Since this mentions variation of the fine structure constant: studies of the Oklo reactor, which has recently come up again at https://news.ycombinator.com/item

Since this mentions variation of the fine structure constant: studies of the Oklo reactor, which has recently come up again at https://news.ycombinator.com/item?id=24739302 https://news.ycombinator.com/item?id=24739302 show no evidence of that over a relevant timescale.