I stated they had to produce “fertile” offspring.
Donkeys and horses produce mules. They are not fertile.
Lions and tigers can produce offspring but they are not fertile.
Dogs are direct descendants of wolves. They are considered separate species but a Husky is a lot closer to a wolf than to a chihuahua.
The article talked of the 2 human species not being descendants.
Actually, tiger lion crosses can be fertile. Also bison and cattle (beefalo). I think they have changed the definition of species in recent years as information became known.
susie