Tracing the evolution of English verbs over 1,200 years - from the Old English of Beowulf to the modern English of The Princess Diaries — researchers have found that the majority of irregular verbs have gone the way of Grendel, felled by the linguistic equivalent of natural selection.

The irregular verbs, governed by confusing and antiquated rules, came under evolutionary pressure to obey the modern “-ed” rule of regular verb conjugation, according to a report in the journal Nature.

That the English language has undergone dramatic change over a millennium will come as no surprise to generations of high school students who have struggled to decipher “Beowulf”, which dates from the ninth century, or Chaucer’s The Canterbury Tales, written about 1200.

Linguists have constructed elaborate “family trees” showing how language has morphed over time but have been unable to detect the principle governing such changes.

The researchers, led by Martin Nowak, an evolutionary theorist at Harvard University, discovered that irregular verbs evolve in a predictable manner — just like genes and living organisms. Analysing databases containing millions of words, Nowak and colleagues showed that the patterns of change depended on how often irregular verb forms were used.

Infrequently used irregular verbs were quickest to evolve. For instance, “holp”, the past tense of “help”, became the modern “helped”. Similarly, “chode” became “chided” and “swole” became “swelled”. Researchers found they could compute the precise rate by which irregular verbs became “regularised” in the same way physicists calculate the half-life of radioactive materials. In general, they discovered, a verb used 100 times less frequently evolved 10 times as fast.

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