Similarly to Darwin’s theories on biological evolution, language has been evolving since its onset. Darwin theorized that biological evolution was driven by a directional force- survival of the fittest. The corollary in language has often been believed to be an innate desire for humans and other communicators to make the language as clear and concise as possible. That being said, linguists admittedly lack significant and consistent evidence that their proposed directional force is the cause for the evolution.
An example of the ambiguous nature of defining the evolution of language comes in the shift of usage from clearness to clarity. In the last century, the usage has entirely shifted in the favor of clarity. By one metric, clarity is more efficient, requiring only seven characters compared to clearness’ nine characters. However, clarity is a more difficult word for beginner and intermediate English speakers, since it is not a standard conjunctional derivative of clear. This would suggest that language evolves to become as concise as possible. Counterexamples of this proposed evolution come in the shift in usage from wove to weaved and smelt to smell. These suggest the opposite effect, rather than staying the course, the most concise possible past-tense conjugation, they shifted to an easier to learn and more universally understood form of the word and ignored the increased pronunciation time. And then to confuse the situation more, in the same period that clearness shifted to clarity, dived shifted to dove, and wove shifted to weave.
These situations led to some linguists abolishing the theory of directional forces in favor of that of drift. They believe that language is driven by individual changes, often randomly motivated, rather than one clear, enveloping goal that biological evolution offers. All in all, charting the evolution of language is a work in progress and unlike biological evolution lacks a clear overarching goal.