evolve

The intransitive partner of the transitive 'change something' meaning. Here the thing that changes is the subject, and no one is named as doing the changing. Its typical construction is evolve into, which names the end state: a few lines of code evolved into a million-line behemoth. Without into, the stress falls on gradual change rather than on any destination.

Here the trait itself takes the subject slot, and the population drops out of the sentence: beaks evolved, rather than birds evolved beaks. That makes it the natural form for asking when a feature arose, since the question is about the feature, not its owners. Its mirror image is the transitive trait sense.

Biologists use the verb with the population as subject and the trait as object: birds evolve beaks, cyanobacteria evolved photosynthesis. The same fact can be turned around so that the trait becomes the subject, as in the intransitive trait sense: beaks evolved. Both patterns are standard. The transitive one keeps the organism in view, which makes it the natural choice when the question is who acquired the trait.

Plans are what people most often evolve in this way. In P. G. Wodehouse's Uncle Fred in the Springtime (1939) a character announces 'That is the plan I have evolved', and Emperor Kōmei, quoted by Donald Keene, asks his ministers to 'evolve a suitable plan with due deliberation'. The verb suggests working something out by thought over time, so it suits plans, methods and translations.

The sense behind the closing lines of Charles Darwin's On the Origin of Species (1859). It is chiefly met in the passive: species are evolved, or have been evolved, and the cause is left unstated. Active sentences that name the cause ('isolation evolved the finches') are possible but less usual. In the perfect, have evolved into reads much like the plain intransitive, so context decides which is meant.

William Whewell's 1840 line 'the principles which Art involves, Science alone evolves' turns on the word's root. The pun sets evolve, Latin 'roll out', against involve, so that art wraps principles up and science unrolls them. The same rolling image shows plainly in the old 'wind or unwind' meaning.

A use that once leaned toward 'unfold': Matthew Hale, writing before 1677, has the animal soul that 'expands and evolves it self to its full orb and extent', pairing the verb with expand and turning it back on its own subject. That reflexive shape is the bridge to the intransitive procession sense, where the moving thing needs no object at all.

Laboratory English keeps the oldest picture in the word: Latin ēvolvō, "roll out," and here a gas quite literally rolls out of a reaction. The verb is transitive, so the reaction or the reacting substance is the subject and the gas is the object, as in a metal evolving hydrogen in acid. It stretches to smells too: a mixture can evolve odors. Keep it apart from the evolutionary sense, since nothing here changes over generations.