Though a knowledge of the material world is essential, it is not the be all and end all. The importance of spirit underlying life must be realised after the research and the differences between life with spirit and life without spirit must be brought out. The Taittiriya Upanisad , one of the ten most important Upanisads of Indian philosophy, has made important observations in the evolution of life. It traces the life evolution to space. Accordingly, space is noted to evolve into air, air into fire, fire into water and water into the earth.
Earth generates the vegetative kingdom which gives rise to food.
From food is life on the earth, it contends. The life or purusa is constituted by anna-rasa . This text very briefly traces the evolution of living matter from space. But then it also advances and traces the steps to realise the underlying truth of the universe, true to a research oriented philosophy. Infusing all the pancabhutas in certain proportions, life has evolved through various stages of the geological history and has been becoming more refined and subtle.