I'm not a scientist, I don't even play one on TV....

I'm just a regular guy trying to occasionally figure things out...

Thinking about giraffes, which have absurdly long necks and as such can reach higher leaves on trees to munch on...

One notion seems to be there was once just one single cell, then over time that single cell became what is basically a horse by many many many very slow rounds of random mutations that happened to be beneficial such as having two functioning eyes... and even though none of the other beasties had this mutation, it was a great advantage and so that freak beast was otherwise completely healthy except for that one mutation, AND it was a trait that he passed onto the next half-horse thing, which also had only this one change and nothing that would make him weaker... and it was through this slow process of mistakes and getting warped that one cell turned into thousands of identical giraffes.

The other theory is giraffes look like that because one day there weren't giraffes and the next day there were.

Dunno, but to me it's more LOGICAL to figure you started with pretty close to the finished product... and not that everything everywhere is the product of millions upon millions of rounds of good luck and fortune in freak mutated wild creatures living to pass on their problems that are secretly superpowers?