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.

The brain is wider than the sky, For, put them side by side, The one the other will include With ease, and you beside.

“People act as if skin color is a determinant of character when all it is is a reaction to sunlight. Biologically, there is actually no such thing as race—nothing in terms of skin color, facial features, hair type, bone structure, or anything else that is a defining quality among peoples.

All humans share 99.9 percent of their DNA, and yet no two humans are alike.

Of course, very occasionally a cancer develops into something more serious and possibly kills you, but overall cancers are rare: most cells in the body replicate billions and billions of times without going wrong. Cancer may be a common cause of death, but it is not a common event in life.

You are truly a wonder. But then so, it must be said, is an earthworm.

It is an arresting thought that all that makes you lovely is deceased. Where body meets air, we are all cadavers.

Your DNA is simply an instruction manual for making you. A length of DNA is divided into segments called chromosomes and shorter individual units called genes. The sum of all your genes is the genome.

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.