We might consider apoptosis as the essential ingredient to consciousness.
Programmed cell death, for which a death-gene has been designed (intelligently or not), if ever manipulated, might theoretically offer immortality. But at a cost: our memory system functions by cutting out some connections while keeping others. Just like the darkness inbetween the stars, the no-thing that was before the Big Bang, makes the stars possible.
This 'natural' selection of memories makes us individual sentient beings. Without apoptosis, all connections would remain live, switched on forever, causing us to remember every single event, evenly producing a grey field of noise. By cutting off the peaks of awareness, we'd become immortal cucumbers.
Derisanamcope, 21th November