We tend to think of evolution in terms of a struggle, a "competitive struggle" in which natural selection favors certain genes, or a collection of genes in a particular organism for continued reproduction and survival. It is adaptation, however, not necessarily competition, that explains survival, and evolutionary theorists commonly explain adaptation in terms of self-interest. In Richard Dawkins' view, for example, genes are "selfish." In nature, however, evolution has favored a rare condition, "eusociality" in a handful of species, who in many respects have come to dominate the earth. As described by biologist Edward O. Wilson, eusociality refers to the "condition of multiple generations organized into groups by means of altruistic division of labor." The social insects --- wasps, ants, termites, bees, and a small number of other insect species --- are the most prominent examples of eusociality. The biomass of ants, for example, exceeds over half of all insects as well as the biomass of all non-human terrestrial vertebrates. Another prominent example, yet very different from the social insect, is the homo sapien.
Eusociality is characterized by a high level of cooperation, but it is important to note that cooperation is only a necessary, but not a sufficient condition for eusociality. We can think of many other examples in the animal kingdom, including symbiosis, multiple forms of reciprocal behavior, parenting, that do not rise to "multiple generations organized into groups by means of an altruistic division of labor." The definition of eusociality is a tight definition; it is not intended to capture all cooperative behavior in the animal kingdom that might be deemed "social." Eusociality does not describe herds, packs, dens, prides, or other groups animals who exhibit social behavior, because their social condition is not composed of multiple generations or their means of organization does not constitute an altruistic division of labor. Our closest living species, the chimpanzee, who exhibits social behavior (see November 9, 2010 post and June 17, 2010 post) is not considered eusocial.
In the world of social insects, the group is organized around the nest (or hive). In all of the examples of species that have attained eusociality, altruistic cooperation, says Wilson, protects a "persistent, defensible nest from its enemies, whether predators, parasites, or competitors," which sets the stage for members of a group belonging to more than one generation to divide labor in a way that sacrifices at least some of their selfish interests to the group. Importantly, multiple generations within the nest stay with the nest. They do not disperse.
While it is not yet proven, Wilson believes that eusociality in the social insects is genetically driven by a gene that silences the insect brain's program for dispersal and prevents the mother and her offspring from dispersing to create new nests, allowing natural selection on the rest of the genome to effectuate more complex forms of social organization. This occurs, says Wilson, because natural selection impacts not only the genotype (gene selection), but it also operates on groups within a species as well (group selection). This is the multi-level selection thesis previously discussed in the prior posting on Holldobler and Wilson's Superorganism (see November 4, 2009 post). The new twist in The Social Conquest of Earth is Wilson's declaration that kin selection, a form of group selection, can no longer be defended because its mathematical underpinning, inclusive fitness theory, had been debunked in a 2010 article co-authored by Wilson, Corina Tarnita, and Martin Nowak. The work of Bill Hamilton and George Price (see October 13, 2010 post), he contends, no longer contributes much to evolutionary analysis.
While multilevel selection remains a significant storyline in The Social Conquest of Earth, the biology of eusocial insects is merely a starting point for the discussion here. Wilson's focus is the homo sapien, humanity, and human nature, explaining his views of how eusociality evolved in homo sapiens. In contrast to the social insects, humans do not congregate in a nest. In contrast to the social insects, humans do disperse. But humans do build and maintain social communities comprised of multiple generations and, Bernard Mandeville's Fable of the Bees notwithstanding (see January 30, 2010 post), humans are organized into groups by altruistic division of labor. For Wilson, the social evolution of humans is not attributable to a single or "major" event such as the development of enlarged brains or bi-pedal mobility, but can only be understood in terms of prehuman adaptations in ancient species and adaptations that distinguish humans from other hominids, evidence from human archaeology, and the co-evolution of human culture, all of which have come to define "human nature." Wilson is a proponent of the "dual inheritance theory." For Wilson, a key event in human history is technological: the mastery of fire. With the ability to control fire, campfires are created and the campfire, in Wilson's view, is the homo sapiens' counterpart of the insect nest. Campfires are the venue that facilitates the sharing of food, and this is the magnet that draws homo sapiens into a cooperative environment.
In my November 4, 2009 post, I commented on Holldobler and Wilson's discussion of multilevel selection as follows: "However powerful the evidence for the superorganism is and the multilevel selection model, the truth remains that the critical unit of evolution is the gene." I made have overstated the uniqueness of the gene in making this statement and uninentionally sublimated the individual: after all, it is the individual (a collection of genes) that reproduces. A comment I made in the November 9, 2010 post discussing Frans DeWaal's The Age of Empathy seems extremely relevant: "Our capacity for cooperation, altruism, and other social instincts is certainly biological, and it is a product of evolution. We have much to learn about what makes us human from learning about the behavior of other species from which humans evolved as we do from observing our own behavior. This is De Waal's primary thesis. And this thesis is no stranger to this blog and previous posts, including De Waal's own The Ape and the Sushi Master (June 17, 2010 post), Oren Harman's The Price of Altruism (October 13, 2010 post), Dacher Keltner's Born to Be Good (July 16, 2010 post), Holldobler and Wilson's The Superorganism (November 4, 2009 post), Michael Gazzaniga's Human (September 27, 2009), Marco Iacobonni's Mirroring People (September 18, 2009 post), and Christine Kennealy's The First Word (August 31, 2009 post)." Natural selection operates on what is biological or chemical; while culture undeniably "evolves," natural selection as we understand it does not operate upon culture. If culture is going to be successful, it is because it supports what natural selection favors. As Frans DeWaal explains in the The Ape and The Sushi Master: "Although the relation between culture and nature can be tense, culture mostly tries to get along with nature." Culture cannot change nature; culture can evolve behavior to act consistently with nature. For example, the incest taboo - an avoidance of sex among family members, long a cultural regulation, is now known to be a form of behavior in the primate world that appears to be innate in some aspects (an aversion rather than an avoidance) and perhaps learned in other respect. (See June 17, 2010 post)." Group selection and multilevel selection are not settled theories, and Wilson's rejection of kin selection is contested by others in the field.
Wilson's discussion of "group selection" suggests that evolution operates at the level of a group within a species. Thus a "group" might be a nation or a religious group or an ethnic group in the case of humans, and here I part company with Wilson . These are cultural groups, and natural selection does not operate upon culture. When I thought about how I would respond to Wilson's discussion here, I realized I had already said in my discussions of Frans DeWaal's The Age of Empathy (November 9, 2010 post) and The Ape and the Sushi Master (June 17, 2010 post) what I want to say (and what DeWaals has to say) about the linkage between genes and culture in those posts. Here is a snippet from the June 17, 2010 post:
"Culture and genetics have one thing in common --- the transmission of information: in the case of genetics information is transmitted by biological/chemical means, in the case of culture it is transmitted by social means. 'This is not to say that both forms of behavioral inheritance --- the one traveling across time via genotypes, the other via phenotypes --- should not or could not be conceptually linked. Ironically, the Lamarckian idea that acquired characteristics can be inherited has found its realization not in the physical characteristics he was thinking of, but in behavior. Genetic predispositions feed into culture, culture affects survival, and survival and reproduction determine which genotypes spread in the population. In other words, there exists a dauntingly complex interplay between genetic and cultural transmission. Brave and inspiring attempts at a theory of dual inheritance, or co evolution, have been made, without, however, in any way confusing the two processes.'" Wilson confuses the two processes. I would have liked to see in his discussion of human evolution and our predisposition to social behavior a more biologically-based discussion of the neurological system and human child development, such as that in the November 9, 2010 post about The Age of Empathy:
"At the biological core of our humanness is the limbic system, which, from an evolutionary perspective, is one of the oldest parts of our neural network in the human brain. It is a part of the brains of other species as well. Antonio Damassio identifies the limbic system as a critical regulator of feelings and emotions in The Feeling of What Happens, and it is central to understanding human consciousness. De Waal says the limbic system allows emotions such as affection and pleasure, and paved the way for family life, friendships, and other caring relationships. Other parts of our neural network allow us to store memories of these feelings and emotions and allow us to recall the context in which we previously experienced them and then to "understand" them. A key line here is De Waal's statement, "Bodily connections come first --- understanding follows." Mirror neurons, as described in Iacobonni's Mirroring People (September 18, 2009 post), are active in these other parts of the neural network known as the brain that allow us to "read" the minds of others, enabling us to connect with others, and facilitate the the experience we call empathy. "De Waal calls this emotional contagion: seeing another's emotions arouses our own emotions, and then we build "a more advanced understanding of another's situation." Later, he adds, "Empathy engages brain areas that are more than a hundred million years old. The capacity arose long ago with motor mimicry and emotional contagion, after which evolution added layer after layer, until our ancestors not only felt what others felt, but understood what others might want or need."
"True to his dualism, just as De Waal recognizes that emotional contagion probably starts immediately with the mother-child relationship and that early communication fosters a bond, a second phase begins just months later in the course of child development when the child begins to develop a sense of self. And empathy, De Waal believes, "requires both mental mirroring and mental separation." The former occurs when we see another person in a particular emotional state. The latter occurs when we parse our own emotional state from the other, and this allows us to "pinpoint the actual source of our own feelings." De Waal attributes our dualism to the existence of VEN cells in the brain --- Von Economo neurons --- that differ from other neurons and are unique to humans and their recent ancestors. Physically, VEN cells are long and spindle-like and reach deeper into the brain. Research shows that when parts of the human brain that contain these cells are damaged, behavior is marked by a loss of perspective-taking, empathy, embarrassment, and future orientation. Besides humans and certain apes, these cells are also found in dolphins, whales, and elephants, where behavioral research shows they have the capacity for empathy that is not found in other species."
Some of this is touched upon by Wilson, but what is touched upon deserves elaboration and much is missing from The Social Conquest of Earth. Yet these biological attributes of homo sapiens are the products of natural selection in humans and they specifically relate to our ability to act cooperatively and altruistically: the neurobiology behind feelings and emotions (see April 8, 2011 post), the neurobiology behind memory (see April 8, 2011 post and November 6, 2011 post, and September 20, 2011 post), the neurobiology behind our sensory system and our ability to communicate and our capacity for storytelling (see October 25, 2011 post, September 27, 2009 post, and August 31, 2009 post), and the biology of human development. For example, we cannot underestimate the role of human memory (including the failings of memory, see September 20, 2011 post) in evolving a human culture, and several prior posts have addressed this subject in one way or the another. (See September 28, 2010 post, September 9, 2010 post, and August 15, 2011 post) Wilson merely summarizes these attributes when he notes:
"What catapulted Home sapiens to this level? Experts on the subject agree that increased long-term memory, expecially that put into working memory, and with it an ability to construct scenarios and plan strategy in brief periods of time, played the key role in Europe and elsewhere, both before the African breakout and afterward. What was the driving force that led to the threshold of complex culture? It appears to have been group selection. A group with members who could read intentions and cooperate among themselves while predicting the actions of competing groups, would have an enormous advantage over others less gifted. . . Morality, conformity, religious fervor, and fighting ability combined with imagination and memory to produce the winner."
These are the human attributes that are genetically determined by evolution, and they are the biological basis of humanity. Our social instincts are derived from these biological attributes.
Notwithstanding my conclusion that much is missing from The Social Conquest of the Earth, Wilson's discussion of the origins of religion and organized religion and the origins of the creative arts are brilliant. These subjects too have been the topics of prior posts. (See January 14, 2012 post, February 4, 2012 post, February 15, 2012 post, and June 12, 2011 post).