>>37277261History shows time and time again that isn't an obstacle for thirsty soldiers or indigenous tribes. Hispanic mestizo races came from extensive Spaniard x Amerindian race mixing, as European women at large didn't like the idea of travelling months to the New World.
If Pokemon existed the practice would be more frowned upon than race mixing, but less than bestiality, specially if human can procreate with Pokemon. In a more established and peaceful society these rules would be more enforced.