All of today's DNA, strung through all the cells of the earth, is simply an extension and elaboration of [the] first molecule.

— Lewis Thomas

Animals have genes for altruism, and those genes have been selected in the evolution of many creatures because of the advantage they confer for the continuing survival of the species.

— Lewis Thomas

Ants are so much like human beings as to be an embarrassment. They farm fungi, raise aphids as livestock, launch armies into war, use chemical sprays to alarm and confuse enemies, capture slaves, engage in child labor, exchange information ceaselessly. They do everything but watch television.

— Lewis Thomas

As evolutionary time is measured, we have only just turned up and have hardly had time to catch breath, still marveling at our thumbs, still learning to use the brand-new gift of language. Being so young, we can be excused all sorts of folly and can permit ourselves the hope that someday, as a species, we will begin to grow up.

— Lewis Thomas

Cats - a standing rebuke to behavioral scientists. . . Least human of all creatures.

— Lewis Thomas

Doctors, dressed up in one professional costume or another, have been in busy practice since the earliest records of every culture on earth. It is hard to think of a more dependable or enduring occupation, harder still to imagine any future events leading to its extinction.

— Lewis Thomas

However, I have a stronger hunch that the greatest part of the important biomedical research waiting to be done is in the class of basic science. There is an abundance of interesting fact relating to all our major diseases, and more items of information are coming in steadily from all quarters in biology. The new mass of knowledge is still formless, in complete, lacking the essential threads of connection, displaying misleading signals at every turn, riddled with blind alleys. There are fascinating ideas all over the place, irresistible experiments beyond numbering, all sorts of new ways into the maze of problems. But every next move is unpredictable, every outcome uncertain. It is a puzzling time, but a very good time. I do not know how you lay out orderly plans for this kind of activity, but I suppose you could find out by looking through the disorderly records of the past hundred years. Somehow, the atmosphere has to be set so that a disquieting sense of being wrong is the normal attitude of the investigators. It has to be taken for granted that the only way in is by riding the unencumbered human imagination, with the special rigor required for recognizing that something can be highly improbable, maybe almost impossible, and at the same time true. Locally, a good way to tell how the work is going is to listen in the corridors. If you hear the word, "Impossible!" spoken as an expletive, followed by laughter, you will know that someone's orderly research plan is coming along nicely.

— Lewis Thomas

I am a member of a fragile species, still new to the earth, the youngest creatures of any scale, here only a few moments as evolutionary time is measured, a juvenile species, a child of a species. We are only tentatively set in place, error-prone, at risk of fumbling, in real danger at the moment of leaving behind only a thin layer of our fossils, radioactive at that.

— Lewis Thomas

It is hard to feel affection for something as totally impersonal as the atmosphere, and yet there it is, as much a part and product of life as wine and bread. Taken all in all, the sky is a miraculous achievement. It works, and for what it is designed to accomplish it is as infallible as anything in nature. I doubt whether any of us could think of a way to improve on it, beyond maybe shifting a local cloud from here to there on occasion. The word 'chance' does not serve to account well for structures of such magnificence... We should credit it for what it is: for sheer size and perfection of function, it is far and away the grandest product of collaboration in all nature. It breathes for us, and it does another thing for our pleasure. Each day, millions of meteorites fall against the outer limits of the membrane and are burned to nothing by the friction. Without this shelter, our surface would long since have become the pounded powder of the moon. Even though our receptors are not sensitive enough to hear it, there is comfort in knowing the sound is there overhead, like the random noise of rain on the roof at night.

— Lewis Thomas

It is in our collective behavior that we are the most mysterious. We won't be able to construct machines like ourselves until we've understood this, and we're not even close. All we know is the phenomenon: we spend our time sending messages to each other, talking and trying to listen at the same time, exchanging information. This seems to be our most urgent biological function; it is what we do with our lives. By the time we reach the end, each of us has taken in a staggering store, enough to exhaust any computer, much of it incomprehensible, and we generally manage to put out even more than we take in. Information is our source of energy; we are driven by it. It has become a tremendous enterprise, a kind of energy system on its own. All 3 billion of us are being connected by telephones, radios, television sets, airplanes, satellites, harangues on public-address systems, newspapers, magazines, leaflets dropped from great heights, words got in edgewise. We are becoming a grid, a circuitry around the earth.

— Lewis Thomas