People who are acquainted with the theory of reincarnation are apt to look at the increasing lifespan and the rising population on Earth and wonder if the population growth invalidates the theory of reincarnation. We all know where babies come from but where are all the new souls which inhabit these bodies coming from? In this article, we address this demand-supply problem.

There are three plausible explanations for why the theory of reincarnation still holds despite being subjected to the undue stress created by human reproductive prowess.

The total number of souls may far exceed the number of incarnated souls. For example, there could be 100 billion souls currently in the life-death cycle out of which only 6 billion are currently living on Earth. (Imagine the number of ghosts who are currently hovering around you as you read this article…!) There are animals which are evolving and taking birth in human bodies. Ancient Hindu scriptures aver that each individual soul which is Divine in nature undergoes a gradual evolution incarnating in plants, animals and then human bodies many times over, and that this process transpires over millions of years. The period spent in afterlife can vary with intervals ranging from a few years to a few hundred years. There could be souls migrating to be born on earth from other planets in the Universe. For more on this aspect, see the article by theosophist David Pratt referenced later on.

David Bishai of the Johns Hopkins School of Public Health attempted to address this question in his 2000 paper “Can Population Growth Rule Out Reincarnation? A Model of Circular Migration” published in the Journal of Scientific Exploration. Applying a Markov model to historical demographic data of the last 52000 years, he showed that population increase can be explained by a decrease in number of years that are spent in the afterlife. This hypothesis was first proposed by noted reincarnation researcher Dr. Ian Stevenson and has been incorporated into a sound mathematical model by Bishai.

Here is a quick layman summary of Bishai’s result. Imagine there are 100 billion souls. A few centuries ago, assume there were 500 million people on Earth with an average lifespan of 33 years, and the number of years an average soul spent between incarnations was (say) 5000 years. Fast forward to the current scenario where there are 6 billion souls with an average lifespan of 70 years. Then the number of years an average soul spent between incarnations will go down from 5000 years to 712 years but it doesn’t change the dynamics of reincarnation drastically. Those who are mathematically inclined can read Bishai’s paper — Can Population Growth Rule Out Reincarnation? A Model of Circular Migration.

What could be the possible reason for a decrease in the time spent in afterlife? To understand that, one has to examine the after-death process. The human constitution is made of layers of five concentric sheaths, and upon death, each of these sheaths dissolve one after another over time (first the physical, then the vital sheath, then the mental sheath, and so on) until the soul itself retires to what Sri Aurobindo called the psychic world for a many years. This is the normal process but it can be subverted if the soul has a strong attraction (e.g. unfulfilled desires) to return to the earthly material plane in which case the time spent in afterlife can be shortened and the soul is reborn immediately without rest after a few years. It is quite possible that in this materialistic age, many people remain attached to their earthly possessions after death and are hence reborn quickly, thereby contributing to a population increase. (So we have no rest at night, and no rest in afterlife either – ugh!)

On the last factor mentioned above about souls migrating to Earth from other planets, see the two-part article by David Pratt, a theosophist, at http://davidpratt.info/population.htm. His explanation relies on the model of evolution conceived by H.P. Blavatsky.

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