The biologists studied the plants in part by sampling the sticky liquid inside their pitchers and testing for enzymes. They could also compare the genes turned on in the pitchers to those turned on in the normal leaves. That’s a direct comparison because the pitchers—like the traps on Venus flytraps—are just specialized leaves. Before carnivorous plants were carnivorous, they were regular photosynthesizing machines. They lived in bogs and other wetlands that have plenty of water, but not many nutrients. And a few of these pre-carnivores evolved the ability to trap insects, digest their exoskeletons, and absorb nutrients from their carcasses. Those plants survived better in places with poor soil quality because they could get carbon and nitrogen and other nutrients from insects. It was a desperate measure.