Seemingly 'useless' organ makes huge soldier ants

Scientists at McGill have found the answer to a question that perplexed Charles Darwin. So much so, that it actually led him to doubt his own theory of evolution. He wondered, if natural selection works at the level of the individual, fighting for survival and reproduction, how can a single colony produce worker ants that are so dramatically different in size – from the “minor” workers with their small heads and bodies, to the large-headed soldiers with their huge mandibles – especially if, as in the genus Pheidole, they are sterile? The answer, according to a paper published today in Nature, is that the colony itself generates soldiers and regulates the balance between soldiers and “minor” workers thanks to a seemingly unimportant rudimentary “organ” which appears only briefly during the final stages of larval development. And only in some of the ants – the ones that will become soldiers. Read more