Posted by: carlsafina | Thursday, February 11 10

Evolution: Only a Theory

Last year on Charles Darwin’s 200th birthday The New York Times carried an article of mine ( for which I took some heat from Darwinian fundamentalists because they thought I was “dissing” Darwin (everyone who thought so has no sense of irony and basically can’t read, but that’s why they’re fundamentalists. Anyway—.) In honor of Charles Darwin’s birthday on February 12 (he was born in 1809), here’s another thought on the great man.

This was deleted from the above essay for space reasons, but it’s included in my upcoming book, The View From Lazy Point:

Evolution: Only a Theory

Carl Safina

That we’re all related by common ancestry is the most fundamental discovery about living things. Religion long ago intuited this; in the Abrahamic religions, God creates all creatures, so in one sense we have always considered ourselves siblings within a family of life. Evolutionary biology and genetics are the scientific mineshafts that get deep into the motherlode discovery: living things change.

The biggest misconception about evolution is that it’s “only” a theory. To most people, a theory is an untested hunch. But in science, a hunch is called a hypothesis. If a hypothesis is tested and confirmed repeatedly, and if all the confirmation creates a pool of knowledge useful for predicting events, the knowledge is called “theory.” That’s very different than a hunch. Imagine a child sitting at a piano for the first time. They notice that some keys sound dissonant together, and others harmonize. Eventually, the child may know how notes will sound before hearing them played; that’s music theory. It’s not “just” a theory. It’s an understanding of music so thorough that one could—as Beethoven did—compose a symphony despite being completely deaf. Listen to Beethoven’s Ninth and you’ll feel the power of theory. This predictive sense of theory is the same way scientists use the word. Atomic theory predicted that a series of procedures would cause a big explosion. Germ theory predicts that if surgeons wash their hands, fewer people will die of infections. Evolutionary theory has the same proven power. It’s not a guess. When insects and bacteria develop resistance to antibiotics and pesticides, that’s evolution. We’re not surprised when they develop such resistance, because of evolutionary theory. For all of civilization, plant and animal breeders who created new strains by selectively breeding individuals with desired traits were, without naming it, using evolutionary theory.

Evolution is as scientifically accepted as gravity. And while we don’t quite understand how gravity works, we know a lot about how evolution works—much more than Charles Darwin, even with all his genius, could have dreamed.

Evolution is not just the making of new species—the question that obsessed Darwin. And it’s not the progress from Protista to say, Protestant. Very primitive things are also evolving now (like the AIDS virus). And plenty of evolution brings neither new species nor progress. Sometimes the progress goes backwards; the ancestors of whales and snakes had legs, and on islands lacking predators, bird species sometimes lose the ability to fly.

Evolutionary theory predicts that the more diversified the living enterprise, the more it will adapt to change. The more diminished, the more trouble it will have adapting. And changes are coming, faster than before, that will challenge us all to adapt. We can predict some important things about how life on Earth is likely to change, and plan to cope, because evolution is a theory.


  1. I know that species change and adapt, but I have yet to see any concrete evidence that they evolve from lower to higher forms.

    • Dear Brittany,
      Darwin could say that he never saw evidence. He had only inference. We, however, cannot make the same claim. The fossil record is full of creatures on their way to somewhere (such as dinosaurs with feathers), and even without fossils the DNA shows that creatures that look similar, like apes and people, are extremely close genetically, with just a relative few substitutions of amino acids making the difference, while the genetic differences are greater in creatures that look less alike. As they change and adapt, organisma sometimes evolve from “lower” or less complex to more complex (larger, more complicated, warm-blooded, with parental care, with increased intelligence) forms. The fossil history reflects the fact that the earliest life was simple, and more complicated forms come later. But a very great deal of change is rather lateral, and in some cases species lose complexity and evolve into simpler forms.

  2. Thank you Carl for your words for Darwin with your words on present-day scientists’ understanding of “lower” / “higher”…Great!
    !: (in consideration of human bio-diversity):
    If ever you touch the tips
    of its eye stalks,
    many a land snail, like as not
    will retract its eyes into its head.

  3. Thanks to Dr. Safina for emphasizing the common ground of religion and science–that the Abrahamic faiths intuited common ancestry behind the unfolding of life in diverse forms. Without the capacity to adapt to changes in the environment, all life would be doomed. And note to Brittany: Genesis 1, written in a different language than the language of science, written before the scientific method had been invented, recognizes a progression over time from simple to more complex life forms [life that can’t move, followed by life that can, followed by life that can tell the story of life’s unfolding].

    • More evidence of life evolving: whales have vestigial pelvic bones and some snakes have vestiges of limbs.

  4. Thanks for the great post. I often have arguments with my brother who is a full on christian. He is always telling me that science is just a theory. It is very hard for him to understand the difference between hypothesis and theory. Or he chooses not to understand out of convenience.

    I also like how you explain that all things are evolving even lower life forms. What often people consider to be a ‘lower’ life form is actually fairly modern. I just wrote a post on Cichlids who in the African lakes have speciated into thousands of species in the last million to hundreds of thousands of years. This is less time than humans have been a species. Does this mean they are more advanced than we are…are we a lower life form? Anyway just my gripe. Not with you but with that terminology.

    • thanks; the way i think of lower and higher life has to do with their complexity. Single celled organisms with no nucleus are lower (though critically important to life on Earth because they’re decomposers and recyclers). Mammals with placentas, warm blood, and parental care are higher. Many lower life forms are indeed fairly modern; viruses are constantly evolving brand-new strains.

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