Practicing Motor Skills
In fact, babies do improve their motor skills much as adults do—as a result of diligent practice. New skills, such as walking independently, don't suddenly emerge out of nowhere but gradually build out of prior, simpler abilities—kicking, standing, and walking with support—after weeks or months of trying. The only difference between infant and adult motor learning (aside from the fact that infants seem to crave the exercise more than most of us) is that babies can train themselves in a ...
notesBy practicing a motor skill, adults and infants allow their brain to find the most efficient neurological pathways for performing the task.
How Brains Grow Into Bodies
Brain wiring begins with the outgrowth of axons. Once a newborn neuron has migrated, planting its cell body in a permanent position, it sends out a fine axon shoot with an enlarged tip known as a growth cone. At the end of the growth cone are about a dozen long tentacles that shoot out in all directions and act like radar, picking up all manner of navigational signals. They feel out the best-textured surfaces, sniff around for chemical cues, and even use tiny electrical fields to help the axo...
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6 Best description yet of the synaptic "pruning" human brains go through as the brain wires up to the body and best reason yet for why children should have rich, mentally-nourishing environments in which to grow so that their synapses don't get unnecessarily pruned, resulting in smaller brains.
Ontogeny Recapitulates Phylogeny
The similarity between different vertebrate embryos is indeed remarkable. Since the early 1800s, embryologists have been struck by the parallel between early development in various animal species and their evolutionary relationship, a resemblance conveniently abbreviated by the saying "ontogeny recapitulates phylogeny." Of course, each of us does not really pass through a "lizard" stage on our way to a fully developed human form. But it is true that animals who are more closely related in ter...Living things go through the forms of their ancestors, not specifically but generally, because it is easier for evolution to add a mutation to the end of a complex sequence of developments than to re-engineer earlier in the process.
The laryngeal nerve's haphazard course through the body
A favourite example, ever since it was pointed out to me by Professor J. D. Currey when he
tutored me as an undergraduate, is the recurrent laryngeal nerve.* It is a branch of one of the cranial
nerves, those nerves that lead directly from the brain rather than from the spinal cord. One of the
cranial nerves, the vagus (the name means 'wandering' and it is apt), has various branches, two of
which go to the heart, and two on each side to the larynx (voice box in mammals). On each side of
the n...Another example of poor biological design.
An Experiment With a Tadpole's Development
An early classic experiment by the Nobel Prize-winning embryologist Roger Sperry
illustrates the principle perfectly. Sperry and a colleague took a tadpole and removed a tiny square
of skin from the back. They removed another square, the same size, from the belly. They then
regrafted the two squares, but each in the other's place: the belly skin was grafted on the back, and
the back skin on the belly. When the tadpole grew up into a frog, the result was rather pretty, as
experiments in embryo... notesTaking a piece of skin from the belly and switching it with a piece from the back caused the frog to scratch its belly when you tickle its back.
