AppId is over the quota
Said to begin around 5 or 6, when toddlerhood has ended and even the most protractedly breast-fed children have been weaned, and to end when the teen years commence, middle childhood certainly lacks the physical flamboyance of the epochs fore and aft: no gotcha cuteness of babydom, no secondary sexual billboards of pubescence.
Yet as new findings from neuroscience, evolutionary biology, paleontology and anthropology make clear, middle childhood is anything but a bland placeholder. To the contrary, it is a time of great cognitive creativity and ambition, when the brain has pretty much reached its adult size and can focus on threading together its private intranet service — on forging, organizing, amplifying and annotating the tens of billions of synaptic connections that allow brain cells and brain domains to communicate.
Subsidizing the deft frenzy of brain maturation is a distinctive endocrinological event called adrenarche (a-DREN-ar-kee), when the adrenal glands that sit like tricornered hats atop the kidneys begin pumping out powerful hormones known to affect the brain, most notably the androgen dihydroepiandrosterone, or DHEA. Researchers have only begun to understand adrenarche in any detail, but they see it as a signature feature of middle childhood every bit as important as the more familiar gonadal reveille that follows a few years later.
Middle childhood is when the parts of the brain most closely associated with being human finally come online: our ability to control our impulses, to reason, to focus, to plan for the future.
Young children may know something about death and see monsters lurking under every bed, but only in middle childhood is the brain capable of practicing so-called terror management, of accepting one’s inevitable mortality or at least pushing thoughts of it aside.
Other researchers studying the fossil record suggest that a prolonged middle childhood is a fairly recent development in human evolution, a luxury of unfolding that our cousins the Neanderthals did not seem to share. Still others have analyzed attitudes toward middle childhood historically and cross-culturally. The researchers have found that virtually every group examined recognizes middle childhood as a developmental watershed, when children emerge from the shadows of dependency and start taking their place in the wider world.
Much of the new work on middle childhood was described in a recent special issue of the journal Human Nature. As a research topic, “middle childhood has been very much overlooked until recently,” said David Lancy, an anthropologist at Utah State University and a contributor to the special issue. “Which makes it all the more exciting to participate in the field today.”
The anatomy of middle childhood can be subtle. Adult teeth start growing in, allowing children to diversify their diet beyond the mashed potatoes and parentally dissected Salisbury steak stage. The growth of the skeleton, by contrast, slows from the vertiginous pace of early childhood, and though there is a mild growth spurt at age 6 or 7, as well as a bit of chubbying up during the so-called adiposity rebound of middle childhood, much of the remaining skeletal growth awaits the superspurt of puberty.
“Adulthood is defined by being skeletally as well as sexually mature,” said Jennifer Thompson of the University of Nevada, Las Vegas. “A girl may have her first period at 11 or 12, but her pelvis doesn’t finish growing until about the age of 18.”
The 18-year time frame of human juvenility far exceeds that seen in any other great ape, Dr. Thompson said. Chimpanzees, for example, are fully formed by age 12. With her colleague Andrew J. Nelson of the University of Western Ontario, Dr. Thompson analyzed fossil specimens from Neanderthals, Homo erectus and other early hominids, and concluded that their growth pattern was more like that of a chimpanzee than a modern human: By age 12 or 14, they had reached adult size.
No comments:
Post a Comment