The value of some knowledge about reincarnation is to help one to avoid reincarnation! Reincarnation is the process of the jîva taking life after life in the physical world - some bodies will be human but most will be non-human bodies. It is during the rare lives in a human body that the jîva has the opportunity for escaping from the cycles of reincarnation. This escape comes when at least Level 1 Moksha is achieved.
The Âtman regulates reincarnation for the jîva and working together with the Grahas designs every physical life for the jîva according to its karma and desires. Bodies may be taken from either human or animal - all mammals, all birds, all reptiles, amphibians. Plants, insects, and fish are almost never bodies for jîvas.
The Creator, Lord Brahma, designed the universe to be populated by humans, cows, plants, insects and fish. Cows are the one animal species ordained by the Divine. All other animals are jîva created. Cows are special jîva incarnations originally reserved for those who wished to serve humanity. The milk products of cows are especially nourishing for humans. In some societies, the Divine origin of cows is still respected, but most societies have no knowledge of this.
The physical world is designed to be a literal "Garden of Eden" in which the food source for humans is dairy products, nuts, grains and vegetables, and water. Fish are for keeping the water clean, insects are to maintain the plants and humans are supposed to tend the cows, eat the dairy products, eat the plants and drink the water. It is not appropriate for humans to eat other human bodies or animal bodies. Fish and insects are not clean food and should be avoided as well.
All mammals and birds are jîva creations that have arisen out of the matrix of karma to satisfy the innumerable desires and karmic patterns that jîvas have generated. Whatever the jîva most desires or fears will structure the lives and bodies. This simple truth should be known and understood by everyone. Reincarnation is not a process to be encouraged.
To escape from the cycles of reincarnation is simple and readily available to every human being that has at least the karma to be able to think a thought. The most simple way to escape from the cycles of reincarnation is to adopt the practice of Atmavedi Meditation. Anyone who learns Atmavedi Meditation and practices it throughout their life is likely to attain at least Moksha Level 1, thereby breaking out of the cycles of reincarnation.
The jîva occupies 12 simultaneous bodies at any point in time, according to the decision of its Âtman, as illustrated in the drawing below, about half of the lives will be in female bodies and the others will be in male bodies. However, the jîva will only inhabit only one human body at a time. Each body that the jîva takes will have a specific package of kârma to balance and an opportunity to attain Moksha.
The kârma that a jîva brings into a life will determine, among other things, the sex of the body, its species and physical appearance, longevity, talents, weaknesses, diseases, accidents, and the course of events for all major and most minor life incidents. The jîva always has its free will to make decisions and take different courses in every life, but is definitely very constrained by the overall package of kârma it has to bear.
If the jîva makes choices that are in accord with the kârma of the lifetime, there will be maximum balancing of kârma and minimum generation of new kârma. The jîva will be aware of the important karmic choices by the pressure of its conscience. If the jîva ignores its conscience or acts contrary to it, the jîva will definitely generate new kârma that must be balanced in another lifetime.
The kârma of the jîva is managed by its Âtman – a direct representative of Krishna that accompanies the jîva throughout its long journey through the cycles of creation. The Âtman arranges a constant flow of 12 different, simultaneous incarnations to provide the jîva with bodies suitable for the balancing of its kârmas. The sex of the body is completely determined by kârma, since the jîva is fundamentally asexual. The jîva may inhabit any number of animal species including all types of mammals, snakes, reptiles, amphibians, fish, and birds. Plants, insects and inanimate objects are not inhabited by jîvas as bodies.
To obtain a birth in a human body is rare, and since only the human nervous system provides for the full expression of the intellect and free will, and is capable of supporting Brahman Consciousness, it is the most important birth. All other births are used strictly to balance kârmas of previous human births. No new kârma can be created in a non-human body, however these non-human births are important for the balancing that is accomplished. As previously mentioned, of the 12 simultaneous incarnations, only one will be in a human body.