Exploring the ancestry of witchcraft beliefs

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– by Sarah Peacey

‘Witchcraft’ has a variety of associations, from pointed hats and broomsticks to the nature-focused, neopagan religion of Wicca. The oldest and most universal definition is the darkest: the idea that people – perhaps members of your community including relatives and neighbours – are secretly working harmful magic to hurt you. In communities where they exist, these beliefs can create fear and mistrust, and can lead to horrific harm coming to those suspected of witchcraft.

But how did belief in witches and the folklore and imagery surrounding them become so widespread? My co-authors and I examined the ancestry and transmission of the ‘witchcraft phenotype,’ or the collection of ideas and beliefs about witches, in linguistically and culturally-related societies in sub-Saharan Africa.

Our study population consisted of Bantoid and Bantu-speaking societies. Bantoid languages are spoken in parts of Nigeria and Cameroon, and approximately 5,000 years ago, people from this region began migrating and settling in places throughout central, eastern and southern sub-Saharan Africa, and started speaking Bantu languages. This vast population movement was a key event that significantly changed Africa’s cultural and biological landscape. As they settled in varied locations, the cultures retained ancestral traits but also began to diversify.

We created our sample of 13 Bantu and Bantoid witchcraft traits by coding information from historical records dating from the 19th-mid-20th century. If there is a linguistic phylogeny (an evolutionary tree showing how languages are historically related to one another like biological species), then cultural traits can be mapped on to the tips. We could then trace their likely patterns of evolution backwards over several thousand years. How were these beliefs transmitted between societies? Were they present in the more ancestral groups or did they arrive more recently?

Belief in witchcraft is widespread in these groups and many have similar words for harmful magic, suggesting an ancient origin. In line with this, witchcraft beliefs were present in all 84 societies which we could acquire data on. The idea that witchcraft belief is globally ancient is echoed by recent archaeological research from Australia, that was able to match artefacts from a ‘witchcraft ritual’ dating back 11,000-12,000 years to a description from the 19th century.

Every society with these beliefs has its own ‘witchcraft phenotype’. In our sample, some hold women are more likely to be sorcerers than men, although others believe witchcraft is a predominantly male undertaking. The elderly may be accused, or the young, as in the disturbing phenomenon of ‘child witches’. Some communities believe witches have familiars (magical helpers) – hyenas and aardvarks in Tanzania can be seen as having the same role as toads and cats in England. Societies often have tests or ordeals for whether an individual is guilty of causing harm through magic. Many societies in our sample had a poison ordeal, where the suspect was given a drink with a noxious substance in it. Guilt was determined by how they responded: the drink itself could kill them or they might suffer ill effects and then be executed. Only those who were not seriously affected were deemed innocent.

The traits we examined were almost all ‘successful’ in cultural evolutionary terms: the results suggest some lasted for hundreds of years in multiple societies, although others appeared to be more recent. It might seem likely beliefs would spread between neighbouring cultures, through trade or other contact, but geographic proximity alone largely couldn’t explain similarity in beliefs between societies. Instead some traits, such as the poison ordeal and belief in familiars, seemed to be passed down from generation to generation, following the divergence of Bantu societies along the tree.

Exceptionally, the evil eye belief may have been transferred between neighbouring societies. It is related to the concept of witchcraft: the idea that a single glance in someone’s direction can cause them mystical harm. We found no evidence that it was ancestral or that its distribution fitted the structure of our tree. An explanation may lie in the fact it was present in societies such as the Kikuyu in Kenya and others who live near groups of Nilotic-language speakers, among whom belief in the evil eye is more prevalent.

Some groups viewed witchcraft as a physical substance in the body, often described as having a greyish appearance and being found above the liver or the heart. This trait had a unique distribution. Our results suggest it has a deep ancestry and was present before the Bantu migration. But at a later point when Bantu populations split again, with one group heading east and another west, the trait disappeared. Why this happened can only be speculated on, but its sudden disappearance is striking.

Who is targeted in accusations probably depends on multiple factors including the structure of relationships within societies.  Where an accusation can free up resources, it may be more beneficial to accuse individuals from some groups than others. It is not that accusations are necessarily cynical, as fear of witchcraft is often deeply held, but they may be associated with various forms of competition. We found that accusations of children appear comparatively recent, which aligns with other research indicating that this has developed in parts of Africa since the late 20th century. Perhaps surprisingly, accusations of men appear not to have been present ancestrally. Even some of the most well-known, stereotypical traits of witches – being elderly and female – appear neither ancestral nor inherited from society to society intergenerationally. Patterns of accusation may change quite rapidly in response to socioecological factors. This appears to have been the case in modern Tanzania and in the European witch trials of the 16th and 17th centuries, where accusations increased during periods of poor harvests.

So what does our study suggest overall about the cultural transmission of witchcraft beliefs? Some traits appear to have a deep ancestry and were stable enough to exist in societies for hundreds if not thousands of years. Some may evolve independently in numerous cultures: this may be because they produce fitness benefits in certain environments. Some (such as the recurrence of familiars) can perhaps best be explained as appealing to pre-existing cognitive processes, while others appear to be preserved and passed down from generation to generation. Therefore the diverse traits in witchcraft phenotypes appear to differ in their patterns of evolution and their likely functions: further research may provide deeper insights into this.

Read the original article: Peacey, S., Wu, B., Grollemund, R., & Mace, R. (2024). The cultural evolution of witchcraft beliefs. Evolution & Human Behavior, 45(5), 106610.

Some “Psychological Weapons” Infants and Young Children Have to Get Others to Love Them

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– by Carlos Hernández Blasi and David F. Bjorklund

It would not be much of an exaggeration to say that a major theme in evolution is “save the children,” especially for a slow-developing species that invests much in few offspring, such as humans. However, although a child’s survival is in the best interest of both parents and children, ancient parents could not be indiscriminate on how much care and attention they give to any one child. For most of our species’ existence, infant mortality rates were high, with nearly half of all children dying before reaching puberty. It is therefore important for infants and young children to endear themselves to adults, particularly their parents, to insure they get the care they need to survive and thrive. To do so, infants and children have developed methods of communication that change over the course of development, from cries and facial expressions to more sophisticated vocal and cognitive cues. In short, children have evolved a set of “psychological weapons” to attract adults to them and increase the chances that they will receive the care they need to grow up and become adult members of their community.

Infants enter the world with some perceptual, motor, and communication systems that serve to promote their interaction with the people who care for them. For example, although newborns’ eyesight is poor, they see most clearly objects that are about 10 inches in front of them, which is about the distance between mother’s and baby’s faces when nursing. Infants’ cries convey their physical and emotional states to adults, and they come into the world with a number of reflexes that, in the right contexts, promote closeness, such as the sucking and grasping reflexes. Babies also possess some physical facial characteristics that are very appealing to adults, even to those adults who profess not to like babies all that much. These include a large head relative to body size, large eyes relative to head size, a flat nose, high forehead, and rounded cheeks. The Nobel Laurette Konrad Lorenz, referred to these features as Kindchenschema, or baby schema. Nearly 80 years of research has shown that adults and even children generally view babies who possess high levels of “baby schema” as cute and respond affectionately toward them. Thus, although in some sense infants are perceptually, motorically, and cognitively immature, from an evolutionary perspective they can be seen as being quite smart, having some features that get adults to pay attention to them and perhaps to care and love them.

However, babies grow up, and they lose the special “cuteness” afforded by the baby schema. Yet, compared to other mammals, human children are dependent on their caregivers for a remarkably long time, and it would make sense for natural selection to provide children (and adults) with other mechanisms that promote care. This has been the focus of our research for more than a decade, examining some features of early childhood (essentially the preschool age, between about two and six years) that may increase attention to and caring for children beyond infancy. Anthropologists tell us that this is the age when in many traditional societies children are weaned and start to spend more time with people outside the family. Children in this period of life are certainly more autonomous than they were as infants, but they are still unable to feed or otherwise fend for themselves. Might preschool-age children also have some “smart” features that, like the baby schema of infancy, promote their surviving and thriving?

In our first studies, we found that one potential “psychological weapon” of preschool children to keep adults tuned to (and informed about) them involved some of the often humorous things they said, reflecting a form of what we called cognitive immaturity. For example, adults and older adolescents listening to a young child talking about some magical- or supernatural-thinking explanation such as, “The sun is not out today because it’s mad” or “The high mountains are for long walks, and the short mountains are for the short ones,” were viewed not only as funny, but as endearing and signaled that these children still likely needed caring and support. However, not all expressions of cognitive immaturity were viewed positively by adults and older adolescents. When the same children made some immature statements about more mundane topics, such as, “I will remember all 20 cards!” (something typically out of the range of their cognitive skills) or “I couldn’t prevent looking into the box for a while, and I lost the treat!” (exhibiting their difficulty to regulate their actions), adults and older adolescents did not typically react the same way they did to immature supernatural thinking. In fact, we found that children expressing immature natural thinking typically don’t make a positive impression. Rather, adults feel a bit overwhelmed, if not bothered, by this type of cognitive immaturity. In other studies, we found that the typical immature voices of preschool children, regardless of speech content, evoke a similar effect to the funny, supernatural thinking of children, triggering a positive impression in adults and adolescents in general and blocking negative feelings towards them. We also found that preschool children’s faces continue to prompt positive feelings in adults and adolescents, but they were not as powerful as either children’s voices or their verbalized thoughts to inform about children’s intelligence or their vulnerability.

Finally, in our most recent study, we found that, overall, when pitted against one another, young children’s voices prevail over young children’s thinking, in terms of conveying to adults both positive affect and some reliable information about their degree of vulnerability. In contrast, young children’s thinking is apparently more relevant than young children’s voices to inform their potential caregivers about their intelligence level – but only when children verbalize magical or supernatural explanations – and for making negative impressions – but only when they verbalize more realistic or natural narrations. In sum, our studies show that, though young children are still highly dependent on others, “nurture” speaking, they are actually very smart in “nature,” displaying different, possibly evolved cues that keep them connected to those who can help them to survive and thrive in their early development.

Read the original article: Hernández Blasi, C., Bjorklund, D. F., Agut, S., Nomdedeu, F. L., & Martínez, M. Á. (2024). Children’s evolved cues to promote caregiving: Are voices more powerful than thoughts in signaling young children’s attributes and needs to adults? Evolution and Human Behavior, 45(5), 106609.

The Perils of Group-Living

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– by Robin Dunbar

Solving the problem of how to live in large, demographically stable groups is probably the single most important achievement of anthropoid primates, and especially so of humans. Group-living does not come for free. A variety of centrifugal forces constantly threaten to destabilise groups. One of these is the infamous public goods dilemma. Being willing to live in a group with others involves – necessitates, in fact – an implicit promise not to cheat on the deal. I have to allow you a fair share of the benefits, just as you have to allow me a fair share. However, as we all know, it always pays me to take a bit more than my fair share because, by doing so, I gain a modest but significant fitness advantage on you – at your expense, of course!

If access to benefits is a function of physical strength, then it will always pay those who can get away with it to use a little extra force to extract a few extra benefits. The issue for everyone else is how much exploitation should you be prepared to put up with as the price of living in the group – given that the opportunity cost (or, as economists used to call it with a lot more literary imagination, your regret) is to live alone and miss out on all the genuine benefits of group life?

The Norse world of medieval Iceland was the archetypal example of the problem. With no formal political structures (it was the Wild West of the early medieval period), it lacked judges and police to enforce good behaviour. The result was that violence was endemic and very disruptive. It spawned psychopaths with fiercesome reputations. One such individual was Egil Skallagrimsson, who made himself very rich by shamelessly helping himself to a lot of other people’s land and property (and occasionally wives). If necessary, he simply killed you. Such behaviour often generated vendettas that dragged on for years. In one such case, a third of all the adult males in the community were killed in a vendetta that lasted a generation. Of 23 families, four lost all their males; only 11 survived without losing any. Analysis of data from hunter-gatherer societies indicates that the proportion of all deaths that are due to homicide increases linearly with living group size, such that in bands of just 50 people half of all deaths are due to homicide (Dunbar 2022). Why do small scale societies put up with this?

In one sense, of course, they don’t. As I have shown (Dunbar 2022), what they do is introduce social institutions that allow them to manage violent behaviour, especially among the young males. These include marital arrangements that increase the number of people who can lean on badly behaved individuals, charismatic leaders (whose friendly advice we heed out of respect), communal feasts (where we bond) and, especially, men’s clubs (where boys who fall out are made to sit down together to make peace – without, by the way, actually talking about it, just by bonding).

This is all very well, of course, but it ignores the elephant in the room: bad behaviour pays. This raises the intriguing question as to whether there is a significant selection factor favouring bad behaviour that promotes whatever genes might be involved, despite the costs to the rest of the community?

Many studies have tried to determine whether violence pays by determining whether males who murder gain more wives and/or reproduce more often. Broadly speaking, they do. But, as the ecologist David Lack (of Lack’s Principle) reminded us back in the 1950s, pumping out babies doesn’t necessarily translate into loads of grandchildren. As often as not, having too many babies results in many dying, such that fitness is lower.

At this point, the medieval Icelanders come to our rescue, because they left us an amazing literary record of their daily lives – the family sagas (or histories) that recount in considerable detail the goings-on in the various communities and families, not to mention who married (or otherwise) who and what offspring they had. Using these records, the Viking Age historian Anna Wallette (of Lund University, Sweden) and I have been able to place all the family pedigrees into a single interlinked database of over 1200 males, for a great many of whom we can trace their ancestry, siblings and descendants over 3-5 generations. We used a sample of 13 known killers (who had killed 1-19 other men) and 31 non-killers to test whether killers had higher fitness than socially matched non-murderers – not just in terms of their own descendants but also in terms of the fitness of their collateral male relatives. In other words, for the first time, we were able to test the hypothesis that violence pays by examining inclusive fitness.

The results (Dunbar & Wallette 2024) revealed that, despite having a 40% higher risk of being themselves killed than the average non-killer, killers had twice of many wives and offspring as matched non-murderers (men who were never recorded as murdering anyone) and nearly four times the inclusive fitness through their male siblings – providing they themselves survived to die in their own beds. More importantly, the brothers benefitted enormously: if the killer survived, their inclusive fitness was around three times that of the brothers of a non-killer.

In other words, violence does pay. This does not, however, mean runaway selection in favour of ever more violent individuals. Too many violent individuals would cause the collapse of communal life. Since our capacity to survive and reproduce depends on the group, this would negatively impact our fitness. In the end, it is a balance of the costs and benefits. Humans seem to be especially good at finding social controls that allow us to live in unusually large groups – not because we are naturally altruistic, but because we are good at finding workable solutions. Viking Iceland offers us a glimpse of how bad it can become when the social controls are absent.

Read the original article: Dunbar, R.I.M. & Wallette, A. (2024). Are there fitness benefits to violence? The case of medieval Iceland. Evolution & Human Behavior 45: 106614

Time or Resources? For Allocare, It Depends on the Environment

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– by Elic Weitzel, Kurt Wilson, & Rich Sosis (Image credit: John Shaver)

Alloparental care—investment in offspring that are not one’s own—takes many diverse forms. Alloparenting can look like an older sister watching over a younger brother while their parents are out. It can look like an aunt or uncle helping to pay for their nieces’ and nephews’ college education. It can look like a grandmother providing her grandchildren with food that she collected, or it can look like a teenage next-door neighbor being paid to babysit for an evening.

These various types of allocare all accomplish a key outcome, providing for another’s offspring, but they each have different costs and benefits. Some involve directly provisioning children with resources of some sort, such as food or money that once given cannot readily be shared or regained. Giving away resources means that the alloparent had to first pay the costs of obtaining the resource and second the cost of not consuming or using it themselves. Other alloparenting activities involve expenditures of time rather than resources, such as supervising or playing with children. These forms of care do not require material resources to be transferred, but the opportunity costs of spending time in allocare can be consequential. Time spent supervising a group of children is time not spent doing anything else.

In thinking about both different forms of care, we theorized that care could be divided up roughly into two types. The first is care which entails an additive cost structure in which an alloparent must pay an equal cost for each additional child they care for. These children receive the benefits of care directly in proportion to the costs paid by the alloparent: a 1:1 ratio. Generally speaking, this most commonly reflects resource investment. For example, when a wealthy aunt pays for $10,000 worth of their nephew’s college education, that is $10,000 the aunt no longer has. The second type of care involves a declining marginal cost structure in which each additional child cared for costs less than the previous (at least up to a point). This is generally exemplified by time investments, such as when an older child cares for their younger sibling. If they were to care for two younger siblings simultaneously, they would certainly incur additional costs but not twice the costs of supervising just one. The second sibling can be supervised more cheaply since the older sibling is already spending the time watching the first child. In contrast, if our hypothetical wealthy aunt were to cover two nephews’ college tuitions, she must fully pay the same amount for the second.

Children require some blend of time and resources invested in them to survive and thrive, but presumably there exist situations to which each of these types of allocare is better suited. To explore this, we constructed a type of computer simulation called an agent-based model. An agent-based model functions like a video game with many different characters, all programed to do certain things. The outcome of the interaction of all the different agents making their own, simple, decisions becomes the focus of study – because these interactions can cause quite complex phenomena to emerge. In our model, we designed four types of characters, or agents, that each behave differently, following the strategy and payoff categories of alloparenting. One type does not alloparent at all, but only provides care to their own children with an additive cost structure, or resource investment. The second type also only provides care to their own children but does so in line with a time investment strategy characterized by declining marginal costs. The third and fourth types of agents both parent and alloparent, providing care characterized by additive and declining marginal cost structures, respectively.

In our model, we gave each of these agents a non-specific “currency,” which can be thought of either as time or resources, and let them go about their lives. These agents age, reproduce, care for children, and die. As they do, we track how much currency they keep, how much they spend, who they share that currency with, and—importantly—how many times they reproduce and how many of their children reach reproductive maturity. We evaluated the evolutionary success of each care strategy by looking at the number of children born to members of that agent type who survive to adulthood themselves.

What we found was that the cost structures of allocare matter differently in different socioecological situations. When we provided agents with abundant currency (think a resource rich environment) the two allocare strategies outperformed the two parenting-only strategies, producing an average of 4.75 surviving offspring versus the parenting-only strategy’s average of 3.75. Agents who provided allocare performed equivalently well in these simulations regardless of whether they paid additive or declining marginal costs. In other words, when resources are abundant the type of care didn’t matter, only the fact that they were providing some form of allocare. However, when we reduced the amount of currency we provided to agents, simulating contexts of scarcity, only agents who provided allocare with declining marginal costs (time investment) did well while the other three types struggled to effectively birth and raise children. This is because time-investment allocare, with its declining marginal cost structure, is characterized by what is known as an economy of scale: an economic situation in which scaling up production allows you to lower your costs. By providing only care that has declining marginal costs, alloparents are able to gain evolutionary fitness benefits by producing more surviving offspring. When an agent alloparents for someone else, or someone else alloparents their children, neither is paying a 1:1 ratio of resource to child but saving some resources to better ensure greater survival.

While this model is necessarily less complex than the real-world, the results from this set of simulations allow us to make several predictions about real-world alloparenting. Based on these insights from our model, we expect that time investments—watching, supervising, or teaching children—will be more common in socioecological contexts of scarcity. In contrast, contexts of abundant time and resources might lead to more varied manifestations of allocare. We also predict that time-investment allocare with declining marginal costs will be more universal than resource-investment allocare with additive costs as it is adaptive over a wider set of socioecological conditions. More work is needed, but available ethnographic observations appear to support this prediction, with many anthropologists noting that time-investment care, such as children’s playgroups, are particularly common across societies and ecological contexts.

There remains much work to be done investigating the costs and benefits of different forms of allocare. Our model is, after all, only a model. Real-world anthropological data must now be marshalled to evaluate the predictions we outline. Future work can also adjust our model in various ways to explore related questions, such as the reality that children often require both forms of allocare or require different forms at different points in their development. As we move forward, combining the power of computational modeling with ethnographic observation provides a uniquely powerful approach to testing complex theoretical ideas that will better help us explain the commonalities and differences in alloparenting strategies across cultures.

Read the original article: Weitzel, E.M., Wilson, K.M., Spake, L., Schaffnit, S.B., Lynch, R., Sear, R., Shaver, J.H., Shenk, M.K., & Sosis, R. (2024). Cost structures and socioecological conditions impact the fitness outcomes of human alloparental care in agent-based model simulations. Evolution & Human Behavior, 45(5), 106613.

Maternal Depression: A Catalyst for Cooperation?

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Image: woman in Uganda

– by Alessandra Cassar

Women around the world experience maternal depression, particularly around the time of pregnancy and childbirth. With around 10-15% of mothers in high-income countries and up to 25% in low- and middle-income countries experiencing depression during or after pregnancy, it is essential that we understand its causes and effects. But from an evolutionary perspective, why would such a costly condition even exist, if it affects not only the mother and her infant but potentially the entire family?

Patricia Schneider, Chukwuemeka Ugwu, and I decided to explore one specific theory rooted in evolutionary psychology: that maternal depression may not be solely a dysfunction but an evolved mechanism. We tested whether maternal depression could act as an unconscious bargaining strategy for mothers who had exhausted all other strategies to elicit help and support from their social network, particularly the baby’s father. This idea is controversial but offers a potential explanation for why a condition so detrimental could have persisted over evolutionary time.

Evolutionary Perspectives on Depression. Several evolutionary hypotheses suggest that depression might have evolved as an adaptive response. Depression could enable individuals to obtain help from others, encourage cognitive changes to solve social problems, or prevent individuals from engaging in risky behaviors. In other words, while depression is painful, it might serve important functions, especially when faced with adverse social situations. This idea gains more traction when we look at maternal depression, where a mother’s wellbeing directly impacts her offspring’s chances of survival.

Perinatal depression, occurring during pregnancy or shortly after birth, presents a particular challenge. Symptoms like sadness, fatigue, and loss of interest in usual activities make it hard for mothers to care for their infants. This has led some researchers to propose that maternal depression might serve as a signal—a costly, honest cry for help—that triggers increased investment from others, particularly those closest to the mother (and genetically closest to the infant).

The Bargaining Model Hypothesis. The bargaining model of maternal depression advanced by Edward Hagen proposes that depression acts as an unconscious strategy for a mother to elicit support. In evolutionary terms, a mother who experiences adversity—such as a lack of support from the baby’s father or social group—could “bargain” for more help by stopping activities that are beneficial to the baby and even to herself. This behavior, costly to everyone, herself included, would signal, through her visible depressive symptoms, that she cannot continue to care for the baby on her own and she truly needs help. This could encourage the father or others to step in and provide the necessary assistance, ensuring the survival of the offspring.

Our Work. To test this hypothesis, we conducted a study in Uganda, involving nearly 300 women around the time of giving birth. Our focus was on whether women showing signs of depression received more cooperation from their social network—specifically, their spouse, kin, and other close individuals—compared to those who did not display such symptoms. In our work, we propose to use a quasi-experimental method called regression discontinuity design (RDD), an empirical method to estimate the potentially positive causal effect of perinatal depression on cooperation within a mother’s social group, despite an expected negative relationship between the two. The negative relationship between social support and maternal well-being is bi-directional: lack of support can cause depression, while depression may reduce support as individuals tend to isolate themselves. This well-known relationship can be seen in the downward sloping predicted lines in Figure 1. However, the bargaining hypothesis suggests that depressive symptoms may also increase cooperation from others, adding a positive effect from depression to support. But how could we test for that since one cannot randomize who is depressed and who is not? Our proposed method is based on the assumption that around the threshold for depression advised by psychiatrists, being a few points below or a few points above is almost random. In this case, we could estimate whether there is a positive “jump” in support between the women right below and those right above such threshold.

Key Findings. Our findings provide some evidence in favor of the bargaining hypothesis. Comparing women just below and just above the threshold for potential depression, we observed that mothers who were at the threshold of displaying depressive symptoms did indeed receive more help, particularly from their spouse (see the positive jump/discontinuity at the threshold in the graphs of Figure 1), maternal grandparents, and a few other close kin. These results suggest that, at least in some cases, maternal depression might trigger increased cooperation from key individuals in a mother’s network.

Interestingly, non-kin such as neighbors and friends, while generally supportive, did not seem to react as strongly to a mother’s depressive symptoms. This aligns with the idea that depression’s signaling function might be more effective among genetic relatives, whose fitness is directly tied to the survival of the child.

Figure caption: Discontinuity plot: Spouse. Each graph represents the predicted line resulting from a linear regression of the corresponding support type on the depression index with a structural break at 0 (equivalent to EPDS=10), and a 95% confidence interval. The vertical axis shows the respondent’s assessment of how often (Always=5, Most of the times=4, Some of the time=3, Rarely=2, Never=1) the individual named above typically: watched children for her (Watch), helped take care of her or the baby in case of sickness (Care), gave guidance about taking care of the baby (Guide), talked with the respondent (Talk), and would give money in case of need (Money). See the original EHB article for other relationships.

The Role of the Spouse: A Critical Relationship. Among all relationships, the one with the baby’s father appeared to be the most important. Women with more support from a loving and helpful partner were at significantly lower risk for depression. Conversely, conflicting or controlling relationships elevated the risk of depression. The baby’s father not only provided the most help but also responded most strongly to his partner’s early signs of depression. This was especially true if the relationship with the mother was one of conflict (a paradox at first, but precisely what is predicted by the bargain idea). This could highlight the evolutionary significance of pair bonding and cooperative parenting.

In ancestral environments, where raising a child often required contributions from both parents (and others), depression could have evolved as a strategy for mothers to secure greater investment from their partner, ensuring the survival of their offspring. Our findings support this idea, suggesting that perinatal depression may indeed catalyze cooperation from fathers and close kin.

Implications for Mental Health and Public Health Policy. While our study provides some evidence for the bargaining model, it’s important to emphasize that the findings do not imply that maternal depression is beneficial or should be left untreated. Depression is a painful condition that requires serious attention and care. However, understanding its potential evolutionary roots could open new avenues for treatment, particularly in the realm of family and marital therapy.

If maternal depression serves as a signal of need within a social group, then interventions that focus on improving relationships and increasing support from family members could be particularly effective. For example, recent research has shown that psychotherapy interventions, such as cognitive behavioral therapy (CBT), can have positive and lasting effects on women’s mental health and their children’s well-being. Our findings suggest that incorporating family therapy, especially to address conflicts with a spouse or other family members, could further enhance these treatments.

Conclusion: Depression as a Call for Cooperation. Maternal depression remains a complex and multifaceted condition. While much of the focus has been on its negative consequences, our research adds to the growing body of evidence suggesting that it may also serve an adaptive function. By acting as a catalyst for increased cooperation, maternal depression might help mothers in challenging environments secure the support they need to care for their offspring.

Understanding depression through an evolutionary lens doesn’t diminish the suffering it causes but offers a deeper perspective on why such a costly condition might exist. As we continue to explore the relationship between mental health and social support, this knowledge could pave the way for more effective treatments that not only address the symptoms of depression but also the underlying social dynamics that contribute to its persistence.

Read the original article: Cassar, A., Schneider, P.H., & Ugwu, C. (2024). Maternal depression as a catalyst for cooperation: evidence from Uganda. Evolution & Human Behavior, 45(4), 106575.

 

Assistant Professor position in Psychology at Knox College

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Knox College is seeking an Assistant Professor in Clinical or Social Psychology, and either way they’re interested in someone who takes an evolutionary approach. Review of applications begins Oct 18th 2024. See here for more details: https://apply.interfolio.com/154607

For more jobs in the evolutionary social sciences, check out our Evolutionary Social Science wiki, which is maintained by members like you. Know of a job in the evolutionary social sciences? Please post it on the wiki.