What is triggering elephant aggression?

If elephant numbers are down and food is plentiful, what is triggering elephant aggression? Have we been the agent for natural selection by culling the least aggressive elephants?

Or has some change in the environment led to a behavioral adaptation leading the elephants to become more territorial? Is that environmental change simply the introduction of humans and our territorial expansion or is it something else?

Or perhaps UV radiation signals a changing epoch and elephants respond by leveraging their dominance?

"Across Africa, elephants seem to be turning on their human neighbours in ever increasing numbers. Although such attacks are nothing new, they have always been seen as a side effect of elephants competing for food and land, either as a result of population explosions or because people have encroached on elephant territory. But that may not be the whole story.

'Elephant numbers have never been lower in Uganda. Food has never been so abundant,' ..."

Elephants on the edge fight back - life - 18 February 2006 - New Scientist:

Rapid evolution and behavioral adaptation

Environmental pressures lead to behavioral adaptation that leads to genetic adaptation through natural selection.

I wonder if natural selection is the only agent at work in selecting the leg-length? If the lizard can adapt its behavior, can it also adapt the genetic predisposition of its offspring.

I also wonder if the behavioral adaptation is learned or inherited? Does the lizard's preference for the trees come from a learned fear of the predator or an intrinsic neurochemical preference for trees?

"Anolis sagrei spends much of its time on the ground, but previous research has shown that when a terrestrial predator is introduced, these lizards take to trees and shrubs, becoming increasingly arboreal over time...

"The behavioral shift from the ground to higher perches apparently caused this remarkable reversal, Losos says, adding that behavioral flexibility may often drive extremely rapid shifts in evolution."

Pressured by predators, lizards see rapid shift in natural selection:

Brain as Persistent Data Storage

Another clue to the workings of the hard drive of the mind.

Science & Technology at Scientific American.com: While Signals Keep Firing, Memories Hold Still in the Brain