system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How did some animals (lizards etc.) get an ability to regenerate limbs evolutionary?

I mean what was the process to aquiring that ability? And maybe the best example is Turbellaria for their amazing ability to divide.
gpt
All species have the capacity for regeneration, some to a higher extent than others. 

What you are referring to is called autonomy (self amputation) and in most cases it was developed as a defence mechanism that allowed an animal to escape by sacrificing a limb and then regrow a substitute one (albeit imperfect one in most cases, as they can and do regrow differently to the natural ones, e.g. Deformed in some way).

A good example of this are certain lizards that will leave a part of their tail as a decoy (it will continue moving after becoming detached) to flee from a predator. The tail will grow back, however it will not have the same bone structure as the original one as it will be mostly replaced by cartilage. 

Edit: a very good example of this in humans is liver regeneration. A human liver will regenerate back to its original size even if 80% of it is removed.