When did Grass Evolve?
Michael Anissimov
Michael Anissimov
Because of its structural simplicity, you might think that grass evolved a very long time ago, along with the first plants. Interestingly, however, the fossil record shows this is not the case. Grass only shows up in the fossil record about 67 million years ago, in the form of phyoliths (small silica flecks in grass that make it difficult to digest) found in fossilized dinosaur dung. Recently, it was thought that grass only evolved about 55 million years ago, becoming abundant after the Age of the Dinosaurs, which ended in a mass extinction 65 million years ago, but the phytolith finding refutes this.
Land plants in general evolved during the Silurian, about 440 million years ago. These were simple mosses and lichens. All throughout the Mesozoic, dinosaurs consumed various plants, but didn't touch grass until it came into existence at the tail end of the period. If you consider the entire duration of land plants to correspond to an hour, grasses evolved in just the last nine minutes. However, today many ecosystems are dominated by grasslands, which are estimated to cover 20% of the Earth's land area, numerous animals live on grass, and members of the grass family are the most agriculturally and economically important plants in the world.
About 65 million years ago, the world was decimated by a massive asteroid strike that made all the non-avian dinosaurs go extinct. The evolution of grasses is often presented in this context, portrayed as the grass colonizing a world left relatively barren by the mass extinction. However, this is a fallacy, as grass did not become widespread until more than 10 million years after the extinction. Even though 10 million years is not extremely lengthy in evolutionary terms, it is still too long for it to be accurate to present grasses as colonizing in the aftermath of widespread plant extinction. The plant cover was probably largely restored just 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 spans the time from the extinction of the dinosaurs until now. Many mammals display close co-evolution with grass, as special adaptations are required to digest its silica-rich tissues. Ruminants like cows solve the problem using a multi-chambered stomach that slowly digests the grass and actually causes it to ferment. Using this, they can consume large amounts of grass to sustain themselves. Humans, being flexible omnivores, lack the adaptations necessary to digest grass, opting for more calorie-rich food sources such as fruits and meat.
Michael Anissimov
Michael is a longtime AllTheScience contributor who specializes in topics relating to paleontology, physics, biology, astronomy, chemistry, and futurism. In addition to being an avid blogger, Michael is particularly passionate about stem cell research, regenerative medicine, and life extension therapies. He has also worked for the Methuselah Foundation, the Singularity Institute for Artificial Intelligence, and the Lifeboat Foundation.
Michael Anissimov
Michael is a longtime AllTheScience contributor who specializes in topics relating to paleontology, physics, biology, astronomy, chemistry, and futurism. In addition to being an avid blogger, Michael is particularly passionate about stem cell research, regenerative medicine, and life extension therapies. He has also worked for the Methuselah Foundation, the Singularity Institute for Artificial Intelligence, and the Lifeboat Foundation.
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By: alessandrozoccThe first plants on land were lichens and mosses.
Discussion Comments
This is actually a little incorrect concerning human digestibility of grass. Humans have seriously harnessed grass, especially to provide as a major food group.
Barley, wheat, rice, sugarcane, bamboo -- in fact, rice alone provides 20 percent of the world's dietary energy. Humans are indeed flexible omnivores, even when something is tough to eat initially, they modify it. That means probably thousands of years of trial and error.
Just look at civilization -- it sprang up often around the cultivation of certain grasses. Our livestock eats it, and so do we.
The theory about certain mammals and grasses evolving at about the same time is interesting. I wonder which one influenced the other? Did grasses start to evolve ahead of the mammals or the opposite?
Maybe the mammals were trying to eat and digest some other plants, but weren't too successful, so some chemical reaction eventually caused plants to change into grass types, and at the same time, mammals digestive systems adapted to grass. Just a guess!
It must have taken a long time and a lot of trial and error for humans to breed and cultivate the lawn grass we enjoy in our yards and in parks. It is really very different than the wild grass.
Planting grass and grass maintenance is a big job. After living in a house with a big grassy area, I think I would prefer just a small patch of lawn.
I think about the amount of water it takes to keep a lawn green in the summer months. And there are people in the world who badly need water to drink.
I never had given any thought as to when grass evolved. It is just something that I have always had in my life and I have spent many summer days mowing grass.
We had a couple springs where we had some really bad flooding in our front yard. This killed a big section of grass and we had to do some more grass seeding.
Before we got the seeding down, the grass that was coming up and growing looked more like weeds, and not the type of grass you want your front lawn to look like.
I have a couple of cows and their field has all kinds of grass in it. Mostly the tall fescue grass, but there are some shorter types too. Every year, I have a local farmer come out to cut and bale my grass. The mix makes great hay for the winter!
It's amazing how many animals around the world depend on grass as their main food source. Cows, horses, zebra, goats, sheep and lots of others. I'm surprised that humans can't digest it, since we are always around it.
I've been considering putting in plastic grass, but it just sounds so bad. It's more plastic for the environment and it can't regrow itself if it gets damaged.
My lawn grass is short and soft. I barely ever have to mow it -- why change it? My only complaint is that there are a lot of worms in it. The plastic grass would probably get rid of them, but I doubt that's good for the environment.
@Almita - Wild grass is nothing like the grass that's on your lawn. It's taller, sharper and tougher. When I was growing up, I lived on a sort of ranch. There was a type of wild grass there that we called "cut grass" -- because you could cut yourself on it if you grabbed it. It literally could give you a paper cut. Of course humans bred grass to suit our needs. The wild stuff isn't very nice.
I spend a lot of time planting grass in my yard every year. It always manages to die off or dug up by my dog. Grass maintenance is hard, but I really love sitting out on the grass on a hot day. It's very relaxing. I think that having a little piece of green in the city is nice. I miss growing up and sitting outside reminds me of it.
I always assumed that humans made grass the way it is. There are so many types of grass -- turf grass, shade grass, centipede grass -- the only way I could think of was if humans made it that way.
A lawn is considered a part of the American dream. Honestly, it seems a little weird that every single person should have a tiny patch of lawn in front of their house. It's save a lot of water if we didn't.
I can't imagine wild grass doing very good – since it takes so much water to manage. It must from in wet areas.
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