On this earth, no other living being has consciousness as evolved to the level of a human being. That is why man is considered as the very image of God in scriptures. The purpose of human life is to evolve to Godliness inculcating in the soul divine virtues - truthfulness, wisdom, knowledge, compassion, love, etc. Presently, not all living beings are evolved to that level, including humans. Most humans are only two legged brutes, we know it. Here comes the significance of the theory of evolution. The soul undergoes various incarnations to evolve to higher states of consciousness drawing from the long trail of experiences. The physical embodiment is decided by the level of the spirit's evolution. As the spirit evolves, its physicality also undergoes transformation. Here lies the basis of Reincarnation theory. Perhaps, Darwin's theory proves it scientifically.
God has first created the basic molecule of life in the waters and nourished it with the divine rays of the sun, moon, planets, stars and constellations surrounding the solar system. So says the Genesis of Hindus: ‘God desiring, seeking to produce various creatures from his own body, first created the waters, and deposited in them a seed. This (seed) became a golden egg resplendent as the sun, in which He himself was born as the progenitor of all worlds…That Lord having continued in the egg divided it into two parts (male and female) by his mere thought.’ (Manu Smriti 1.9).
God has a plan that the life He created evolves and becomes one with Him through the evolution of consciousness. The living beings undergo misery because they are not awakened to their divine nature. So all living beings are driven by this very quest - realize its divinity and eternal existence. If God alone existed here, there would be no world, no living beings to experience Him. So this duality is an eternal process making the presence of God in nature.
A universal spiritual culture can evolve only on the premise of universal spiritual truths that can stand the test of time, logic and science. The disagreement between different religions and schools of thought on the basic concepts about God, the creation, its purpose and the scheme of man’s spiritual evolution have led to the present conflicts. The sages of India had brought to light some original ideas about the origin of universe as well as the spiritual evolution of man which happens through the course of many cosmic ages known as Manvantara. The avatar theory in the Hindu scriptures points to the gradual evolution of man. In the long course of a cosmic age, there are many dawns and dusks corresponding to the origin and dissolution of different human civilizations.
The avatars and messiahs of God appear when there is utter emotional unrest or social degeneration. At the summit of such social and spiritual turmoil, a messiah appears as the guide of man, who inspires the hope of his betterment and salvation. ‘Whenever dharma is in peril, I (God) manifest myself (in the form of a Mahatma)’, says the Bhagavat Gita. We know that all religions in the world have originated from such messianic movements. However, despite the work of any number of gurus and prophets, humanity is still groping in the dark unable to get on to the path of peace and spiritual fulfillment. Today we are more and more convinced about the desirability of evolving a universal spiritual culture for harmony and peace.
God, that Master Craftsman who conceived and projected this universe presides over human evolution through the medium of epochal spiritual masters. They are magnificent souls who have ascended higher spiritual planes and unified with the Light of God through their self-sacrificing effort spanning several births. They remain as luminescent souls in the astral world. It is said that the innumerable stars in the distant sky are such souls, whether we believe it or not. These spiritual luminaries occasionally adorn human forms and come down to the earth plane for the spiritual guidance of man. Mankind has received spiritual wisdom only through such souls. These spiritual authorities have their own spiritual incumbency according to their spiritual merit and the commission of God. Their spiritual incumbency may be for 1000, 1500, 2000, 2500, 3000, 5000 years etc. according to the civilizational requirement related to man’s spiritual evolution.