[Joe Hadenuf]

If conditions are ideal on earth for the development of one intelligent species, why haven't two species developed? A strong conclusion would be that we are unique.

Make that,

There can only be one human species, and there are plenty of other types of species on this planet, literally thousands, some that do have a limited degree of intelligence.

[ThirdMate]

Let me clarify what I mean by an intelligent species. By intelligent species I mean one which is capable of making and using tools and communicating abstract thought.

That I believe is the condition of intelligence posited in the article.

rgds,
3/M