I hunt in NE North Carolina mostly for 50+ years. We do not often kill 200 lb deer. Go west 150 miles and they become more common. No hounds allowed there and a shorter season makes a big difference. For some reason, we have huge black bears in coastal warmer counties. A 700lb bear is taken almost every year. Our mountain counties have many bear but about half the size of coastal bears. All are black bear.

Diet, genetics, and age matter. Hardly any B&C bucks taken anywhere in N.C. Go figure. Too much pressure. Long season, and hound hunting seem to work against a whitetail growing old in eastern N.C.

None in the wild.

15 years could be 6 or more generations though. The study basically attributed that better nutrition over at least 2 generations may turn the growth gene on that would otherwise be turned off as better mass and antler sizes are probably not necessary if nutrition is not there. Generally turning poor or mediocre habitat into good habitat takes a few years. When only mama ate good, bucks showed better growth but when granny and mama both eat a better diet, the bucks from the "poor" genetic region ended up being just as big as those from the delta.

It was a cool long term study and has really reflected what I've seen in several places.

Southern Ga and most of Florida have a subspecies of whitetail deer named Seminole whitetails. Generally these deer are adapted to lower quality habitat such as pine flatwoods that have a lot of browse but none of it is very nutritious. A mature buck (3.5 plus) will weigh around 135 to 150 live weight. 1.5 year old bucks average about 100 pounds live. The nutrition level of the native vegetation is low because of the soil its growing on...mostly sandy soils that dont hold nutrients well. Seminole whitetails that have access to large agricultural areas or other sources of higher nutritional plants such as large amounts of fertilized browse will exhibit heavier weights and better antlers because of the better food sources, but for this to show up it takes a deer generation. Also, the females will be more productive and fawn survival will be better. In these south Ga/Florida agricultural areas there will be older bucks that reach 200 pounds live weight and very good antler growth. It's all based on the soils......good soils =good deer. Two counties north and west of where I live there is the occasional B&C buck and several that that too 200 live weight....but there are more ag fields there than forest. Here its nearly all pine plantations and cypress swamps....a few miles from state line.

The picture below is a 4.5 year old buck on my place a few days ago. I know he's 4.5 because I have pics of him since he was 1.5. He has a solid black tail so he's easy to identify in pictures. At first glance he could be mistaken for a 175 plus pound deer....but he is closer to 135 pounds. Our rut peak here is late October and by first of November he will weigh about 120 or less.

I've hunted deer in only 2 states...Georgia and north Missouri. Whew! Night and day difference. It takes some focus to realize what your looking at when your used to looking at a mature buck that weighs 135 and then seeing one that weighs 200 plus. Thank goodness for a good rangefinder or I would still be misjudging them midwest brutes. Took me some time to adjust to seeing big deer with what appeared to be average racks when they actually had large racks....but their body size made their racks seem smaller. Had this same problem when hunting the coastal islands on the Georgia coast. Average buck there weighs less than 100 pounds and that makes his rack look large....but it ain't so.

Same buck...he looks as big as a midwest mature buck but his frame isnt as large as it appears. Someone mentioned Bergman's rule in this thread. This holds true.....there are exceptions....but not many.

Btw...his inside spread is only about 14 inches. Another optical illusion. If this was a pic of an Iowa buck you could say he weighed about 200 and had at least an 18 or more inside spread...

there are deer in florida that weigh 200 lbs but they are few and far between , i lived there for twenty years and never killed one over a 130lbs but i saw other deer that where killed that made the 200lb mark but you could count the number on your hand of the deer who made it to that mark, the nice thing use to be there was no horn restrictions and you could kill two deer a day every day of the season as long as you didn't have more than four in possession ,

The rare exception big bodied deer in the deep South will be corrected by the Bergmanns Rule during extreme hot years.
Same for a scrawny, or late born yearling will suffer the wrath of Bergmanns rule in the far North during extreme cold winters.
That would explain why these exceptions are rare.