Parental investment and body temperature explain encephalization in vertebrates

The massive increase in relative brain size during vertebrate evolution remains poorly understood. Given the high energetic costs of brain development, we predicted that encephalization (major evolutionary brain size expansion) is only possible in species capable of greater parental investment per offspring. Comparative analyses across all major vertebrate classes (N=2600 species) revealed that protecting or provisioning eggs or embryos is associated with larger newborns. Subsequent analyses confirmed that newborn size and adult brain size underwent correlated evolution in birds, mammals, and cartilaginous fishes, but not in other fishes, amphibians, and reptiles, even if the latter had large offspring. Thus, greater pre-hatching investment is necessary but not sufficient for encephalization in vertebrates. A second prediction from the high costs of brain tissue is that encephalization is impeded in species with low or fluctuating body temperatures. We found a positive relationship (alb..., , , # Data from: Parental provisioning is a precondition for major encephalization in vertebrates

[https://doi.org/10.5061/dryad.sn02v6xd5](https://doi.org/10.5061/dryad.sn02v6xd5)

This study presents comparative analyses across all major vertebrate classes, examining the impact of relative offspring size and egg/parental care behavior on the evolution of brain size.

## Description of the data and file structure

**ParProv_Song_etal2025_Data_submit.xlsx**

The dataset includes brain mass (**BrainMass.BrM..g.**) and body mass (**Bodymass.BdM..g.**) combined with offspring mass (**Offspring**).

* **Offspring_note**: Indicates whether the offspring mass was calculated from hatchling/neonate mass or converted from egg volume.
* For some species, adult brain specimens were unavailable. In such cases, the provided body mass (BodyMass.BdM.g) was often too small compared to common adult sizes, leading to an overestimation of relative offspring size. To address this, the common adult body mass (...,