Thursday, July 14, 2011

Notes on Fatherhood (ch. 1)

I am just starting to read through Fatherhood: Evolution and Human Paternal Behavior a book I have been looking forward to reading for a while.

The book is written by these two anthropologists- here and here. My interest in the evolution of fatherhood stems from two professional interests: (a) my interest in evolutionary biology (especially the biology of aging), and (b) the creation and evolution of patriarchy (something males have obviously played a major role in!).

Scholars in the humanities and social sciences often fail to take seriously the latest insights of findings from the evolutionary sciences, in terms how they might enhance our understanding of human behaviour. And I want to try to help bridge this gap.

I also have a personal interest in the topic of fatherhood as I am the father of three children myself. So I am looking forward to making my way through this book in the weeks to come. I thought I would keep some notes here on the blog, for future reference.

From Ch. 1, the chapter starts by noting the experiments of the geneticist Angus John Bateman who bred captive fruit flies. Bateman found that, when food was in ample supply, male and female fruit flies had different opportunities for reproductive success. The most important limiting factor for female reproductive success is resources. But for males the most important limiting factor is access to females. If access to females increases so to does the number of offspring the male fruit fly fathers. So access to one female yields the male X offspring, access to two mates yields 2X offspring, etc. But the same is not true for females. Access to more mates does not increase the number of offspring of the female. This insight helps explain the internal biological priorities that males and females make. Males compete for limited reproductive opportunities, females prioritize access to those resources necessary for reproduction. Males and females that failed to do this successfully were evolutionary "losers" in the sense that the genes of those more successful at mating and getting resources were more likely to have been passed on to future generations.

The chapter also mentions the work of Robert Trivers who argues that the key to understanding sexual differences is the relative parental investment between males and females. A contrast is later drawn between mammals and birds which bears this out. Birds lay eggs and so, in principle, either male or female could invest in the care of siting on the egg. But for mammals the stakes are very different, due to fact that mammals have internal gestation. In birds 90% of species are socially monogamous and males invest in offspring. But for mammals that number is very low, 3-5%. This raises important questions like - in which species of mammals does parental care arise? And what does this care entail? The tiki monkey in South Africa is an example. Males play an important role in transporting the young. But the male tiki monkey is the exception rather than the norm. Male parental care is "largely absent among our more closely related primate cousins, Old World monkeys and apes" (11). "...[O]ur ancestors from 6 million years ago were living in polygynandrous mating systems [which means any given male cannot know with much certainty which specific offspring, if any, are his] and not providing parental care. At the start there is no glimmer of parental care in our ancestors' eyes" (16).

What about parental care during early Hominin and Homo life? The authors note the important fossil finds of recent years and the sketchy picture we have of life in the past 6 million years. But one important factor that is emphasized is the human brain. The evolution of bipedalism (walking on two feet) limited the wider maternal pelvis needed to make large brained hominin babies possible. Instead, the timing of the brain growth was delayed until after birth (rather than prenatal). A consequence of this was that human babies are more needy. More care is needed than a mother alone can provide. "The process of slower brain development (and more helpless newborns) appears to have been more important with Homo heidelbergensis but did not reach its modern pattern until Homo sapiens 150,000 years ago. Accordingly, other caregivers, from grandmothers to aunts, older daughters to fathers, likely took on increased roles, the closer our ancestors came to the present Homo sapiens." (21).

The authors then summarize (pp. 26-30) their account of when and how human parental care originated (I have broken things down into numbered points to make it easier for me to keep track of the main points, and below are just some of the main conclusions noted):

(1) parental care today is recent in our evolution (it did not exist when our ancestors split from today's chimpanzees and bonobos 6 million years ago)

(2) human pair bonds may have originated in male mate-guarding

(3) with (2) permanent associations that made a greater sexual division of labour and greater male provisioning were possible.

(4) (3) brought about other changes....couples that slept next to each other at night meant that fathers would be in close proximity to their offspring. This helps foster parental-offspring attachment.

(5) reductions in mortality also allow more fathers to survive to watch their children grow and to partake in their socialization.

That concludes my notes from chapter 1 of the book. It may be a while before I can return with notes from the next few chapters (I have a paper I need to finish this summer). But there is a wealth of information and insights in this first chapter. And the authors have given me plenty to think about in terms of how these insights from evolutionary anthropology can help us better understand the complex social life of human beings today.