Across the animal kingdom, we see remarkable variation in brain size. This variation has
even increased over evolutionary time. Traditionally, studies aiming to explain brain size …

In the ongoing discussion about brain evolution in vertebrates, the main interest has shifted
from theories focusing on energy balance to theories proposing social or ecological benefits …

To explain variation in relative brain size among homoiothermic vertebrates, we propose the
Expensive Brain hypothesis as a unifying explanatory framework. It claims that the costs of a …

Background Brain signaling requires energy. The cost of maintaining and supporting
energetically demanding neurons is the key constraint on brain size. The dramatic increase …

Brain size differs substantially among species, and several hypotheses have been proposed
to explain the evolution of brain size. Because the brain is among the most energetically …

Costs and benefits of encephalization are a major topic of debate in the study of primate and
human evolution. Comparative studies provide an opportunity to test the validity of a …

Despite decades of research, much uncertainty remains regarding the selection pressures
responsible for brain size variation. Whilst the influential social brain hypothesis once …

The expensive brain hypothesis predicts that the lowest stable level of steady energy input
acts as a strong constraint on a species' brain size, and thus, that periodic troughs in net …

Relative brain size has long been considered a reflection of cognitive capacities and has
played a fundamental role in developing core theories in the life sciences. Yet, the notion …

Many studies assume that an increase in brain size is beneficial. However, the costs of
producing and maintaining a brain are high, and we argue that brain size should be …