Back in the Pliocene epoch a volcano called Sadiman erupted depositing a layer of ash across the landscape. Some time later it rained at Laetoli in modern day Tanzania turning the ash into wet cement.
Birds and animals walked across the cement, then Sadiman erupted again sealing the footprints under a second layer of ash.
Fast-forward to 1976. A team of paleontologists led by Mary Leakey are searching for human origins on the Serengeti Plain when Andrew Hill ducks out the way of elephant dung being thrown at him by a colleague. He lands on top of the fossilised animal prints. In 1978 further excavation revealed not just animal prints but an 88 foot long trail of hominid footprints.
The early humans who left the trail belonged to the same group as Lucy known as Australopithecus afarensis. Despite being 3.6 million years old their footprints are hardly distinguishable from those of modern humans. Unlike apes their big toes were in line with the rest of their toes and their gait was heel-strike followed by heel-off just like modern humans.
Volcanic ash is a perfect medium for radiometric dating, I will post details about the process in a future thread in this series but you can see an excellent resource here..
Initial investigation suggested there were prints of three individuals - two walking together with a third smaller individual walking behind and stepping in the footsteps of one of the others. The tracks were covered up to protect them but in February 2011 a section was re-excavated for evaluation as a future museum site. Using a photographic technique that provides high-resolution three-dimensional views of the footprints it was determined that it is more likely that four individuals made the prints. One individual's right foot was angled strangely compared with the left foot possibly indicating a disability.
Fossil remains of approximately 300 Australopithecus afarensis individuals have been discovered and this is just one of many species of our ancestors. These small-brained hominids were walking upright just like us. Perhaps they had fun making the prints just as Andrew Hill's game led to their discovery 3.6 million years later.