Wheat, rice, and upright walking were probably all 'domesticated' by grass
Biologist David Haskell argues that grass is a 'co-creator' of human evolution—it determined not just what we eat, but possibly why we stand upright on two legs.
The video won't play here. Listen to the audio instead:
The argument · tap a timestamp to hear it
Climate change created grasslands that drove primate evolution forward
About 30 million years ago, human and ape ancestors lived mostly in forests, eating insects and fruit, in a landscape with almost no grassland. As Earth cooled and ice sheets expanded, the climate dried, and patches of grass began appearing in forests. Between 20 and 10 million years ago, grasslands expanded dramatically, turning forest-covered continents into mixed forest-grassland landscapes. This wasn't grass 'defeating' trees—grass simply exploited two external conditions: the dropping CO₂ concentration in the atmosphere and seasonal drought.
— David George HaskellBuried growth points let grass thrive where trees burn
Grasslands face constant drought and fire. Grass's key adaptation is burying the sensitive tissue that produces new stems, leaves, and roots deep underground or flush with the surface. When fire sweeps through, the disposable leaves above ground burn away, but the growth tissue below survives untouched. As soon as the fire passes, grass shoots back up. This is why large grazing animals like horses and hippos could leave the forest and make grasslands their home by eating this fireproof vegetation—grasslands themselves were shaped by repeated burning.
— David George HaskellGlass particles in grass leaves protect against excessive grazing
Nearly every grass species has silicate particles—essentially glass—embedded in its leaves. These particles prevent wind from tearing leaves apart and prevent animals from eating grass excessively. David offers a vivid example: when dogs eat grass, they vomit not because they're eating randomly, but because grass works as a natural dewormer—the leaf strands tangle together and pull parasitic worms out of the intestines, which either get vomited or pass through as feces. This explains why human ancestors didn't spend much time chewing grass directly—the glass shards are irritating. Instead, they took a different path: eating seeds.
— David George HaskellGrass seeds are 80% stored nutrients; humans capitalized on this design
Grass produces flower stems and makes seeds at the tip. A seed contains an embryo capable of becoming a new grass plant, but it also contains a massive package of stored starch, protein, and fat—up to 80% of the seed's total volume—meant to feed the seedling through its first days and weeks of life. Human ancestors discovered this nutrient package and began eating grass seeds rather than grass leaves. This pivot is where grass and humans truly became locked together. Since then, wheat, oats, rice, corn, millet, barley, sorghum, and sugarcane have all emerged as enlarged versions of the same grass body plan.
— David George HaskellThree grass crops now fuel 60% of human calories
When you add up all the calories humans consume globally, wheat, corn, and rice together account for approximately 60% of the total. What we perceive as meat—beef, lamb, chicken—comes largely from animals that eat grass, corn, oats, or other grain-based feed. For at least the last 10,000 years, humanity's work has amounted to selectively breeding and growing grass varieties with fuller seeds and seeds that don't fall off the stem when ripe. Most of what appears on the modern table traces back to the same plant—an enlarged version of the lawn grass in your yard.
— David George HaskellWalking upright became efficient when grasslands removed the climbing imperative
David offers an explanation for upright walking: bipedalism likely emerged in direct connection to grassland life. In forests, four-limbed primates could grasp tree branches, but on open grasslands, there were no branches to hold. This freed the front limbs for more refined tasks, and moving on two legs across open terrain actually costs less energy than moving on four. He adds an interesting detail: human feet are covered with sensors exquisitely sensitive to grassland terrain—precise enough to distinguish individual grass blades. This is precisely why some physical therapists prescribe barefoot grass walking for certain movement disorders.
— David George HaskellHumans fit the definition of grass ape better than jungle ape
If humans were renamed based on our staple food and evolutionary habitat, we'd be called grass apes rather than jungle apes—most conceptions of apes picture forest dwellers or animals only at the grassland margins. David jokes about inventing the term Homopoaceae, combining Homo with Poaceae (the botanical family name for grass), to distinguish us from true forest apes like bonobos and chimpanzees. This echoes the Gen Z phrase ‘touch grass’—in a sense, humans are supposed to be spending long-term time around grass anyway.
— David George HaskellGrass calms humans through sound absorption and scent chemistry
The relaxed feeling of lying in a grass field isn't just psychology. Each grass blade points in a slightly different direction, so sound waves that hit the uneven grass surface scatter in all directions; high-frequency sounds especially get absorbed, making ambient noise sound gentler overall. Meanwhile, crushing grass blades releases aromatic molecules that attach to nerve cells and may even enter the bloodstream, producing a calming effect. The smell released by soil microbes and fungi when rain hits the earth forms part of this calming combination—it's the same olfactory signal that ancestors relied on for hundreds of thousands or millions of years to judge ‘this is a good place to be.’
— David George HaskellIn their own words · checked verbatim
Indeed, if you had to pick one group of plants that we could count as our co-creators, a group of plants that are vitally important to the appearance of humans on this planet, it would have to be the grasses.
David George Haskell7:16
And the genius of most grasses was that they figured out how to thrive in a very fire-prone environment by keeping their growing tissue very low to the ground or in the ground.
David George Haskell9:18
Yeah, so your dogs are probably actually eating it to purify their gut. It can act as a dewormer because it will cause the animal to vomit or it will poop it out the other end.
David George Haskell10:23
In fact, wheat, corn, and rice together comprise about 60% of all the calories that humans eat on this planet.
David George Haskell13:30
If you're in a grassland, there's no more branches to cling on to. So your forelimbs are freed up to do clever things with your hands.
David George Haskell17:37
I love thinking of us as grass apes, not jungle apes.
Molly Webster19:46
If we were named for our primary food source and for the habitat in which we evolved, we would be the grass apes.
David George Haskell19:46
Figures
| Nutrient reserve content in grass seeds | Up to 80% of seed volume | 13:30 |
| Proportion of human calories from wheat, corn, and rice | Approximately 60% | 13:30 |
| Years of human cereal crop domestication | At least 10,000 years | 13:30 |
Glossary
- silicate (phytolith)
- Glass-like silicon dioxide particles in grass leaves that prevent wind damage and deter excessive grazing.
- Poaceae
- The grass family that includes rice, wheat, corn, and all major cereal crops.
- Homopoaceae
- David Haskell's playful term combining Homo with Poaceae, referring to humans as ‘grass apes’ defined by diet and evolutionary habitat.
How to listen
Anyone interested in human evolution, the origins of agriculture, or botany, or who wants a fresh perspective on the grass around them and the food on their table.
Skip the first 3 minutes and 8 seconds—that's membership recruiting and merchandise promotion. The actual episode on grass starts at 4:12.