UFO

A man was taken for testing his level of intelligence by the crew of an alien spaceship. When he opened his eyes a voice in his head was heard which told him to be quite and explained the aim of alien's mission. They needed to know only one thing: How do human females become pregnant? The young man had explained it without opening his mouth and was understood by them very well.
- Can I ask you something also? - he said.
There was nobody seen inside the spaceship, but the same voice replied:
- Sure!
- How do you reproduce yourselves on your planet?
- Oh, it's very simple. In our world it's enough to wish the same thing looking into the eyes of each other for the both parents of a future kid.
- Aha, that's why you've been hiding from us! Now I understand. Yes, your world is much better organuzed and wiser in comparing to the Earth's one as you are able to survive in such supersexy conditions!