As defined by the Cambridge Dictionary, the social sciences are a federation of disciplines dedicated to the “study of the customs and culture of a society, or a particular part of this subject, such as history, politics, or economics.” ¹ Oxford Dictionaries ² identify the “scientific study of human society and social relationships” as the unifying principle around which the social sciences are organized. Merriam Webster ³ expands on this definition without changing its substance: “A branch of science that deals with the institutions and functioning of human society and with the interpersonal relationships of individuals as members of society.” As can be seen in these and other definitions, the social sciences are bound together under one banner by virtue of their shared mission to explain human nature and society. Equally important to note, the social sciences have unity of purpose even as they have no meta-theory; no foundation from which variables can be connected, causally sequenced, or ultimately explained.

Many social scientists feel the absence of such a meta-theory. Take the celebrated sociologist Charles Murray , who, as previously described (Hertler 2017), intuited the biological unity underpinning the divisions of class about which he wrote in Coming Apart : The State of White America 1960–2010. At one point, Murray explicitly predicted that “advances in evolutionary psychology are going to be conjoined with advances in genetic understanding, leading to a scientific consensus…” This is actually part of a longer quote that Murray originally wrote as a contributor to Culture and Civilization: Volume 2: Beyond Positivism and Historicism. ⁴ In both works, Murray continues describing his intuition thus:

There are genetic reasons, rooted in the mechanisms of human evolution, why little boys who grow up in neighborhoods without married fathers tend to reach adolescence not socialized to the norms of behavior that they will need to stay out of prison and to hold jobs. These same reasons explain why child abuse is, and always will be, concentrated among family structures in which the live-in male is not the married biological father. These same reasons explain why society’s attempts to compensate for the lack of married biological fathers don’t work and will never work.

Charles Murray is not alone. Social scientists of every variety routinely struggle to glean patterns, relate individual traits to group norms, and infer causal relationships among correlated variables.

Evolution has been advanced as this missing meta-theory. And of course, it is only through evolution that humans have been embedded within the natural world. Prior to evolutionary theory, most understood animals to be of a different order; subservient beasts to be exploited for the good of mankind. An evolutionary perspective, properly absorbed, contextualizes humans as Eukarya, Animalia, Chordata, Mammalia, Primates, Hominidae, Homo, Sapiens. Evolutionary branching inferred through geologic time tells us so much about our function, origins, and history. Evolution’s unifying utility has long been recognized within the biological sciences, as demonstrated by the following excerpt from Henry Ward Beecher’s Evolution and Religion written in 1885 (Beecher 1885/1934; pp. 50–51):

The theory of Evolution is the working theory of every department of physical science all over the world. Withdraw this theory, and every department of physical research would fall back into heaps of hopelessly dislocated facts, with no more order or reason or philosophical coherence than exists in a basket of marbles, or in the juxtaposition of the multitudinous sands of the seashore. We should go back into chaos if we took out of the laboratories, out of the dissecting rooms, out of the fields of investigation, this great doctrine of Evolution.

Faith in evolution’s synthesizing ability was likewise precociously expressed in the writings of Robert G. Ingersoll (1900) and is similarly found amidst the inadmissible evidence of expert scientists testifying in the 1925 State of Tennessee v. John Thomas Scopes . Evolution’s sway extended steadily over the life sciences following the modern synthesis, wherein the likes of J. B. S. Haldane and Ronald Fisher reconciled the work of Darwin with that of proto-geneticist, Gregor Mendel .

For many social scientists, however, evolution was established as something to respect, but was also subject to neglect. Evolution remained a rarified background theory that seemed of little import to the questions that most social scientists were absorbed in asking and answering. A general reading of evolutionary theory provided the social scientist with some direction concerning human universals, but less so of particulars. Evolution may for instance explain what is common to all cultures, while not sufficiently explaining differences between cultures; just as evolution seemed to specify species-specific norms without thoroughly explaining differences within and between populations. As can be seen in the following quote, this is precisely the point that Marvin Harris, the anthropologist featured in Chapter 13, makes in his magnum opus, Cultural Materialism : The Struggle for a Science of Culture:

Natural selection, however, has repeatedly been shown to be a principle under whose auspices it is impossible to develop parsimonious and powerful theories about variations in human social life. (Harris 2001; p. 121)

Some social scientists had gone as far as Comte, ⁵ absorbing the general positivist doctrine wherein social science was grounded in natural science. Nevertheless, they were far from genuinely embracing E. O. Wilson’s call to consilience , a form of scientific convergence wherein social science is reducible to natural science.

It is not to say that what may be regarded as classical evolutionary theory had nothing to say on the matter of cultural and personal differences, but only that such knowledge was not easily accessible, sharp or unified, leading many social scientists to regard evolution only as a useful backdrop. For in truth, throughout the 1960s and 1970s, evolution slowly enlarged its explanatory sphere to include the domains customarily reserved to the social sciences. It was during this fecund time when cooperation was explained via inclusive fitness ⁶ (Hamilton 1964) and reciprocal altruism ⁷ (Trivers 1971). Also within these decades, a rationale for sexual reproduction was expressed in the form of Muller’s Ratchet ⁸ (Gabriel et al. 1993), a foundation for group selection was laid through the selfish gene , ⁹ and an explanation of senescence and death was articulated in The Disposable Soma Hypothesis ¹⁰ (Kirkwood 1977; Kirkwood and Austad 2000).

In these same progressive decades, E. O. Wilson and Robert H. MacArthur (1967) were terrorizing the flora and fauna of small islands within the Florida Keys, tarping and gassing entire ecosystems in an effort to learn about migration and the growth of populations. From this work on island biogeography (MacArthur and Wilson 2001; Losos and Ricklefs 2009), combined with input from Dobzhansky (1950), Pianka (1970), Roff (2002), Charnov (1993), Stearns (1992), Harvey and Clutton-Brock (1985), came Life History Theory, an evolutionary framework immediately, urgently, palpably, directly, and compellingly relevant to the social sciences and their shared mission to explain human nature and society.

Life history evolutionary theory remains obscure enough for a synopsis to be required even within some biological and evolutionary journals and books. Life history evolution is considered by some to be a sub-discipline or mid-level theory (Buss) within evolutionary biology. Beyond situating it thus, there have been many approaches to it...