I've been programming since I was eight, but truly fell in love with biology in 12th grade chemistry: the first introduction to organic chemistry and biochemistry. It was the first time I truly started grokking the application of systems-level thinking to the biological world; how do trees "know" to turn red in the autumn? How do fetuses assemble themselves from two cells?
I decided to purse a double major in biochemistry and evolutionary biology and it was one of the best decisions I've made in my life. The perspective you gain from understanding all life in terms of both networks and population dynamics of atoms, molecules, cells, tissue, organisms and populations -- and how every layer reflects the layer both underneath and above it in a fractal pattern -- is mind-expanding in a way I think you just don't and can't get designing software systems alone.
I work as a software engineer / founder now, but always reflect wistfully on my time as a biologist. I hope to get back to it some day in some way, and think what the Arc Institute team is doing is inspirational [0].