Researchers studied more than 1,400 protein-coding genes in fleas and found out their location on the tree of life, as well as identified their closest relatives.
The dataset was analyzed using new statistical methods: the researchers used more sophisticated algorithms to test all the historically advanced hypotheses about the placement of fleas on the insect tree of life, and also looked for new potential relationships.
The findings contradict preexisting flea theories, which argued that their unusual anatomy meant that fleas were not included in evolutionary classification. According to the study authors, contrary to popular belief, fleas are technically scorpions that evolved when they began to feed on the blood of vertebrates: this happened somewhere between the Permian and Jurassic periods, approximately between 290 and 165 million years ago.
The closest living relatives of fleas are members of the scorpion family Nannochoristidae. This rare group has only seven species and is found in the southern hemisphere. Unlike blood-sucking fleas, adults of Nannochoristidae feed on nectar.
Previously, it was believed that all blood-sucking insect parasites began their life either as predators or together with vertebrate hosts. However, it turned out that blood nutrition can develop in groups that originally consumed nectar or other plant foods.
Scientists believe that because of their discovery, textbooks on entomology will need to be revised.