A common protein that was a part of the scorpion's immune system was actually the origin of the scorpion's venom, a team of researchers found.
Shunyi Zhu of the Institute of Zoology at the Chinese Academy of Sciences along with his colleagues looked at proteins in the scorpions called defensins, compounds found in many plants and animals that fight bacteria, the Independent reported.
By sequencing the genetics of the amino acids in defensin, they found that all it took was a change in a single gene to turn the defensin into a poison.
Zhu said the emergence of toxins from defensins is a consequence of adaptation of scorpions to their decreased size that increases difficulty in capturing prey when they emerged from the seas.
Scorpions were larger in the water but had to shrink physically over the course of their evolution on dry land, and it became harder to kill and catch some prey, therefore they developed venom.
The study was published in the journal Molecular Biology and Evolution.