Photo: X
Scientists have always known that two relatives of today's humans existed on Earth at the same period of time - but whether the two different species of hominin ever met or interacted was unknown.
Now a recent discovery proves not only did they meet - they co-existed and possibly even worked together in the same region for thousands of years.
Two sets of footprints made 1.5 million years ago found by explorers were found to have been made within days, maybe even hours or minutes of each other.
Analysis showed the footprints were made by individuals with different gaits and stances, which experts believe to be Homo erectus and Paranthropus boisei - both members of the hominin family tree.
Kevin Hatala is a paleoanthropologist who studies the evolution of human locomotion. He is an associate professor of biology with Chatham University and is one of the team who made the discovery.
He speaks to Kathryn Ryan.
