@xris,
No.
1.This universe is infinite in extent. In an infinite universe, all possible possibilities become reality. Terrestrial life (in all likelihood) does not constitute all possible theoretical possibilities life can take. These possibilities must therefore exist
somewhere, ergo there is life on other worlds.
2. Humanity exists on a planet in a totally average part of a totally average galaxy orbiting a totally average sun. Therefore, conditions feasible to the inducement of life form the
average state of condition in the universe. By the law of averages, what is average must be replicated in such a way as to make it average (e.g., because our cosmological situation is average, there must be many other places where the cosmological situation, being average, is conducive to the formation of life). Where life
may in theory exist life
should exist should the availability of resources be there. Ergo, there should be other places in the universe life exists (both within and without our time cone). Note this argument does not imply
intelligent life exists elsewhere: I think we can all agree intelligence is almost certainly a most unusual evolutionary adaptation. (If it were common there should be intelligent fish and birds and reptiles and possibly even plants.) Another thing to note is that there could be many planetary configurations inducive to life--A Centauri A & B (
Rigil and
Kent, respectively, following the Arabic name of the star:
centaur's hoof), which orbit each other at roughly 8 AU, or the distance from the Sun to Saturn, would cause a Jupiter effect on each other's (theoretical) planetary systems, for example.
Therefore, we are
not alone in this infinite existence.