D "evolving" to DARWIN, what a fun idea! I usually think of "evolving" as one element changing for the better, so my first thought as a constructor might have been a word ladder (from ... (some six letter word) to DARWIN?). But word ladders can be pretty dull, so I like the concept here.
Each of the themers is so colorful. DARN TOOTIN, they are! Great work there.
Now that I think of it, the progression from amoeba to invertebrate to mammal, etc. is a kind of growth, isn't it? Okay, maybe this interpretation is a lot more appropriate than a word ladder.
Never mind me. Ahem.
Ah, five themers squished together. That was almost necessary since DARWIN at the very end forced BOBBY DARIN to move to row 12, instead of row 13, where it'd usually be. Everything gets crunched up, and O ME did we get a lot of crossword glue.
Will strives to avoid non-common abbreviations and initialisms since if you don't know them, there's no way to infer them. NMI is a prime example (no middle initial). Along with HALER ORY SYL TAUR ERL etc. it felt like a lot to wade through.
Thankfully, there was a good amount of long(ish) fill to help lift the solving experience, IRON MAN, GAP YEAR, PAR THREE making me wonder if I ATE CROW on my critiques! It's still not a trade-off I would have personally made, but I can see the appeal.
Heck, even BIRYANI, PERUSAL, CASSETTE are pretty interesting. Okay, that's a lot of solid bonus fill! Definitely helps to balance out the grid liabilities.
Perhaps an evolutionary step (sorry, couldn't help myself) would have been to shift DARN TOOTIN all the way to the left, so that DARWIN could be placed vertically, down off that D. Total grid redesign of course, but that would have allowed for better spacing of the long themers (BOBBY DARIN moving to row 13).
Overall though, it was something new for me, and the novelty was much appreciated. Really neat to get a theme from a debut constructor related to her profession!