A National Public Radio news investigation on toxic leadership in the military inspired me to write a commentary on my Forbes.com blog with Jonathan Haidt. Here is how the US Army defines toxic leadership:Toxic leadership is a combination of self-centered attitudes, motivations, and behaviors that have adverse effects on subordinates, the organization, and mission performance. This leader lacks concern for others and the climate of the organization, which leads to short- and long-term negative effects. The toxic leader operates with an inflated sense of self-worth and from acute self-interest. Toxic leaders consistently use dysfunctional behaviors to deceive, intimidate, coerce, or unfairly punish others to get what they want for themselves. The negative leader completes short-term requirements by operating at the bottom of the continuum of commitment, where followers respond to the positional power of their leader to fulfill requests. This may achieve results in the short term, but ignores the other leader competency categories of leads and develops. Prolonged use of negative leadership to influence followers undermines the followers' will, initiative, and potential and destroys unit morale..The problem is surprising not only in its extent--an estimated 20% of soldiers suffer from toxic leadership—but the degree to which the US Army was taken by surprise. It wasn’t even noticed until an investigation of high suicide rates revealed toxic leadership as a major contributing factor. Army soldiers who take their own lives often have personal problems, but toxic leaders push them over the edge by making their lives a living hell, or “smoking” them in military parlance. It is not an exaggeration to say that US casualties due to toxic leadership rival casualties due to enemy combat.Why was the US Army ambushed by this problem? From an evolutionary perspective, it is obvious that self-aggrandizing behaviors of the sort that define toxic leadership are often favored by genetic and cultural evolution. Special conditions are required for them not to evolve. An ounce of evolutionary thinking would have made the US Army more aware of the problem lurking in its midst, which one retired general calls “an institutional cancer”This article supplements my Forbes.com essay by providing resources for understanding the nature of toxic leadership from an evolutionary perspective--in the military or any other modern human social organization..• The problem of toxic behavioral strategies of all sorts follows from the basic dynamics of multilevel selection, as covered by numerous articles in TVOL in addition to the academic literature (e.g., 1,2,3).• Toxic leadership pervades the animal world, as graphically depicted for hyenas and lions in the National Geographic documentary Eternal Enemies. Note the toxic interactions that exist within species, in addition to between species.• Humans are unique among primates in their ability to suppress self-aggrandizing behaviors, as argued by Christopher Boehm in his books Hierarchy in the Forest: The Evolution of Egalitarian Behavior and Moral Origins: The Evolution of Virtue, Altruism, and Shame. We can even be defined as the species that (largely) solved the problem of toxic leadership at the scale of small groups.• Evolutionary social psychologist Mark Van Vugt synthesizes the vast literature on leadership from an evolutionary perspective in his book Naturally Selected: The Evolutionary Science of Leadership, which shows how toxic leadership and other self-aggrandizing behaviors are an ever-present danger in all groups unless protective mechanisms are in place.• Barbara Oakley’s Evil Genes: Why Rome Fell, Hitler Rose, and My Sister Stole My Mother’s Boyfriend provides a fascinating account of toxic social strategies at all scales, from families to nations.• The idea that toxic leadership is an “institutional cancer” is more accurate than the retired general probably imagined. Cancer cells growing at the expense of the body, leading eventually to their own demise, reflect the same dynamic as toxic leaders benefiting themselves at the expense of their groups, often leading to their own demise. Go here for more on this comparison.I am repeatedly asked how an evolutionary perspective adds value to the study of human-related topics that have been pondered by the best and brightest minds, sometimes for millennia. The fact that the US Army was ambushed by the problem of toxic leadership provides a good answer. It is in front of everyone’s faces. It is costing lives. Nevertheless, whatever worldviews predominate in military life render it invisible. Einstein was right when he said that the theory determines what we can observe. Peer through the evolutionary lens, and that which was invisible leaps into view.