> Humans owe their big brains and sophisticated culture to a single genetic mutation that weakened our jaw muscles about 2.4 million years ago, a new study suggests.
_A new study suggests_
I don’t think you can treat these claims as categorically true. It’s plausible and probably warrants further study, like most things in biology.
Edit: I could not read the second article you linked as it was behind a paywall, but I found the full text of the original paper[1]. The paper appears to make a much weaker claim: that a weakening of jaw muscles in humans coincided with acceleration in brain size. This is certainly intriguing, but correlation does not imply causation.