 Feb 7.
Some researchers support the belief that man evolved philandering behavior because of the greater reproductive success of promiscuous males. According to this idea, deserting behavior from the man should be expected along with null paternal involvement in offspring care. Paradoxically however, the average offspring investment in the human male is far higher than that of any other male mammal, including other primates. In our work, we have addressed this conundrum by employing evolutionary game theory, using objective payoffs instead of, as are commonly used, arbitrary payoffs. Payoffs were computed as reproductive successes by a model based on trivial probabilities, implemented within the Barreto's Population Dynamics Toolbox (2014). The evolution of the parent conflict was simulated by a game with two players (the woman and the man). First, a simple game was assayed with two strategies, 'desert-unfaithful' and 'care-faithful'. Then, the game was played with a third mixed strategy, 'care-unfaithful'. The two-strategy game results were mainly determined by the offspring survival rate (s) and the non-paternity rate (z), with remaining factors playing a secondary role. Starting from two empirical estimates for both rates (s = 0.617 and z = 0.033) and decreasing the offspring mortality from near 0.4 to 0.1, the results were consistent with a win for the 'care-faithful' strategy. The 'desert-unfaithful' strategy only won at unrealistically high non-paternity rates (z>0.2). When three-strategy games were played, the mixed strategy of 'care-unfaithful' man could win the game in some less frequent cases. Regardless of the number of game strategies, 'care' fathers always won. These results strongly suggest that offspring mortality was the key factor in the evolution of paternal investment within the Homo branch. The 'care-faithful' strategy would have been the main strategy in human evolution but 'care-unfaithful' men did evolve at a lesser frequency. It can therefore be concluded that human populations, under most of the likely ecological situations, would arrive at a polymorphic state where alternative strategies might be present in significant quantity.
一些研究人员支持这样一种观点，即人类进化出滥交行为是因为滥交男性在繁殖方面更成功。按照这种观点，人们应该预期男性会有遗弃行为，并且不会参与后代的照料。然而，矛盾的是，人类男性对后代的平均投入远高于其他任何雄性哺乳动物，包括其他灵长类动物。在我们的研究中，我们通过运用进化博弈论来解决这个难题，使用客观的收益而非通常使用的任意设定的收益。收益是通过一个基于微小概率的模型计算得出的繁殖成功率，该模型在巴雷托人口动态工具箱（2014年）中实现。亲代冲突的进化是通过一个有两个参与者（女性和男性）的博弈来模拟的。首先，用两种策略“遗弃-不忠”和“照料-忠诚”来检验一个简单博弈。然后，加入第三种混合策略“照料-不忠”来进行博弈。双策略博弈的结果主要由后代存活率（s）和非父率（z）决定，其他因素起次要作用。从这两个比率的两个实证估计值（s = 0.617和z = 0.033）出发，将后代死亡率从接近0.4降低到0.1，结果与“照料-忠诚”策略获胜一致。“遗弃-不忠”策略仅在不切实际的高非父率（z>0.2）时获胜。当进行三策略博弈时，“照料-不忠”男性的混合策略在一些不太常见的情况下可能获胜。无论博弈策略的数量如何，“照料”型父亲总是获胜。这些结果强烈表明，后代死亡率是人类分支中父代投资进化的关键因素。“照料-忠诚”策略本应是人类进化中的主要策略，但“照料-不忠”的男性确实以较低频率进化而来。因此可以得出结论，在大多数可能的生态情况下，人类群体将达到一种多态状态，其中不同的策略可能大量存在。
