Monogamy in Mammals

The readings in class lightly touched on monogamy in mammals, stating that lactation was the main reason for biparental care; the offspring was vulnerable during this weaning process, and the male would function as the protector of both female and offspring. In class, we discussed which types of parenting were best for which environments. We came to the conclusion that biparental care is only advantageous in some cases, like humans and some primates, because of the ratio of energy expended is very high, along with the offspring survival rate. However, there can’t be as much mating if a lot of energy is being spent on caring for the young.

Christopher Opie and other researchers determined that male infanticide was the main factor for social monogamy in primates. While other factors, such as mate guarding and parental care, were present in monogamous species, male infanticide preceded these factors, leading the researchers to believe that this was the driving force behind the development of social monogamy; the other traits came after. Apes were referenced many times, as they have a very high rate of male infanticide in their communities and are not socially monogamous. The other article by Lukas and Clutton-Brock suggests that this hypothesis of male infanticide is not the case; they argue that social monogamous groups evolved from ancestors where the males couldn’t defend access to more than one female at a time due to the female’s solitude, and thus had to become monogamous. This then led to paternal care and mate guarding, when communities began to form. They referenced the article by Opie et al, saying that there weren’t enough species tested in their study and their conclusions were not completely exclusive (regarding lactation).

Lukas’and Clutton-Brock’s article proved to be more convincing. Not only did they include many relevant statistics about species studied or previous studies (i.e. the 2545 species that were studied overall, the Z-score, or number of standard deviations from the mean, regarding the sociality of species, etc), but they rendered the first article inconclusive by their mention that the BayesTraits model doesn’t prove the association between the evolution of social monogamy and lactation periods in females; the BayesTraits model suggests an independent evolution of the aforementioned traits. This makes me believe that the studies and statistics presented by Lukas and Clutton-Brock are more developed and sophisticated, compared to those of Opie et al.

These articles did change my understanding, but not by a lot. I work with Lincoln Park Zoo as a new type of teen intern (dubbed Career Explorer), and I have spent a lot of time reviewing primate behavior and their social structures. Seeing monkeys and apes interact up close put these studies into perspective, and gave me a better understanding of how social monogamy can be advantageous to some but detrimental to others. The evolutionary aspect of both articles was very enlightening as well.

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