A recent documentary broadcast on Radio 4 presented by Victoria Gill no doubt sparked a recent editorial in The Guardian on the topic of the increased post-fertility lifespan, the menopause, in orcas. The documentary followed Darren Croft of the University of Exeter and Daniel Franks of the University of York and other studying the Southern Resident orca clan, which boasts a number of older female orcas who have survived well after their reproductive years have ending, including J2 or “Granny” who had her last calf in the 1960s and is still swimming at somewhere between 80-100+ years old today. This is similar to the menopause seen in women today, and in only a single other mammal species, the short-finned pilot whale. The phylogenic oddity of the menopause, appearing not in our close relatives the chimpanzee but in animals with very different evolutionary histories and habitats to us is enough alone to spark a inquiring scientist to investigate how the menopause evolved.
Furthermore, under an earlier and more narrow definition of evolutionary fitness, the menopause has been seen to be evolutionarily inexplicable. An understanding of the reproductive success of an individual as increasing the frequency of their alleles in subsequent generations means that suddenly stopping reproducing seems the exact opposite of a trait that evolved by natural selection. But Croft and Franks argue in this programme that the orca menopause did evolve by natural selection in part due to the post-reproductive females taking care of their adult sons they already have rather than pushing out as many kids as possible. This therefore increasing the number of their sons’ children surviving to breed and so on, so her genes increase in frequency in the population. Rather than increasing her own personal reproductive fitness, the post-reproductive orca uses her sons to increase the frequency of her genes in the population. This account is not particularly revelatory, it is an application of W.D. Hamilton’s ideas of inclusive fitness applied to a particular case.
However, in The Guardian editorial, the author argues that research into the evolution of any trait in any non-human animal is irrelevant to human society and attempts to infer “what constitutes a well-ordered society”, in this case the value of older women in a society, from facts about how a trait has evolved is dangerous. But such a wholesale dismissal of the cultural importance of an understanding of the evolutionary basis does not accomodate the view of biology and nature having a dialectic materialist relationship, the phenomenon of gene-culture coevolution which has been proposed to occur in both humans and several whale species notably including the orca. In the scientists studying animal culture, culture is considered to be behavioural practices transmitted through a population through social learning and not genetic inheritance, this is the lowest common denominator definition of culture and not as intricate as human culture, but significant none the less. By the gene-culture coevolution model, as Hal Whitehead and Luke Rendell describe in The Cultural Lives of Whales and Dolphins, the two streams of information in a cultural species, the genetic and the cultural, can interact. Whilst, as E.O. Wilson termed it, “genes hold culture on a leash” as our culture cannot reach beyond the limits of our biological limits, the favouring a behaviour by a culture, such as adult milk drinking in humans, can lead to the natural selection of genes allowing the most successful use of a cultural trait, which is why the frequency of genes for lactose tolerance is highest in pastoral populations.
Using an understanding of gene-culture coevolution, we can try to understand the evolutionary origins of our cultural practices, or most likely how the biological capacities to develop such cultural practices arose. Indeed, in the orcas the menopause may be one of the key elements in allowing the orcas to transcend the realm of purely genetic inheritance and learn socially and so develop their own culture.
As Whitehead and Rendell discuss, the menopause may have evolved as a means of preserving cultural knowledge. The older females are saved by the menopause from the risks of increasingly infrequent pregnancy at the age of 40 or older and so can live into their 80s and older. These grandmothers play an important role in helping raise children, especially in systems which Sarah Blaffer Hrdy describes as cooperative breeding, where the child is reared by a large extended family of parents, aunts and uncles, siblings, grandparents etc., the proverbial village it takes to raise a child, which she believes is likely the social organisation of early humans.Additionally, these older members of the (human) group will have amassed a great knowledge of the environment over time, which is very useful if a group is blighted by famines every 60 or so years and have to turn to alternative food sources, the knowledge of their edibility is preserved in the mind of the oldest grandmothers. Thus, cultural transmission of information may rely on these elders to preserve information, as in non-literate societies there is no way of preserving cultural information like DNA preserves genetic information, and applied to the early humans as to orcas. We look to orcas to give us clues as to how the human menopause evolved in part because of one of the key philosophical drivers of Darwin’s work, the principle of the consilience of inductions, as termed by William Whewell. By this, the power of a theory increase the more domains of empirical evidence it can explain. This is way Darwin bolstered this theory of evolution by natural selection using examples drawn from biogeography, embryology, behavioural instinct and the fossil record, and why modern menopause researchers use the evidence from orcas to increase the explanatory power of their theories. Crucially, the vast differences between women and whales, not least of all the lack of medical care received by the 80+ orcas, means that the menopause cannot be a pathological state in the orcas as their extended lifespan relative to the males cannot be explained by longevity alone. And explaining how the menopause evolved and therefore shows its advantages in a past environment, rather than dismiss as a pathological aberration of living longer, like Alzheimer’s disease, as some would argue, cannot be a dangerous thing.
I sense that I may be accused of spinning another “very interesting” evolutionary story, which has no relevance to human values and society now. But this society and values are supported by biological and social structures which have evolved, and upon which we have built our complex ethical and social systems. But we did not imagine these systems out of thin air a few thousand years ago, they have a long a gradual pre-history. We eventually had an explosion of social complexity in humans when our culture began to “rachet”, to become increasingly more complex as we built upon the knowledge of others, we stood on the shoulders of giants. It would be intellectually dishonest to refuse to try to encompass politically charged phenomena under an evolutionary frame-work if we call ourselves modern biologists, especially one so counter-intuitive as the menopause, in humans and in orcas. Indeed, not giving an accurate account of the origins of the menopause, gives power to those who would like to dismiss the menopause as pathological and showing womens’ inherent inferiority. Understanding the events of your body as having been selected for in evolutionary time for the advantages it brought your genes can only help understand and learn to value how you experience life. As Croft mentions in the radio programme, many menopausal women draw strength from learning of the menopasual orcas, as it shows “the important of older females in society really valued that story [and] empowered them to think what might be their role in society”. Revealing the evolutionary importance of a trait, thorugh comparison with those who also share this trait across the animal kingdom, can lead us to consider whether our social prejudices are the only way to be, and whether we could reassess our values in light of this.
I believe some of the confusion on these issues are draw in part from the different meanings of the word “value”. The evolutionary biologists uses the concept of evolutionary value as how a trait performs in a cost-benefit analysis in terms of the survival of the organisms. In contrast, value is used most commonly to refer to ethical values, which I will argue are mostly socially determined, though by the laws of causation these must have some sort of basis within the limits of biological possibility. Therefore the science vs. humanities debate comes to its apotheosis. Critics may claim that biologists equate is with ought, that what had the greatest evolutionary value in the human past is what we should value ethically today. I disagree with this position, but doing so does not mean that we should ignore the role of biology in being the basis from which culture springs, but something which does not tether all its ties to biology, as it can reach down and change it biological basis. Life is dialectic; never anything but subtle and dynamic.