It is a little ironic that 2 of the lightest things in nature, oxygen and hydrogen, when combined form one of the heaviest, but that’s nature for you.
That is unquestionably the most astounding thing about us — that we are just a collection of inert components, the same stuff you would find in a pile of dirt. The only thing special about the elements that make you is that they make you. That is the miracle of life.
The length of all your blood vessels would take you 2.5 times around Earth.
Yet somehow when all of these things are brought together, you have life. That is the part that eludes science. I kind of hope it always will.
What is perhaps most remarkable is that nothing is in charge. Each component of the cell responds to signals from other components, all of them bumping and jostling like so many bumper cars, yet somehow all this random motion results in smooth, coordinated action, not just across the cell but across the whole body as cells communicate with the other cells in different parts of your personal cosmos.
DNA exists for just one purpose — to create more DNA.
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 3 errors, or mutations, per cell division. Most of those mutations the body can ignore, but just occasionally they have lasting significance. That is evolution.
It’s a lightly humbling thought that the genes you carry are immensely ancient an possibly — so far anyway — eternal. You will die and fade away, but your genes will go on and on so long as you and your descendants continue to produce offspring. And it is surely astounding to reflect that not once in the 3B years since life began has your personal line of descent been broken. For you to be here now, every one of your ancestors had to successfully pass on its genetic material to a new generation before being snuffed out or otherwise sidetracked from the procreation process. That’s quite a chain of success.
All humans share 99.9% of their DNA, and yet no two humans are alike.
And how do we celebrate the glory of our existence? Well, for most of us by eating maximally and exercising minimally. Think of all the junk we throw down your throat and how much of your life is spent sprawled in a near-vegetative state in front of a glowing screen. Yet in some kind and miraculous way our bodies look after us, extract nutrients from the miscellaneous foodstuffs we push into our faces, and somehow hold us together, generally at a pretty high level, for decades. Suicide by lifestyle takes ages.
Nearly all animals produce their own vitamin C, but we can’t. We undertake every part of the process except, inexplicably, the last step, the production of a single enzyme.
Beauty is only skin deep, but ugly goes clean to the bone.
The outermost surface of the epidermis, called the stratum corneum, is made up entirely of dead cells. It is an arresting thought that all that makes you lovely is deceased. Where body meet air, we are all cadavers. These outer skin cells are replaced every month. We shed skin copiously, almost carelessly: some 25K flakes a minute, over 1M pieces every hour. Run a finger long a dusty shelf, and you are in large part clearing a path through fragments of your former self. Silently and remorselessly we turn to dust.
We each trail behind us about a pound of dust every year.
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.
In regions like northern Europe and Canada, it isn’t possible in the winter months to extract enough vitamin D from weakened sunlight to maintain health no matter how pale one’s skin, so vitamin D must be consumed as food, and hardly anyone gets enough — and not surprisingly. To meet dietary requirements from food alone, you would have to eat 15 eggs or 6 pounds of swiss cheese every day.
We are actually as hairy as our cousins the apes. It’s just that our hair is much wispier and fainter.
The idea that all fingerprints are unique is actually a supposition. No one can say for absolute certain that no one else has fingerprints to match yours. All that can be said is that no one has yet found two sets of fingerprints that precisely match.
Chimpanzees have only about half as many sweat glands as we have, and so can’t dissipate heat as quickly as humans can. Most quadrupeds cool by panting, which is incompatible with sustained running and simultaneous heavy breathing, especially for furry creatures in hot climate. Much better to do as we do and seep watery fluids onto nearly bare skin, which cools the body as it evaporates, turning us into a kind of living air conditioner. The loss of most of our body hair and the gain of the ability to dissipate excess body heat through eccrine sweating helped to make possible the dramatic enlargement of our most temperature-sensitive organ, the brain.
Sweating is activated by the release of adrenaline, which is why when you are stressed, you break into a sweat. Unlike the rest of the body, the palms don’t sweat in response to physical exertion or heat, but only from stress. Emotional sweating is what is measured in lie detector tests.
At their scale, your skin to them is like a giant crusty bowl of cornflakes. If you close your eyes and use your imagination, you can almost hear the crunching.
One other thing the skin does a lot, for reasons not always understood, is itch. Although a great deal of itching is easily explained (mosquito bites, rashes, poison ivy), an awful lot of it is beyond explanation. As you read this passage, you may feel an urge to scratch yourself in various places that didn’t itch at all a moment ago simply because I have raised the matter.