Then one day, a student asked Lambert, “But what about the dads?”
Lambert was embarrassed that she hadn’t thought to ask the question herself. She, her students and colleagues soon began experimenting with the California deer mouse and the common deer mouse.
She pulled out photomicrographs of the brains, comparing the two species. The brains of the more paternal California deer mice have much thicker bundles of vasopressin and oxytocin cell bodies and fibers that function “like an interstate highway” to more easily move the bonding “love” hormones through the hypothalamus, the reward and motivation center of the brain.
The brains of the uninterested common deer mouse fathers, in contrast, are wired to fear pups, she said.
But when Lambert began exposing virgin males of both species to pups, that’s when things got really interesting.
The hippocampus — the area of the brain involved in learning, deciding what to pay attention to and memory — began producing new cells when virgin males were exposed to pups. The vasopressin fibers that move love hormones began to grow thicker even in the virgin non-nurturing common deer mice.
“That’s what’s so exciting,” Lambert said. “We know moms’ brains are wired from the start for nurture. But this shows that dads just may need more time to come on line and be paternal.”
Adapt or die
As Lambert packed up the brain slices, she contemplated the ongoing controversy about what’s “natural” for mothers and fathers.
Lambert’s own mother stayed home, but, with only a high school education, she felt trapped in an unhappy marriage. Lambert worried about what was best for her two daughters when they were young, but having loving babysitters, a husband who shared caregiving responsibilities and a flexible job made her decision easier.
“I worried what I would be preparing them for if I were home full time — I’m not the best homemaker — and I wanted them to learn to be self-sufficient,” she said. “So I took them to conferences with me, to my lab. I use what I do to prepare them for the world.”
If nature teaches anything, Lambert said, it’s that those species flexible enough to adapt to changing environments are the ones that survive.
“Life is messy. Every role is not carved in stone,” she said. “If we say every family should be one particular way, if anything changes you run the risk of becoming extinct.”