Is child abuse a genetic trait, or is it something that gets passed-down, through experience, from one (older) person, to another? One man made it his business to study monkey and their behaviors.
Sadly, children who are abused by their parents are more likely than unharmed children to grow up to become abusive parents themselves. Whether this behaviour is inherited or learned is unclear. Dario Maestripieri at the Yerkes National Primate Research Centre investigated this issue in rhesus macaque monkeys, among whom infant abuse is also known to occur.
To compare the influence of genes vs. experience, Maestripieri used a cross-fostering technique that involved taking a new-born female monkey from her biological mother and passing her within 48 hours of her birth to a different adult female who would raise the infant as her own. Some monkeys born to abusive mothers were passed to a non-abusive foster mother and vice versa. Other monkeys in the experiment were raised by their abusive or non-abusive biological mother as usual. Later on, Maestripieri observed which infants went on to abuse their own offspring.
Maestripieri found no evidence for abusive behaviour being genetically inherited, rather it appeared to be acquired through experience of being abused. Nine of the 16 monkeys who were reared by abusive mothers went on to be abusive themselves, including four adopted monkeys whose biological mother was not an abuser. In contrast, none of the monkeys raised by non-abusive mothers went on to abuse, including six adopted monkeys whose biological mother was an abuser.
Maestripieri said abused female monkeys might learn to be abusive themselves either based on their own direct experience of being abused, or through observation of their mother abusing their younger siblings, or because of neural changes caused by being abused. That not all abused monkeys went on to be abusive themselves also points to other protective or risk factors.
“The availability of a primate model of child maltreatment provides the opportunity not only to conduct research on the causes and consequences of this phenomenon but also to test various forms of intervention and therefore contribute to its prevention”, Maestripieri concluded.
Maestripieri, D. (2005). Early experience affects the intergenerational transmission of infant abuse in rhesus monkeys. Proceedings of The National Academy of Sciences, USA, 102, 9726-9729.
More on this study can be found here -- "Infant Abuse Linked To Early Experience, Not Genetics", http://www.sciencedaily.com/releases/2005/07/050701062300.htm