The tracks run north/northwest in a straight line in one direction before disappearing into the dunes. Next to them are the remains of the return south/southwest return journey, which appears to have been made by the same person, judging by the size of the footprints and the stride length.

Along the way, the adult tracks are sometimes accompanied by the footprints of a child under 3 years old. Northbound, the adult tracks are a little asymmetrical, evocative of a woman holding a child on one hip. At times, the child’s footprints appear, perhaps during rest breaks when the adult put the squirmy toddler down. There are no child footprints on the return southbound journey, suggesting that perhaps the trip was taken in order to drop off the child somewhere.

“Motivation is something we can’t really speak to in the fossil record, but it’s something we want to know,” Reynolds told Live Science. Reynolds speculated that perhaps the child was ill and needed to be taken to another camp where someone could help him or her. Whatever the reason for the journey, it seemed very goal-oriented: The footprints didn’t deviate and the walker didn’t dawdle. The stride length suggests that the person was walking about 5.5 feet (1.7 meters) per second, a brisk pace. The region was arid, but the journey was near an ancient, now-vanished lake, and the ground was muddy and slippery.

“We do know the journey was faster than normal speed and over terrain that would have been more tiring than normal,” Reynolds said.

Animal encounters

The journey would have taken the pair through a landscape prowled by predators such as dire wolves and saber-toothed cats. Fortunately, the woman and child seem not to have been menaced; instead, they may have scared some of the animals that encountered their trackway. After the pair pᴀssed north, a set of animal tracks shows that a giant sloth approached their tracks, reared up — perhaps sniffing the air? — and then shuffled in a circle before veering away. The human then stepped on these sloth tracks when returning southbound. Previous research in the area suggests that humans hunted giant sloths, perhaps explaining why the sloth footprints reveal signs of nervousness on the part of the animal.

At another point, a mammoth crossed the humans’ northbound trail (before the southbound return journey). The mammoth showed no signs of slowing or stopping, perhaps suggesting that it did not see the recent presence of a human as a threat.