Breast Milk "Signals" Infant Behavior and Temperament in Rhesus Monkeys

Monkey mama's milk signals behavior and development

Have you ever wondered what your breast milk provides for your child beyond simple nourishment? Animal research may expand our knowledge of the power of breast milk.

Studying rhesus macaque monkeys, researchers have found “that a mother’s milk sends a reliable signal to infants about their environment”.

How does one’s environment affect temperament and behavior? Scientists have long debated environment versus genetics in human development, but rhesus monkeys may give us a new clue at an even deeper connections involving breast mikl. Physorg explains:

Scientists from the Smithsonian Institution and the University of California, Davis are using this natural variation in breast milk quality and quantity to show that a mother’s milk sends a reliable signal to infants about their environment. This signal may program the infant’s behavior and temperament according to expectations of available resources and discourages temperaments that prove risky when food is scarce.

Published in the American Journal of Primatology, researchers analyzed the milk of 59 monkeys. Katie Hinde, the study’s lead author, expounds:

This is the first study for any mammal that presents evidence that natural variation in available milk energy from the mother is associated with later variation in infant behavior and temperament. Our results suggest that the milk energy available soon after birth may be a nutritional cue that calibrates the infant’s behavior to environmental or maternal conditions.

Does this trait of rhesus breast milk carry over to humans? Rhesus monkeys are “more distant from humans than chimpanzees or orangutans;” however, they are often used in disease research because of “genetic, physiologic and metabolic similarity to humans”. It is also interesting to note that humans are the only primate with a “broader geographic distribution” than the rhesus macaques. I wouldn’t doubt that human babies receive similar signals from their mother’s milk given the similarities.