Saṁsāra—the cycle of repeated birth and death in the material world; The baddha-jīva (conditioned soul), captivated by the modes of material nature, is moved as if on a wheel through 8,400,000 kinds of births, lifetime after lifetime. At the lower range of the cycle are births within aquatic, vegetative and animal forms. At the middle range are births within human forms. At the upper range are births within superhuman forms, such as the demigods. But as high as the soul may reach, even up to the position of Brahmā, there is no freedom from saṁsāra. Impelled by prakṛti, kāla and karma, the jīva will surely be forced into another womb, until the day that soul surrenders to the origin of the force that turns the wheel of saṁsārathe īśvara, Kṛṣṇa. The materialistic theory of evolution put forward by Anaximander and Darwin imperfectly recapitulates the Vedic description of the cycle of birth and death. It is true that we were once microbes, fish, reptiles, mammals and apes. But who are we? We are spirit souls. Materialists have no knowledge of the soul. They are unable to explain how and why dead matter assumes the forms of the gradient species. The Vedas explain that the gradient species mark the evolution and devolution of the soul's material desires. See Evolution, Karma, Life after death, Reincarnation.