On our last Moment of Science we opened up the Big and Bad file to see what the record-holder was for oldest human footprint. The award went to prints discovered in Italy that were made by some people running down a volcano. The flow of ashes covered the impressions left by their feet and preserved them until the present day--some three hundred and fifty thousand years later.
But wait, some of you are saying: "Didn't I hear something about footprints found in Africa that were over a million years old?" You did indeed; in fact, they were significantly older than that. In nineteen seventy seven, researchers working in Tanzania discovered footprints left in volcanic mud that have been dated at three point six million years old. That's ten times the age of the Italian footprints!
So why doesn't the Tanzania find get the Big and Bad File record for oldest footprint by a person? Can you think of a reason?
Well, when you go that far back in history you have to start asking whether these footprints were made by "people." The folks who left the prints in Italy were what we now call archaic Homosapiens. They were squat, hairy hunters, a little under five feet ...but if you met one you'd probably agree they fit your general definition of a "person."
The Tanzania prints, on the other hand, were made by Australopithecus afarensis. Anthropologists call such animals "prehuman," meaning that far back along the evolutionary tree they were different enough from us to constitute a separate species altogether. They were indeed our very ancient ancestors... but they weren't really human.