This entry was written by Dean Rub as part of a project done in BIAN 6133 ‘Human Reproductive
Strategies’ at The Australian National University in 2019 Semester 2.
Introduction
The expression of paternal care amongst most mammalian species show a strong lack. However, small segments within the primate linage show incidences of behavioral paternal qualities amongst a small few species of nonhuman primates. These few expressions have been attributed to their sociality and biological makeup. A strong association amongst these nonhuman primate species is the expression of monogamy or pair-bonded mating systems. Nonhuman primate species that will be covered throughout this wiki entry, will include two marmoset species, the common marmoset (Callithrix jacchus) and the wied’s marmoset (Callithrix kuhlii). Two owl monkey species, the night monkey (Autus azarai azarai) and the southern night monkey (Aotus azarae), and only one Hylobatidae example, the siamangs (Symphalangus syndactylus). The causative hormones for the expression of paternal care behaviors include Prolactin, Vasopressin, Testosterone and Oxytocin (Storey and Ziegar, 2016; Fenandez-Durque et al, 2009). This entry provides an overview of the hormones that are associated with expression of these paternal care behaviors, and hypothesizes on how it’s heavily expressed in monogamous and pair bonded nonhuman primate mating systems.
In this entry, I will provide a brief overview of literature and create a discussion from their results, as well provide some evolutionary explanations on a biological level, with a link to the social networks that support the expression of these paternal care behaviors
Main text
Hormones involved in paternal care in nonhuman primates
Hormonal parameters indicate how certain behaviors are exhibited in terms of nonhuman primate paternal care. Storey and Ziegar (2016) investigated the biology in nonhuman primate paternal care, and how it influences social interactions. What they found was that early periods of post-peripartum, correlated with androgen hormones like testosterone concentrations, significantly declining, this had been associated with a contrasting reaction in the increase of oxytocin levels. Once testosterone is lowered, prolactin phases in to uphold the male’s body weight for paternal care. They also suggested that prolactin aids in infant contact. Thus, the time spent with one’s offspring is influenced by this hormonal change (Storey an Ziegar, 2016). These biological parameters can be considered an evolutionary explanations to how nonhuman primates initiate paternal care.
Further evidence supporting Storey and Ziegare’s (2016) findings on paternal care was elaborated more in, Fernandez-Durque et al’s (2009) investigation on the biology of parental care in human and nonhuman Primates. What they uncovered was that physiological substrates like vasopressin and prolactin aids in the facilitation for expressions of paternal based behaviors, and encourages the neuroanatomical reward pathways that are suggested to formulate these attachment bonds amongst fathers and infants, witnessed in monogamous and pair bonded mating systems. These findings further illustrate the evolutionary benefits pathed by these neuroanatomical reward pathways, which have encouraged the expression of paternal behaviors within monogamous and pair-bonded nonhuman primates.
Paternal Care in Siamangs
Incidences of proximity amongst siamangs seem to coincide with hormonal changes that further encourage these paternal qualities. The following paper conducted by Rafez et al (2012), examined these hormonal changes that bring out these paternal behaviors in the Hylobatidae branch. What Rafez et al uncovered is that S. syndactylus demonstrated direct forms of paternal care through infant carrying. Father-infant proximity drastically influence the hormonal chemistry of the father. This had been demonstrated in fecal examinations, with the androgen levels decreasing significantly during later period’s post-peripartum, where infant carrying had been apparent. Estrogen levels increased pre-peripartum and further in the first 8 weeks post-peripartum, this aided in father-infant proximity and correlated with the manifestation of paternal care behaviors (Rafez et al, 2012). These expressions of proximity and infant carrying is linked to fluctuating levels of androgen and estrogen These fluctuations are important evolutionary components that further our understanding on how paternal care has evolved within the S. syndactylus.
Polyandrous mating systems are exhibited in small portions of the Hylobatidae branch, that is predominantly monogamous and pair bonded. Lappan (2008) investigated the level of paternal care within S. syndactylus populations that were both monogamous and polyandrous. What Lappan found was that all males whom lived in polyandrous groups expressed a small level of paternal investment. Furthermore, monogamous based S. syndactylus exhibited significantly higher investments of paternal care, even considering the combined effort for polyandrous males and paternal care. These results hypothesize an evolutionary explanation that monogamy-based S. syndactylus, whom exhibit more paternal care due to higher confidences in paternity with comparison to polyandrous mating systems that are exhibited within certain populations of S. syndactylus.
Paternal Care In Marmosets
Hormonal changes within marmosets C. jacchus brings further supporting evidence to how paternal bonds are mediated amongst contact within monogamous driven species. This is expressed in Mota et al (2006) investigation which looked at hormonal changes that influence paternal and alloparental care in C. jacchus. What they found was prolactin weren’t influenced by infants’ birth, although the levels of prolactin drastically increased upon contact with infants and with incidences of infant caring. Cortisol was mediated with experienced fathers shortly before infant births, with respect to initiate affiliative bonds (Mota et al, 2006). The evolutionary explanation behind prolactin hypothesizes that it is an infant contact hormone, whilst cortisol is predominantly expressed for preparation of paternal care.
Marmosets have an interesting social paternal and alloparental care system that intrigues evolutionary biologists. Chimerism in animals is defined as an individual resulting from two or more zygotes. The expression of chimerism within the marmoset species C. kuhlii, has an interesting paternal component, that is further uncovered in Ross et al (2007) paper, on germline chimerism and paternal care within C. Kuhlii. What they found was that chimerism alters perceived relatedness amongst family members. Thus, influencing distribution of paternal care amongst all infants. As chimerism exhibits self-matching phenotypes, males had been seen carrying chimeric infants more often than non-chimeric infants. Chimerism is a strong evolutionary attribute for paternal investment amongst close family, whilst paternity isn’t guaranteed the perception of paternity greatly influences the group’s overall fitness.
Paternal care in owl monkeys
Paternal care amongst nonhuman primates is not normally exhibited, although in owl monkeys paternal care is quite intense and prevalent. The following study conducted by Rotundo et al (2005) examined infant development and paternal care amongst free ranging A. a. azarai. What they found was that infants were almost always carried within the first 4 weeks of life by both parents. After nursing periods, infants never returned to the mothers and had always been witnessed in proximity of adult males. Thus, suggesting that infants have a strong attachment towards fathers within the group, compared to their own mothers. These father-infant attachments give evolutionary biologist a glimpse into reasoning why A. a. azarai have chosen males as the primary caretaker.
A. azarae paternal care has many sociality components that influences the level of paternal care investment. This is further elaborated in Huck et al (2014) study on the links of genetic monogamy in social monogamous mammals. What they found was that the sharing of spaces and social proximity, formulates activities which influence pair bonding relationships. This in-turn reassures a high level of paternity for the A. azarae males, which had further correlated with an intense expression of paternal care behaviors. This development of monogamous based social structure further supports the evolutionary hypothesis that paternal investment is correlated with paternity assurance.
Conclusion
With concluding comments to this entry, this paper demonstrated that the expression of paternal based behaviors is heavily influenced at a hormonal and social level. Testosterone, vasopressin, oxytocin and prolactin concentrations are biological attributes that enable the expression of paternal based behaviors. These paternal care behaviors had only been expressed by nonhuman primates whom lived in monogamous and pair bonded mating systems. When looking into species we found that S. syndactylus had higher incidences of paternal care in monogamous mating systems compared to polyandrous individuals. Moreover, the expression of paternal care had been closely linked to low levels of androgens and proximity. C. jacchus demonstrated that prolactin drastically increases upon male-infant contact, thus encouraging paternal care behaviors. Furthermore, C. kuhlii confused adult males with false perception of paternity through chimerism, this enabled higher group paternal investment. A. a azarai demonstrated to form stronger bonds with fathers, compared to mothers suggesting that males are the primary caretakers. Moreover, A. azarae shared spaces and had a social framework around proximity, which influenced the creation of pair-bonding, this in-turn reassured high levels of paternity. These concluding comments support the evolutionary hypothesis that monogamous and pair bonded based nonhuman primates, formulate social environments that enables reassurance of paternity, this in-turn further enables the expression of paternal based behaviors that enhances offspring survivability to further promote ones individual fitness.
Literature Cited
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(1), 115–130.
Huck, M., Fernandez-Duque, E., Babb, P., & Schurr, T. (2014). Correlates of genetic monogamy in socially monogamous mammals: insights from Azaras owl monkeys. Proceedings of the Royal Society B: Biological Sciences, 281(1782), 20140195.
Lappan, S. (2008). Male care of infants in a siamang (Symphalangus syndactylus) population including socially monogamous and polyandrous groups. Behavioral Ecology and Sociobiology, 62(8), 1307–1317.
Mota, M. T. D. S., Franci, C. R., & Sousa, M. B. C. D. (2006). Hormonal changes related to paternal and alloparental care in common marmosets (Callithrix jacchus). Hormones and Behavior, 49(3), 293–302.
Rafacz, M. L., Margulis, S., & Santymire, R. M. (2012). Hormonal Correlates of Paternal Care Differences in the Hylobatidae. American Journal of Primatology, 74(3), 247–260.
Ross, C. N., French, J. A., & Orti, G. (2007). Germ-line chimerism and paternal care in marmosets (Callithrix kuhlii). Proceedings of the National Academy of Sciences, 104(15), 6278–6282.
Rotundo, M., Fernandez-Duque, E., & Dixson, A. F. (2005). Infant Development and Parental Care in Free-Ranging Aotus azarai azarai in Argentina. International Journal of Primatology, 26(6), 1459–1473.
Storey, A. E., & Ziegler, T. E. (2016). Primate paternal care: Interactions between biology and social experience. Hormones and Behavior, 77, 260–271.