The Hinduism School of Thought in Creation Concept and Human Evolution through Physiological Growth to Psychological Growth (Text: SRIMADBHAGAVATHAM - DASAAVATARA)
The theory of evolution states that in order to preserve the Universe that was Created by Lord Brahma, God descends when the world passes through a moral or spiritual decadence to uphold "Dharma" and protect the noble.
Bhagavad Gita Chapter IV v.7
"yada-yada hi dharmasya glanir bhavati bharata abhyutthanam adharmasya tada tmanam srjamy aham"
O Bharata (Arjunan), whenever there is a decline of righteousness and a rise of unrighteousness, then I manifest Myself.
Hence, Lord Bishnu (Vishnu) took Dasa Avatars i.e.
1. Matsya Avatar (Fish); 2. Koorma Avatar (Tortoise); 3. Varah Avatar (Wild Boar); 4.Narasimha Avatar (Man-Lion); 5. Vamanah Avatar (Dwarf boy); 6. Parashuram Avatar (Cave man or Pre-man); 7. Rama Avatar (Ideal man); 8. Krishna Avatar (Super man); 9. Buddha Avatar (Equipoise man); 10. Kalki Avatar (Perfect, Complete & Accomplished man)