Science Magazine reports that dogs in Croatia and neighboring countries are thought to have doubled in size between 2,000 and 8,000 years ago, based on a study led by zooarchaeologist Martin Welker of Arizona State Museum. Some 8,000 years ago, Neolithic farmers from Anatolia and the Middle East brought dogs weighing about 33 pounds with them to central and southeastern Europe.

Analysis of the isotopes in the teeth of Neolithic sheep in the region shows that they were taken high into the mountains to graze, where they would have needed to be protected from wolves and bears, Welker explained. By about 6,000 years ago, the average dog in Central Europe weighed about 37 pounds.

By the Roman period, the average dog weighed more than 50 pounds. Roman records indicate that some dogs used for herding or as guard dogs reached 70 pounds or more. Depictions in murals, however, show that the Romans also bred smaller lapdogs.

source archeaology.org