The cultural evolution of adaptive-trait diversity when resources are uncertain and finite

In this paper, we seek to build on existing mathematical studies of cultural change by exploring how the diversity of adaptive cultural traits evolves by innovation and cultural transmission when the payoff from adopting traits is both uncertain and frequency dependent. The model is particularly aimed at understanding the evolution of subsistence trait diversity, since the payoff from exploiting particular resources is often variable and subject to diminishing returns as a result of overexploitation. We find that traits that exploit the same shared resource evolve most quickly when intermediate rates of cultural transmission promote fluctuation in trait diversity. Higher rates of cultural transmission, which promote predominantly low diversity, and lower rates, which promote predominantly high diversity, both retard the adoption of traits offering higher payoff. We also find that the distribution of traits that exploit independent resources can evolve towards the theoretical Ideal Free Distribution so long as the rate of cultural transmission is low. Increasing the rate of cultural transmission reduces trait diversity, so that a more limited number of "niches" are occupied at any given time

A Multi-Level Choice Theory

The Great Recession has called into question many tenets of Neo-classical Microeconomics. Neo-classical theory allows each agent only one fixed type, homo economicus, while not denying other possible types as in adverse selection. We propose that economic agents not only choose their market basket but also their types. Agents are members of groups and each group has social norms to which the agent more or less conforms. His/her market behavior trades off private well being which responds to prices but also social well being which responds to norms. We show how deviation from norms are determined. We also discuss other anomalies in the light of this model.

Cultural Incubators and Spread of Innovation

Several forms of social learning rely on the direct or indirect evaluation of the fitness of cultural traits. Here we argue, via a simple agent-based model, that payoff uncertainty, that is the correlation between a trait and the signal used to evaluate its fitness, plays a pivotal role in the spread of beneficial innovation. More specifically, we examine how this correlation affects the evolutionary dynamics of different forms of social learning and how each can generate divergent historical trajectories depending on the size of the sample pool. In particular, we demonstrate that social learning by copying the best model is particularly susceptible to a sampling effect caused by the interaction of payoff uncertainty, the number of models sampled (the sample pool) and the frequency with which a trait is present in the population. As a result, we identify circumstances in which smaller sample pools can act as ‘cultural incubators’ that promote the spread of innovations, while more widespread sampling of the population actually retards the rate of cultural evolution

Behind, Between, and Beyond Anthropomorphic Models

The plurality of models of ultimate reality is a central problem for religious philosophy. This essay sketches what is involved in mounting comparative inquiries across the plurality of models. In order to illustrate what advance would look like in such a comparative inquiry, an argument is presented to show that highly anthropomorphic models of ultimate reality are inferior to a number of competitors. This paper was delivered as a keynote address during the APA Pacific 2007 Mini-Conference on Models of God

Vengefulness Evolves in Small Groups

We discuss how small group interactions overcome evolutionary problems that might otherwise erode vengefulness as a preference trait. The basic viability problem is that the fitness benefits of vengeance often do not cover its personal cost. Even when a sufficiently high level of vengefulness brings increased fitness, at lower levels, vengefulness has a negative fitness gradient. This leads to the threshold problem: how can vengefulness become established in the first place? If it somehow becomes established at a high level, vengefulness creates an attractive niche for cheap imitators, those who look like highly vengeful types but do not bear the costs. This is the mimicry problem, and unchecked it could eliminate vengeful traits. We show how within-group social norms can solve these problems even when encounters with outsiders are also important.

Learning in evolutionary environments

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Forgetting and the Value of Social Information

Information is everywhere in nature, however it can be deceitful or incorrect, so not all information should be used. Foraging pollinators utilize variable and ephemeral resources so learning about patch quality and nectar replenishment rates are essential to success and survival. However, remembering information after it is no longer relevant is not advantageous. It has been theorized that a pollinator’s memory should reflect their environment. Bumblebees are known to use both personal information (information gathered through trial and error) and social information (information gained through observations of or interactions with other animals or their products) in foraging decisions; however, it is currently unknown how social and personal information are valued in bumblebee memory. We conducted an experiment to illuminate the rate at which bumblebees (Bombus impatiens)learn and forget personal and social information. We manipulated the value of social and personal information by varying their reliabilities, and tested the retention of that learned information after 4, 8, and 24 hours. We found that social information is retained better than personal information, and retention decreases as time since learning increases. This experiment is a first step toward elucidating when social or personal information is more valuable to a forager