I think there is a tendency to think we are either aliens ourselves, or influenced by aliens in some way in the past because we are sapient and most other animals are not, or don’t seem to be at least. No one knows why we are the way we are; why we have complex dreams; why we fall in love instead of simply mating; I think we don’t know enough to say anything for definite about our past, perhaps we are aliens from another planet? Perhaps aliens influenced us? But what does aliens really mean? On our own planet we call people from other countries who come into our country, aliens; so to me aliens are just more people from other planets, it doesn’t matter to me where we came from or how we became the way we are – people discover new things all the time, either by themselves or by other people (or aliens) giving them ideas. If there are aliens on other planets I imagine that they will be very similar to ourselves; I also think there is a possibility that the universe is very new, which is why we know so little, and that Earth could be the first civilisation and that we will spread out into space much the same as we did on Earth – more likely there are lots of little pockets of life like ours, slowly developing like ours, and eventually they will travel across space and meet up with everyone else – some developing more quickly than others, again like on Earth.

Edit: on the agriculture thing; learning to farm the land depends a lot on geography and environment, earlier humans lived in areas where there were lots of roaming beasts to kill but where the land wasn't good for growing stuff, like Africa. The humans were, and still are, nomadic in nature and some found themselves in more temperate areas where things grew easily, it is natural to settle in such places and learn how to harvest the local vegetation and develop upon that. In some parts of the world people still just eat mostly animals, Mongolia for instance, because their environment does not support vegetation.