1 00:00:01,840 --> 00:00:07,520 Speaker 1: Welcome to Brainstuff, a production of iHeartRadio, Hey brain Stuff, 2 00:00:07,560 --> 00:00:13,119 Speaker 1: Lauren vogelbam here. Zombies are a horror trope for a reason. 3 00:00:13,720 --> 00:00:17,560 Speaker 1: For many reasons, really, but one is that we humans 4 00:00:17,680 --> 00:00:20,520 Speaker 1: tend to like the idea of being in control of 5 00:00:20,520 --> 00:00:24,360 Speaker 1: our own bodies and behavior, and in stories, the walking 6 00:00:24,440 --> 00:00:29,240 Speaker 1: dead are reduced to mindless doers of damage and often modernly, 7 00:00:29,600 --> 00:00:33,839 Speaker 1: spreaders of whatever infectious disease has caused the dead to rise. 8 00:00:36,000 --> 00:00:39,400 Speaker 1: There are many real life infections and conditions that can 9 00:00:39,440 --> 00:00:42,639 Speaker 1: alter a person's behavior, all horrific in their own right, 10 00:00:43,240 --> 00:00:45,880 Speaker 1: but none we know of could cause a full on 11 00:00:46,000 --> 00:00:50,960 Speaker 1: George Romero's style apocalypse or the Last of Us style apocalypse. 12 00:00:51,920 --> 00:00:54,640 Speaker 1: In the video games and television series The Last of Us, 13 00:00:54,960 --> 00:00:58,800 Speaker 1: a brain hijacking fungus evolves from the infecting insects and 14 00:00:58,880 --> 00:01:03,400 Speaker 1: other arthropods to infecting human beings. And don't worry, that's 15 00:01:03,440 --> 00:01:06,360 Speaker 1: the only spoiler we're going to give here. But today, 16 00:01:06,640 --> 00:01:10,280 Speaker 1: let's talk about the real life fungi that inspired the series. 17 00:01:12,160 --> 00:01:15,839 Speaker 1: Cordyceps and Afia. Cordyceps are each a genus of fungi 18 00:01:15,920 --> 00:01:21,080 Speaker 1: that are often parasitic to arthropods like ants, spiders, and wasps. 19 00:01:21,840 --> 00:01:26,160 Speaker 1: Fungi in general grow from spores, then consume living or 20 00:01:26,200 --> 00:01:29,600 Speaker 1: dead material like wood in order to grow root like 21 00:01:29,640 --> 00:01:34,399 Speaker 1: structures called mycelium and fruiting bodies like mushrooms that produce 22 00:01:34,480 --> 00:01:38,840 Speaker 1: more spores. But instead of in wood, Cortceps and Affia 23 00:01:38,840 --> 00:01:43,760 Speaker 1: cordyceps tend to grow in arthropods that in itself is 24 00:01:43,880 --> 00:01:47,440 Speaker 1: nothing very special. A fossil evidence of fungi growing in 25 00:01:47,440 --> 00:01:49,760 Speaker 1: insects has been found as far back as one hundred 26 00:01:49,800 --> 00:01:52,960 Speaker 1: and five million years ago, and over a thousand fungi 27 00:01:53,040 --> 00:01:57,280 Speaker 1: with insect hosts are known to exist today. But these 28 00:01:57,360 --> 00:02:01,040 Speaker 1: two genera of fungi can actually change an animal's behavior 29 00:02:01,320 --> 00:02:03,960 Speaker 1: when they're ready to spore in order to spread those 30 00:02:04,000 --> 00:02:08,679 Speaker 1: spores as far as possible. Take, for example, a species 31 00:02:08,720 --> 00:02:12,799 Speaker 1: of Apia cordyceps. The parasitizes carpent durants and hijacks the 32 00:02:12,840 --> 00:02:16,600 Speaker 1: ants behavior during the last days of its life. This 33 00:02:16,760 --> 00:02:20,520 Speaker 1: phenomenon caught the eye of British naturalist Alfred Russell Wallace 34 00:02:20,560 --> 00:02:23,160 Speaker 1: when he was in Indonesia back in eighteen fifty nine. 35 00:02:23,880 --> 00:02:26,600 Speaker 1: Even a newcomer to the area could see that something 36 00:02:26,680 --> 00:02:29,559 Speaker 1: was seriously wrong with some of the ants in the rainforest. 37 00:02:30,560 --> 00:02:34,440 Speaker 1: After all, carbondurants are generally pretty predictable in their behavior. 38 00:02:35,040 --> 00:02:37,320 Speaker 1: They work as a team, and each ant has a 39 00:02:37,400 --> 00:02:41,040 Speaker 1: very specific job, like building the nest, gathering food, or 40 00:02:41,080 --> 00:02:45,040 Speaker 1: caring for the queen. When an ant is infected with 41 00:02:45,080 --> 00:02:48,240 Speaker 1: the fungus, the fungus grows unnoticed in the ant's body 42 00:02:48,280 --> 00:02:51,160 Speaker 1: for a while, feeding on the ant until the fungal 43 00:02:51,160 --> 00:02:54,160 Speaker 1: cells account for over half of the ant's body mass. 44 00:02:55,280 --> 00:02:57,959 Speaker 1: All this time, the ant has been doing its usual 45 00:02:58,080 --> 00:03:01,600 Speaker 1: job and living its life. One day it begins to 46 00:03:01,639 --> 00:03:06,280 Speaker 1: act very differently. Breaking off from the colony. It stumbles 47 00:03:06,320 --> 00:03:09,600 Speaker 1: around by itself all day and night, climbing higher and 48 00:03:09,680 --> 00:03:13,760 Speaker 1: higher into the trees. Eventually, the ant clasps a leaf 49 00:03:13,800 --> 00:03:19,720 Speaker 1: for stem with its strong mandibles and dies. Check in 50 00:03:19,800 --> 00:03:22,440 Speaker 1: a week later, and you'll find the dead ant's body 51 00:03:22,560 --> 00:03:25,920 Speaker 1: covered in a brown mat of hair like structures, with 52 00:03:26,040 --> 00:03:29,359 Speaker 1: a beige stalk having erupted from a place near its head. 53 00:03:30,000 --> 00:03:33,720 Speaker 1: This stalk releases millions of tiny spores that float away 54 00:03:33,720 --> 00:03:36,800 Speaker 1: on the air for more ants to step on, thus 55 00:03:36,880 --> 00:03:43,360 Speaker 1: beginning the whole cycle over again. That chomping onto a 56 00:03:43,440 --> 00:03:45,920 Speaker 1: leaf for stem behavior by the way is how we 57 00:03:46,040 --> 00:03:49,440 Speaker 1: know that this kind of behavior altering fungal parasitism is 58 00:03:49,600 --> 00:03:53,680 Speaker 1: pretty ancient. Leaf scars created by an ant death grip 59 00:03:53,800 --> 00:03:56,640 Speaker 1: have been found on fossils at least forty eight million 60 00:03:56,720 --> 00:04:01,920 Speaker 1: years old. In all that time, carbenter ants have evolved 61 00:04:01,960 --> 00:04:06,119 Speaker 1: some strategies for avoiding these fungi, at least they try 62 00:04:06,120 --> 00:04:09,600 Speaker 1: their best. Many ant species groom each other in an 63 00:04:09,640 --> 00:04:13,200 Speaker 1: attempt to remove spores from their friends, while others fray 64 00:04:13,280 --> 00:04:16,359 Speaker 1: their nests with fungicidal poisons and seal off parts of 65 00:04:16,360 --> 00:04:20,240 Speaker 1: their nests. When infections arise, a whole ant colony will 66 00:04:20,320 --> 00:04:26,440 Speaker 1: relocate if necessary. But how does the fungus affect the 67 00:04:26,480 --> 00:04:29,440 Speaker 1: ants behavior to the extent that it does. It's a 68 00:04:29,520 --> 00:04:33,840 Speaker 1: question that's baffled generations of scientists over the years. Some 69 00:04:33,920 --> 00:04:36,839 Speaker 1: have argued that the ants aren't hijacked at all, that 70 00:04:37,000 --> 00:04:40,159 Speaker 1: certain protocols have evolved in response to a fungal infection, 71 00:04:40,560 --> 00:04:43,360 Speaker 1: and that the individual ants wander off not because they're 72 00:04:43,360 --> 00:04:46,200 Speaker 1: being influenced by the fungus, but to avoid infecting the 73 00:04:46,200 --> 00:04:50,760 Speaker 1: rest of their colony. And despite the tropes about zombies 74 00:04:50,800 --> 00:04:54,720 Speaker 1: and brains, a twenty seventeen study published in the Proceedings 75 00:04:54,760 --> 00:04:58,040 Speaker 1: of the National Academy of Sciences found that it's possible 76 00:04:58,080 --> 00:05:00,840 Speaker 1: that the ant's brain isn't involved in the whole process 77 00:05:00,880 --> 00:05:04,920 Speaker 1: at all. The researchers found that as the fungus grows 78 00:05:04,920 --> 00:05:08,679 Speaker 1: inside the ant's body, its cells create an interconnected network 79 00:05:08,680 --> 00:05:12,479 Speaker 1: of fibers that surround the ants muscle fibers, and that 80 00:05:12,520 --> 00:05:16,120 Speaker 1: it's this network that is most likely coordinating the ants movements. 81 00:05:16,880 --> 00:05:19,560 Speaker 1: They did find the fungus in the insect's head, but 82 00:05:19,720 --> 00:05:24,159 Speaker 1: not in its actual brain. In a press release, the 83 00:05:24,240 --> 00:05:26,720 Speaker 1: lead author of the study, an entomologist by the name 84 00:05:26,760 --> 00:05:30,400 Speaker 1: of David Hughes, said, we found that a high percentage 85 00:05:30,400 --> 00:05:33,800 Speaker 1: of the cells in a host were fungal cells. In essence, 86 00:05:34,120 --> 00:05:40,640 Speaker 1: these manipulated animals were a fungus in ants clothing. Pretty 87 00:05:40,720 --> 00:05:43,880 Speaker 1: much everything except the brain had been taken over entirely 88 00:05:43,920 --> 00:05:47,240 Speaker 1: by fungal cells, which led the researchers to believe that 89 00:05:47,279 --> 00:05:49,920 Speaker 1: the fungus might be preserving the brain for a reason, 90 00:05:50,480 --> 00:05:53,039 Speaker 1: maybe in order to help the ants survive until it 91 00:05:53,040 --> 00:05:57,760 Speaker 1: can perform its final death bite. To be fair, ant's 92 00:05:57,800 --> 00:06:00,359 Speaker 1: brains are pretty small, and they make up for that 93 00:06:00,440 --> 00:06:03,520 Speaker 1: by having clusters of neurons throughout their bodies that help 94 00:06:03,600 --> 00:06:06,200 Speaker 1: control different work, like the movement of a pair of 95 00:06:06,279 --> 00:06:12,560 Speaker 1: legs or receiving signals from an antenna. So although these 96 00:06:12,600 --> 00:06:16,320 Speaker 1: findings are compelling, it's still not crystal clear what's going 97 00:06:16,360 --> 00:06:20,240 Speaker 1: on between these parasitic fungi and their victims. But at 98 00:06:20,320 --> 00:06:23,320 Speaker 1: least it is clear that it would be extremely difficult 99 00:06:23,360 --> 00:06:26,080 Speaker 1: for a fungus to start hijacking human bodies in the 100 00:06:26,120 --> 00:06:29,520 Speaker 1: way that cordyceps and a few cordyceps do with arthropods, 101 00:06:30,000 --> 00:06:37,680 Speaker 1: so that's one less thing to worry about. Today's episode 102 00:06:37,760 --> 00:06:40,279 Speaker 1: is based on the article Meet the Zombie ant Fungus 103 00:06:40,279 --> 00:06:43,080 Speaker 1: that inspired HBO's The Last of Us on how Stuffworks 104 00:06:43,080 --> 00:06:46,279 Speaker 1: dot com, written by Jeslin Shields. Brain Stuff is production 105 00:06:46,320 --> 00:06:48,840 Speaker 1: of iHeartRadio in partnership with how Stuffworks dot Com and 106 00:06:48,960 --> 00:06:52,320 Speaker 1: is produced by Tyler Klang. Four more podcasts my Heart Radio, 107 00:06:52,560 --> 00:06:55,640 Speaker 1: visit the iHeartRadio app, Apple Podcasts, or wherever you listen 108 00:06:55,720 --> 00:07:02,400 Speaker 1: to your favorite shows.