Why is there almost never more than one intelligent species on a planet in Scifi.

[philosophicalbastard]

Have you considered the two species being separated by the geography of the planet, like two continents on either side of the world seperated by water? Because, unless a large amount of either species travels to the other continent they should be able to develop in peace.

Unless they evolve their society and technology at roughly the same pace (highly unlikely, tech leaps happen by chance and need) one race will simply dominate the "primitives" look at what happened on Earth.

Yes, but at least the under developed species would have a fighting chance, unless the more advanced species diseases were communicable.

 

[xqxm]

multiple intelligent species on a planet would quickly lead to genocide, and a single victor.