About a year ago now, scientists working in White Sands National Park discovered the largest trail of fossilized human footprints ever found. Over the course of 1.5 kilometres there is a long straight trail of footprints made about 12,000 years ago when the surface was wet and slick with mud.
At several places along the path there are small child tracks, that appear and disappear along the adult footprints. It appears that someone (likely a woman) was carrying a child, and at intervals put the child down then picked him up again.
A sloth crossed their trail, moving perpendicular to the humans. Apparently, the sloth crossed their path once the adult and child had passed, and obscured some of their prints. Then the adult human walked back, now alone, and in turn crossed the tread created by the sloth. So we know which direction the woman walked in first: she was with the child while laying down the earlier (pre-sloth) footprints, then was alone walking the other way.
Strange New Worlds:
One has to wonder: what exactly was going on there, 12,000 years ago along the muddy route? One hypothesis, suggesting a complex social organization, is that our walking woman was a temporary caretaker returning a child to his mother.
This path offers us an arbitrary but fascinating moment in time.