My memory was that the emperor adoptions were more pragmatic than anything, either because the emperor didn't have a son or as insurance against a power struggle caused by a single son dying. It's been a while so I could be mistaken.
This is the same mechanism that business succession planning reduces risk. Failure to train and groom new talent for leadership roles is a good way to ensure a company dies with its current staff.
> My memory was that the emperor adoptions were more pragmatic than anything, either because the emperor didn't have a son or as insurance against a power struggle caused by a single son dying.
Yeah, generally, but they're just the most famous examples (because emperor); this was standard behaviour for the time if you had something to pass on and didn't have kids. Adopting adult men was really commonplace in Roman society; Roman infant mortality was _astronomical_. The Japanese adoptions mentioned above were pragmatic, too.
Arguably, it's unfortunate that the custom died out for European aristocracy (though it did continue to some extent for normal people). A _huge_ number of wars were caused by failure to produce an heir.
This is the same mechanism that business succession planning reduces risk. Failure to train and groom new talent for leadership roles is a good way to ensure a company dies with its current staff.