Man can be replaced by robot?

Why not? The people there are saying:

"nobody is irreplaceable" - or almost anyone

Yet the truth is that the robot could not replace humans in every field - in occupations that involve people is need people.  A robot would not do well in professions such as: doctor, policeman, lawyer, judge, teacher, journalist, scholar, advisor, analyst, etc. - For these professions need people.

The robot will always be rigidly confined to the parameters of his discipline, limited to the schedule. On the other hand, man, beyond technical knowledge by his job, man use something else, something that the robot will not have: soul, emotion, instinct, conscience - is exactly those things that define humanity.

It is known that many investigators used (among scientists) of suspicion (instinct). That some cops overlook some minor mistakes (mercy - emotion) as ... and so on.

The robot will be fixed rigidly. Inappropriate human needs.

Survival of the human species

Only human children needing hospital to birth, offspring of animals not. Why?
Humans are a little weak and  fragile. They can not live in the wilderness like the other animals. They live in a society, sorrounded by other people - human race is very sociable.More than that, people depend each other, and this dependence make the civilization.
Once with the advent of technology, people became more artificial, they change the natural habitat with the comfortable houses, but become more isolated of other people day after day. And even this isolation is the one who will destroy the human race.
The only hope for people to survive is to maintain the relations with other people. Together, people are the civilization itself.

There are other inhabited planets?

Why not? What makes us so special that people consider that I be alone in this universe. Even religion talks about being outside of our world - eg.: Angels.

But to be taken into account that a lot of great distances (million billion light years) makes it impossible to interference between civilizations inhabited planets.

From a Christian point of view (according to some opinions), between humans and aliens would be a split gate, because the farmers are under the burden of sin (virus in the universe).