Humans experience and interact with the world around them using five senses whereas some vertebrates, such as sharks, rays, catfish, sturgeons, and salamanders, utilize an extra sixth sense – they can detect weak electrical fields and use this information to detect prey, sense danger, communicate, and orient themselves in their environment. A new study published in Nature Communications suggests that 96% of existing vertebrates, including humans, descended from a common ancestor that had a highly-developed sixth sense – an electroreceptive system (which begs the question, could remnants of this sixth sense still exist in modern-day humans).
Cornell University professor Willy Bemis noted the study was 25 years in the making:
“This study caps questions in developmental and evolutionary biology, popularly called ‘evo-devo,’ that I’ve been interested in for 25 years.”
Researchers propose that there was a split in the evolutionary tree of vertebrates which lead to two different groups – ray-finned fishes and lobe-finned fishes. The later, lobe-finned fishes, are believed to have evolved into land vertebrates including salamanders and human beings. Many ray-finned fish and some lobed-finned fish (and the lines that evolved from them; e.g. salamanders), still have these electroreceptive systems required for this “sixth sense” to function properly. Until now, scientists did not know if the electroreceptive organs in the two different groups were evolutionary or developmentally the same.
To prove their finding, researchers took animals from both groups and studied their development from the embryonic stage forward. They found that the electrosensory organs develop adjacent to the “lateral line” (a system of organs that is used to detect movement and vibration) providing compelling evidence “that these two sensory systems share a common evolutionary heritage”. They also found that the electrosensors develop in precisely the same pattern in both groups which confirms that this is a related, ancient sensory system, common to practically all vertebrates.