1.4.a Biological and Cultural factors in human evolution

Biocultural Evolution–An Overview

“Biocultural evolution” is a really useful phrase for anthropologists. Many of us agree that the term captures something fundamental about humanity’s identity, about our place in the world. The phrase efficiently points toward the simultaneous tension and intimate proximity between our biological evolutionary origins and inheritance, on the one hand, and our symbolically structured, socially entangled, and technologically shaped lives, on the other.

Indeed, biocultural evolution is a staple term that college students learn in introductory anthropology courses. It gives a thematic focus to exploring the evidence for how prehistoric culture, technology, population migrations, and interbreeding patterns contributed to the rise of sickle cell anemia in Central and West African populations … as a biological adaptation to resist malaria infection! Students who have taken Anthro 101 or an Introduction to Physical/Biological Anthropology course will find the concept–and very possibly the example I just mentioned–familiar. When we see one of the few, really clearly documented examples of biocultural evolution, we immediately get a more profound appreciation about how we shape our own biology, perhaps just as much as it shapes us.

The phrase is not problem-free. From the beginning, there has been–and there certainly remains–a conceptual imbalance between the concept’s biological and cultural dimensions. The evolutionary theory foundation for understanding biological change in populations enjoys a solid disciplinary history, with both healthy debates and advancing scientific knowledge. However, when it comes to culture and its connection to biology, moments of clarity tend to be obscured by clouds of intellectual confusion and disagreement. Thus, a major point of departure for this blog is consideration and clarification of the culture concept and the phenomenon of culture’s evolutionary emergence as a major factor–interlinked with biology–in shaping human diversity.

FIRST DEFINITIONS

The definition given in the textbook that I use in teaching Oxford College of Emory University’s Anthropology 201: Concepts and Methods in Biological Anthropology is straightforward:

Biocultural Evolution: The mutual, interactive evolution of human biology and culture; the concept that biology makes culture possible and that developing culture further influences the direction of biological evolution; a basic concept in understanding the unique components of human evolution. (Jurmain et al. 2012: 7)

The middle part of the definition above is the sense in which the term most often gets used in current academic literature on human evolution. A key part of the definition is that there is a dynamic feedback over time between biological and cultural changes. Consider recent archaeological research that has provided striking evidence for big game hunting, transport, butchering, and small-group meat sharing around a campfire around 300,000 years ago in the Near East (Stiner et al. 2009). The biocultural-feedback concept helps us to place this finding in a bigger framework of human evolution. The nutritional and resulting fitness benefits of cooperative hunting and food-sharing–which were presumably socially learned, cultural behaviors that our Middle Pleistocene ancestors exhibited–would have shaped natural selection over subsequent generations for direct and indirect reciprocity and reputation monitoring behaviors (for a clear definition of direct versus indirect reciprocity, see Nowak 2006). Culture can influence biological evolution. And in turn, biological evolution shapes cultural behavior patterns in later generations. So far, so good.

However, I would suggest that the first part of the biocultural definition above (“mutual, interactive evolution”) means very different things to different specialists within the umbrella discipline of Anthropology. This raises one problem. Different anthropologists who use the term “biocultural evolution” mean very different, sometimes logically incompatible things when they talk about culture. We see this most clearly in the contrast between dual-inheritance theory research and biological/medical anthropological research on the cultural causes of health disparities. Dual-inheritance theorists were–as far as I have been able to discern–the first to use the term biocultural evolution, back in the 1970′s. Researchers such as Eugene Ruyle, William Durham, Charles Lumsden, E. O. Wilson, Luca Cavalli-Sforza, Robert Boyd, and Peter Richerson offered variations on the theme that intergenerational inheritance in human populations occurs on two main channels: the genetic and the cultural. Reasoning along this line was common then. (Mark Flinn and Dick Alexander [1982] provided a nice early review of dual-inheritance models.) Richard Dawkins coined his now-famous (and social-media-transformed) “meme” in his best-seller The Selfish Gene(1976). In popular essays around the same time, Stephen Jay Gould described cultural inheritance as Lamarckian. We socially pass on learned or socially acquired traits to the next generation. (In comparison, genetic inheritance is mainly only modified by random mutation, and it is natural selection that shapes adaptation over the generations on the population level.) In any case, inquiry into cultural inheritance as being analogous to genetic inheritance–and thus forming a dual-channel inheritance dynamic in human evolution–has certainly been productive. Boyd and Richerson’s work (collected in their 2004 volume) highlights three robust, albeit very general, insights from dual-inheritance theory:

1. The socio-cognitive capacity to learn fitness enhancing behaviors from conspecifics is most likely to evolve in populations inhabiting substantially unpredictable environments. In other words, cultural learning can be an adaptive strategy when your environment really varies randomly and over space and over time.
2. Status, resource-holding power, and reputation may be especially important in shaping the social dynamics of learning and imitation, producing cultural transmission dynamics that are “horizontal” (within generations) as well as “vertical” (between generations).
3. Reputation-monitoring, punishment of free-loaders, AND punishment of non-punishers (that is, “second-order free-loaders”) were additional behaviors favored by natural selection in complex, uncertain environments; this was because, in such environments, groups with genetic instructions influencing the development of reciprocal altruism AND reputation monitoring AND second-order punishment would have had higher growth and dispersal rates, leading to the formation of more and more (and perhaps larger, more socially and behaviorally complex) groups over the generations.

As I will discuss in another post, second- (or higher-order) free-loading, reputation-monitoring and punishment emerges as an especially interesting problem–one which Boyd and Richerson’s work, in particular, deserves credit for bringing to light … and one that may further help us to understand human evolution as biocultural evolution.

Of course, the notion of culture having to do with transmission and inheritance of ideas, behaviors, and artifacts is not unique to dual-inheritance research, which is a quite specialized area of inquiry within Biological Anthropology and Human Biology. Thus, most introductory textbooks in Cultural Anthropology also emphasize that culture is what is historically transmitted, especially in the process of childhood enculturation, across generations. The problem is that dual inheritance theory would define culture only as the vertical or horizontal transmission of behaviors and ideas, whereas cultural anthropologists tend to use the concept of culture as a much more encompassing socio-cognitive and symbolically structured phenomenon, often constraining and guiding our embodied social actions … but sometimes opening up possibilities for agency, social change, and resistance. From the biological anthropologist’s perspective, once you allow that everything that humans do–and how we do it–is culture, the possibility of clear definition recedes quickly toward the horizon.

It is telling, then, that biological/medical anthropologists most sympathetic to the idea that culture pervasively influences disparate health experiences and outcomes–especially in the context of income and power inequality–call their approach “biocultural,” but they do not clearly define culture. Consider the otherwise excellent volume edited by Alan Goodman and Thomas Leatherman, Building a New Biocultural Synthesis (1998). A lot of attention is given to biological variation and its measurement. A lot of argument–usually well-reasoned, with clear scholarly support–is devoted to themes like political economy and inequality. In contrast to Richerson and Boyd’s similarly well-reasoned Not By Genes Alone (2006), no contributor to the Goodman and Leatherman volume starts out by defining culture. I underscore that this is a problem precisely because Goodman and Leatherman, in their introductory chapter, state that their goal is to TRAVERSE THE CHASM between biology and culture. This is sort of hard to do if you don’t know where the chasm begins or ends on the culture side of the gap. They and other contributors present compelling arguments and evidence that symbolic structures and power relationships influence human health, well-being, and demography. Yet, their version of biocultural synthesis does not define culture.

I will state up front that there are a lot of reasons to conclude that human culture is indeed about more than transmitting ideas and behaviors. Insights from dual-inheritance research are highly valuable scientifically, but they ignore why Goodman and Leatherman perceive a chasm between evolutionary and cultural analysis frameworks.

This finally brings us to the last part of the definition given above (“understanding the unique components of human evolution”). One might think, then, that maybe it’s not so important to define culture. It may be enough to argue that culture is not just social transmission of behaviors. It’s all of that complex symbolic and social stuff, which is part of dialectics rather than evolution … And which can–and has been–analyzed from an enormous variety of interweaving humanistic and social science approaches. But the evolutionary emergence of human culture (whatever it may actually be) is a compelling scientific problem. When it comes down to it, anthropologists broadly agree that biocultural evolution is an important concept, so much so that it is a staple of what we teach undergraduates at the introductory level. The evolution of human culture is somehow connected to our capacity for language, tool-making and use, and effective participation in really complicated social networks. The point of departure in this blog–as I try to clarify biocultural evolution as a human-specific evolutionary process–is that exploring where we came from will help us to break down and define the phenomenon of culture much more clearly. In doing so, we will also better understand the relationship between culture and biology.

 source : https://blogs.emory.edu/bioculturalevolution/biocultural-overview/