Myelination of our brains. In super simplified terms, it is over clocking our brains part by part. It continues until mid to late 20s.
>After infancy, the rate of myelination slowed during childhood and adolescence, but exhibited continued growth until the end of the third decade. Specifically, mean MFLD during later adulthood (defined as ≥28 y) was significantly greater than in adolescence and early adulthood (11–23 y; Welch t, P = 0.000059; Mann–Whitney U, P = 0.00016).
Our (dorsolateral) prefrontal cortex is one of the last parts to myelinate.
>The last areas to myelinate are the anterior cingulate cortex (F#43), the inferior temporal cortex (F#44) and the dorsolateral prefrontal cortex (F#45).
Yes, to the extent we accept it so much we made it into law. Though the law does seem to pick a few different age groups for other things based on a seemingly arbitrary standard. Lower for driving, even though bad driving could kill innocent bystanders. Higher for smoking, even though smoking only kills yourself. You can even sign up and join the military a year before you are able to vote for the politicians who control it.
They probably should have made all accounts under 50 private.