However, one place it didn't happen was in North America. A recent study of DNA, used both the maternal and paternal lines of fossil and recent dogs. The new analyses confirmed that American wolves have not contributed any genes to living dogs today. Furthermore, the DNA of the ancient wolf fossils comes from wolf lineages that no longer exist! That is, no wolf still living contributed to dogs, alive or recently dead. The wolves that did contribute either became extinct or they themselves all became proto dogs
The latest DNA discoveries, which included DNA samples from fossil wolf and dog genes, showed that today's dogs have little in common with today's wolves anywhere in the world. The dog's shared wolf inheritance comes not from modern wolves, but from small wolves who are now extinct. So all those people bragging about how wolf-like their pit bulls or German Shepherds actually are mistaken, if they think that Timber wolf genes are in their dog's makeup.
Yes, I do know about real wolf-dogs: the mating of a captive wolf with a dog. Those scientists in years to come who are tracing dog lineages will be able to trace this new lines of dogs, and will add modern wolves to the genetic mix of such wolf-dogs and their progeny.
My cousin, Dr. David Ostrach, has trained both captive wolves and wolf-dog mixes to be service dogs. David is wheelchair bound and his wolf-dogs are essential to him. There are 100% dogs who can meet his needs. But he prefers to train these handsome animals himself from cubs to adults. The one I met recently, 3/4 wolf, lay quietly in a crowded restaurant for about two hours. She didn't seek handouts at all. Nor did she seek attention. I patted her on the head. She didn't object, nor did she wag her tail or look me in the eyes. She tolerated my pat, but otherwise ignored all of us. When we left the restaurant, and she could face David, she howled to let him know she wanted to go home. The sounds she made were definitely not a dog's.
These modern wolf-dog mixes do exist, but they aren't from the same wolf-dog ancestry that created the dogs we know today.