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Thanks for the note! For supporting this SciShow compilation video on all things related to domestication, you can go to Lenode.com/scishow - that link gives you a 100-60 day credit on a new Lenode account! We have domestication to thank for some of our favorite foods, furry friends, and even a mode of transportation. Apple’s domesticated cats and domesticated zebras - well, we tried. It’s such a huge part of our daily life that we might not know just how much of our world is domesticated - that’s probably because of the broad effect that domestication can have. Domestication can mean that we’re selecting for one specific trait, narrowing the species diversity, but it can also mean introducing new diversity. Take for example how we have domesticated our food - domestication made wild cabbage into many of the distinct greens we know today, like broccoli, kale, and Brussels sprouts. Here’s why those foods are actually all the same species.
One of the most extraordinary things about dogs is how different they all are - like we took one wolfy species and made over 200 breeds, from adorable wrinkly pugs to lanky powerful Greyhounds. We didn’t just do this kind of whole body tinkering with dogs - we’ve done it with plants too! Just about all the fruits and veggies you can buy at the supermarket have been shaped by human breeding, most look totally different from their wild ancestors. But there is one plant species that has produced so many different varieties that it’s known to biologists as the ‘dog of the Plant World’ - you probably know it as kale and broccoli and cabbage and Brussels sprouts - that’s right, those are all the same species of plants!
Foodie favorites like kale and cauliflower are just a couple of the cultivars, or human-modified and grown varieties, of Brassica oleracia, and there are dozens more - from the logarithmic spiral of Romanesco broccoli to this distinct pointed shape of Caraflex cabbage. You might think that tons of variety is just what happens when humans selectively breed something for generations, but that’s not entirely true - after all, we’ve been growing and breeding lettuce for about the same amount of time, and yet all lettuce varieties look…you know, pretty lettucey.
It turns out that Brassica oleracia is kind of a special plant - it was so transformable because it underwent some massive genomic events during its evolution. The story of why we have such a variety of this kind of plant starts millions of years ago - back then, an ancient Brassica ancestor did something quite remarkable - it tripled its genome! That massive genome was whittled back down to a more reasonable size by the time wild cabbage emerged as its own species around 4 million years ago. Still, it meant that wild cabbage ended up with a lot more genetic variation than your average garden plant.
You see, broccoli and kale and Brussels sprouts don’t just look different - they’re very genetically distinct too. And we’re not just talking about little tweaks to genes - in a 2016 paper, researchers sequenced the genome of nine different cultivars to construct the plant’s pan genome, the total genetic variation that exists in the species, and they found that nearly 20 percent of the genes in that pan genome are only present in some varieties. So not only do cultivars have a lot of mutational difference, they also have whole genes that are not present in other members of their own species - even though they all came from the same wild cabbage.
That plant, as far as we can tell, originated in the coastal areas of southern and western Europe. We don’t know exactly when our species first grew and domesticated it, but genetic evidence suggests it may have been around 2000 BCE. The earliest written records come from ancient Greece, and they suggest the first cultivars were leafy veggies like kale and collard greens. And the Greeks weren’t the only ancient people who tinkered with wild cabbage - scientists are pretty sure that the plant was domesticated many times in several locations. Some of these domesticated varieties found their way back into wild populations, and that’s why there are so many wild brassicas around the world. There is still some room for genetic changes even when cloning trees, like a new branch appearing with a chance mutation that makes the apples a different shade of red. This deeper color is often chosen over flavor, which is why some food scientists believe Red Delicious apples taste “like misery incarnate”. The goal of apple growers for the last century or two has been to produce sweet, consistent apples, such as Honey Crisps and Galas. Johnny Appleseed was not wasting his time, as most apples were used for hard cider and any apple would do. In fact, he may have helped apples maintain their genetic diversity up to the present day.
Domesticated apples have more genetic material in common with European apples than Asian apples, and only modern genetic studies can establish where they came from. These European domesticated strains were introduced to North America, and stayed diverse. This may be because of interbreeding with North American species, or because of the chance seedlings created when different varieties were planted all over North America. Red Delicious and Golden Delicious apples were both chance seedlings, as was the Macintosh, which is so popular it has a type of computer named after it. Chance seedlings have given us many delicious apples, and were discovered all the way back in 1811. uddles up with a wild animal
There is a lot to be said for planting apple seeds when you don’t know what will sprout from them; genetic diversity isn’t just valuable for its own sake. Apple breeders rely on that huge gene pool to create new varieties, though these days we’re lucky enough to have genetic sequencing to cut down on the guesswork. Apple growers aren’t just looking for things that improve flavor; hiding amongst those genes are also the keys to resisting pests and disease, growing in different climates, or making apples that are heartier and easier to transport.
Soap breeders hope in fact, there’s some evidence that a gene for disease resistance made the jump from wild to domestic apples as recently as the 1970s, and the need for resistance isn’t just theoretical. Both pests and a changing climate have been making life harder for North American apples in recent years, that’s why efforts are ongoing to preserve apple diversity.
See, apples as a whole are diverse, but as of 2008, 90% of apples produced in the U.S. consisted of just 15 varieties. If we want to keep creating new, tasty apple varieties that can survive whatever gets thrown at them, we’ll need to do better than that. Fortunately, researchers are on it; much like Johnny once did, they’re planting all sorts of seeds, and by doing so, they’re ensuring that apples stay wonderfully diverse. The rest of us will just have to wait for the fruits of their labor. It appears that humans have been shrinking in size due to the emergence of more complex societies and the division of labor. Other scientists suggest that our brains have become smaller due to domestication, similar to how wild animals have larger brains than their domesticated counterparts. This could be because humans are no longer worried about things like being attacked by predators.
However, a recent study of American skulls showed that they have been getting bigger since the mid-1800s, likely due to better nutrition. If we factor out this effect, it’s possible that the shrinking trend will continue in the future.
Humans may even artificially evolve themselves through genetic engineering. As we learn more about our genes, we will be able to modify them to eliminate certain genetic disorders and diseases related to aging. We may even be able to design people like avatars in video games, altering traits like height, intelligence, athleticism, and more.
Whether the changes are natural or artificial, humans of the future may be very different. We have domesticated plants, animals, and even people on purpose or by accident. To learn about the first mammal to be domesticated for scientific research, you can watch our video about the lab rat. Thanks for watching this SciShow compilation!