Cooperative breeding and monogamy in mammalian societies

Cooperative breeding and monogamy in mammalian societies
Dieter Lukas & Tim Clutton-Brock (2012)


Abstract

Comparative studies of social insects and birds show that the evolution of cooperative and eusocial breeding systems has been confined to species where females mate completely or almost exclusively with a single male, indicating that high levels of average kinship between group members are necessary for the evolution of reproductive altruism. In this paper, we show that in mammals, the evolution of cooperative breeding has been restricted to socially monogamous species which currently represent 5 per cent of all mammalian species. Since extra-pair paternity is relatively uncommon in socially monogamous and cooperatively breeding mammals, our analyses support the suggestion that high levels of average kinship between group members have played an important role in the evolution of cooperative breeding in non-human mammals, as well as in birds and insects.

Social bonds in birds are associated with brain size and contingent on the correlated evolution of life-history and increased parental investment

Social bonds in birds are associated with brain size and contingent on the correlated evolution of life-history and increased parental investment
Susanne Schultz & Robin Dunbar; April 2010
Biological Journal of the Linnean Society


Abstract

In birds, large brains are associated with a series of population-level phenomena, including invasion success, species richness, and resilience to population decline. Thus, they appear to open up adaptive opportunities through flexibility in foraging and anti-predator behaviour. The evolutionary pathway leading to large brain size has received less attention than behavioural and ecological correlates. Using a comparative approach, we show that, independent of previously recognized associations with developmental constraints, relative brain size in birds is strongly related to biparental care, pair-bonding, and stable social relationships. We also demonstrate correlated evolution between large relative brain size and altricial development, and that the evolution of both traits is contingent on biparental care. Thus, biparental care facilitates altricial development, which permits the evolution of large relative brain size. Finally, we show that large relative brain size is associated with pair-bond strength, itself a likely consequence of cooperation and negotiation between partners under high levels of parental investment. These analyses provide an evolutionary model for the evolution of and prevalence of biparental care, altricial development, and pair-bonding in birds.

Evolution of Monogamy, Paternal Investment, and Female Life History in Peromyscus

Evolution of Monogamy, Paternal Investment, and Female Life History in Peromyscus
Eldin Jasarevic, Drew H Bailey et al.; 2013


Abstract

The timing of reproductive development and associated trade-offs in quantity versus quality of offspring produced across the life span are well documented in a wide range of species. The relation of these aspects of maternal life history to monogamy and paternal investment in offspring is not well studied in mammals, due in part to the rarity of the latter. By using five large, captive-bred populations of Peromyscus species that range from promiscuous mating with little paternal investment (P. maniculatus bairdii) to social and genetic monogamy with substantial paternal investment (P. californicus insignis), we modeled the interaction between monogamy and female life history. Monogamy and high paternal investment were associated with smaller litter size, delayed maternal reproduction that extended over a longer reproductive life span, and larger, higher quality offspring. The results suggest monogamy and paternal investment can alter the evolution of female life-history trajectories in mammals.

Constrained mate choice in social monogamy and the stress of having an unattractive partner

Constrained mate choice in social monogamy and the stress of having an unattractive partner
Simon C Griffith at al.; 2011
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3145185/


Abstract

In socially monogamous animals, mate choice is constrained by the availability of unpaired individuals in the local population. Here, we experimentally investigate the physiological stress endured by a female (the choosy sex) when pairing with a non-preferred social partner. In two experimental contexts, female Gouldian finches (Erythrura gouldiae) socially paired with poor-quality mates had levels of circulating corticosterone that were three to four times higher than those observed in females that were paired with preferred mates. The elevated level of this stress hormone in response to partner quality was observed within 12 h of the experimental introduction and maintained over a period of several weeks. Our findings demonstrate the extent of intra-individual conflict that occurs when individuals are forced to make mate-choice decisions that are not perfectly aligned with mate-choice preferences. The elevated level of corticosterone also suggests a mechanistic route through which females might adaptively manage their responses to intersexual conflict over reproductive investment.

Automatic inattention to attractive alternatives: the evolved psychology of relationship maintenance

Automatic inattention to attractive alternatives: the evolved psychology of relationship maintenance
Jon K. Maner et al., 2008

http://freud.psy.fsu.edu/faculty/maner/maner%20rouby%20gonzaga%20EHB%2008.pdf

Abstract

There can be important reproductive benefits to maintaining a long-term romantic relationship. As a result, humans may possess evolved psychological mechanisms designed to help them maintain their commitment to a long-term mate, particularly when faced with attractive alternative relationship partners. The current study identifies a relationship maintenance process that involves being inattentive to alternative relationship partners. Experimentally eliciting thoughts and feelings of romantic love — an emotion thought to have evolved for the purpose of relationship maintenance —reduced attention to alternative partners at an early, automatic stage of visual perception. Consistent with evolutionary models of mate selection, this reduction in attention was observed only for opposite sex targets displaying high levels of physical attractiveness. This research illustrates the utility of integrating evolutionary models of mating with theory and method from cognitive science.

The riddle of monogamy:

>Evolutionary psychologists have stressed, perhaps even overstressed, the philandering nature of men. In their defence, they often cite the fact that 84 per cent of world societies condone polygyny. (The implicit or explicit contrast is with the tiny prevalence of polyandry (0,5 per cent) which is often used to document the greater sexual appetite and sexual proprietariness of males compared with females.) But counting societies is not the same as counting people. The vast majority of the world's population inhabitat societies that prohibit polygyny and, even where it is legal, only about 10 per cent of men take multiple wives. A central question about human behaviour therefore is why men, who can gain such reproductive advantages from promiscuity and polygyny, in the main elect to be monogamous? As yet there is no definite answer, but there is no shortage of contenders. Some believe that monogamy was driven by women, some by men, but most agree that it was a compromise that benefited both sexes.<

Anne Campbell, A mind of her own, 2002

Monogamy and Brain Size:

Among the birds and mammals in general, the spezies with the biggest brains relative to body size are precisely those that mate monogamously. Those that live in large anonymous flocks or herds and mate promiscuously have much smaller brains.

The birds make it especially clear that the real issue is strong, resilient, long-lasting pairbonds. Birds that mate monogamously come in two quite different kinds. There are those, like many common garden birds such as robins and tits, that chose a new mate each breeding season. But there are many others, such as many birds of prey, the owls and most of the crow and parrot families, that mate for life. It is this second group, which have the biggest brains of all among the birds, far bigger than those that are seasonally monogamous, and this is true even when we control for differences in lifestyle, diet and body size.

Robin Dunbar, How many... Dunbar's Number and other Evolutionary Quirks