[Photo from Wikimedia. Click for link.]
Remember hobbits on Flores Island, Indonesia. Tiny people, debatably non-human — or rather, their skeletons.
Looking into the past through the scraps that have survived to the present is tantalising.
Imagine if other sentient species had survived (like the hobbits and Neanderthals) and humans were only one of many groups. How different would Earth be and our perception of ourselves?
But all the intangibles — language, song, social structure, religion — are gone beyond recall. Broken bones, stone implements and the occasional fossilised footprint are all we have — just enough to create academic debate.