One linguist tried to carbon-date languages using their most basic words
In the 1950s, Morris Swadesh compiled a list of core concepts — words like 'water', 'hand' and 'star' every language has a term for — assuming this vocabulary changes at a roughly constant rate, like radioactive decay. Comparing how much two languages' lists have diverged, a method called glottochronology, was meant to estimate when they split apart. The constant-rate assumption proved shakier than hoped, but Swadesh lists are still used to judge language relatedness.