Mentioning mules reminds me of the Neo-Darwinist beleif that two similar things not being able to reproduce is the only and solid proof of specizations. Interesting. So does that mean a horse and a donkey are the same species since they can reproduce? The evo logic seems flimsy.
I believe it is hinnies - jennies are female donkeys
Wrong.
Different species are defined as groups who do NOT reproduce, not those who CAN'T.
You might want to read up on the subject a bit more.
I would imagine early herdsmen attempted to interbreed every variety of goat to every variety of cow, or deer, or whathaveyou "just to see what happens".
Today, with modern science at our command, we will succeed in creating a kosher pig.
It's not a "belief", it's part of the definition of "species".
Take an island with plenty of grass and water. Introduce 100 stallions and 100 jennies. 100 years later it will be free of equids. Same thing with 100 mares and 100 (male) donkeys. If you have co-ed horses and asses, 100 years later you still will have two popoulations that breed true. Therefor horses and donkeys are different species.