To help us deal better with this fractional lag, the brain does a truly extraordinary thing: it continuously forecasts what the world will be like a fifth of a second from now, and that is what it gives us as the present. That means that we never see the world as it is at this very instant, but rather as it will be a fraction of a moment in the future.
In 1915, the average American spent half his weekly income on food. Today it’s just 6 percent.
An interesting thing about touch is that the brain doesn’t just tell you how something feels, but how it ought to feel. That’s why the caress of a lover feels wonderful, but the same touch by a stranger would feel creepy or horrible. It’s also why it is so hard to tickle yourself.
Curiously, we don’t have any receptors for wetness. We have only thermal sensors to guide us, which is why when you sit down on a wet spot, you can’t generally tell whether it really is wet or just cold.
DNA passes on information with extraordinary fidelity. It makes only about one error per every billion letters copied. Still, because your cells divide so much, that is about three errors, or mutations, per cell division. Most of those mutations the body can ignore, but just occasionally they have lasting significance. That is evolution.
Every bit of penicillin made since that day is descended from that single random cantaloupe.
Declarative memory is the kind you can put into words—the names of state capitals, your date of birth, how to spell “ophthalmologist,” and everything else you know as fact. Procedural memory describes the things you know and understand but couldn’t so easily put into words—how to swim, drive a car, peel an orange, identify colors.
When loss of balance is prolonged or severe, the brain doesn’t know quite what to make of it and interprets it as poisoning. That is why loss of balance so generally results in nausea.
You also have within you about a hundred personal mutations—stretches of genetic instructions that don’t quite match any of the genes given to you by either of your parents but are yours alone.
When more than one teenager is in a car, for instance, the risk of an accident multiplies by 400 percent.
What is certain is that in a few tens of years at most you will close your eyes forever and cease to move at all. So it might not be a bad idea to take advantage of movement, for health and pleasure, while you still can.
What genes specifically do is provide instructions for building proteins. Most of the useful things in the body are proteins. Some speed up chemical changes and are known as enzymes. Others convey chemical messages and are known as hormones. Still others attack pathogens and are called antibodies.