Harvard scientists predict the future of the past tense

Verbs evolve and homogenize at a rate inversely proportional to their prevalence in the English language, according to a formula developed by Harvard University mathematicians who've invoked evolutionary principles to study our language over the past 1,200 years, from "Beowulf" to "Canterbury Tales" to "Harry Potter."

Writing this week in the journal Nature, Erez Lieberman, Jean-Baptiste Michel, and colleagues in Harvard's Program for Evolutionary Dynamics, led by Martin A. Nowak, conceive of linguistic development as an essentially evolutionary scheme: Just as genes and organisms undergo natural selection, words -- specifically, irregular verbs that do not take an "-ed" ending in the past tense -- are subject to powerful pressure to "regularize" as the language develops.

"Mathematical analysis of this linguistic evolution revealsthat irregular verb conjugations behave in an extremely regular way -- one that can yield predictions and insights into the future stages of a verb's evolutionary trajectory," says Lieberman, a graduate student in applied mathematics in Harvard's School of Engineering and Applied Sciences and in the Harvard-MIT Division of Health Sciences and Technology, and an affiliate of Harvard's Program for Evolutionary Dynamics. "We measured something no one really thought could be measured, and got a striking and beautiful result."

"We're really on the front lines of developing the mathematical tools to study evolutionary dynamics," says Michel, a graduate student in systems biology at Harvard Medical School and an affiliate of the Program for Evolutionary Dynamics. "Before, language was considered too messy and difficult a system for mathematical study, but