Everyone loves the dinosaurs. A lot of people – if the Jurassic Park films are to be believed – would like to see them come back. But without their extinction, we wouldn’t be here today.
Even now, it’s still not clear what exactly caused the extinction event – but the best known hypothesis is that of Luis and Walter Alvarez, which states that a meteoric or cometary impact caused a nuclear winter-like effect that altered the climate drastically, wiping out something like 75% of all species alive at the time. The effects were particularly felt by larger species – which included most dinosaurs.
In the wake of the event, now open evolutionary niches were occupied by mammals and birds, including our own ancestors.