*seal one's doom = 運命を決定づける、

As these societies developed, so did social structures, such as justice and religious ethics, which increasingly keep people from unnecessary aggression and move the moral needle towards good. Mr Wrangham contrasts the trajectory of Homo sapiens with the Neanderthals, a human species that became extinct around 35,000 years ago, after living in Europe for a half a million years. It was their cognitive inability to work and learn together, he contends, that sealed their doom.

The kindness of strangers, The Economist May 4th 2019 人類の倫理観と社会性の起源(書評)