modern dogs were domesticated from a single population of wolves 20,000 to 40,000 years ago.

Modern dogs are thought to have been domesticated from wolves, but exactly when is unclear -- in 2017, a study published in the journal Nature Communications found that modern dogs were domesticated from a single population of wolves 20,000 to 40,000 years ago.
end partial quote from:
https://www.cnn.com/travel/article/frozen-puppy-intl-scli-scn/index.html

If this is true then all dogs now come from this one population where people started to domesticate wolves. Then through selective inbreeding for traits all dog populations have been created through selectively breeding for specific Traits in wolves becoming dogs. So, likely when people liked a specific trait in one dog they bred that dog to maintain that trait or those traits they liked.

It is likely that humans did this to with other humans especially if they were in the Royal Class wherever they were on earth. Because unless people were free they often likely were bred like Dogs were over time until democracies came to be here on earth where most people had freedom not to be treated like slaves and bred for traits.

  Birth Control pills helped women a lot even in the U.S. in regard to this starting in 1960 when they became legal.