60 bpm is about typical for a resting heart rate, I suppose. So that could make sense.

About as much sense as positing that humans use decimal numeral systems (ignoring whatever the fuck the Romans used) because they have ten fingers.

No way to really confirm, but it seems a likely guess.

I wonder if Parmenides talks about it at all...

Also, how did they even standardize this before digital clocks? Like did the first clock maker tell all his apprentices "This clock ticks every second. One tick is one second. Every clock you make must tick at exactly the same rate."