Since humans are made of matter and energy
And matter is energy in compressed state <- (overly simplified explanation) scientific fact energy cannot be destroyed just change conditions and has existed and will exist in eternity in the past to forward ALWAYS.. The assembly of our energy disbands and is dispersed back to the eternal energy of all existence. Space and time have no beginning and no end Thus proof life (energy) is eternal,, but the myths of nirvana have no proof and thus ,,,, awareness is unknowable Like a gallon of water taken from the sea and then poured back into the sea.
The concept of eternity fails most people. While many grasp at eternity after death, they fail to realize eternity existed as well before birth (backwards if you will). While people speak of the beginning,,, there was not one and there is no end.
The big bang is a measuring point of “one” point in time not of eternal beginning – there have been many many big bangs all over eternal space so far from us and each other’s they are independent. In speculation there is life all over that has always existed for all eternity and there is no first / beginning / act of creating or start of it all. It is eternity.
If you want; YOUR eternity started at “your” birth and ends at “your” death from the question
Note,, the one big bang in our area (like one grain of sand on earth) of eternal space as all did not come from noting it came from a highly compressed point that sucked in all the mater around it including all other starts planets people creatures organizes dust etc to one item so intense it exploded because it ran out of matter to pull in ….. an cycle of compression and explosion repeating over and over for all eternity – infinite number of times.
think of "our big bang" like your city on the earth and there are many more cities and planets and solar systems etc.