WASHINGTON — In her new book Mom Genes: Inside the New Science of Our Ancient Maternal Instinct, author Abigail Tucker argues that maternal instinct can be measured in a lab. 

“I had never thought of maternal behavior, maternal instinct, as something you could study under a microscope,” Tucker told CNA in an interview. However, she said that a trip to Emory University and a study of rodents made her consider the distinctiveness of a mother’s brain. 

“We are just beginning to understand what makes moms moms,” Tucker said. “And that’s to the detriment of the human species.” 

Weaving her own experience as a mother with an examination of the ways motherhood changes body and mind, Tucker’s book explores the biology of motherhood.

Tucker said that while most of her career was spent writing about animals, one area of expertise she could contribute to was her own experience having four children.

“By repeating the experience four times, I was able to see some of the hidden forces and wild card factors that were shaping me,” she said. 

Maternal instinct, she told CNA, is really a “change in motive.” She noted that some of these changes are physical. The brain, for example, is “a very key organ of childbirth,” she said. 

“Maternal instinct is really the awakening of this core, pro-baby motive, it's a sensitization to infant cues and a desire to respond to them,” Tucker said. “One scientist called it an ‘unmasking of a latent identity.’” 

A host of variables — financial, social, stress, partner and familiar relationships — also contribute to the type of mother a woman becomes, Tucker said.

“As mothers, we make babies, but we are also being made,” Tucker said. “What are the forces that are invisibly working on us that help account for this staggering variation you see in maternal variation, just in one American city or one American block?” 

Tucker said that humans are “notable” among mammals in that they do not have what scientists call “fixed action patterns” with motherhood, patterns that other species have. 

“There’s so much variation in the way moms do their jobs globally, it's hard to pinpoint one thing we uniformly do,” she said, adding that scientists have noticed that many human mothers have a “left-sided cradling bias” - meaning they are more likely to cradle an infant on their left side. 

Tucker said she hopes the fact that birth rates are currently in “a swan dive” will prompt increased scientific study of maternal health and science, so that mothers, babies, families, and society can all thrive. 

“At a moment where moms are becoming a bit more of a scarcity than they were before, it might be worth kind of weighing some of these things we can do to help moms be at peak performance, because that’s good for everyone,” she said.