Problem 19 - Animal Behavior: An Evolutionary Approach

Question

Richard Prum argues that researchers need a "null model" of the effects of sexual selection in order to determine whether in fact mate choices lead to adaptive outcomes, with female preferences for certain male attributes providing the choosy females with better genes or superior parents. 162 For Prum, the Lande-Kirkpatrick models provide the null in which preferences have no utilitarian adaptive effect but instead are the arbitrary products of a nonselectionist process. He argues that we need to test the predictions from the null model first, rather than focusing on predictions from adaptationist hypotheses about such things as signal honesty and fitness benefits of female preferences. Why have so many researchers employed the adaptationist approach? Do we also need a null hypothesis for behavioral traits that adaptationists have assumed (for the purposes of hypothesis development and testing) promote survival by defeating predators?

Step-by-Step Solution

Answer

Researchers favor adaptationist approaches due to the assumption of direct survival benefits, but testing null hypotheses refutes preconceived advantages in mating and behavior.

Step 1: Understand the Main Argument

Richard Prum argues for the necessity of using a 'null model' in sexual selection research. This null model assumes female mate preferences do not necessarily lead to adaptive benefits, being the result of arbitrary nonadaptive processes.

Step 2: Identify the Null Model Approach

The Lande-Kirkpatrick models serve as Prum's null model by positing that mate preferences are arbitrary and have no adaptive effect. This contrasts with adaptationist models that link mate choice to adaptive benefits.

Step 3: Evaluate the Adaptationist Approach

Many researchers focus on adaptationist hypotheses, which assume that mate preferences offer direct or indirect survival advantages (e.g., better genes or parental care).

Step 4: Consider the Role of the Null Hypothesis

A null hypothesis helps to falsify adaptationist claims by testing the predictions that preferences do not necessarily result in adaptive advantages before exploring adaptationist theories.

Step 5: Apply to Behavioral Traits

The existence of a null hypothesis is also necessary for behavioral traits, challenging the assumption that behaviors assumed by adaptationists inherently promote survival.

Key Concepts

Null Model

In the study of sexual selection, a 'null model' is an essential concept helping researchers dissect the complex dynamics of mate preferences. A null model proposes a scenario where certain traits or preferences appear without any adaptive significance or survival advantage. For instance, females choosing mates based on arbitrary traits rather than traits that provide a genetic or survival benefit. This approach assumes that the preference seen in mate choice doesn't necessarily result in better offspring or higher survival rates.

Richard Prum emphasizes that by starting with a null model, researchers can objectively evaluate if certain mate choices truly provide adaptive outcomes. By understanding this model, scientists aim to differentiate between traits that evolve due to selection pressures and those that might exist merely due to random or nonadaptive factors.

Mate Choice

Mate choice plays a pivotal role in the evolution of species as it directly impacts reproductive success. In sexual selection, mate choice involves preferences that individuals exhibit when selecting possible mates. Such preferences might be for traits reflecting better genes, superior parental abilities, or simply physical attractions.

The debate lies in whether these choices are adaptive. Do they lead to offspring that are better suited for survival? Prum's argument questions the convenience of always assuming that mate choice pertains to evolutionary benefits. Instead, he proposes a closer examination using a null model to determine if some preferences are not associated with survival advantages, but are rather arbitrary. Understanding this helps scientists to better interpret patterns observed in nature.

Adaptationist Approach

The adaptationist approach is a widely used framework in evolutionary biology. It assumes that traits and behaviors in organisms develop primarily because of the adaptive benefits they confer. This means mate choices reflecting a preference for certain traits are often perceived to increase fitness, offering direct or indirect evolutionary advantages.

Many researchers are drawn to this approach for its ability to provide clear hypotheses about survival benefits. However, Prum criticizes overreliance on adaptationist theories without first exploring whether these traits might result from nonadaptive processes. By employing a null model, we can challenge the presumption that all mate choices are adaptive, broadening the scope of evolutionary inquiry.

Lande-Kirkpatrick Models

The Lande-Kirkpatrick models serve as an example of how null models can be utilized in evolutionary studies. These models suggest that mate preferences can be arbitrary, without any adaptive effect on the population. This framework challenges the adaptationist view by proposing that certain sexual selection traits may arise independently of survival benefits.

In use, these models allow researchers to explore the implications of nonadaptive preferences, offering a unique lens through which to view evolutionary processes. By contrasting these models with adaptationist ones, scientists gain a deeper understanding of whether certain mate preferences drive evolutionary change because of selection or due to random factors. This, in turn, enriches the study of sexual selection and broadens the potential interpretations of empirical data.