The difference between a pet dog and a wolf could be down to as few as 40 genes, according to a study into tameness.
The research also found that to adapt to a life on the farm or in the home takes many more changes in gene activity than that required to love humans.
A Swedish team compared two groups of farm-raised silver foxes in Siberia, one where for 40 generations the foxes have been selected for their friendly nature, while the other was raised in the farm but not selected for tameness.
In the tame foxes, they found surprisingly limited changes in gene activity in the brain compared with the non-selected silver foxes. Foxes have about 25,000 genes.
When compared with wild foxes both groups had 3,000 differences. There were a similar number of differences with dogs revealing that being friendly to humans takes far fewer genetic changes than being domesticated.