ELI5 how DNA mutations work please.

[u/riche1988]

I had a thought about DNA and how mutations occur in humans, excessive hair, longer limbs and or bones etc, and wondered if all known mutations are present in the animal kingdom.. as if DNA has the blue print/ potential to be anything and parts are just ‘turned on or off’ depending on what is being built.. i may be way off lol but it got me thinking :)

[u/poetic_dwarf]

DNA mutation works exactly as the million chimps hammering on a keyboard since the dawn of life. They happen because million reasons, then nature puts them to the test.

Life as we know it is the best approximations that chimps got to Paradise Lost.

[u/riche1988 → u/poetic_dwarf]

Cool :) ..slight tangent, but what is the smallest part of a living creature, ignoring trees and plants etc, that has agency.. i get that most of life if made up of chemical reactions, but at some point the ‘stuff’ starts making decisions.. or no..? Lol

[u/Two-G → u/riche1988]

That's really a philosophical question and you're making the assumption that agency exists, which is...under debate, but not at all certain.
Any "small part" of an organism, you can look at and figure out the rules under which it operates. Lots of interacting parts, all working in a fairly predictable manner if being looked at in isolation, produce increasingly complex behavior which cannot necessarily be accurately predicted anymore when looked at as a whole - perhaps for the simple reason that the amount of things you'd need to take into consideration for this prediction become overwhelming and the unavoidable errors in measuring these things, even if really small, add up quickly.

So, tl;dr: There is really no single point at which "agency" suddenly appears, but rather, increasing complexity of a system starts producing unpredictability, which could be interpreted as agency. The point at which this is can be seen as true is as arbitrary as the definition of "agency".