As a rule we get 1.5 billion heartbeats and then we stop. Our dogs and cats also get 1.5 billion heartbeats and then they stop. The same applies to mice, giraffes, whales, wallabies, manatees, monkeys, pigs and elephants. As a generality and applied to all mammals as a group, they have an absolute lifespan that is defined by 1.5 billion heartbeats. Some species have hearts that beat slower and some beat faster, that accounts for the different lifespans as measured chronologically.
It does not matter whether we believe that we are unified by some universal gene expression passed down through time via an evolutionary mechanism or that we are unified according to the larger plan of entity whose magnitude is far beyond our very limited ability to comprehend. What truly matters, is what actually is; that we are both unified with the life around us and that we are finite. Remember that and you will make every heartbeat count.