Existence is relative, not absolute. I agree that what 'humans have in common' may be ostensibly more than physiology.
'Commonality' viewed from a nested systems pov, takes on semantic issues of different 'levels of discourse'. So refering to the Einstein scenario, at the neurological level we might consider 'structural uniqueness' as a factor. And at the social level, we might consider Einstein's patent office duties examining time keeping inventions as a factor. And then of course we have the scientific
zeitgeist in which paradigms operate...etc. All these are possible contributory factors to the shift in the utility of the concept denoted by the word 'time', that shift being expressed by modifying words like 'local time'.
But at the end of the day, I suggest all those levels of discourse culminate in
observational criteria (aka evidence) regarding the utility of the concept and 'observation' is basically a physiological act.
As an aside, my neurophilosophy thread discusses 'evidence' of brain functioning which might correlate 'paradigm dynamics' which might indicate further 'physiological reductionist' possibilities.