system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why are we not able to domesticate bears?

I really want a pet bear.
gpt
We could. There's a guy in Russia who domesticated foxes in a period of just a few generations. 

What has to happen though is a number of specimens need to be repeatedly bred. From each litter you select the most docile and only breed those for the next generation. 

Some problems exist. First of all, bears are very strong, so interacting with them to determine the most docile is difficult.  Second, foxes (and dogs and cats) reach sexual maturity within 9-10 months, in time to breed for the next season, and an average litter is 4-6 kits. On the other hand, American black bears only reach sexual maturity in 3-5 years and have an average of 2-3 cubs. 

And then there's the amount you have to feed bears vs foxes. And the space they require.