Why and when does one attain the human body?

One attains the human body after passing through the cycle of 84 Lakh Yonis (Lower life forms). This Soul wanders in the 84 Lakh Yonis. These Yonis have been divided into four Khanies (species as per their habitation and Birth etc.). The Jivas who live in water, are called as water dwellers. Those who live under the earth, are called as Ukmaj. It takes 75 Lakh years to shift from one Khani to the other. That is to say, it takes 3 crore years to complete the cycle of 84 Lakh Yonis. It means, one attains the human birth after such a long time. This is, in fact, the opportunity to seek Salvation. In no other Yoni, except that of a human being, one can hope to attain Salvation.