April 7, 2008

Towards a Scientific Theory of Cultural Evolution

Pioneering researchers Deborah S. Rogers and Paul R. Ehrlich, in an open access article, have made an important contribution to understanding cultural evolution. In this article the authors differentiate some clear mechanisms for cultural emergence and change - and point out the distinctions between the dynamics of human development and cultural evolution:
Natural Selection and Cultural Rates of Change
by Deborah S. Rogers and Paul R. Ehrlich

It has been claimed that a meaningful theory of cultural evolution is not possible because human beliefs and behaviors do not follow predictable patterns. However, theoretical models of cultural transmission and observations of the development of societies suggest that patterns in cultural evolution do occur.

Here, we analyze whether two sets of related cultural traits, one tested against the environment and the other not, evolve at different rates in the same populations.

Using functional and symbolic design features for Polynesian canoes, we show that natural selection apparently slows the evolution of functional structures, whereas symbolic designs differentiate more rapidly. This finding indicates that cultural change, like genetic evolution, can follow theoretically derived patterns


... said...

Reviewer Stephen Shennan summarizes the article:

"In the most general terms, parallel mechanisms for inheritance, mutation, selection, and drift act on culture as they do on genes...In the case of culture, the inheritance mechanism is social learning: People learn ways to think and act from others...natural selection can also act on cultural attributes, in the sense that those individuals who inherit or acquire certain cultural attributes may have a greater probability of surviving and/or reproducing than those who do not; as a result, those cultural attributes will become increasingly prevalent.

For example, it is clear that, in many parts of the world, adopting an agricultural rather than a hunting-and-gathering way of life led to greater reproductive success; as a result, the cultural traits that characterize agriculture spread and, in some cases, subsequently influenced genetic evolution [e.g., the ability to digest lactose]...It is also important to look at things from what Dawkins called "the meme's eye-view," the perspective of the cultural attributes themselves...in the case of the canoe attributes analyzed by Rogers and Ehrlich, these culturally transmitted features are the data that archaeologists and anthropologists have available...

What Rogers and Ehrlich have done is make progress in this area by showing that variation that is believed to be under selection is patterned differently from other variation that is believed not to be under selection, or at least not in the same way. It seems to be more conservative and, therefore, under negative selection. Perhaps more surprisingly, they find that there is no correlation at all in the similarities between island groups in terms of functional canoe variation and the similarities based on symbolic variation. One might have expected some correlation, either because both would be affected by the distance between the islands, or because the process of island colonization by groups in canoes would have brought both their functional and their symbolic attributes.

The fact that selection appears to have been sufficiently powerful to overwhelm evidence of descent history is extremely interesting and confirms the importance of regarding cultures not as hermetically sealed entities, a bit like species, but as bundles of distinct packages of traits affected by different forces.”

Jory Talhardi said...

A recent Stanford study shows
the process of natural selection can act on human culture as well as on genes.

Scientists at Stanford University have shown for the first time that cultural traits affecting survival and reproduction evolve at a different rate than other cultural attributes. Speeded or slowed rates of evolution typically indicate the action of natural selection in analyses of the human genome.

This study of cultural evolution, which compares the rates of change for structural and decorative Polynesian canoe-design traits, is scheduled to appear Tuesday, Feb. 19, in the online Proceedings of the National Academy of Sciences.

"Biological evolution of inherited traits is the essential organizing principle of biology, but does evolution play a corresponding role in human culture"" said Jared Diamond, a professor of geography at the University of California-Los Angeles and author of Guns, Germs and Steel. "This paper makes a decisive advance in this controversial field."

The Stanford team studied reports of canoe designs from 11 Oceanic island cultures. They evaluated 96 functional features (such as how the hull was constructed or the way outriggers were attached) that could contribute to the seaworthiness of the canoes and thus have a bearing on fishing success or survival during migration or warfare. They also evaluated 38 decorative or symbolic features (such as the typeae design traits from island group to island group. Statistical test results showed clearly that the functional canoe design elements changed more slowly over time, indicating that natural selection could be weeding out inferior new designs. This cultural analysis is similar to analyses of the human genome that have been successful in finding which genes are under selection.

The field of cultural evolution is controversial because not all historians, social scientists or even biologists agree that cultural change can be understood in an evolutionary context. Some say that human beliefs and behaviors are too unpredictable.

But Nina Jablonski, chair of the Anthropology Department at Pennsylvania State University, said she is sold on the research. "This paper is revolutionary in its approach ... one of the most significant papers to be written in anthropology in the last 20 years," she said.

Authors of the study said their results speak directly to urgent social and environmental problems.

"People studying climate change, population growth, poverty, racism and the threat of plagues all know what the problems are and what we should be doing to solve them," said Paul Ehrlich, the Bing Professor of Population Studies at Stanford.

Ehrlich, author of The Population Bomb and other books on dilemmas facing contemporary human society, said he does not understand why more effort is not going into urgently needed solutions. "What we don't know, and need to learn, is how cultures change and how we can ethically influence that process," he said.

"Unfortunately, people have learned how to avoid natural selection in the short term through unsustainable approaches such as inequity and excess consumption. But this is not going to work in the long term," she said. "We need to begin aligning our culture with the powerful forces of nature and natural selection instead of against them."

Examples of cultural approaches that are putting humans at risk include "everything from the economic incentives, industrial technologies and growth mentality that cause climate change, pollution and loss of biodiversity, to the religious polarization and political ideologies that generate devastating conflict around the globe," Rogers said. "If the leadership necessary to undertake critically needed cultural evolution in these areas can't be found, our civilization may find itself weeded out by natural selection, just like a bad canoe design."

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