The crust aversion....inborn or learned-behavior?

Let me give a little background on this...when Logan was about 2-3yrs old I was in the kitchen making him a sandwich when Glenn came in asked me what I was doing. I was carefully cutting the crust off his bread, I told him, so that he would eat more of the sandwich since he did not like the crust. He believed at the time that I was "encouraging" him not to eat the crust by cutting it off. I argued that he would leave a good portion of the sandwich behind along with the crust, so by cutting off the crust only I was actually preventing waste. Needless to say the arguement was never solved until now. One day Glenn made Mikala a sandwich and did not cut off the crust and low-and-behold when she handed him the plate she was finished with it contained the crust in its entirety! So the question remains...is this something children are born to do, or something they learn to do? I have joked many times that we could make a fortune selling "crustless" bread!