Yes, EVOLUTION is a Scrabble word!

Letter values in Scrabble US: E 1, V 4, O 1, L 1, U 1, T 1, I 1, O 1, N 1.

Is it a valid word?

EVOLUTION is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

a process in which something passes by degrees to a different stage (especially a more advanced or mature stage)
(biology) the sequence of events involved in the evolutionary development of a species or taxonomic group of organisms

Also: organic evolution.

Not playable in Scrabble US: PHYLOGENESIS.