Matter can’t be created or destroyed.
The world got created with a finite number of atoms for every element. So the count of atoms of gold, silver, uranium, oxygen, carbon or for that matter any basic element that exists on our planet in fixed.
We keep discovering new elements but never create them. What we see around is elements combining with other elements, naturally or synthetically, to create new compounds. However, those equations have their checks and balances, maintaining the cardinal rule that the number of atoms of each basic constituent is fixed.
So as an example, the number of atoms of Oxygen is fixed. You cant create an Oxygen atom. You can trade though. So you can chemically split the water molecule to derive oxygen but you cant produce an oxygen atom without an input oxygen atom.
This is how nature operates and dictates how everything around us exists, evolves & perishes
So it's logical to conclude that even the life on our planet follows the same basic principles.
Life gets formed when specific atoms in specific conditions combine together to create biological compounds. Although unlike a machine, life carries consciousness in it, albeit at a different level in each specie. Let's call that consciousness as the soul for the time being.
So given the soul exists in the same natural framework and so must follow the same principles of natures, the count of souls should be fixed too. Souls can change forms (acquire bodies of different species) but cant be created or destroyed. So souls would exists forever in the eternal loop of birth-death cycles. Whatever is born must die and whatever dies must be born again.
One may argue, how then the human population is ever increasing if the number of souls are fixed?
Well, all species forms - animal, fishes, bees, birds, humans etc- are to be considered when we arrive at the super set of souls. Also, in our planets history we have seen many species have gone extinct while many have evolved, possibly keeping the sum of all souls across all species constant.
We are part of nature and nature is part of us. We live. We Die. And we are born again.
It must comfort anyone who has lost a loved one that the nature will certainly bring them back.
Albeit in what life form & where for re-birth remain a mystery. There must be a nature’r law that decides the specie form for re-birth. The Law of Karm (Karma) fits in. It accounts for all actions in a lifetime and may be it determines the specie one is born in as the outcome. However, one doesn't carry conscience of previous birth and so it seems the previous life account gets squared off at the birth.
The cycle of life after all is not a Zero sum game.
