There are few who can (and will) contest the fact that human knowledge reached a high point during the Vedic period in the Indian sub-continent. While contemporary civilizations were busy constructing huge pyramids and great walls, Indians were indulging in the pursuit of knowledge. The Vedas, Upanishads, Puranas etc., stand eloquent testimony to this remarkable endeavor of our forefathers. On a closer unbiased analysis, one can easily notice that most of the inventions and discoveries of modern times are in fact re-inventions and re-discoveries of what was known to man during the Vedic period. Much of the finer aspects of the present day Hindu philosophy were also developed during the period, though the religion itself was called 'Sanatana Dharma' then. What is left of those glorious days are only some of the 'eternal pillars' in what is now called as Hinduism.
Evolution of Souls
If there is one aspect about Hinduism that differentiates it drastically from other religions, it is the unique theory of Karma and Re-births. In essence, this highly evolved 'Theory of Karma' propounds that all living beings (souls) are in an eternal cycle of births and deaths, each rebirth decided according to 'Residual Karma' of the previous lives. This unique recycle theory offers a logical explanation about why we are born in a particular place and also accounts for the case of children born with severe birth defects. The cycle of births and deaths continues till one reaches the highest form of spiritual existence and ultimately merge in Brahman, the cosmic soul of the universe. Though a majority of Hindus accept this as an axiom never to be questioned, doubts are aplenty in the minds of ordinary about what is 'Dharma' and 'Adharma', and how Karma gets computed. Trans-migration of souls is another aspect that has passed the judgment of the ordinary but has met with many questions from the 'doubting Thomases' who keeps any faith alive and vibrant.
Whatever be the views of believers and agnostics on the subject, there has been strong evidences in the past substantiating the belief of rebirth among Hindus. There have been recorded instances where young children could clearly recollect their deeds and incidents in their past lives. Instead of subjecting such instances to severe scientific scrutiny, the insecure and diffident scientific community have always brushed aside such cases as superstitions and myths. But many a time we notice strong synergy in the much acclaimed scientific theory of evolution and equally strong Hindu belief of rebirths. All the living species are evolving as they adapt to their current environment and I believe same is the case with souls as they evolve over successive lives. It is essential to believe in such a continuum, spread across subsequent lives, to fully substantiate the theory of evolution of species. Otherwise, how could a simple 'fifol' (first form of life) evolve into a complicated biological and spiritual entity like a human being. Mere mutation of the gene structure cannot fully explain the 'spiritual' evolution of species. At the very beginning, it would have been full of the least evolved 'fifols' and as time passed by some of them must have evolved into 'higher' forms of existence. Proposing some new ideas about the constancy of these indestructible units of life (souls) may also be not out of place.
An Italian scientist Amedeo Avogadro successfully postulated (in mid Nineteenth century) that one mole of any substance shall contain 6x1023 units of that substance at standard conditions. The said postulate was with specific reference to the field of Chemistry. But given the fact that Avagadro could establish such an unbelievable uniformity underlying an unlimited number of substances in this universe, it is not unreasonable to believe that the constant he had tumbled upon is just not another one of those numerous constants in theoretical science. We have seen that all fundamental aspects of Nature, be it principles or entities, are symmetric. There is striking resemblance between the molecular structure at micro level and solar systems at macro level. Natural laws of fundamental nature are equally applicable at all levels of existence. I wonder whether Avagadro was postulating such a fundamental natural law when he was trying to explain a simpler chemical problem. Avagadro, quite unknowingly, might have unraveled one of most important secrets of nature when he accidentally provided a theory for a very limited purpose. It is very much possible that the 'divine constant' of 6x1023 also pertains to a 'higher' truth, like the total number of living beings (souls) at any given time in this whole universe. As in the case of other elements, the constant may be denoting the number of units in the case of souls. The continuous extinction of species and evolution of new ones offers enough clue about the existence of such an overall constant. As mankind increases in number so are the other species becoming extinct. Mother Nature maintains the constancy of souls by invoking natural forces at its disposal to limit the overall count to the divine constant.
Presently we have 6x109 human beings in this world and further drastic increase seems highly unlikely given the fact that every 6 seconds someone somewhere is getting infected with HIV. If the divine constant is true, we can have a trillion each of a total of 600 billion more living species apart from human beings. Even if Avagadro number is exactly not the divine constant we are looking for, it is for sure somewhere near it.