coz there are plenty of species who's population is decreasing, increasing and that has nothing to do with incarnation........ We have made earth such a facilitative planet for humans in every way, meanwhile some species completely lost their habitats, white rhinos just last week went extinct if you have read......

I don't know if i strongly believe in incarnation or not but, hinduism stats that, just like a drop of water gets splashed and separated from ocean for a while, our souls are the same.

We have departed from the "brahman", the single eternal consciousness like ocean of water, and our souls are on a journey to find its way back, it will keep taking birth on planet untill we figure out how to merge with the brahman. Heaven and hell are the same place we live in, we chose what to make out of it.

There are ways given in the sacred texts. Which honestly just teachings to lead a life that in an ideal heaven will be.