Larger brains linked to fewer, larger offspring across birds, mammals, and reptiles

Researchers from the American Museum of Natural History and Princeton University report a link between relative brain size and offspring size across living vertebrates, helping explain oversized bird eggs versus many nonavian dinosaurs, SciTechDaily reported of a Royal Society Open Science study. The team found species with relatively larger brains tend to produce fewer, larger young. Drawing on reproductive and anatomical data from mammals, birds, and reptiles, the results indicate growing a large brain requires more energy and developmental investment per offspring, whether as a larger egg or a larger newborn. Lead author Stephanie Lechki, a Princeton postdoctoral fellow, said many non-avian dinosaurs were enormous yet even the biggest dinosaur eggs were smaller than the largest bird eggs, and that larger bird brains may have pushed larger offspring and eggs. Birds and mammals usually invest in fewer relatively large offspring, while reptiles, including most dinosaurs, often produce many smaller ones. Analyzing mammals, birds, and reptiles in one evolutionary framework showed a consistent brain-offspring pattern, the writeup said.