In the process of weaving their histories together, it became clear that there was another species that belonged in the mix: humans. The more I sought common threads—themes uniting the stories of diverse animal species—the more apparent it became that these threads applied to our own weapons, too. In the end, my book about animal weapons evolved into a book about extreme weapons everywhere. I pored deeper into the literature surrounding our past, searching for the environments and circumstances in which our most elaborate weapons evolved. To my amazement, these circumstances truly were the same, and I realized I couldn’t tell one story without telling the other.

Emlen, Douglas J, Animal Weapons_ The Evoluti…, loc. 7