When we are told that we can be reborn as animals or even insects. That is pretty tough to understand, is it not?
Yes, it does get more complicated.
We can so easily accept the concept of evolution which states that human beings evolved from single cell beings. However, even for those of us who can accept reincarnation it is very difficult to accept that human beings can also devolve into what we consider ‘lower’ forms. It is a threat to our identity. We think, ‘How can I turn into fly or a fish or whatever?’
People ask: A few centuries ago there was only a fraction of the current world population. Even if you add the animal population there would not have been six billion spirits. So, how did the population grow to six billion and how does it continue to grow? If new lives are based on rebirth where did all these new bodies come from?
Relax. All living beings are energy. Moreover this universe extends far beyond planet Earth. The entire space is energy. So there is enough energy to populate many planets, not only to overpopulate this Earth!
Mahavatar Paramahamsa Nithyananda.