This is supported by an episode seen in the history of man over and over again, when the more advanced species of man simply outperforms older species of man. Take for example the interction of neanderthal and cro-magnon man.
In the time following the last ice age, Neanderthal man was the dominant species of human in europe. However, as time passed, a growing threat presented itself. Cro-Magnon man began to encroach upon neanderthal's territory.
Cro-Magnon is what can be considered the first example of 'Modern' man. He walked completely upright, used tools, and had the ability to solve complex problems, as well as the capacity for a 'full' language.
This sort of interaction has happened throughout history, so that the one race whom would dominate the earth would also be the most advanced. It is from these episodes that I make the assumption that there can be only one sentient species on a planet. However, there are some limits to this...
When I say that there can be only one species, I really mean that in the long-term sense. While two species of man existed at a time, they were very similar, and also, neither of them were advanced technologically. I contend that once a race begins to become more and more technologically advanced, the chance of another race evolving and striving becomes less and less, until the possibility is no longer possible.
Again, I remind all observers that this is not a debate that can be adequately proven with facts, rather, it is very much a debate of theories. I now leave the floor to my opponent, Ktprktpr.
[Edited on 10-11-2003 by John bull 1]
