MADRID, 8 Mar. (EUROPA PRESS) –
Women have to resort to aids such as charts, test strips, or wearable technology to identify periods of fertility, while animals undergo obvious physical changes during ovulation. One advocated explanation is that hiding fertility from males helps females obtain resources from males to raise children. But a new model from evolutionary scientists suggests that human females may have evolved to hide ovulation from each other and not from males.
For almost half a century, it has been explained that the evolution of hidden ovulation in human females is helpful in finding male partners to help raise and support children. However, a new study published in the journal Nature Human Behavior casts doubt on this long-standing idea.
Using computer models, a team of evolutionary scientists has shown that hidden ovulation could have evolved to allow females to hide their fertility status from other females.
“The study of human evolution has tended to look at things from a male perspective, and even the specific adaptations of women, such as their social behavior and hidden ovulation, have been seen in terms of how men shape them. Athena Aktipis, associate professor of psychology at Arizona State University and lead author of the paper – This study challenges the idea that the role of female sociability is to better secure male partners and their resources; our computational model shows that female sociability is much more than ensuring male investment. “
The idea that females evolved to conceal ovulation from males to encourage them to help with offspring, called the male inversion hypothesis, was proposed as a way to understand why human females do not advertise ovulation. This hypothesis has been the predominant explanation for female sociability and hidden ovulation for decades, although it has undergone little empirical testing and has not been formally modeled until now.
But females don’t just interact with males, they also interact with each other, sometimes cooperating and other times in conflict. “I’ve been puzzled by the male inversion hypothesis for years, and since you can’t argue with a verbal hypothesis, I started working on how to test it,” recalls Aktipis.
“At the same time, I was working on female sociability and I realized that women might have been assaulting other women who were showing signs of ovulation, which would generate a benefit to hide ovulation,” he adds.
The team of evolutionary scientists tested the idea that female conflict might have driven the evolution of occult ovulation, which they call the female rivalry hypothesis, using an agent-based computational model.
Evolutionary adaptations in humans occur on the timescale of many generations, making it difficult to test whether or how traits can evolve. Computational modeling allows researchers to test ideas that would be difficult to test in the real world.
In agent-based computational models, an agent represents an individual whose behavior can be programmed and analyzed. Each agent follows a specific set of rules and can interact with other agents and with the environment. In the model developed to test the female rivalry hypothesis, male and female agents followed rules governing their movement, reproductive behavior, and attractiveness.
Male agents varied in terms of their promiscuity. Promiscuous men did not partner with women to help raise subsequent children, while non-promiscuous male agents stayed behind to share resources and support future children.
The female agents had physical cues that indicated when they were ovulating or when ovulation was hidden. Female officers could also assault each other.
Male and female agents interacted with each other and had the opportunity to procreate and form parental associations. The model supported the female rivalry hypothesis by showing that women who concealed ovulation fared better. They had more children, avoided aggression between women, and managed to form nurturing relationships with men.
“Social science work has tended to assume that male cognition and behavior are the default. But women recurrently face some unique challenges, particularly in their interactions with other women. This work is the result, in part , to take that idea seriously, “explains Jaimie Arona Krems, assistant professor of psychology at Oklahoma State University and first author of the paper.” When we do that, I think we’ll learn more, not just about the female mind, but about the human mind”.
The research team also used the model to test the male investment hypothesis, running scenarios that did not allow women to assault each other. But there was no clear benefit of hiding ovulation in this scenario, suggesting that hidden ovulation in women might not have evolved due to interactions with men, but rather due to interactions with other women.
“This work represents a necessary shift in thinking about how human females have evolved. Female sociability and other adaptations are not just about securing male investment, although that has long been the underlying assumption about the purpose of social behavior. female, “says Aktipis.