This entry was written by Lachlan Barrett as part of a project done in BIAN 2133 ‘Human Reproductive Strategies’ at The Australian National University in 2019 Semester 2.
Introduction
Mothers are predominantly the primary carers of their offspring, carrying the burden of gestation, lactation, and more often than not, caregiving (Abraham & Feldman, 2018). This responsibility can be quite cumbersome for the mother. To mitigate that strain, humans have evolved cooperative breeding; where the care of offspring can be undertaken by individuals other than the mother (Nishiyama, Oishi, & Saito, 2015), including the father
This essay will present the case that human males have evolved to place greater emphasis on fatherhood; having a more significant role in the upbringing of their offspring. To do this; humans will be compared to other mammals to discern core similarities and differences of fatherhood. Then, Life History Theory (LHT) will be used to help explain the fundamental trade-offs that occur when human males invest more in parenting. Finally, Female Mate Choice (FMC) will also be used to ascertain the role sexual selection has had on shaping fatherhood.
Main Text
Fatherhood, A Rarity in the Mammal Class
Within the class of Mammalia, most species have internal gestation and some form of suckling mechanism after birth, which is experienced solely by the mother. Most mammals’ males, on the other hand, do not provide much parental investment in their offspring beyond the contribution of sperm (Geary, 2000). This majority includes our closest living relatives, Chimpanzees which will generally ignore infants, with predominate care being carried out by females (Nishiyama et al., 2015).
For the remaining species of mammals that have a somewhat equitable investment in offspring, they demonstrate specific patterns in their behaviour. Such patterns include living shorter life spans, having large litter sizes, or living in isolated family groups (Geary, 2000). Humans do not follow any of these generalised patterns, as they have long life spans, usually have only one offspring per birthing period, and live in groups that have multiple males and multiple females. This deviation presents a peculiar case as to why humans have evolved the mechanism of fatherhood.
Comparing humans to other primates also shows some unique features of fatherhood. In Siamangs, for example, females take complete care of their offspring for their first year of life, then in the second year, Siamangs other than the mother, including males will carry the infant (Fernandez-Duque, Valeggia, & Mendoza, 2009). This example highlights that paternal care exists in some capacity in Primates. Even within human societies, levels of paternal care can be highly variable between cultures (Abraham & Feldman, 2018). Despite fatherhood in humans shown to be more prevalent compared to other mammals, it is far from obligatory.
Life History Theory: The Trade-off Between Mating and Parenting Investments
LHT presents a framework to conceptualise strategies undertaken by organisms; investing in specific strategies results in fundamental trade-offs between other competing strategies. These trade-offs include investing in somatic or reproductive efforts; within reproductive effort, organisms can ‘choose’ to invest in mating or parenting effort. Males, as opposed to females, focus more into their mating effort, which means they dedicate more time and resources into finding and acquiring mates (Gettler, McDade, Feranil, & Kuzawa, 2011). As mentioned previously, fatherhood in humans is not universal between different cultures and societies; however, paternal care should be considered as contributions by the male in terms of direct and indirect care.
One such contribution is assisting females in direct childcare of their offspring; this can include: carrying the offspring, teaching the moral, cultural, or social rules; or simply being present to assist the mother (Gray & Crittenden, 2014). As for indirect care, paternal investment can provide: protection against infanticide and other dangers, food provisioning for both offspring and the mother, and wealth transfers in terms of inheritance or maintain wellbeing (Geary, 2000). Furthermore, research has shown that fatherhood reduces levels of testosterone, it is hypothesised to occur to allow for a better hormonal environment for being a better caregiver (Abraham & Feldman, 2018; Gettler et al., 2011).
From an evolutionary perspective, this is beneficial for the mothers as they have opportunities for rest, which can bring them back to a receptive period faster, and for fathers, this may assist in paternal certainty, as being close to the family can allow males to defend against cheating.
Female Mate Choice, Shaping Better Fathers
It is believed that FMC has had a role in shaping the prevalence of fatherhood in humans. FMC is when females of the species inspect potential mates for signals that indicate quality, whether that be in the form of ornamentation or more subtle social behaviours or cues. FMC may have shaped the need for fatherhood due to females requiring assistance in caring for offspring. For a hominid of our size, humans have relatively short inter-birth intervals, of which can be cumbersome for females, as raising multiple dependent infants is costly, both energetically and time-consuming (Gray & Crittenden, 2014).
When looking for a long-term relationship (i.e. a father for their children), females tend to look for mates that show attributes that correlate with forming lasting bonds; they also look for abilities that highlight viable provisioning (Gray & Crittenden, 2014). These traits are important because they have two evolutionary functions: to screen potential mates for their capacity to provide for the female and the subsequent offspring and to avoid potential mates that may abandon the offspring and their partner (Abraham & Feldman, 2018). Males that display these kinds of behaviours may not be necessarily the ‘fittest’ from a natural selection perspective, but through FMC, human males have evolved to be more caring, considerate, and resourceful as they indicate a good potential father.
Conclusion
The evolution for fatherhood in humans has provided a mechanism for males to invest more in their offspring beyond the cost of contributing gametes. Humans are unique within the animal kingdom, as they contradict the primary traits of fatherhood: isolated family groups, short life spans, and large litter sizes. LHT highlights the importance of trade-offs as investing more in parenting; males miss out of maximising their mating opportunities. Finally, FMC has shaped the utility of forming long-term relationships and the importance of provisioning by males, essentially making better fathers.
Literature Cited
Abraham, E., & Feldman, R. (2018). The neurobiology of human allomaternal care; implications for fathering, coparenting, and children's social development. Physiology & Behavior, 193, 25-34. doi:10.1016/j.physbeh.2017.12.034
Fernandez-Duque, E., Valeggia, C. R., & Mendoza, S. P. (2009). The Biology of Paternal Care in Human and Nonhuman Primates. Annual Review of Anthropology, 38, 115-130. doi:10.1146/annurev-anthro-091908-164334
Geary, D. C. (2000). Evolution and Proximate Expression of Human Paternal Investment. Psychological Bulletin, 126(1), 55-77. doi:10.1037/0033-2909.126.1.55
Gettler, L. T., McDade, T. W., Feranil, A. B., & Kuzawa, C. W. (2011). Longitudinal evidence that fatherhood decreases testosterone in human males. Proceedings of the National Academy of Sciences, 108(39), 16194. doi:10.1073/pnas.1105403108
Gray, P. B., & Crittenden, A. N. (2014). Father Darwin: Effects of Children on Men, Viewed from an Evolutionary Perspective. Fathering, 12(2), 121. doi:10.3149/fth.1202.121
Nishiyama, K., Oishi, K., & Saito, A. (2015). Passersby Attracted by Infants and Mothers' Acceptance of Their Approaches: A Proximate Factor for Human Cooperative Breeding. Evolutionary Psychology, 13(2), 147470491501300210. doi:10.1177/147470491501300210