My mom and her older brother both had feet with the toes overlapping one another like Steven Tyler's. In their case, it was brought on growing up during WWII in Germany and never having shoes that fit properly. They wore shoes that were way too small and their feet ended up looking awful - and painful at that.
That goodness my parents always saw to it that I had good, well-fitting shoes as a child. I ran around in bare feet a lot (still do to this day) and thank God I have straight toes, no corns, no bunions, no ingrown toenails. Growing up with the sight of my mom's feet, I turned into a bit of a foot freak, pampering mine each night.