 GMOs, or genetically modified organisms, have been in the news a lot in the last few years, and while many in the scientific world have championed their widespread use, they're not without their drawbacks. While the benefits GMOs bring to the table may still outweigh their drawbacks, often knowledgeable people completely ignore their harms, or even deny that there are any. With so much available about the scientifically legitimate pros of GMOs, we thought we'd take a look at their scientifically based downsides. This video is part of a collaboration with Scienceverse, here on YouTube. In this video, we'll be looking at the harms GMOs pose to the environment and in our food supply, and they'll be uploading a partner video focusing on the more direct harms to human health. So be sure to check out their video after this one, so you can get the whole picture. And let's jump in. GMOs are one of the most controversial areas of science, but humans have actually been genetically modifying plants and animals for thousands of years. Maybe a few of your crops had very good yields. Maybe one of your wolves was especially loyal, so you did the smart thing, and bred the plants and animals that had the traits most beneficial to you. Traits that were indirectly linked to the genes that coded for them. So with each generation, those genes got more pronounced, and now, after thousands of years, almost every single plant and animal around us is vastly different from their pre-domesticated states. While artificial selection has allowed mankind to grow more plentiful crops, it's also substantially decreased the genetic diversity of them. As a direct result of humans' artificial selection, it's estimated that more than 80% of natural genetic diversity has been lost, and this makes plants much more susceptible to diseases. Do you know those banana-flavored candies you sometimes got as a kid for Halloween? Do you ever wonder why they don't really taste like bananas? Well, that's what bananas used to taste like. In the 1950s, various fungal plagues devastated banana cultivation, and since nearly all large-scale banana production relied on one species, the Gros Michel, that were made effectively extinct in terms of large-scale farming. Cultivators had to go back to the drawing board, and came back with the Cavendish Banana, a banana resistant to the fungal plague, and the one we still see lining grocery store shelves today. This wasn't even the first time a banana species went extinct, and it doesn't look like it will be the last. Today, the Cavendish Banana is already being wiped out by a new fungal strain, ripping its way through the South Pacific. And the Cavendish is our last full-size banana option, so if it goes extinct, we'll only have baby bananas to look forward to. You might be asking yourself, if all this is already happening, how does it have anything to do with genetic engineering? Well, the reason multiple banana species have gone extinct was because large-scale production demanded millions of bananas taste virtually identical, and so their genetic diversity had to be whittled down to near a zero. While this is great from a quality control standpoint, it means that once a disease can take down one banana, it can take down them all, likely before we can even mount the resistance. Genetic engineering is like stepping on the gas, but once took generations to achieve through artificial selection is now possible to achieve in only a few years through direct gene modification. An artificial selection at least keeps genes within one species, so by artificially selecting bananas, we were only ever dooming bananas, but now, scientists are taking genes from some crops and putting them in dozens of others. That means instead of risking one crop getting wiped out, we're risking handfuls. In this danger has never been more real than it is today. Around the world, 50 crops contribute to 90% of the world's food supply, and 4 individual crops make up the majority of calories consumed for more than half the world's population. So in genetically engineering these crops, we risk endangering the food sources that billions of people rely upon. But if we're already modifying crops to produce greater yields, why don't we just engineer them to be more resistant to diseases? At first, this sounds like a very rational idea, but to see what could happen, let's go back a century in time. In 1928, antibiotics were first discovered and seen as a miracle cure. Commonplace pathogens like viral and bloodstream infections that once killed millions were now suddenly treatable. But today, less than a century later, the number of people dying from antibiotic resistant bacteria has more than doubled in the last four years, and the director of the CDC describes the rise of superbugs as one of the greatest threats to our country. While antibiotics helped in the short term, they forced bacteria into evolutionary overdrive to develop resistance to these defenses, and a similar fate could happen in agriculture. By giving plants unnatural evolutionary advantages today, we're creating a selective pressure, forcing the pathogens that prey on them to evolve as well. And while these stronger pathogens may have a hard time killing these modified plants, all natural plants growing nearby would have no such protections and would thus be susceptible to these stronger pathogens. These risks, although scarier and easier to understand, aren't the only ones. For one, genetically engineered crops could bring new and deadly allergens into the food supply. Virtually all known food allergens are proteins, and genetic engineering routinely moves proteins into the food supply from organisms that were never previously consumed as foods. This problem is unique to genetic engineering, because it alone can transfer proteins between species into completely unrelated organisms, and scientists have a limited ability to predict whether a particular protein will be a food allergen to some people. So genetically modified food can risk severe allergic reactions in the people that consume them. And coming back to the topic of antibiotics, genetic engineering often uses genes for antibiotic resistance as success markers. Early in the engineering process, these markers help show what cells have taken up the inserted genes. Although they have no further use, these genes continue to be expressed by plants in the field. As a result, most genetically engineered plant foods carry fully functioning antibiotic resistant genes. The presence of these genes in foods has two harmful effects. The first, these genes produce enzymes that can degrade antibiotics, and so modified foods would undermine the effectiveness of any antibiotics a person was taking. And the second, the resistance genes could be transferred to human or animal pathogens, further exacerbating our antibiotic resistance crisis. Another problem is that many plants have the ability to produce toxic substances, but these genes are normally turned off. Gene activation is very complex and affected by many factors, and so by changing the genetic makeup of the plant, these genes could be inadvertently turned on. And since any combination of local stimuli, like the presence of a nearby bug species, or a specific mix of temperature and humidity could activate them, this would be impossible to test for in advance in a lab setting. The last, and probably most important harm, is the unknown element. Now to people generally aware of arguments made about GMOs, this probably sounds like the part of the video where we start fear mongering. But science is filled with unknown risks, and they can make risk management very challenging. Something biologists have to grapple with is the fact that in many cases, once you release a genetically modified organism into the wild, you might never be able to get rid of it. An easy comparison is with invasive species. In the 1850s, a handful of rabbits escaped captivity into the Australian outback. Those few rabbits managed to slip through human hands and proceeded to breed like, well, like rabbits. And today, more than 200 million rabbits are spread across the continent. After those rabbits were released, there was virtually no way to contain them in the wild, and GMOs could work the same way. If there were unintended consequences to using GMOs for any of the reasons given above, they could be very hard to mitigate. Now scientists have proposed ways to get around this, like ensuring GMO organisms released into the wild were infertile and couldn't reproduce on their own. In agriculture, this would mean farmers would have to buy brand new seeds from manufacturers every year, an idea the agricultural industry has already shot down. And this ignores the fact that genetically modifying organisms isn't a perfect process. All it would take was a few organisms in the millions mass produced to not have this infertility mutation and bam, the entire plant falls apart. Not to mention all the ways genes can be altered in the wild, like by radiation or bacteria. In what we've certainly listed, a handful of harms that come with genetic engineering. These are just the harms associated with the environment and food supply. Outside of the ecological threat that genetic engineering potentially poses, genetic engineering also brings up a whole bunch of ethical issues leading to questions like, is it all right to design our future generations to have certain traits? And will genetic engineering one day set a societal standard for what the perfect human is? Well, hop on over to the science first to find out the answers. And also, don't forget to subscribe to everything science while you're here. To learn more about the potential harm genetic modification poses directly to humans, click here to watch this video from our collaborators over at Science First. Have a great day and remember, there is always more to learn.