Grass Apes

Radiolab host Molly Webster was invited to create a story about a park space and initially overlooked grass as an uninteresting subject until a horticulturist explained its significance. Webster and producers interviewed New York City park visitors about grass, finding that most people viewed it as an invisible background element, a "green screen" to be ignored. To understand grass's true importance, Webster speaks with biologist and writer David George Haskell, who argues that grasses are humanity's "co-creators" and essential to our evolutionary story. Haskell explains that 30 million years ago, our primate ancestors lived in forests, but as the planet cooled and dried, grasslands began to expand starting around 10-20 million years ago. Grasses possess remarkable adaptations: they survive fire by keeping growing tissue low or underground, they concentrate carbon dioxide efficiently, and they developed silicate (glass-like) particles in their blades as defense against grazing animals. Our ancestors discovered grass seeds, which contain large nutritious food stores of starch and protein, leading to a dietary transformation. Today, wheat, corn, and rice—all grasses—comprise approximately 60% of all human calories consumed globally, with additional grass-based foods including oats, barley, sugar cane, and animal feed. Haskell argues this makes us fundamentally "grass apes" (Homo poaceae) rather than jungle apes. The grassland environment also shaped our physical evolution: the open terrain freed our forelimbs for tool use and made bipedalism more energy-efficient, while our feet developed extraordinary sensitivity to grass topography. Beyond nutrition and evolution, spending time in grass provides multisensory benefits: grass absorbs high-frequency sounds and dampens harsh urban noise, grass aromas contain compounds that calm us, and soil microbes activated by moisture produce additional calming scents linked to ancestral habitats. The episode concludes with Webster sitting barefoot in grass, recognizing this as reconnecting with millions of years of human history.