London: Believe it or not, humans also had a sixth sense, but in our fish-like form some 500 million years ago, scientists say. Researchers at the University of Cambridge and Cornell University in New York discovered that humans have descended from a predatory fish-like ancestor which had "electrosensors" that helped it to detect electric fields in water.

The creature, which roamed the oceans 500 million years ago, used this skill to detect prey, communicate and to find its way around, a daily reported.

The researchers believe that not just humans, but 65,000 living vertebrate species -- that's any creature with a spine or backbone -- are descended from that beast.

This includes 30,000 species of land animals – including humans -- and a similar number of ray-finned fish, they found.
The findings, which are appeared in the journal Nature Communications, mark the culmination of 25 years of work into the subject, the researchers said.

"This study caps questions in developmental and evolutionary biology, popularly called 'evo-devo' that I've been interested in for 35 years," senior study author Willy Bemis, a professor of ecology and evolutionary biology at Cornell University, said.

Hundreds of millions of years ago, he explained, there was a major split in the evolutionary tree of vertebrates. One lineage led to the ray-finned fishes, or actinopterygians, and the other to lobe-finned fishes, or sarcopterygians.

The latter gave rise to land vertebrates, some of which, such as the Mexican axolotl salamanders, retained electrosense ability. Some ray-finned fish, including paddlefish and sturgeon, also retained these receptors, he said.

Prof Bemis and his team found that the electrosensors of the ray-finned fish and the salamander developed in precisely the same pattern from the same embryonic tissue in the developing skin, confirming that this is an ancient sensory system.
"These two sensory systems share a common evolutionary heritage," added Bemis.

However, over the years reptiles, birds and mammals lost their electrosense as it wasn't needed for life on terra firma.

(Agencies)