Some initial caveats: I am by no means an expert in biological evolution, nor would I claim to be (for an easy-to-approach expert work on the ABCs, see Mayr 2002). It is imperative that sociologists become familiar with the principles, evidence, and logic of evolution for two reasons. First, despite recurring resistance and rejections against biological reductionism in the social sciences, sociology risks continuing to narrow its relevance, shrink its potential audience, and weaken its importance. Second, from a purely pedagogical standpoint, evolution is one of the best evidenced theories in scientific history. What theory is (a post, believe me, for another day), how to test it rigorously, and how a discipline can emerge and coalesce around a theory are all on display.

One further point worth disclosing: I readily embrace, in Randall Collins’ words, the fact that we are hairless apes. Simultaneously, I emphasize that this position does not have to equate “to human nature causes human behavior”. It means recognizing that (a) humans are animals, specifically mammals, primates, and one of the four great apes alive today (along with Orangutans, Gorillas, Chimps/Bonobos). (b) As such, our anatomy and behavioral propensities evolved over many millions of years. Modern humans, anatomically speaking, are approximately 250,000 years old, and those with the same cognitive abilities as us, today, are about 70000-50000 years old (Klein 2009). (c) If we do not recognize and examine our cousins and closest relatives, sociology is notably going to be missing key elements of understanding and explanation. (d) A science of society does not get to pick and choose which societies serve as models for explanation, theory-building, or empirical generalization. And, thus, without further ado…

Natural Selection

In the simplest nutshell, biological evolution can be summarized as such: traits that allow an organism to survive and biologically reproduce in an environment or traits that reduce the organism’s chances are subject to natural selection. Though traits are often erroneously thought of as genes, it is actually the phenotype – or the expression of a gene – that is the trait selected for or against. Selection, in turn, modifies the distribution or frequency of expressed traits in a given population over successive generations; usually, several thousand, but some argue that evolution may sometimes be punctuated or more rapid than it is usually understood. The traits or phenotypes that matter, or that make one organism fitter or better adapted than another, have little to do with the types emphasized by Social Darwinists or eugenicists. Rather, strength or intelligence – however defined – may be fit in some environments, whereas other traits at other times may be more fit. To be sure, strength has and will probably always matter. Many predators are strong, including your favorite dog, whose jaw is extremely powerful.

However, the story of human evolution – or more accurately, the evolution and success of Homo sapiens (“wise humans”) – is about the selection for cognitive abilities like planning ahead, contemplating and expressing fine-grained affectual states, and morality predicated on our primate sense of fairness and an intensely enlarged emotion center that equipped us with empathy on steroids. Indeed, as evolution worked on these cognitive abilities, our natural defenses like strong jaws, agility, excellent auditory or olfactory senses, speed, and so forth atrophied. In short, any trait that improves the chances of reproducing one’s DNA as many times as possible and for those offspring to survive will be more likely to emerge.

One final point is worth noting: it does not take a PhD in entomology, for instance, to notice that there are a lot of insect species. If you were reading closely, you would have noticed, above, that humans are one of four great apes. We split from our closest living relatives about 6 million years ago, from gorillas 8 million years ago, and from Orangutans 15+ million years ago. And, the great apes split from Gibbons, which are classified as apes 20+ million years ago and from monkeys 31+ million years ago. In any case, four remaining species is truly an indictment of the fitness of apes. But, it also underscores just how evolved the cognitive abilities of apes vis-a-vis other orders and classes of animals are. Gorillas and, especially, Chimps/Bonobos are incredibly smart creatures. [Though, this is not to say other primates are not smart or that other mammals are not smart, the foundations upon which our grey matter evolved is discernible in many other animals (Lents 2016)].

Other Evolutionary Processes

Natural selection is not the only process in the modern synthesis. Most readers will recognize mutations or the errors that occur in replication of or when damage is done to DNA. Mutations are usually neutral in that selection rarely works on them. However, they may also be maladaptive and, in the rare case, adaptive. Gene flow, or what sociologists will recognize as the result of migration, occurs when genes are exchanged between populations (e.g., marriage alliances between two groups) or species (e.g., geneticists recently proved Neanderthals and Homo sapiens did, in fact, mate, though the amount of Neanderthal DNA is quite low). Genetic drift occurs when there is a natural change in the frequency of an extant gene variant (allele). In some cases, the allele frequency declines, making the allele extraordinarily rare, while in the most dramatic cases, a rare allele increases in frequency causing the gene pool to change drastically.

Human Intervention

Biological evolution is often described as blind, purposeless, directionless, and this is true to some degree. One of the most important forces driving natural selection for the first 240,000 years of Homo sapien existence was climactic change (Fagan 2008, 2010). For a people lacking scientific understanding of climactic change, it is a testament to our cognitive powers that we are even still alive. 73500 years ago, Mt. Toba in Sumatra erupted and was so explosively powerful, that geneticists estimate that 10000 or fewer Homo sapiens survived (Fagan 2010:93ff.). In turn, this event created a bottleneck – or significant reductions in the size of a population that contributes to the extinction of myriad genetic lineages – in which the entire 7 billion people alive today can trace their genetic heritage to 4000-10000 African women of reproductive age who survived (compared to a billion women of reproductive age in the world today). There is, ultimately, nothing about those climactic changes that was purposive, nor could Homo sapiens purposefully alter the change. What they could do, was use their extant material and ideational tool kits to survive, and those that were best at it, passed certain traits on that were revolutionary. By the time the climate returned to a warmer, wetter climate, the cognitive abilities we have today had evolved and human history began, in earnest, to write itself.

That being said, humans do in fact drive biological evolution purposefully. One need only look at their pet, if they have a dog, to see how much effort our ancestors put into selecting certain canids with certain traits; over several thousand years of selective breeding, we have a tame, loyal best friend. More recently, one need only look to Mesopotamia 5000-6000 years ago. There, farmers had begun to select some strands of barley because they were drought-resistant, easier to harvest and process, and produced more barley per plant (Postgate 1992). Again, several thousand years of selection modified the traits farmers preferred.

Individual-Level Selection

At the heart of Darwinism, then, is the idea that selection works on individual organisms. Though most folks are familiar with Richard Dawkins’ “selfish gene” argument, in which the position is that our genes demand we reproduce them, there are many debates about whether it is the gene, the individual organism, and, as noted in my previous post, the group that is selected upon. In any case, one of the primary dilemmas faced by evolutionary theorists is how to explain altruism and cooperation if one takes the position that humans are naturally self-interested. The nitty gritty of this discussion goes far beyond my expertise and far beyond the needs of this audience, but it is worth highlighting the basic points as it will inform the follow up to this essay on social evolution.

First, many biologists were confronted by the fact that organisms will often sacrifice themselves for close others; particularly blood relatives, but also fictive kin (e.g., you spouse). The act of sacrifice directly violates the principle of self-interest, as the organism risks its own ability to pass on its genetic code. The answer was kin selection or reciprocity. That is, in some cases, individuals will risk their own reproductivity to ensure their identifiable kin’s reproductivity. In humans, however, the problem of sacrifice is greater in magnitude and complexity. For one thing, humans will often work against their interests with non-kin, such as gift giving. Of course, the explanation can be reciprocal altruism: if I give to person A now, they will return the favor. Vampire bats, for instance, engage in this (Lents 2016). However, people donate organs and blood, give to charities, and sometimes help random strangers with no guarantee of reciprocation.

At risk of not providing a deeper discussion or unnecessarily wading into tumultuous waters, I leave the reader here pondering this puzzle. In part, this issue of competition v. cooperation is unintentionally central to one key debate in sociological theory – e.g., to over simplify, between functionalisms and conflict theories. But, more importantly, this issue begins to open the door to both the promises and problems of thinking evolutionarily in sociology. Besides rational-choice theorists – who many sociologists vehemently disagree with – sociologists, for the most part, explicitly or implicitly reject the idea that humans are self-interested. The Marxian strand of sociology has canonized the maxim that humans are naturally good, communal creatures and it is the existing social structure that makes us bad. Less recalled is Durkheim’s counter narrative in which humans are naturally self-interested creatures in need of social integration and moral regulation.

Ironically,  neither position is wrong, per se. Humans are, like all animals, self-interested. Given the right circumstances, many humans – though, importantly, not all – resort to cannibalism if it means survival; and, not just eating dead relatives, but in some cases, killing to survive. However, cultural maxims, like the Golden Rule, exist in all societies that we know of, which implies humans are inclined to help kin, fictive kin, close others, and, potentially, strangers. But, this inclination requires, particularly the further out we go in terms of closeness, some normative pressure and real/imagined sanctions. Our ability to self-regulate (e.g., shame) points towards evolution favoring altrusitic behavior (more on this in a future post), but we also need structural and cultural formations to support and amplify these propensities vis-a-vis our other inclinations.

Ultimately, the sociologist must deal not only with the thorny issues of self-interest v. altruism when thinking evolutionarily, but as we will see in the next post, with a whole host of issues regarding selection, variation, and fitness.