"In other words, the researchers used CRISPR-Cas9 to remove a naturally occurring hormone (vasopressin, and its receptor, Avpr1a) that is typically expected to

"In other words, the researchers used CRISPR-Cas9 to remove a naturally occurring hormone (vasopressin, and its receptor, Avpr1a) that is typically expected to regulate things like teamwork and bonding. Their hypothesis was that, by removing this hormone, the hamsters would stop regulating their friendliness, and just give in to being cuddly and adorable bosom buddies all the time. But in fact, in had the opposite effect: they were incredibly aggressive, territorial, and violent towards other hamsters of the same sex." - boing boing