I can't understand why the author used 'have' instead of 'had', though the context clearly indicate the past?
It was only 50 years ago that humanity began to extend its presence into space — first with robots, then with animals and finally with humans. This tentative expansion of our species towards other worlds has been made possible by the development of technology, which has finally started to reach a level that can complement and support our imagination and desire for exploration. However, considering the size of the universe and the growing number of promising sites on many worlds where life might quite like to snuggle up, the search has barely begun. When we finally find life on another world — and we will — it will be one of the most significant cultural events in human history, having a profound impact on the question of our origins. It is not surprising, therefore, to find that such possibilities have been discussed by every human civilisation and culture, primitive or advanced, as far back as we have written records. Even before these thoughts were given a name, such extraterrestrial wonderings found their outlet through myths, cave paintings, fictional literature, music and poetry, then later through films and TV shows.