Humans are one of 60,000 species that share a 500 million year old common ancestor. This creature was the ancestor of almost every vertebrate species, but it had a sixth sense that most of its descendants long since lost.
Our evolutionary great-great-great-grandparent possessed electroreception, which means it was able to detect weak electric fields. This ancestor was a marine animal, like most living examples of vertebrates with electroreception, and so it used this sense to detect prey in the water, communicate with other members of its species, and determine direction.
Cornell researchers have spent the last 25 years researching this common ancestor, and they now believe the species in question was a predatory fish with good eyesight, strong jaws and teeth, and a horizontal stripe along its flank that allowed it to detect lateral movement. And yes, our common ancestor does sound rather disturbingly like a shark, which is one of the few living examples of a predatory, electroreceptive fish.
This species ultimately evolved into two divergent groups. The first became the ray-finned fishes, or actinopterygians, which account for most of the vertebrate fish we see today. The second group became lobe-finned fish, or sarcopterygians, which ultimately made its way to land and diverged into most of the different land vertebrates - us included - that we see today. Over the hundreds of millions of years, most land vertebrates lost electroreception and the lateral line, but a few land animals like the salamander and axolotl retain them to this day.
It was unclear whether these lizards' electrosense was the same thing as that possessed by sharks and other fish, or whether this represented an independent evolution of the ability. Cornell researcher Willy Bemis says he and his team found that both land and marine vertebrates that possess the electrosense all share the same patterns and structures in the development of the receptors, meaning it's most likely a shared, ancient adaptation that most species have subsequently lost.