The famous scientist , J B S Haldane, who gave up his British citizenship and became an Indian and settled in Calcutta, observed that the Dasavataras are a true sequential depiction of the great unfolding of evolution.
If you analyse the avatars of Vishnu , you can observe an uncanny similarity to the biological theory of evolution of life on earth.
The first avatar of Vishnu is Matsya or fish.( According to science, life originated in water).
The second avatar of Vishnu is Kurma or tortoise.( the evolution of the fish to the amphibean tortoise)
The third avatar of Vishnu is Varaha or the boar. ( the evolution of the amphibean to the strictly land animal).
The fourth avatar of Vishnu is Narasimha or the man-lion. ( the evolution of the land animal to a humanoid form with animalistic charecterestics ).
The fifth avatar of Vishnu is Vamana or dwarf ( the evolution of the animal-man to purely human in dwarf form).
The sixth avatar of Vishnu is Parashurama ( the evolution of the dwarf to a physically well-developed and ferocious warrior).
The seventh avatar of Vishnu is Rama ( the evolution of the ferocious warrior to Rama, who is considered as the ideal man or the maryada purushottama and the embodiment of morality , ethics and righteousness).
The eighth avatar of Vishnu is Krishna ( the evolution of Rama , the ideal man to Krishna who is considered as the ideal yogi, the superman who is known for his manysidedness and allrounded character , as I mentioned in the thread 'Krishna : Zorba the Buddha'.)
The animal evolution and development connotations bear striking resemblances to the modern scientific theory of Evolution.