A new study reports that domestic dogs experienced a sharp reduction in brain size during the Late Neolithic period, at least 5,000 years ago, coinciding with the rise of farming and permanent human settlements. By that time, dog brains had shrunk to volumes comparable to those of modern small terrier and dwarf breeds. The findings were published in Royal Society Open Science.

Researchers analyzed skulls of wolves and dogs dating from 35,000 to 5,000 years ago using endocranial volume measurements from computed tomography scans. They found that dog brains were approximately 32 percent to 46 percent smaller than those of ancient and modern wolves. This reduction aligns with patterns seen in domesticated species, where anatomical changes reflect adaptation to life under human care.

Earlier dogs living alongside humans did not immediately show smaller brains, and some even had slightly larger brain volumes than wolves. The evidence suggests that brain size may have initially increased during early domestication before contracting significantly in the Late Neolithic. Scientists link this shift to more stable food supplies and protection in agrarian societies, where social and communication skills with humans became more advantageous than survival traits needed in the wild.