Inferring social behavior from sexual dimorphism in the fossil record

Area of Science:

• Paleontology
• Evolutionary Biology
• Behavioral Ecology

Background:

• Sexual dimorphism is frequently used to infer mating systems and behavior in extinct species.
• However, the reliability of these inferences based on dimorphism alone is often questioned.
• Few studies rigorously examine extant comparative data to validate such behavioral reconstructions.

Purpose of the Study:

• To evaluate the relationship between measures of sexual dimorphism and various estimates of mating systems and intrasexual competition.
• To determine if extant comparative data support behavioral inferences drawn from dimorphism in extinct taxa.
• To assess the predictive power of dimorphism for reconstructing specific mating systems.

Main Methods:

• Analysis of relationships between quantitative measures of dimorphism (e.g., size, ornamentation).
• Comparison of dimorphism data with behavioral classifications derived from extant species.
• Statistical evaluation of the strength and reliability of correlations between dimorphism and mating system indicators.

Main Results:

• Sexual dimorphism alone provides limited resolution for reconstructing the behavior of extinct species.
• A significant proportion of behavioral inferences based on perceived dimorphism are not supported by extant comparative data.
• The large standard errors in the relationships between dimorphism estimates and behavioral classifications highlight uncertainty.

Conclusions:

• While sexual dimorphism can offer a tentative clue about extinct species' behavior in some instances, it is an unreliable sole indicator.
• In many cases, dimorphism can only suggest polygyny without specifying the exact mating system.
• Relying solely on dimorphism for reconstructing complex behaviors of extinct organisms is cautioned against due to poor predictive power.