Origin of the domestic dog or the result of natural introgression as the dog expanded across Eurasia. In 2018, a study found a small amount of dog ancestry in 62% of Eurasian wolf specimens looked at, that hybridization had occurred across a wide number of timescales and not just recently, however in contrast there was almost no admixture detected in the North American specimens. There was introgression of the male dog into the wolf, but also one hybrid detected which was the result of a male wolf crossed with a female dog. Wolves have maintained their phenotype differences from the dog, which indicates low-frequency hybridization.
Origin of the domestic dog to be the cellular correlate of learning and memory, and this change may have altered the learning and memory abilities of dogs in comparison to wolves. Unlike other domestic species which were primarily selected for production-related traits, dogs were initially selected for their behaviors. In 2016, a study found that there were only 11 fixed genes that showed variation between wolves and dogs. These gene variations were unlikely to have been the result of natural evolution, and indicate selection on both morphology and behavior during dog domestication. There was evidence of selection during dog domestication of genes that affect the