Getting a human birth should be quite rare as the number of organisms in non-human yonis are much much high than human yoni.
How should one ensure that one doesn't fall in animal or plant yoni in his next birth. (As not everyone can get Moksha)
Getting a human birth should be quite rare as the number of organisms in non-human yonis are much much high than human yoni.
How should one ensure that one doesn't fall in animal or plant yoni in his next birth. (As not everyone can get Moksha)
Jivas whose sins are at the maximum level get born as plants, Jivas who have large amount of sins but comparatively lesser than the preceding group get born as various types of animals and so on.
Quoting from Vishnu Smriti XLIV:
Now after having suffered the torments inflicted in the hells, the evil-doers pass into animal bodies.
Criminals in the highest degree enter the bodies of all plants successively.
Mortal sinners enter the bodies of worms or insects.
Minor offenders enter the bodies of birds.
Criminals in the fourth degree enter the bodies of aquatic animals.
Those who have committed a crime effecting loss of caste, enter the bodies of amphibious animals.
Those who have committed a crime degrading to a mixed caste, enter the bodies of deer.
Those who have committed a crime rendering them unworthy to receive alms, enter the bodies of cattle.
Those who have committed a crime causing defilement, enter the bodies of (low-caste) men (such as Kandâlas), who may not be touched.
Those who have committed one of the miscellaneous crimes, enter the bodies of miscellaneous wild carnivorous animals (such as tigers).
One who has eaten the food of one whose food may not be eaten, or forbidden food, becomes a worm or insect.2
So, basically one needs to avoid committing the greatest sins like killing Brahmins, committing sexual intercourse with motherly figures (like one's own mother, sister, Guru mother etc.) and various other such sins in order to avoid getting born in the lowest of Yonis.