I think a big part of the explosion in Texas has to do with how deer are hunted. It wasn't until the '70s and the '80s that hunters began to put grain feeders out. When they did, hog numbers exploded.
A hog doesn't need corn to survive, but what that did was make them even more prolific breeders. Sows that were well fed on deer hunters' corn year around could have even more litters of piglets than those relying on natural food sources.
As noted, hogs have always been around a little, but it has only been in the last thirty years that their numbers have exploded. That explosion seems to coincide with the change in deer hunting practices in the Southeast from hunting with dogs and the like to stand hunting over feeders.
It is just a theory of mine, but I think there is some merit to it.
