Once-hidden prints, visible only in certain conditions, detail a dramatic chase
Jaime Chirinos/Science Source
People tracking giant sloths thousands of years ago in what is now New Mexico left footprints that confirm humans once hunted the giant creatures, researchers report April 25 in Science Advances.
Giant ground sloths, which vanished at the end of the last Ice Age around 10,000 years ago, could weigh more than an elephant. With their lethal claws and muscle, the herbivores would have been formidable prey, says David Bustos, a biologist with the National Park Service at White Sands National Monument in New Mexico.
In April 2017, researchers stumbled across more than 100 tracks in White Sands. These “ghost tracks” had previously remained hidden because they can be seen only under the right moisture conditions — too little or too much water in the soil, and the outlines of the prints were invisible.
Tests of sediment showed the sloth and human prints were made at the same time.