When a stone sits on the Earth’s surface, cosmic rays quietly pepper it, leaving behind rare isotopes like tiny time stamps. Bury the stone deep enough, and that cosmic “printing press” shuts off. From there, those isotopes decay in a predictable way. In geology, that is as close as you get to a stopwatch. That stopwatch, along with two other independent clocks, has helped researchers build a sharper timeline for ‘Ubeidiya, an early prehistoric site in Israel’s Jordan Valley. The site has long mattered to anyone trying to map how early humans moved beyond Africa. A new study argues the site is at least 1.9 million years old, older than many past estimates and among the earliest known records of early humans outside Africa. The work was led by Prof. Ari Matmon of the Hebrew University of Jerusalem, Prof. Omry Barzilai of Haifa University, and Prof. Miriam Belmaker of the University of Tulsa. Their approach leaned on three dating methods that ask the same question in different ways: how old are the sediments and artifacts …