The ideas of cultural evolution and of the evolution of societies provide a set of theories that anthropologists (see anthropology and cultural anthropology) have both promoted and criticized. Today anthropologists distinguish between "unilinear cultural evolution" and "multilinear cultural evolution".
Cultural anthropologists and sociologists assume that human beings have natural social tendencies and naturally form shifting groups - and that this forms a basic trait of the Hominids or Hominidae. But they further argue that particular human social behaviors have non-genetic (i.e. purely social, or cultural) causes and dynamics. They use the word "society" to refer to a group with more or less clear boundaries that reproduces itself over time and has a degree of relative autonomy (thus, a family or a football team may exemplify a social group, but not a society). Basic issues in social theory follow from this definition: what holds a society together? How do societies change? How do different societies interact? Although these questions fascinate contemporary anthropologists and sociologists, Europeans have grappled with these questions since the Enlightenment.
Prior to the 18th century, Europeans predominantly believed that societies on Earth continued to decline from the perfection that had existed in the Garden of Eden. In East Asia, the prevailing notions involved the Buddhist concept of circular history and the Neo-Confucian concept of a decline from the era of the sage kings. As such state-level societies encountered other cultures, their philosophies and theologies would clash, adapt, and alter each other, e.g. the absorption of Pagan culture by Roman Catholics in Dark Ages' Europe, the adoption of Catholic customs and saints by the Maya, the spread of Islam.
Two processes, one that began before the Enlightenment, and one that began during the Enlightenment, converged to produce a new attitude in Europe. The first process was colonialism, which required European powers to govern non-European peoples. Although colonial powers settled most questions of cultural difference by force, effective administration required some degree of understanding of other cultures. Emerging theories of social evolution allowed Europeans to organize their new knowledge in a way that reflected and justified their increasing political and economic domination of others: colonized people were less-evolved, colonizing people were more evolved. The second process was the Industrial Revolution and the rise of capitalism which allowed and promoted continual revolutions in the means of production. Emerging theories of social evolution reflected a belief that the changes in Europe wrought by the Industrial Revolution and capitalism were improvements.
In the late 19th centuryHerbert Spencer developed an avowedly-scientific theory of "social evolution". He argued that societies over time progressed, and that progress was accomplished through competition. Later social theorists have argued that this view of society legitimizes 19th century capitalism, and in fact reflected the views of people in capitalist societies rather than any objective or universal understanding of social change. (This theory could be said to inspire modern Gaians who view social evolution as a competition to protect, mimic, and make minimal use of nature's bounty.) Around the same time as Spencer, Karl Marx argued that human progress was accomplished through class struggles, which involved alienation, but which would end with a society based completely on co-operation.
Conflict between such views, and the inherent conflict of both with nationalism and religion, seems to have defined much of 20th century history. Today most political science focuses on the expression of these theories on a finite planet of humans prone to ethnic and ethical disputes.
The 18th-century theories were given a language and legitimacy by Charles Darwin's theory of the evolution of species through natural selection. Some theorists have applied Darwin's language metaphorically to social dynamics. Others have argued that biological and social evolution operate in identical ways; this is frequently connected with Social Darwinism. Others have argued that there is no connection between biological and social evolution.
Most contemporary thought about social evolution typically separates ecological (or "natural") from sexual (or "mate"), ethical (or "social") and moral (or "spiritual") selection - the last is generally not a scientific view but rather an attempt to detect a set limit beyond which rationalism must fail, and where individual autonomy, creativity, safety and closure must prevail: leaving room for the traditional assumptions about human morality and spirit.
Some, however, call attention to the discovery that some Great Apes' social behaviors have "non-genetic (i.e. purely social, or cultural) causes and dynamics" as well. This led to the reclassification of some apes as Hominids, sparking fresh debate on the value of biodiversity, the nature of "animal" societies, and the optimal structure of human society. Current political theories of the new tribalists seem to be attempts to consciously mimic ecology and so-called primitive life-ways that have stood the test of time amongst indigenous peoples, augmenting them with modern sciences.
Ecoregional Democracy attempts to confine the "shifting groups" or tribes, within "more or less clear boundaries" that a society inherits from the surrounding ecology, to the borders of a naturally-occurring ecoregion. Progress can proceed by competition between but not within tribes, and it is limited by ecological borders or by Natural Capitalism incentives which attempt to mimic the pressure of natural selection on a human society by forcing it to adapt consciously to scarce energy or materials. Gaians argue that societies evolve deterministically to play a role in the ecology of their biosphere, or else die off as failures due to competition from more efficient societies exploiting nature's leverage.
These theories seem to assume that optimizing the ecology and the social harmony of closely-knit groups is a more desirable or necessary evolution of societies than the various paths proposed by earlier theorists. A 2002 poll of experts on Nearctic and Neotropicindigenous peoples (reported in Harper's Magazine) revealed that all of them would have preferred to be a typical New World person in the year 1491, prior to any European contact, rather than a typical European of that time. Evolution of societies in an ethical direction may well be driven by such choices.
This approach has been criticized by pointing out that there are a number of historical examples of indigenous peoples doing severe environmental damage (such as the deforestation of Easter Island and the extinction of mammoths in North America) and that proponents of the goal have been trapped by the European stereotype of the noble savage. Anthropologists consider social evolution a Western myth seldom based on solid empirical grounds. Critical theorists argue that notions of social evolution are simply justifications for power by the elites of society.
Postmodernists question whether the notions of evolution or society have inherent meaning and whether they reveal more about the person doing the description than the thing being described. Observing and observed cultures may lack sufficient cultural similarities (such as a common foundation ontology) to be able to communicate their respective priorities easily. Or, one may impose such a system of belief and judgement upon another, via conquest or colonization. For instance, observation of very different ideas of mathematics and physics in indigenous peoples led indirectly to ideas such as Lakoff's "cognitive science of mathematics", which asks if measurement systems themselves can be objective.
As there is no notion of evolution that does not include some measurement of progress or change, whole societies observing and measuring each other may simply be beyond the capacity of any rational or reasonable method known.
These 19th century ethnologists used these principles primarily to explain differences
in religious beliefs and kinship terminologies among various societies.
By the early 20th century, as cultural anthropology shifted to ethnography and more rigorous empirical methods, most anthropologists rejected the theory of unilinear cultural evolution. At first, they argued that the third premise was speculative. As they studied different religious and kinship systems more closely, they argued that evolutionary theory systematically misrepresented ethnographic data. More importantly, they soon came to reject the first premise, the distinction between "primitive" and "civilized" (or "modern"), pointing out that so-called primitive contemporary societies have just as much history, and were just as evolved, as so-called civilized societies.
By the 1950s cultural anthropologists such as Leslie White and Julian Steward sought to revive an evolutionary model on a more scientific basis. White rejected the opposition between "primitive" and "modern" societies but did argue that societies could be distinguished based on the amount of energy they harnessed, and that increased energy allowed for greater social differentiation. Steward rejected the 19th century notion of progress, and instead called attention to the Darwinian notion of "adaptation", and argued that all societies had to adapt to their environment in some way. He argued that different adaptations could be studied through the examination of the specific resources a society exploited, the technology the society relied on to exploit these resources, and the organization of human labor. He argued that different environments and technologies would require different kinds of adaptations, and that as the resource base or technology changed, so too would a culture. In other words, cultures do not change according to some inner logic, but rather in terms of a changing relationship with a changing environment. Cultures would therefore not pass through the same stages in the same order as they changed--rather, they would change in varying ways and directions. He called his theory "multilinear evolution".
The anthropologists Marshall Sahlins and Elman Service wrote a book, Evolution and Culture, in which they attempted to synthesize White's and Steward's approaches. Other anthropologists, building on or responding to work by White and Steward, developed theories of cultural ecology and ecological anthropology. The most prominent examples are Peter Vayda and Roy Rappaport. (See also Marvin Harris's Cultural Materialism.)
Today most anthropologists continue to reject 19th century notions of progress and the three original assumptions of unilinear evolution. Following Steward, they take seriously the relationship between a culture and its environment in attempts to explain different aspects of a culture. But most cultural anthropologists now argue that one must consider the whole social environment, which includes political and economic relations among cultures.