Lord Buddha the son of King Suddhodana who lived in India 2500 years ago had given a very agreeable and more rational explanation about how to determine the next birth of a person.
One day a group of monks approached the Buddha and wanted to know where, a person known to them was born after his recent death. Buddha showed them a nearby tree and told, Monks, suppose you go and cut that tree down, where do you think that tree falls. Monks answered O, Lord Buddha there is no doubt that the tree will fall in the direction it is inclined or leaned now.
Then the Buddha answered as same as that, a person's next birth is determined by the way he spends his current life. If he lives the life in a way a god is living in earth with kindness love ect. Then he will return to gods realm after his death. If he lived like a man then he will be born like a man, if he lived like an animal then will be born like an animal. That was Lord Buddha Answer."
