Alien, Human and Donkey

An alien who came to our planet told others the following: ---Humans are very interesting, because they are the only beings who have been able to over live with a number of contrasts and inequalities such as; laughing and crying, loving and hating, rejoicing and grieving, marrying and divorcing, making weapons and then using them against themselves, dirtying clean water and then purifying it again to drink it. --- Really! said the listeners. ---Yes, but what struck me most is that they are the only ones who have not needed other worlds to live. For they have theirs with a complete system of unequalled biodiversity, in paramos, snow-capped mountains, rivers, seas, forests, jungles, mountain ranges, deserts, savannahs, and so on. However, I have heard them say that they are looking for a better one than the one they have. What do you think? They were silent for a moment and then there was a burst of hahahahahahahahaha.