Babies: As we reported yesterday, they just keep getting bigger. And while they haven’t always been trending towards obese, human babies have always been larger, relative to their mothers, than the infants of most other species. This make birth difficult and could have even changed the social structure of early hominids, steering human evolution.
Human babies are about 6.1 percent of their mother’s weight at birth, while chimp babies are about 3.3 percent. A new paper published in the Proceedings of the National Academy of Sciences takes a look at our extinct relatives to determine when this shift occurred, and suggests that it could even have encouraged our ancestors to come down from the trees and to form more complex social arrangements.
As anthropologist Jeremy DeSilva of Boston Univeristy pointed out in his new paper, “carrying a relatively large infant both pre- and postnatally has important ramifications for birthing strategies, social systems, energetics, and locomotion.” [Scientific American]
Most children shed their “baby fat.” But researchers say that in more and more cases, chubby babies (which are about 30 percent of all babies) are primed for obesity later in life.
“We are certainly not saying that overweight babies are doomed to be obese adults,” study researcher Brian Moss, PhD, of Detroit’s Wayne State University tells WebMD. “But we did find some evidence that being overweight at 9 months of age is a predictor of being overweight or obese later in childhood.” [Web MD]
The study followed a group of 7,500 babies born in 2001, classifying them by their position on the baby growth chart as “at risk” (those falling in the 85th to 95th percentile weight group) or “obese” (the 95th and above percentile). When the babies were nine months old and again at the age of two years, the parents filled out surveys about their child’s length and weight, their socioeconomic status, and race. The researchers found that 32 percent of the 9-month-olds were overweight, and 34 percent of the toddlers were. The study was published in the American Journal of Health Promotion.
DNA may dictate your development, but you also wouldn’t be you without the unique mix of bacteria that make their home on your body. This week in the Proceedings of the National Academy of Sciences, researchers say that the very moment of your birth can decide for a lifetime what kind bacteria live in your body, and even whether you’ll be at a higher risk for conditions like asthma.
The uterus is a sterile environment. So, in the womb, babies don’t have any bacteria to call their own. It’s only once they enter the world that they begin to collect the microbes that will colonize their bodies and help shape their immunity [Scientific American].
How babies enter the world is the key, the team says. The studied surveyed the bacterial colonies of 10 mothers just before birth; four of those women gave birth traditionally and six did through cesarean section. When the scientists then checked up on the bacteria living in the newborns, they found that the difference in birth method decided what microbes the baby would get. Those born vaginally tended to pick up the bacteria from their mother’s vagina, while those born via C-section harbored bacterial colonies that tend to come from skin.
Don’t be deceived by the peaceful look of a newborn baby asleep in a crib–that little tyke may actually be hard at work, soaking up information about the world. A new study has found that newborns are capable of a rudimentary form of learning while they’re asleep, which may be an important process, considering that infants spend between 16 to 18 hours a day in the land of Nod.
Researchers recruited one- and two-day-old infants for the study, published in the Proceedings of the National Academy of Sciences. With each sleeping baby, the researchers played a musical tone and followed that by a puff of air to the eyes, a mild annoyance that caused the infant to automatically scrunch up its eyes. As this sequence of events was repeated, the sleeping babies learned to associate the air puff with the tone, and soon began to to tighten their eyelids as soon as they heard the musical note, even if the air puff didn’t follow. Electrodes stuck to their scalps also showed activity in the prefrontal cortex, which is involved in memory.
Babies pick up their parents’ accents while still in the womb, according to a new study. After studying the crying patterns of 30 French and 30 German newborns, researchers concluded that the French newborns cried with a rising “accent” while the German babies’ cries had a falling inflection [BBC News]. The researchers believe that by mimicking their mothers’ inflections, the babies are attempting to form an early bond with their mothers.
Scientists already knew that a baby in the womb can memorize sounds from the outside world, and is particularly sensitive to the melodies of her mother’s language. But the new research showed an “extremely early” impact of native language and confirmed that babies’ cries are their first proper attempts to communicate specifically with their mothers [Reuters]. The data support the idea that crying seeds language development for infants, according to the scientists, who published their research in the journal Current Biology.
To hear the different between German and French crying babies for yourself, click here to listen.
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Image: flickr / chalky lives
The tender interactions between human mothers and their newborn babies may have deep evolutionary roots: a new study found that rhesus macaque monkey mothers engage in strikingly similar behavior with their infants.
The researchers found that the mothers would gaze intently at their newborns, sometimes even taking their baby’s face with their hands and gently pulling it towards them to get an even closer look. They would also engage in “lipsmacking” – an affectionate form of expression, where the macaques rapidly open and close their mouths [BBC News]. Several videos taken by the researchers show that just like human babies, the infant monkeys responded to their mothers by mimicking their facial expressions and returning their stares.
The rate at which infants gain weight in the first six months of their lives is linked to those babies’ risk of becoming obese by age three, a new study has found. Researchers determined that sudden weight gain in early infancy was more important than how much a baby weighed at birth, the weight of the infant’s parents, or the number of pounds put on by the mother during pregnancy. “The perception has been that a chubby baby and a baby that grows fast early in life is healthier and all the baby fat will disappear,” said the paper’s lead author, Dr. Elsie Taveras…. “But [that] is not the case” [Chicago Tribune].
While the researchers note that early childhood obesity does not necessarily lead to obesity later in life, they say it does raise the risks. Obesity rates among U.S. children have doubled in the last 20 years, and almost a third of American children are either overweight or obese. The epidemic of obesity is linked to a host of health problems such as higher risks for heart disease, diabetes and cancer [Reuters].
Babies just a few days old can already identify a rhythmic pattern, and their brains show surprise when the music skips a beat, according to a new study. Researchers played recordings that used high-hat cymbals, snare drums, and bass drums to make a funky little beat while monitoring the infants‘ brain activity with non-invasive electroencephalogram brain scanners, and found that newborns respond to a skipped beat in the same way that adults do.
The ability to follow a beat is called beat induction. Neither chimpanzees nor bonobos — our closest primate relatives — are capable of beat induction, which is considered both a uniquely human trait and a cognitive building block of music. Researchers have debated whether this is inborn or learned during the few first months of life, calibrated by the rocking arms and lullabies of parents [Wired News]. While the researchers who conducted the new study say their findings are evidence that beat induction in innate, others argue that the newborns could have already learned to identify rhythmic patterns by listening to their mothers’ heartbeats while in the womb.
The fossilized pelvis of a Homo erectus woman who lived 1.2 million years ago on the banks of an Ethiopian river has been discovered, and while researchers say it casts new light on human evolution, some of their conclusions are challenging previous theories about these early human ancestors. The pelvis reveals a short, squat woman who wasn’t built for long-distance running, but also a woman with a wide birth canal to accommodate big-brained infants.
Study coauthor Scott Simpson says the pelvis’s wide birth canal indicates that hominds’ increasing brain size was a driving factor in human evolution. Getting through the birth canal is “the most gymnastic thing we ever do,” he says. To accommodate big-brained babies, humans must have developed larger and wider birth canals over time, but with few pelvic fossils, researchers had little idea when these changes began. The Busidima pelvis shows that a wide birth canal was already in place 1.2 million years ago [New Scientist].
A new analysis of the skulls of three Neanderthal babies shows that the cranium of a newborn Neanderthal was about the same size as that of a newborn Homo sapiens, and that the Neanderthal children grew faster than modern humans in the first few years of life. The report on the young skeletons, which date from between 45,000 to 50,000 years ago, adds fuel to the debate over how similar Neanderthal culture was to that of our early Homo sapiens ancestors.
A big-headed infant skeleton found in Russia suggests that childbirth was no easy task for for Neanderthal women. Neanderthal mothers had slightly larger birth canals, but the prominent face of Neanderthal babies made it just as hard to push out as a modern human. This suggests that both groups had the social structures needed to help with childbirth [New Scientist].