Why Plants Eat Animals

Carnivorous plants evolved in nutrient-poor environments — bogs, swamps, and sandy soils where usable nitrogen and phosphorus are scarce, locked away in waterlogged, acidic peat. Rather than competing for what little the soil offers, they evolved to harvest these nutrients directly from animal bodies.

There are over 800 species of carnivorous plants spanning at least 12 independent evolutionary lineages. Carnivory arose separately in unrelated plant families many times over, which suggests that when soil is poor enough, eating animals becomes a winning strategy.