Hasn’t the standard been the awareness of one’s own mortal existence, including one’s ability to influence their reality.
I’d choose your first definition: the sum of flesh. After all, nature’s plan for us was to see how long we could sustain our species, just the same for “animality” and “plantity”.
If you were to sum our collective actions, our collective values, I’d posit this would be the only significant result: reproduction.
Being a believer in the many-worlds interpretation of QM, I’d say it’s not entirely necessary. However, time travel would likely violate many physical laws, so even something as outlandish as the MWI of QM might be turned on its head.
It could be argued that one would be required to arrange for the copulation of his parents in the case that time travel existed. If one’s parents met and married in the normal fashion, one would be compelled to ensure time travellers did not disrupt this process, just as one whose parents included a time traveller would be compelled to ensure they did travel at some point in time. This, however, would obliterate the concept of free will.
My reasoning in invoking the MWI is that in the case where the “time travelling dad” was never sent back to copulate with mom, there would be another chain of events that would lead to the child’s conception. Perhaps another person would send “dad” back in time, but he copulated with the wrong mom, or with several moms. The very fact that the child exists ensures some chain of events occurred… although one or more parties in the event may not be able to put cause and effect together to explain the situation.
Of the questions you’ve asked, BRM, this is the most interesting. I’d suggest we start a new thread, as time travel has many consequences which may not be forseen without a great deal of thought and discussion.