The fearful ape hypothesis proposes that heightened fearfulness in humans is adaptive. However, despite its attractive anthropocentric narrative, the evidence presented for greater fearfulness in humans versus other apes is not sufficient to support this claim. Conceptualization, context, and comparison are strongly lacking in Grossmann's proposal, but are key to understanding variation in the fear response among individuals and species.

Grossmann's impressive article indicates that – along with attentional biases, expansion of domain-general processes of learning and memory, and other temperamental tweaks – heightened fearfulness is part of the genetic starter kit for distinctively human minds. The learned matching account of emotional contagion explains how heightened fearfulness could have promoted the development of caring and cooperation in our species.

Fear can undermine cooperation. It may discourage individuals from collaborating with others because of concerns about potential exploitation; prompt them to engage in defensive aggression by launching a preemptive strike; and propel power-seeking individuals to act dominantly rather than compassionately. Therefore, accumulated evidence requires a more contextualized consideration of the link between fear and cooperation in adults.

Children's cooperation with peers undergoes substantial developmental changes between 3 and 10 years of age. Here we stipulate that young children's initial fearfulness of peers' behaviour develops into older children's fearfulness of peers' evaluations of their own behaviour. Cooperation may constitute an adaptive environment in which the expressions of fear and self-conscious emotions regulate the quality of children's peer relationships.

Grossmann's argument for the “fearful ape hypothesis” rests on an incomplete review of infant responses to emotional faces. An alternate interpretation of the literature argues the opposite, that an early preference for happy faces predicts cooperative learning. Questions remain as to whether infants can interpret affect from faces, limiting the conclusion that any “fear bias” means the infant is fearful.

Grossmann presents an exciting and interesting theory on the function of fearfulness. In this commentary it is argued that fearfulness may be a byproduct of a larger executive functioning network and these early regulatory skills considered more broadly may be key building blocks for later cooperative behaviors.

Grossmann used evolutionary analysis to argue for the adaptive nature of fearfulness. This analysis, however, falls short of addressing why negative affectivity is maladaptive in contemporary Western societies. Here, we fill the gap by documenting the implied cultural variation and considering cultural (rather than biological) evolution over the last 10,000 years to explain the observed cultural variation.

In his article, Grossmann argues that, in the context of human cooperative caregiving, heightened fearfulness in children and human sensitivity to fear in others are adaptive traits. I offer and briefly defend a rival hypothesis: Heightened fearfulness among infants and young children is a maladaptive trait that did not get deselected in the process of evolution because human sensitivity to fear in others mitigates its disadvantageous effects to a sufficient extent.

According to Grossmann, the high levels of cooperation seen in humans are the result of a “virtuous caring cycle” on which the increased care that more fearful children receive brings increased cooperative tendencies in those children. But this proposal overlooks an equally well supported alternative on which children's anxiety – not a virtuous caring cycle – explains the cooperative tendencies of humans.

Humans are not only fearful apes, but we also communicate our fear using social cues. Social fear displays typically elicit care and assistance in the real world and the lab. But in the psychology and neuroscience literature fearful expressions are commonly interpreted as “threat cues.” The fearful ape hypothesis suggests that fearful expressions should be instead considered appeasement and vulnerability cues.

We review research suggesting that several of the functions attributed to fear, in the target article's fearful ape hypothesis, also apply to supplication and appeasement emotions. These emotions facilitate support provisioning from others and the formation and maintenance of cooperative relationships. We therefore propose that the fearful ape hypothesis be expanded to include several other distinctively human emotional tendencies.

Grossmann proposes the “fearful ape hypothesis,” suggesting that heightened fearfulness in early life is evolutionarily adaptive. We question this claim with evidence that (1) perceived fearfulness in children is associated with negative, not positive long-term outcomes; (2) caregivers are responsive to all affective behaviors, not just those perceived as fearful; and (3) caregiver responsiveness serves to reduce perceived fearfulness.

The fearful ape hypothesis revolves around our ability to express and perceive fearfulness. Here, we address these abilities from a social learning perspective which casts fearfulness in a slightly different light. Our commentary argues that any theory that characterizes a (human) social signal as being adaptive, needs to address the role of social learning as an alternative candidate explanation.

While infant fearfulness, and its expression via crying, may have been adaptive in our evolutionary history, for modern parents, crying can be challenging to respond to. We discuss how and why prolonged crying can raise the risk for difficulties with adult care. Given that crying is the most-reported trigger for shaking, its potential to elicit maladaptive responses should not be overlooked.

In the fearful ape hypothesis, Grossmann argues that heightened fearfulness increases human-unique cooperation. We suggest that this conclusion, however, may be premature. In particular, we question Grossmann's singling out of fear as the affective trait that enhances cooperative care. Additionally, we problematize the extent to which heightened fearfulness in humans, and its association with human-unique cooperation, are supported empirically.

The target article posits that caregiver cooperation rendered heightened expression of childhood fear an adaptive response to threat. I argue that caregiver cooperation rendered childhood fear expression less accurate as a signal of actual threat, and hence less effective for harm avoidance. Further, other emotional expressions that avoid unwarranted caregiver stress may be more likely to evoke needed care.

The “fearful ape hypothesis” could be regarded as one aspect of a more general “suffering ape hypothesis”: Humans are more likely to experience negative emotions (e.g., fear, sadness), aversive symptoms (e.g., pain, fever), and to engage in self-harming behavior (e.g., cutting, suicide attempts) because these might motivate affiliative, consolatory, and supportive behavior from their prosocial environment thereby enhancing evolutionary fitness.

In order to address why the number of patients suffering from anxiety and depression are seemingly exploding in Western, educated, industrialized, rich, and democratic (WEIRD) countries, it is sensible to look at the evolution of human fearfulness responses. Here, we draw on Veit's pathological complexity framework to advance Grossmann's goal of re-characterizing human fearfulness as an adaptive trait.

Grossmann proposes an interesting framework to explain how heightened fearfulness among humans could be evolutionarily adaptive in the context of cooperative care. I would like to propose that cooperative care may also be a potential mechanism promoting enhanced happiness expression among humans, shedding light on questions about the scope and boundary of the fearful ape hypothesis.