A study on suicidal E. coli sheds light on why organisms throughout the animal kingdom, big and small, sometimes decide to do themselves in.
The good news is that suicide appears to be comparatively rare in larger animals, but more common among microscopic life forms, such as microbes, according to the study, published in the latest Proceedings of the Royal Society B.
Natural selection -- the process by which organisms that adapt to their environment tend to survive and produce more offspring -- favors suicide when the death guarantees the survival of relatives and the individual is less likely to reproduce in future.
An example of this, according to study co-author Rolf Kümmerli, is when "a parent saves his children out of a burning house. This is beneficial because the rescued relatives share many of the genes with the suicidal helper." Many people are driven to save their kids and close loved ones, no matter what.
Other forms of suicide among humans, such as bombers on a kamikaze mission, likely have nothing to do with natural selection, and instead reflect the by-product of something else. In the case of the bomber, that could be the individual's environment and life's experiences. Depression or other forms of mental illness, however, could be inherited.