The user can make adaptions to their body befitting whatever situation they are in such as increase strength, speed, senses, or intelligence; in general a highly advanced being. There are also special cases such as transforming arms into wings if they are falling or developing armored skin to prevent blunt force trauma, etc. The user can also cause similar evolutions in other people, animals, or plants he touches for a limited amount of time. Generally an evolved being is either a monsterous version or a hyper intelligent version of itself.
The user has a unique advantage against the rare ancient zoan devil fruit user. By evolving say a dinosaur zoan into a chicken zoan the opponent is made exceptionally weaker.
The user is limited to physical adaptions and can't develop any ability for energy or elemental attacks. There is a limit to how many and what adaptions can be made at a time, if the limit is met the user must revert back and start over. Evolutions that increase strength will decrease the users intelligence, and vice versa. Standard devil fruit abilities apply, including a weakness for water, so the user can't make aquatic adaptions such as evolving gills for themself.