Humans display many of the same traits as animals we've domesticated. (Credit: Zadorozhna Natalia/Shutterstock) Humans have turned many wild animals into cuddlier creatures. We've domesticated wolves into dogs, boars into barnyard pigs and mountain goats into livestock that do yoga. But in addition to helpful animals and adorable pets, humans may have also domesticated an altogether different creature: Homo sapiens. The so-called self-domestication hypothesis, floated by Charles Darwin and formulated by 21st century scholars, is now popular among anthropologists. They see parallels between changes over the past 200,000 years of human evolution and those observed when wild animals became domesticates, creatures selectively bred to be docile and friendly. According to proponents, as human societies grew in size and complexity, more cooperative, less combative individuals fared better. These behavioral traits are heritable to some extent and also linked with physical traits, such as stress hormone levels, testosterone during development and skull robustness. Tamer individuals more successfully passed on their genes, and so these traits prevailed in the human lineage. Over time, our species became domesticated.