important chapter on physical development shows why the “exercise” begun in the womb must continue, with caretakers encouraging infants to vary their positions during awake time. Holding infants in various positions not only strengthens muscles, but it also gives infants a view of the world from more than one perspective, each view affecting the synapses being formed.
Almost universally, parents, regardless of their circumstances or limitations, want to do the best for their children. But with conflicting advice from the media, and with an array of books and toys promising smart and happy infants, parents can be confused about what course to follow. To put their minds at ease, a chapter on stimulation summarizes appropriate sensory stimulation. Loving attention to cries, along with soothing voices, comforting touches, eye contact, and closeness to the mother's body (or an equally loving caretaker's body) are the kinds of stimulation an infant needs. A view of a mother's face, a father's profile, the sound of live voices, the touch of skin or flannel or tweed, the smells of healthy foods cooking, and the taste of milk are preparing infants for the inimitable world that envelops them. For millions of years, trees, grass, voices, music, cuddling, constant proximity to mothers, and loving human interaction have provided all the stimulation infants need.
Finally, the book steps away from the newborn to delve into research on parents. Physical and psychological studies examining the postpartum months as experienced by mothers are extensive, and there are exciting new indications that, just as human interaction is sculpting infant brains, those same interactions are reshaping maternal brains. Research into fathers’ health is fledgling, but science now knows that men, too, are susceptible to postpartum depression and that welcoming a child into a family can be stressful for both parents.
The multiple lines of research upon which this book is based show that a well-equipped brain is grown from the normal, simple, and readily available seeds of playful activity and loving parents and adults. The chatter of everyday life, lullabies of love, and glimpses of blue sky through green branches surrounding a newborn are naturally programming language, art, music, math, dexterity on the playground, and lifelong social skills.
This book will help put to rest the remnants of a century of cultural misconceptions that still linger: infant independence, fixed IQ, and a substitution of quality time for quantity time.
Cultural norms, fading but not entirely gone, once encouraged parents to make their largely unformed infants partly independent from day one. Infants were expected to go it alone in their own rooms, to figure out how to soothe themselves by crying themselves to sleep, to wait through hunger pangs for an appointed feeding hour—or to eat more than they wanted, which, the parents could hope, would then cause them to sleep longer. About a hundred years ago, this approach was encouraged by “male physicians who not only had never changed a diaper, but had never—in any substantial way—associated with, or taken care of their own infants,” according to Dr. James McKenna, director of the Mother-Baby Behavioral Sleep Laboratory at the University of Notre Dame.4 Separating infants from their parents was supposed to foster independent toddlers, children, and adults, and this approach was practiced for decades. Current research shows that it has the opposite effect.
The mid-twentieth century was also a time when people believed intelligence was fixed, set in stone at birth. In the 1950s and 1960s, research began to cast doubt on that assumption. We now know that a child's IQ is influenced greatly by either environmental stimulation or environmental neglect.5 Science now sees the human brain in a kind of computer model: hardware delivered at birth, and software continually programmed by experience. The programming begins at birth at a breathtaking pace.
The 1970s introduced to popular culture the concept of “quality time.” Parents could be absent for long stretches of their infants’ days, the reasoning went, as long as they compensated for lost time by making every available moment of togetherness count with joyful, stimulating interaction. The trouble is, brain development doesn't take time off, and infants don't learn on a convenient schedule. When it comes to time, infants need both quality and sheer quantity. There are no shortcuts. A parent or a consistent, loving caretaker must be there when infants need them. During the fourth trimester, that's all the time.
This book goes a long way in removing the cloak of mystery that has always surrounded the fourth trimester. It presents an original perspective on the period following birth, identifying it as a continuation of the period of development within the uterus and, simultaneously, an interval that helps infants make the transition to the world.
This fresh way for parents, educators, and health care workers to understand newborns points to a difficult societal dilemma. Newborns require constant loving attention. That is a truth that must not be compromised by simple ignorance. Evolution and biology clearly prefer the bond to be between the newborn and the mother, though, as I've noted, infants can be well cared for by fathers, adoptive mothers and fathers, or other consistent, loving, attentive adults. This book points to the need to pay attention to infants twenty-four hours a day throughout the fourth trimester. Coming up with policy solutions that are truly family centered is beyond the scope of this book. But as a society, we need to come up with ways—paid parental leave for biological and adoptive mothers or fathers or both, for example—to support young families by ensuring that every infant is able to spend this crucial period of development held tightly in the arms of love.
CHAPTER ONE
Evolution and the Primitive Brain of a Newborn
Why Infants Arrive Unfinished
Blame Lucy. In the throes of labor contractions and delivery, remember that it was this 3.2-million-year-old human ancestor who first had the big idea to stand up and walk on two feet. Lucy is considered by many scientists to be the mother of humankind, and her skeletal remains, discovered in 1974, provided scientific evidence of one of the first upright walkers in our family tree.1 From that point onward, the human ability to walk on two feet would demand some reworking of the adult pelvis and a major overhaul of the birth canal. Those evolving alterations would, in all descendant female hominids leading up to Homo sapiens, introduce a host of inefficient twists and turns, making the process long and painful for mothers and a brutal challenge for babies.
Lucy's hypothetical offspring, no longer able to survive with the limited brainpower required to climb a tree or flee from danger on four legs, needed more time to grow a bigger brain in order to outwit predators. But a maximum of forty weeks’ gestation is all that biology allowed our ancient ancestors and modern babies. They would need a fourth trimester of intense development experienced outside the uterus while remaining physically and emotionally bound to their mothers, just as they had been for the previous nine months. The tight fit through that circuitous birth canal set absolute limits on how much brain development could occur during pregnancy. The additional brain growth required to keep the species thriving would have to happen outside the uterus, an astonishing amount of it occurring during the fourth trimester.
Modern human infants are at the receiving end of millions of years of evolutionary progress, but the tradeoff for upright walking has been immature brain development at birth.
Walking on two feet has been a mixed blessing. Standing upright altered the entire skeletal structure, and the changes came with physical costs for males and females: flat feet, aching backs, and stiff necks. “Ultimately, every part of the human body had to change to adapt to bipedalism,” says Dr. Wenda Trevathan, evolutionary anthropologist at the University of New Mexico.2
Women and infants have suffered especially onerous consequences of upright posture. What was once a straight shot down a roomy birth canal in our four-legged ancestors has evolved into something akin to an amusement park ride through the modern female pelvis.
Once humans had only two feet for mobility, they could no longer climb as well as, or run as fast as,
