Just because you repeat something doesn't make it true.[1] Do you have any actual support for your clam that it took thousands of years?
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[1]: Except for the Goebbelian definition of "true".
He found that by breeding and selecting for the more human friendly animals they became tamer and tamer. Now they are to the point of domestication. True domestication as I have heard from some means that the animal cannot thrive in the wild as its wild counter part can. This is a technical labeling issue as in some dogs have reversed domestication on some islands etc.
The fox story in russia is interesting since they found that there was a reduction in adrenaline in the fox's as they became tamer and tamer. The reduction caused them to adopt traits similar to domesticated dogs: wagging tails, floppy ears, coat color change. They did embronic transplants and found wild mothers with tame embryo's raised tame offspring and the opposite was also true. So it was a genetic change that resulted in this taming. It only took 50 generations to result in the change.
It would not be that far off to think that humans gave food to cooperative animals and killed the aggressive ones.
Under labor conditions I would say at least 50 generations. But without these perfect conditions it is easy to imagine that it takes longer.
2) Foxes. The plural is “foxes”. “Fox's” is the singular possessive, as in “Wow, look at that fox's beautiful pelt!”.
No, seems fifty horse generations would span about 100-150 years: https://thehorse.com/16463/when-are-fillies-fertile/
Source: https://animalcorner.org/blog/horse-lifespan/
In the longest case, we could assume 50 x 30 = 1500 years. If you say that every generation came to live after 5 years, then 50 x 5 = 250 years. Again, you want to pick the absolute lowest bound (lowest number of generations) of the lowest bound (shortest years of generations) under labor conditions, which did not happen in reality. But if you think it took only 100-150 years to domesticate horses, then fine. I cannot provide a definite proof that you are wrong.