Sod the chemistry! Every assumption we make is only that. We know
almost nothing about our own planet. Particularly below the surface of
the seas which cover much of our own world. We cannot imagine any
dominantly intelligent species not having our avarice, aggression and
chronic immorality. It is completely beyond our way of thinking except
in sci-fantasy terms. Our intelligence is based on learning to take
something from somebody else, by force, rather than obtaining it for
ourselves. Hierarchy is a corruption built into our genes. A coat of
paint to disguise theft by the strongest from the weakest. Strongest
always wins. We even equate this with survival of species. Survival of
the fittest. Fittest for what exactly? Resource depletion and
genocide?

We assume that no other "alien" species is as curious or driven to
explore because they haven't yet taken advanatge of the White House
Lawn's excellent landing facilities. Did any other species need to
escape endlessly from the destruction of its habitat due to
overcrowding, corruption at the top of the local mafia and yet more
resource depletion? Africa has hardly moved on in millions of years.
Is Afria on another planet? Are the present inhabitants another race?
Or have they merely borrowed our more destructive toys to continue
their inter-tribal wars of stick waving? Is modern America any more
than a bunch of stick wavers ihabiting the last remaining vestiges of
their particular bit of the global jungle? They took it from the last
lot and it seems that others will soon outbreed them. To repeat the
land theft trick in a more subtle way. Survival of the fittest? Fit
for what? Slum dwelling, crime and drugs abuse?

Who knows how many intelligent races out there see the scourge of the
human race as the most dangerous threat to *their* survival? They may
be operating a no-go zone around us out to dozens of light years. Just
to keep us safely locked in. If we ever go hyperdrive we may suddenly
cease to exist. Survival of the fittest may have not count for us when
we finally have the ability to spread the human infection. The bared
teeth are only ever a moment away. Pass me my stick. No, I like yours
better. I will take yours!