Animals, Plants, and Humans all have eternal spirits

Your thoughts? This is in Hinduism, Buddhism, and Mormonism. References from The Pearl of Great Price, D&C, and the non-Canon Journal of Discourses indicate this important eternal truth. Hinduism and Buddhism (both?) believe that the soul/energy of a human may have been in a past life or may become in a future life, the soul/energy of a plant/animal. In this salient similarity, I do not see a radical change of type but rather a difference of degree. For example, and this is totally speculative, NON-doctrine of any kind, my postulating here, would it not be possible that the spirit bodies organized from intelligences once were the spirits of animals or plants on previous worlds? Since it is true, that "As man is now, God once was and as God is now, man may become," why would this not be possible? The Spirit seems to whisper to me that this is not true but I'd like to hear what you, dear reader, think about this. Toward a common origin? My thoughts are: A fullness of the truth was taught to Adam and Eve who then taught their posterity. As their posterity moved and the truth was diluted, modified, apostatized, etc. over time, a fullness of the truth was lost (or diluted). Hence, the 7 main Rishis of Hinduism understood, as did the ancient prophets who wrote the Book of Mormon, that time and history is ahistorical or in other words, cyclical. Whether one examines the Nephite Pride Cycle or Hinduism's waning (as Buddhism spread) and Hinduism's Renaissance (late 14th Century AD/CE), history repeats itself and mankind, in general, does not learn from the past.