Cat brains have shrunk significantly since humans began looking after them as pets 10,000 years ago, according to a new study that sheds more light on the effects of domestication on mammals.
While reduced brain size, compared with wild individuals, is believed to be a key characteristic of domesticated mammal species, researchers, including Raffaela Lesch from the University of Vienna, said such brain size comparisons are often based on old, inaccessible literature.
In some cases, they say studies that drew comparisons between domestic animals and wild species may no longer represent the true progenitor species of the domestic species being assessed.
In the new research, published in the journal Royal Society Open Science on Wednesday, scientists replicated studies on cranial volumes in domestic cats – published in the 1960s and 1970s – that compared wildcats, domestic cats, and their hybrids.
They assessed the skull sizes of domestic cats (Felis catus) and compared them to those of European wildcats (Felis silvestris) and African wildcats (Felis lybica).
The study found that domestic cats indeed have smaller skulls – indicating smaller brains – than both European and African wildcats. It also revealed that the skull size of hybrids of domestic cats and European wildcats have cranial volumes between those of the two parent species.
In these felines, researchers said natural selection for tameness in domestication led to the production of fewer neural crest cells, which are linked to excitability and fear, contributing to smaller skull and brain size.
The scientists believe further studies on more species can help better understand other effects of domestication on cats, adding that there are several limitations to drawing information from old literature that is not easy to access.
“Much of the literature that compares wild and domestic animals is difficult to access, or may have methodological issues,” Dr Lesch said. “We have to put effort into replicating old findings to further the field of domestication research and to see whether hypotheses, like the neural crest/domestication syndrome hypothesis of Wilkins and colleagues, are built on a solid foundation.”
In further research, the scientists plan to replicate more old studies, not only for cats, but across other domestic species.
