Gram.
Due to its structural simplicity, one might think that grass evolved long ago, along with the first plants. Interestingly, however, the fossil record shows that this is not the case. Grass only appears in the fossil record about 67 million years ago, in the form of phytoliths (tiny specks of silica in grass that make digestion difficult) found in fossilized dinosaur dung. Grass was recently thought to have only evolved about 55 million years ago, becoming abundant after the Age of the Dinosaurs, which ended with a mass extinction 65 million years ago, but the discovery of phytoliths disproves this.
The first plants on earth were lichens and mosses.
Land plants in general evolved during the Silurian, about 440 million years ago. They were simple mosses and lichens. Throughout the Mesozoic, dinosaurs ate various plants but did not touch grass until it appeared late in the period. If you consider that the total duration of land plants corresponds to one hour, grasses have evolved in the last nine minutes. However, today many ecosystems are dominated by grasslands, which are estimated at 20% of the planet’s land surface, many animals live on grasses and members of the grass family are the most important plants in the world from a agricultural and economic point of view.
Some 65 million years ago, the world was decimated by a massive asteroid impact that wiped out all non-avian dinosaurs. The evolution of grasses is often presented in this context, portrayed as the grass colonizing a world left relatively barren by mass extinction. However, this is a fallacy, as the grass did not become widespread until more than 10 million years after the extinction. Although 10 million years is not a long time in evolutionary terms, it is still too long to present grasses as colonizers after widespread plant extinction. The plant cover was probably largely restored only a few tens of thousands of years after the extinction, if not sooner.
Grass is considered one of the characteristic features of the Cenozoic era, which goes from the extinction of the dinosaurs to the present day. Many mammals closely co-evolve with grass, as special adaptations are required to digest its silica-rich tissues. Ruminants like cows solve the problem by using a multi-chambered stomach that slowly digests grass and ferments it. Using this, they can consume large amounts of grass to sustain themselves. Humans, being flexible omnivores, lack the necessary adaptations to digest grass, opting for more caloric food sources such as fruit and meat.