Sunday, September 16, 2012

Charles Perreault - The Pace of Cultural Evolution

Charles Perreault is the Omidyar Fellow at the Santa Fe Institute. He holds a Ph.D. in anthropology from UCLA and a master’s in anthropology from the Université de Montréal.
SFI provided him with the opportunity to collaborate with colleagues from many disciplines, he says, and to incorporate methods and ideas into his work that “are not typically available in the standard social science environment.

While at SFI he will pursue a deeper understanding of cultural evolution through the use of theoretical models and cross-cultural comparisons. As part of this work, he will compare the changes brought by evolutionary forces on both cultural and biological phenomenon.
In this analysis, Perreault shows that cultural evolution is faster than biological evolution, that this is true even when the "generation time of species is controlled for," and that culture allows us to evolve over short time scales. Cool paper - humans are definitely a complex adaptive system.

The Pace of Cultural Evolution

Charles Perreaul
Santa Fe Institute, Santa Fe, New Mexico, United States of America


Today, humans inhabit most of the world’s terrestrial habitats. This observation has been explained by the fact that we possess a secondary inheritance mechanism, culture, in addition to a genetic system. Because it is assumed that cultural evolution occurs faster than biological evolution, humans can adapt to new ecosystems more rapidly than other animals. This assumption, however, has never been tested empirically. Here, I compare rates of change in human technologies to rates of change in animal morphologies. I find that rates of cultural evolution are inversely correlated with the time interval over which they are measured, which is similar to what is known for biological rates. This correlation explains why the pace of cultural evolution appears faster when measured over recent time periods, where time intervals are often shorter. Controlling for the correlation between rates and time intervals, I show that (1) cultural evolution is faster than biological evolution; (2) this effect holds true even when the generation time of species is controlled for; and (3) culture allows us to evolve over short time scales, which are normally accessible only to short-lived species, while at the same time allowing for us to enjoy the benefits of having a long life history.

Full Citation: Perreault C. (2012, Sep 14). The Pace of Cultural Evolution. PLoS ONE 7(9): e45150. doi:10.1371/journal.pone.0045150

Here is a little bit of the introduction:


Humans dominate the earth’s ecosystems [1]. Today, our uncommonly large range encompasses most of the world’s terrestrial habitats, and human populations thrive in environments as diverse as the Amazonian jungle and the Arctic desert. This adaptive radiation has been explained by our capacity to socially learn information (culture) [2][4]. Culture is an inheritance system that parallels and interacts with the genetic system [5][8]. Cultural variation and innovations accumulate in a population throughout time, allowing for complex cultural adaptations to evolve [9][13]. Because it is assumed that cultural evolution occurs faster than biological evolution on average, humans can adapt to new ecosystems more rapidly than other animals [4]. Yet, the evidence for the hypothesis that cultural evolution is faster than biological evolution is anecdotal [3], [14] and there are no systematic comparisons of cultural and biological rates of change. Moreover, we do not know how much faster, if at all, culture can change compared to biological phenotypes.

Cultural evolution is expected to be faster than biological evolution because of its Lamarckian nature, and because cultural information is transmitted through different routes than genetic information. While variation in biological evolution arises from random mutations, Lamarckian-like guided variation, which occurs through modifications to knowledge, skills and technologies made by an individual that are subsequently transmitted to other individuals, is a potent source of cultural variation [3], [5], [7], [15], [16]. Thus, in contrast to biological evolution, which is blind, cultural evolution can be a directed and consequently faster process. The pace of biological evolution is also constrained by the generation time of the species, since genetic information is transmitted vertically through sexual reproduction. While cultural information can be transmitted from parents to offspring, it is also transmitted obliquely, between non-parents from a previous generation, and horizontally, between contemporaries. This transmission mode gives cultural evolution the potential to spread rapidly in a population, much like an epidemic disease [3], [5], [7], [15], [17].

However, it is not entirely obvious that cultural evolution is faster than biological evolution. On the one hand, the archaeological record is full of instances where traditions have remained remarkably stable over hundreds of years. Microlithic tools, for example, appeared in Northern Asia around 17–18,000 Before Present (BP), and remained part of the hunter-gatherers toolkit until after 14,000 BP [18]. In addition, the Japanese sword, which is a much more complex technology, has been fabricated following essentially the same steps for nearly 700 years [19], [20]. On the other hand, biologists regularly observe evolutionary change over much smaller time scales. Darwin’s Finches, a group of bird species inhabiting the Galapagos Islands, undergo morphological change on a yearly scale in what has become a textbook, classic example of biological evolution [21]. These examples indicate that the distributions of biological and cultural rates of change are, at the very least, overlapping ones. Culture might be less constrained than biology and have the potential to change instantaneously. However, much of what we know from anthropological and psychological research tells us that culture will rarely change instantly. Deviation from a group’s social norms can be costly, and can result in punishment [22][25], while social and psychological mechanisms, such as the ones that lead individuals to mark their ethnic identity [26] or conformism [27], will also tend to act against rapid change in an individual’s behavior. Thus, given these forces that can act against cultural change, one can ask what is the characteristic pace of cultural evolution, and how does it compare to the pace of biological evolution? In this study, I try to answer these questions by comparing the rates of change in technologies, as observed in the historical and archaeological record to the rates of morphological change, as seen in contemporary and fossil animal populations.

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