1 00:00:03,040 --> 00:00:06,840 Speaker 1: Welcome to Stuff to Blow Your Mind, a production of iHeartRadio. 2 00:00:13,240 --> 00:00:15,440 Speaker 1: Hey you welcome to Stuff to Blow Your Mind. My 3 00:00:15,520 --> 00:00:16,759 Speaker 1: name is Robert Lamb. 4 00:00:16,920 --> 00:00:19,639 Speaker 2: And I'm Joe McCormick, and today we're going to be 5 00:00:19,680 --> 00:00:26,160 Speaker 2: talking about a concept in the realm of genetics and reproduction, 6 00:00:27,000 --> 00:00:31,880 Speaker 2: a concept known as mutational meltdown. Very enticing name, Rob 7 00:00:32,000 --> 00:00:37,040 Speaker 2: I understand you became interested in mutational meltdown earlier this week. 8 00:00:37,080 --> 00:00:38,520 Speaker 2: What got you going on this. 9 00:00:39,280 --> 00:00:41,920 Speaker 1: Well, it actually didn't have anything to do directly with 10 00:00:42,680 --> 00:00:44,640 Speaker 1: any melt movies we might have been talking about on 11 00:00:44,680 --> 00:00:48,000 Speaker 1: Weird House Cinema. I actually, I think I was on 12 00:00:48,000 --> 00:00:50,400 Speaker 1: a walk with my family and I said, hey, I 13 00:00:50,400 --> 00:00:52,159 Speaker 1: think we're going to need an episode for Thursday. What 14 00:00:52,159 --> 00:00:55,440 Speaker 1: should we do it on? And there my wife and 15 00:00:55,440 --> 00:00:56,760 Speaker 1: my son are like, oh, you should do it on 16 00:00:57,120 --> 00:01:01,720 Speaker 1: asexual reproduction. So okay, let's just started looking around a 17 00:01:01,760 --> 00:01:04,840 Speaker 1: little bit. And Yeah, this particular term kind of jumped 18 00:01:04,880 --> 00:01:07,160 Speaker 1: out at me. I wasn't familiar with it, and it 19 00:01:08,319 --> 00:01:10,920 Speaker 1: basically gets down into and I think for our purposes 20 00:01:10,959 --> 00:01:12,360 Speaker 1: here on the show, you know, it's a reason to 21 00:01:12,440 --> 00:01:15,440 Speaker 1: sort of provide an overview of sort of asexual reproduction. 22 00:01:15,560 --> 00:01:21,680 Speaker 1: Versus sexual reproduction as sort of competing ways of going 23 00:01:21,720 --> 00:01:25,360 Speaker 1: about sort of the same thing for an organism, but 24 00:01:25,560 --> 00:01:29,840 Speaker 1: one with more short term benefits versus long term benefits. 25 00:01:29,880 --> 00:01:31,399 Speaker 1: And I don't know, I just found it to be 26 00:01:31,520 --> 00:01:36,640 Speaker 1: kind of a neat way to re examine and think 27 00:01:36,680 --> 00:01:40,920 Speaker 1: about these concepts that I imagine we've covered on the show before, 28 00:01:41,080 --> 00:01:46,360 Speaker 1: and many of you out there have encountered in varying formats. 29 00:01:47,040 --> 00:01:49,560 Speaker 2: Sure well, I know over the years we have alluded 30 00:01:49,600 --> 00:01:53,240 Speaker 2: to the big question in biology of like where sex 31 00:01:53,280 --> 00:01:56,560 Speaker 2: comes from, the where, when and why of sexual reproduction 32 00:01:57,200 --> 00:02:00,640 Speaker 2: as a part of the history of organisms on planet Earth. 33 00:02:00,720 --> 00:02:04,400 Speaker 2: Not going to solve that problem today, but yeah, I 34 00:02:04,480 --> 00:02:08,160 Speaker 2: think maybe this little subtopic could help shed a little 35 00:02:08,200 --> 00:02:08,920 Speaker 2: bit of light there. 36 00:02:09,360 --> 00:02:13,760 Speaker 1: Yeah, so let's start with the basics, though, we're going 37 00:02:13,800 --> 00:02:17,000 Speaker 1: to just approach it as if you're not really familiar 38 00:02:17,080 --> 00:02:20,480 Speaker 1: with any of the topics that we're discussing here. So 39 00:02:20,800 --> 00:02:25,520 Speaker 1: asexual reproduction versus sexual reproduction on a very basic level, 40 00:02:25,680 --> 00:02:28,679 Speaker 1: here's how it all goes down. So, with sexual reproduction, 41 00:02:28,919 --> 00:02:32,920 Speaker 1: you have the offspring of two genetic parents inheriting a 42 00:02:33,000 --> 00:02:36,880 Speaker 1: mix of genes from those parents, genetically distinguishing itself from 43 00:02:36,960 --> 00:02:40,840 Speaker 1: either parent. The resulting genetic variation is highly adaptive because 44 00:02:40,880 --> 00:02:44,720 Speaker 1: it provides individuals with varying traits that may prove necessary 45 00:02:44,760 --> 00:02:49,079 Speaker 1: for survival in an ever changing environment. The resulting genetic 46 00:02:49,080 --> 00:02:52,639 Speaker 1: diversity makes the population more resistant to disease as well. 47 00:02:52,840 --> 00:02:55,040 Speaker 2: I think one of the theories we've talked about before 48 00:02:55,240 --> 00:02:59,880 Speaker 2: is that an advantage of sexual reproduction is that it 49 00:03:00,160 --> 00:03:04,280 Speaker 2: helps protect the host organism against various types of parasites 50 00:03:04,320 --> 00:03:08,600 Speaker 2: by introducing genetic variability that makes it harder for the 51 00:03:08,639 --> 00:03:13,400 Speaker 2: parasite to target each successive generation of the host. 52 00:03:13,720 --> 00:03:17,840 Speaker 1: Yeah, this is a clumsy analogy at best, but I 53 00:03:17,880 --> 00:03:19,560 Speaker 1: can't help but think too about like to say that, 54 00:03:20,360 --> 00:03:23,400 Speaker 1: because essentially, when you're talking about asexual reproduction, you're talking 55 00:03:23,919 --> 00:03:27,080 Speaker 1: essentially about making a clone of oneself. And so the 56 00:03:27,160 --> 00:03:32,160 Speaker 1: clone army in the Star Wars prequels highly susceptible, to say, 57 00:03:33,320 --> 00:03:35,640 Speaker 1: a single order coming out and telling them to turn 58 00:03:35,640 --> 00:03:38,480 Speaker 1: on the Jedi, that sort of thing. But that's just 59 00:03:38,520 --> 00:03:40,880 Speaker 1: a very very rough idea of how to think about it. 60 00:03:42,160 --> 00:03:46,040 Speaker 1: But more specifically for our purposes here, another key benefit 61 00:03:46,440 --> 00:03:48,840 Speaker 1: that comes up in the literature is looking at is 62 00:03:48,840 --> 00:03:53,440 Speaker 1: that you can think of sex, and genetic recombination is 63 00:03:53,520 --> 00:03:59,000 Speaker 1: ultimately a means of purging deletarious mutations. 64 00:03:58,760 --> 00:04:01,560 Speaker 2: Right, So the impact of mutations that might be harmful 65 00:04:01,600 --> 00:04:06,360 Speaker 2: to the organism can be blunted by sexual recombination. 66 00:04:06,960 --> 00:04:08,640 Speaker 1: Yeah. Yeah, So you end up with this, I mean, 67 00:04:09,280 --> 00:04:11,040 Speaker 1: roughly speaking, you know, you have kind of like a 68 00:04:11,160 --> 00:04:14,760 Speaker 1: randomization of these different traits, and the individuals that end 69 00:04:14,800 --> 00:04:19,120 Speaker 1: up the offspring with that end up with the negative traits, 70 00:04:19,160 --> 00:04:23,440 Speaker 1: the harmful traits, they don't survive. The ones that have 71 00:04:23,520 --> 00:04:26,839 Speaker 1: been purged of those mutations do survive, and therefore it 72 00:04:26,880 --> 00:04:30,520 Speaker 1: can purge the mutation from a particular lineage. Okay, all right, 73 00:04:30,640 --> 00:04:34,680 Speaker 1: So moving on to asexual reproduction. This is a case 74 00:04:34,680 --> 00:04:36,800 Speaker 1: in which you have the offspring of a single genetic 75 00:04:36,920 --> 00:04:40,000 Speaker 1: parent inheriting the genes of the parent, making it a 76 00:04:40,040 --> 00:04:43,040 Speaker 1: clone identical to the parent. The advantage here is that 77 00:04:43,080 --> 00:04:47,599 Speaker 1: you can reproduce rapidly without all of the energy expenditure 78 00:04:47,720 --> 00:04:50,719 Speaker 1: of mating. And I mean that's a pretty big statement 79 00:04:50,800 --> 00:04:54,480 Speaker 1: to think about, because so many organisms we end up 80 00:04:54,480 --> 00:04:57,360 Speaker 1: discussing on the podcast. You know, what is the key 81 00:04:57,400 --> 00:04:59,840 Speaker 1: thing that makes them interesting? Well, in some cases many 82 00:04:59,839 --> 00:05:02,400 Speaker 1: ca is it's how they acquire their food. But in 83 00:05:02,480 --> 00:05:04,560 Speaker 1: other cases it's how do they get a mate? How 84 00:05:04,600 --> 00:05:07,440 Speaker 1: do they attract a mate or pursue a mate, and 85 00:05:07,520 --> 00:05:10,080 Speaker 1: it ends up taking up a whole lot of time, 86 00:05:10,240 --> 00:05:12,680 Speaker 1: a whole lot of energy. And what if you didn't 87 00:05:12,720 --> 00:05:15,200 Speaker 1: have to do that? What if instead you could just 88 00:05:15,360 --> 00:05:16,520 Speaker 1: essentially clone yourself. 89 00:05:16,800 --> 00:05:19,160 Speaker 2: It would be very convenient and safer in a lot 90 00:05:19,200 --> 00:05:22,080 Speaker 2: of cases, because I mean it varies by organism, but 91 00:05:22,360 --> 00:05:24,520 Speaker 2: in many cases, yeah, if you have to go seeking 92 00:05:24,600 --> 00:05:28,200 Speaker 2: out a mate, it is not only, you know, an 93 00:05:28,320 --> 00:05:31,360 Speaker 2: energy expense to go looking around, but you're also often 94 00:05:31,600 --> 00:05:35,760 Speaker 2: removing yourself from safe locations and going into dangerous ones. 95 00:05:36,080 --> 00:05:37,719 Speaker 1: Yeah. I mean it's kind of like when you get 96 00:05:38,520 --> 00:05:41,440 Speaker 1: some sort of new kit to a symbols of Ikia furniture, right, 97 00:05:41,839 --> 00:05:44,520 Speaker 1: and the first thing you notice is that on the 98 00:05:44,560 --> 00:05:46,719 Speaker 1: instructions it says, oh, you have to have two people 99 00:05:46,760 --> 00:05:49,440 Speaker 1: to do this, and you're like, oh, that totally wrecks 100 00:05:49,480 --> 00:05:52,120 Speaker 1: my day. Now I've got to get my significant other 101 00:05:52,360 --> 00:05:54,279 Speaker 1: or a friend to help with this. We've got to 102 00:05:54,279 --> 00:05:56,880 Speaker 1: align our schedules and we have to both work together 103 00:05:57,040 --> 00:06:00,440 Speaker 1: to build this thing, as opposed to one where I 104 00:06:00,440 --> 00:06:03,000 Speaker 1: can just build it myself. And put it where it 105 00:06:03,040 --> 00:06:05,719 Speaker 1: needs to go in the house. Now, there are multiple 106 00:06:05,720 --> 00:06:07,880 Speaker 1: types of asexual reproduction, and we're not going to go 107 00:06:07,920 --> 00:06:09,560 Speaker 1: into all of them, but you have all sorts of 108 00:06:09,560 --> 00:06:13,880 Speaker 1: things like asexual budding and so forth. The sources I 109 00:06:13,920 --> 00:06:18,240 Speaker 1: was looking at dealt a lot with parthenogenesis, which occurs 110 00:06:18,279 --> 00:06:21,880 Speaker 1: widely and invertebrates. This word stems from the Greek for 111 00:06:22,000 --> 00:06:25,840 Speaker 1: virgin creation parthenos plus genesis. 112 00:06:25,960 --> 00:06:29,039 Speaker 2: Okay, so this would describe, for example, a lot of vertebrates, 113 00:06:29,120 --> 00:06:33,360 Speaker 2: like maybe some lizards or fish that can give birth 114 00:06:33,440 --> 00:06:36,880 Speaker 2: without ever having without ever having their game meets fertilized 115 00:06:36,920 --> 00:06:38,320 Speaker 2: by a member of the opposite sex. 116 00:06:38,800 --> 00:06:44,200 Speaker 1: Yeah. Yeah, we're talking about lizards, geckos, various insects, particularly 117 00:06:44,200 --> 00:06:48,840 Speaker 1: some sharks. And it's of course very important to note 118 00:06:48,920 --> 00:06:54,160 Speaker 1: that there are obligate sexual reproducers and then they're obligate 119 00:06:54,240 --> 00:06:57,560 Speaker 1: asexual reproducers. But then there are also organisms that can 120 00:06:57,600 --> 00:07:01,760 Speaker 1: do either depending on environmental pressure. So a classic example 121 00:07:01,880 --> 00:07:05,760 Speaker 1: of a sexually reproducing organism engaging in asexual reproduction is, 122 00:07:05,800 --> 00:07:09,120 Speaker 1: of course, when an individual cannot find a mate. It's 123 00:07:09,240 --> 00:07:11,040 Speaker 1: kind of there is I guess you could think of 124 00:07:11,080 --> 00:07:16,280 Speaker 1: it as kind of a backup plan or some sort 125 00:07:16,280 --> 00:07:18,880 Speaker 1: of a you know, an emergency button that can be pushed. 126 00:07:19,200 --> 00:07:20,840 Speaker 1: And this has been the case with some of the 127 00:07:20,880 --> 00:07:23,640 Speaker 1: famous examples of say sharks or lizards such as the 128 00:07:23,720 --> 00:07:29,480 Speaker 1: Komodo dragon, reproducing in captivity, These so called virgin births 129 00:07:30,080 --> 00:07:32,280 Speaker 1: that will suddenly occur in shock zoo keepers. 130 00:07:32,800 --> 00:07:37,200 Speaker 2: So the ideal is to mix and match your genetic 131 00:07:37,240 --> 00:07:40,840 Speaker 2: material with somebody else's. But in a pinch, you could 132 00:07:40,880 --> 00:07:43,800 Speaker 2: just make a copy of yourself if you're the. 133 00:07:43,840 --> 00:07:46,960 Speaker 1: Right species correct, Yeah, and if I'm remembering correctly. This 134 00:07:47,000 --> 00:07:49,200 Speaker 1: also pops up in the plot of Jurassic Park, right, 135 00:07:49,240 --> 00:07:52,120 Speaker 1: something to do with the way that they're recreating dinosaur 136 00:07:52,200 --> 00:07:53,880 Speaker 1: DNA using amphibian DNA. 137 00:07:54,080 --> 00:07:56,760 Speaker 2: Well, I don't know if this is parthenogenesis or if 138 00:07:56,800 --> 00:07:58,240 Speaker 2: it would be different. I think what they say, at 139 00:07:58,280 --> 00:08:00,120 Speaker 2: least in the movie, I don't remember what happens in 140 00:08:00,120 --> 00:08:02,400 Speaker 2: the book. In the movie they say that because they 141 00:08:02,480 --> 00:08:07,240 Speaker 2: use some frog DNA to cover up patches in the 142 00:08:07,360 --> 00:08:10,440 Speaker 2: DNA sequence. This I'm just recalling from memory what mister 143 00:08:10,520 --> 00:08:15,360 Speaker 2: DNA tells us, that that some frogs are able to 144 00:08:15,480 --> 00:08:19,280 Speaker 2: spontaneously change sex in a single sex environment. And thus 145 00:08:19,360 --> 00:08:21,960 Speaker 2: even though all of the dinosaurs in the park were 146 00:08:22,000 --> 00:08:25,080 Speaker 2: supposed to be female, some changed into males and thus 147 00:08:25,080 --> 00:08:26,600 Speaker 2: were sexually reproducing. 148 00:08:27,160 --> 00:08:29,480 Speaker 1: Ah okay, I think that's the main thing. I'm either 149 00:08:29,520 --> 00:08:32,800 Speaker 1: misremembering that or maybe there's something from one of the 150 00:08:32,880 --> 00:08:36,280 Speaker 1: later like Jurassic World films that I'm only like half 151 00:08:36,320 --> 00:08:39,400 Speaker 1: processing here. All right, So you have these two basic 152 00:08:39,440 --> 00:08:42,120 Speaker 1: ways of reproducing. Then this of course means that there 153 00:08:42,160 --> 00:08:45,480 Speaker 1: are drawbacks to either one. So in sexual reproduction, again, 154 00:08:45,920 --> 00:08:47,440 Speaker 1: you got to put a whole lot of energy and 155 00:08:47,520 --> 00:08:52,800 Speaker 1: time into mating behaviors. It necessitates the existence of males, 156 00:08:53,280 --> 00:08:56,400 Speaker 1: which in some cases like do little or nothing else, 157 00:08:56,800 --> 00:09:00,600 Speaker 1: Like you know, an entire division of the species just 158 00:09:00,720 --> 00:09:05,480 Speaker 1: for reproduction. Mating can prove fatal in and of itself, 159 00:09:06,520 --> 00:09:09,760 Speaker 1: not necessarily in a way that actually has any impact 160 00:09:09,800 --> 00:09:12,840 Speaker 1: on the species. But still it's like the again, you 161 00:09:12,880 --> 00:09:15,400 Speaker 1: get into these situations where the male's whole role is 162 00:09:15,679 --> 00:09:20,360 Speaker 1: reproduction and then afterwards has no purpose except maybe death. 163 00:09:21,000 --> 00:09:24,559 Speaker 1: And it can of course also be nutrition, could be nutrition. Yeah, 164 00:09:24,600 --> 00:09:27,679 Speaker 1: so it's not a complete ways. But also just mating 165 00:09:27,800 --> 00:09:31,320 Speaker 1: in general creates opportunities for predators in a number of ways. 166 00:09:31,920 --> 00:09:34,960 Speaker 1: It could be something very specific like well, while you're mating, 167 00:09:35,040 --> 00:09:37,520 Speaker 1: it's possible that something could could prey on you. But 168 00:09:37,600 --> 00:09:41,959 Speaker 1: also again, just think of all the links that creatures 169 00:09:42,040 --> 00:09:47,720 Speaker 1: end up going to inmate selection and so forth. Various 170 00:09:47,760 --> 00:09:51,040 Speaker 1: examples of this, even if it's just say sexual dimorphism, 171 00:09:51,679 --> 00:09:53,880 Speaker 1: could mean that one member of the species is more 172 00:09:53,920 --> 00:09:55,080 Speaker 1: likely to be consumed than the other. 173 00:09:55,559 --> 00:09:57,760 Speaker 2: Yeah, it makes me think about all of the I 174 00:09:57,760 --> 00:10:02,480 Speaker 2: don't know, like birds that essentially where male birds are 175 00:10:02,480 --> 00:10:08,600 Speaker 2: trying to attract mates, specifically by being conspicuous. Yeah, you 176 00:10:08,679 --> 00:10:10,840 Speaker 2: got to think that that also that comes with some 177 00:10:11,040 --> 00:10:13,480 Speaker 2: amount of predation risk, at least in many cases. 178 00:10:13,920 --> 00:10:17,160 Speaker 1: Yeah. Another thing could be, yes, particular places you know 179 00:10:17,240 --> 00:10:19,839 Speaker 1: they have to travel to in order to engage in 180 00:10:19,880 --> 00:10:24,880 Speaker 1: the mating, et cetera. But another drawback to sexual reproduction 181 00:10:25,160 --> 00:10:27,520 Speaker 1: is that if it's your only option, it means that 182 00:10:28,040 --> 00:10:33,319 Speaker 1: isolated members of a particular species or population just cannot reproduce, 183 00:10:33,800 --> 00:10:36,880 Speaker 1: and it also means that sufficiently reduced populations are just 184 00:10:37,000 --> 00:10:40,560 Speaker 1: already at a dead end. Now in asexual reproduction, there's 185 00:10:40,600 --> 00:10:44,240 Speaker 1: also a potential dead end there as well, because if 186 00:10:44,280 --> 00:10:48,360 Speaker 1: you don't have genetic variation occurring, if you're basically just 187 00:10:48,400 --> 00:10:51,200 Speaker 1: putting out the same model after the same model, after 188 00:10:51,200 --> 00:10:54,959 Speaker 1: the same model. It may well improve, it may well 189 00:10:55,000 --> 00:10:59,319 Speaker 1: prove impossible for the species to adapt or to change. 190 00:11:00,240 --> 00:11:01,880 Speaker 1: So it's you know, if you're just putting out the 191 00:11:01,920 --> 00:11:05,880 Speaker 1: same model after the same model, and like the market 192 00:11:06,000 --> 00:11:08,160 Speaker 1: is the same for that product, then I guess you 193 00:11:08,160 --> 00:11:10,160 Speaker 1: don't have anything to worry about so long as the 194 00:11:10,200 --> 00:11:13,400 Speaker 1: market doesn't change. Is Suddenly, if the demand for a 195 00:11:13,440 --> 00:11:17,679 Speaker 1: particular you know, toy or item, we were to alter 196 00:11:17,800 --> 00:11:21,000 Speaker 1: in some way and you couldn't alter the product, then 197 00:11:21,040 --> 00:11:24,319 Speaker 1: you'd be in trouble. And the same goes for any 198 00:11:24,400 --> 00:11:27,880 Speaker 1: kind of biological form. What happens when say, things begin 199 00:11:27,920 --> 00:11:31,560 Speaker 1: to dry up or there's warming or cooling, or whatever 200 00:11:31,600 --> 00:11:35,240 Speaker 1: the case may be. Sexual reproduction is what gives you 201 00:11:35,320 --> 00:11:40,200 Speaker 1: the ability to bust out these these different variations on 202 00:11:40,320 --> 00:11:44,240 Speaker 1: the genetic code that could prove adaptive to change. 203 00:11:44,600 --> 00:11:46,840 Speaker 2: Yeah, it gives you options, diversity. 204 00:11:46,720 --> 00:11:53,160 Speaker 1: Yeah, yeah, diversifies your portfolio. Now, we mentioned disease and 205 00:11:53,200 --> 00:11:55,920 Speaker 1: parasites already, so that's very much the case. If you 206 00:11:56,040 --> 00:11:59,040 Speaker 1: just have a whole bunch of clones, then they all 207 00:11:59,080 --> 00:12:04,120 Speaker 1: have the same susceptibility to illness or parasites. Overall, the 208 00:12:04,160 --> 00:12:07,600 Speaker 1: big drawback is just a lack of genetic diversity, which 209 00:12:07,600 --> 00:12:12,160 Speaker 1: can also result in the accumulation of harmful mutations. And 210 00:12:12,200 --> 00:12:14,680 Speaker 1: another thing about the difference between the two though, that 211 00:12:15,240 --> 00:12:17,040 Speaker 1: I guess I hadn't really thought about too much, is 212 00:12:17,080 --> 00:12:19,640 Speaker 1: that it being a difference between short term and long 213 00:12:19,720 --> 00:12:24,280 Speaker 1: term benefits. So, asexual reproduction is great for rapidly growing 214 00:12:24,280 --> 00:12:27,440 Speaker 1: a population during a time of plenty, but the resulting 215 00:12:27,480 --> 00:12:31,320 Speaker 1: population can run into problems long term. Meanwhile, sexual reproduction 216 00:12:31,440 --> 00:12:35,720 Speaker 1: requires more energy and time, but generates diversity that may 217 00:12:35,720 --> 00:12:38,400 Speaker 1: come in handy in the long term again when there 218 00:12:38,400 --> 00:12:42,440 Speaker 1: are changes and obstacles that arise. Anyway, coming back to 219 00:12:42,480 --> 00:12:46,880 Speaker 1: this idea that via asexual reproduction you can have this 220 00:12:46,960 --> 00:12:52,920 Speaker 1: accumulation of harmful genetic changes. This brings us to the 221 00:12:52,920 --> 00:12:56,320 Speaker 1: topic of Muller's ratchet, which is not something I was 222 00:12:56,320 --> 00:13:01,199 Speaker 1: familiar with previously. The basic theory here is that long 223 00:13:01,280 --> 00:13:06,960 Speaker 1: term reproduction, particularly a sexual reproduction, some of the studies 224 00:13:07,000 --> 00:13:11,760 Speaker 1: we're looking at they're also looking at it with sexual reproduction. Basically, 225 00:13:11,800 --> 00:13:15,240 Speaker 1: you see this accumulation of harmful genetic mutations, and after 226 00:13:15,520 --> 00:13:19,840 Speaker 1: thousands of generations pass by, you can eventually reach a 227 00:13:19,920 --> 00:13:25,200 Speaker 1: tipping point, which we refer to as mutational meltdown. And 228 00:13:25,240 --> 00:13:27,600 Speaker 1: we'll get back to mutational meltdown in just a second. 229 00:13:28,000 --> 00:13:33,440 Speaker 1: But interestingly, the namesake for Muller's ratchet is Hermann Joseph Muller, 230 00:13:33,480 --> 00:13:37,480 Speaker 1: who lived eighteen ninety through nineteen sixty seven an American geneticist, 231 00:13:38,120 --> 00:13:42,640 Speaker 1: mostly known for his work on mooda genesis, and for 232 00:13:42,679 --> 00:13:48,040 Speaker 1: being like an outspoken critic and just sort of communicator 233 00:13:48,040 --> 00:13:51,240 Speaker 1: on the dangers of radioactive fallout. He won the nineteen 234 00:13:51,280 --> 00:13:54,720 Speaker 1: forty six Nobel Prize in Physiology or Medicine, and he 235 00:13:54,800 --> 00:13:59,480 Speaker 1: was also the father of mathematician and computer scientist David E. Muller, 236 00:14:00,320 --> 00:14:04,080 Speaker 1: who also has various things named after him. So you'll 237 00:14:04,080 --> 00:14:08,400 Speaker 1: find a number of things in both genetic concepts and 238 00:14:08,440 --> 00:14:12,680 Speaker 1: what have you, in genetics and mathematics that have the 239 00:14:12,720 --> 00:14:14,080 Speaker 1: Mueller name attached to them. 240 00:14:14,320 --> 00:14:17,200 Speaker 2: Now, Rob, before you suggested this, I had never heard 241 00:14:17,200 --> 00:14:20,240 Speaker 2: of mutational meltdown or Mueller's ratchet, at least as far 242 00:14:20,280 --> 00:14:22,440 Speaker 2: as I know. But one of the things that I 243 00:14:22,480 --> 00:14:26,880 Speaker 2: got really interested in here is how it violates sort 244 00:14:26,880 --> 00:14:30,720 Speaker 2: of the simple assumptions that you make when you think 245 00:14:30,720 --> 00:14:33,400 Speaker 2: about evolution on a surface level, because of course, it 246 00:14:33,480 --> 00:14:37,680 Speaker 2: makes this reference to the idea of harmful genetic mutations 247 00:14:37,760 --> 00:14:42,560 Speaker 2: accumulating over time in the species, and at a surface level, 248 00:14:42,560 --> 00:14:45,600 Speaker 2: you might think, well, wait a minute, why would harmful 249 00:14:45,720 --> 00:14:50,240 Speaker 2: genetic mutations accumulate. Isn't natural selections supposed to get rid 250 00:14:50,280 --> 00:14:54,400 Speaker 2: of those? And so over time, with enough enough opportunities, yes, 251 00:14:54,560 --> 00:14:58,560 Speaker 2: mutations that bring more harm than benefit to an organism's 252 00:14:58,760 --> 00:15:02,680 Speaker 2: ability to survive and rep produce will tend to disappear. 253 00:15:03,000 --> 00:15:07,080 Speaker 2: But under certain circumstances, bad genes can accumulate. And one 254 00:15:07,080 --> 00:15:10,280 Speaker 2: of the key concepts to understand here is what's known 255 00:15:10,360 --> 00:15:15,720 Speaker 2: as genetic drift. So genetic drift is a change in 256 00:15:15,800 --> 00:15:19,880 Speaker 2: the frequency of a particular gene variant also known as 257 00:15:19,880 --> 00:15:25,240 Speaker 2: an allele in a population due to random chance rather 258 00:15:25,400 --> 00:15:30,520 Speaker 2: than to natural selection. So random genetic drift is always happening. 259 00:15:30,560 --> 00:15:33,240 Speaker 2: It's always going on in the background in the evolution 260 00:15:33,360 --> 00:15:36,440 Speaker 2: of species. While you might think of natural selection as 261 00:15:36,480 --> 00:15:41,640 Speaker 2: sort of acting in the foreground amplifying or diminishing alleles 262 00:15:42,040 --> 00:15:46,400 Speaker 2: because they are helpful or harmful. So you might think of, 263 00:15:46,480 --> 00:15:50,720 Speaker 2: say a gene for blue feathers in some kind of bird. 264 00:15:51,040 --> 00:15:56,240 Speaker 2: That gene might increase in the population, not for any 265 00:15:56,320 --> 00:16:00,000 Speaker 2: reason having to do with blue feathers making the birds 266 00:16:00,040 --> 00:16:04,520 Speaker 2: survive or reproduce more. Maybe it's just you know, sheer 267 00:16:04,600 --> 00:16:07,960 Speaker 2: luck one season. Or maybe there might be some kind 268 00:16:07,960 --> 00:16:11,160 Speaker 2: of random thing that happens in the popular lakes. Maybe 269 00:16:11,160 --> 00:16:13,960 Speaker 2: a big population of blue feathered individuals come across a 270 00:16:13,960 --> 00:16:16,760 Speaker 2: big cache of food or something, or there is just 271 00:16:17,160 --> 00:16:21,520 Speaker 2: the standard fluctuations in the sampling rate of the different 272 00:16:21,520 --> 00:16:25,840 Speaker 2: alleles that get recombined in sexual reproduction. The smaller a 273 00:16:25,920 --> 00:16:30,480 Speaker 2: population is, the more likely it is to be irreversibly 274 00:16:30,680 --> 00:16:36,120 Speaker 2: changed by random trends in genetic drift. Now you might wonder, 275 00:16:36,160 --> 00:16:39,040 Speaker 2: how would that work if the trends in genetic drift 276 00:16:39,160 --> 00:16:42,120 Speaker 2: or just random, it's just chance, how would that cause 277 00:16:42,240 --> 00:16:46,000 Speaker 2: irreversible changes? I think one way you might be able 278 00:16:46,000 --> 00:16:49,320 Speaker 2: to compare this is if you think about gambling. Okay, 279 00:16:49,360 --> 00:16:54,120 Speaker 2: imagine you're making bets on somebody flipping a coin. If 280 00:16:54,160 --> 00:16:57,240 Speaker 2: you have an infinite pot of money to bet with, 281 00:16:57,480 --> 00:16:59,680 Speaker 2: you could just keep doing this forever, right Like you 282 00:16:59,760 --> 00:17:01,440 Speaker 2: might get a run of good luck, you might get 283 00:17:01,440 --> 00:17:03,880 Speaker 2: a run of bad luck. You might call the coin wrong. 284 00:17:04,200 --> 00:17:06,120 Speaker 2: You know, I don't know how many times it would 285 00:17:06,119 --> 00:17:08,399 Speaker 2: be plausible eight times in a row and lose a 286 00:17:08,400 --> 00:17:12,080 Speaker 2: lot of money, But eventually, on average, you'd have a 287 00:17:12,080 --> 00:17:14,440 Speaker 2: winning streak again and you'd win your money back as 288 00:17:14,480 --> 00:17:17,560 Speaker 2: long as you can keep gambling, as long as you've 289 00:17:17,600 --> 00:17:20,360 Speaker 2: got like an infinite pot to play from. But if 290 00:17:20,400 --> 00:17:23,800 Speaker 2: you are gambling with a fixed amount of money, you 291 00:17:24,000 --> 00:17:27,399 Speaker 2: eventually will hit a random run of bad luck and 292 00:17:27,480 --> 00:17:30,080 Speaker 2: lose it all. You will play to extinction. 293 00:17:31,000 --> 00:17:32,119 Speaker 1: Very fitting, very fitting. 294 00:17:32,480 --> 00:17:36,720 Speaker 2: So for my analogy here, you could compare the size 295 00:17:36,760 --> 00:17:39,080 Speaker 2: of your purse you're going into gamble with with the 296 00:17:39,119 --> 00:17:42,600 Speaker 2: size of the population where the random genetic drift is happening. 297 00:17:43,119 --> 00:17:47,879 Speaker 2: Genetic drift in a small population can easily drive certain 298 00:17:47,960 --> 00:17:52,360 Speaker 2: alleeles extinct, even though those alleles had no negative effect 299 00:17:52,440 --> 00:17:56,159 Speaker 2: on survival. The other side of the other side of 300 00:17:56,200 --> 00:17:59,680 Speaker 2: that is that in small populations, random genetic drift can 301 00:17:59,720 --> 00:18:02,840 Speaker 2: also so do the inverse. It can take an allele 302 00:18:02,960 --> 00:18:06,760 Speaker 2: and make it the only version of that gene left 303 00:18:06,800 --> 00:18:10,560 Speaker 2: in the population, present in one hundred percent of individuals. 304 00:18:10,960 --> 00:18:14,520 Speaker 2: And there's a term for this. The population genetics term 305 00:18:15,280 --> 00:18:19,040 Speaker 2: for when an allele becomes present in the entire population 306 00:18:19,240 --> 00:18:23,439 Speaker 2: is fixation. When that allele is the only version of 307 00:18:23,440 --> 00:18:26,520 Speaker 2: that gene left. It is said to be fixed in 308 00:18:26,560 --> 00:18:29,760 Speaker 2: the population. Everybody's got it. And of course, once a 309 00:18:29,840 --> 00:18:33,000 Speaker 2: gene variant is fixed in a population, of course that 310 00:18:33,119 --> 00:18:35,800 Speaker 2: means the individuals in that population are stuck with it, 311 00:18:35,880 --> 00:18:40,000 Speaker 2: you know, unless there is new information introduced. Now that 312 00:18:40,040 --> 00:18:43,160 Speaker 2: could be maybe a random mutation causes a new version 313 00:18:43,200 --> 00:18:45,720 Speaker 2: of that gene to appear, and then it can maybe compete, 314 00:18:46,240 --> 00:18:50,040 Speaker 2: or there is inflow of new alleles of that gene, 315 00:18:50,080 --> 00:18:54,439 Speaker 2: maybe by interbreeding with another population or something like that. 316 00:18:54,680 --> 00:18:59,159 Speaker 2: But for a closed population, once a gene variant is 317 00:18:59,200 --> 00:19:11,439 Speaker 2: fixed with it. Now the important thing to realize is 318 00:19:11,440 --> 00:19:15,840 Speaker 2: that alleles don't have to be the best version of 319 00:19:15,880 --> 00:19:18,639 Speaker 2: that gene. They don't have to be helpful to survival 320 00:19:18,720 --> 00:19:22,960 Speaker 2: or reproduction in order to become fixed in a population. 321 00:19:24,040 --> 00:19:28,840 Speaker 2: In big populations, harmful versions of genes will not tend 322 00:19:28,920 --> 00:19:31,520 Speaker 2: to dominate over time, they will tend to get removed 323 00:19:31,600 --> 00:19:35,480 Speaker 2: or remain in the background. But in small populations, because 324 00:19:35,600 --> 00:19:39,960 Speaker 2: you're essentially gambling with a small purse, those deleterious alleles 325 00:19:40,000 --> 00:19:44,320 Speaker 2: can become fixed just through bad luck. So you imagine 326 00:19:44,320 --> 00:19:48,919 Speaker 2: maybe every season within a population, you pick a randomly 327 00:19:48,960 --> 00:19:52,280 Speaker 2: assorted number of the individuals in that population, you say, 328 00:19:52,320 --> 00:19:56,080 Speaker 2: whichever allele they've got, make another copy of that one, 329 00:19:56,560 --> 00:19:58,840 Speaker 2: and then you just keep doing that over and over. 330 00:19:59,400 --> 00:20:02,920 Speaker 2: You can at random results where suddenly a gene that's 331 00:20:03,000 --> 00:20:06,480 Speaker 2: not very good for the population is suddenly the only 332 00:20:06,520 --> 00:20:12,840 Speaker 2: one left. So that's how genetic drift can cause deleterious, 333 00:20:13,160 --> 00:20:17,520 Speaker 2: harmful genes to become fixed in a population. But I 334 00:20:17,520 --> 00:20:19,800 Speaker 2: was wondering, Okay, so what's the deal with this idea 335 00:20:20,000 --> 00:20:24,200 Speaker 2: of mutational meltdown? What's happening there? Well, I was reading 336 00:20:24,240 --> 00:20:27,359 Speaker 2: about this in a in a biology textbook I found 337 00:20:27,359 --> 00:20:33,000 Speaker 2: called Practical Conservation Biology, edited by David Lindenmeyer and Mark Bergmann. 338 00:20:33,240 --> 00:20:36,680 Speaker 2: And you know, one of the things that the authors 339 00:20:36,680 --> 00:20:39,960 Speaker 2: mention is that every population carries some load in the 340 00:20:39,960 --> 00:20:46,119 Speaker 2: background of deleterious, recessive genes. But the core theory of 341 00:20:47,080 --> 00:20:51,240 Speaker 2: mutational meltdown again, it's something that really applies in particular 342 00:20:51,320 --> 00:20:55,480 Speaker 2: to small populations. That's where it's really dangerous. The author's 343 00:20:55,560 --> 00:20:59,840 Speaker 2: rite quote. In small populations, the dominant genetic process is 344 00:21:00,840 --> 00:21:03,840 Speaker 2: if the size of the breeding population is very small, 345 00:21:03,960 --> 00:21:08,320 Speaker 2: then random drift can overwhelm natural selection and a population 346 00:21:08,480 --> 00:21:13,120 Speaker 2: can accumulate and become fixed for quite deleterious mutations. If 347 00:21:13,160 --> 00:21:16,600 Speaker 2: the decline in fitness that results from the accumulation of 348 00:21:17,200 --> 00:21:22,440 Speaker 2: new mutations reduces fecundity, so reduces birth rates and reduces 349 00:21:22,480 --> 00:21:28,520 Speaker 2: survival to the extent that the population declines, feedback between 350 00:21:28,720 --> 00:21:33,320 Speaker 2: random genetic drift and mutation is set in motion. As 351 00:21:33,400 --> 00:21:38,520 Speaker 2: the population size decreases, random genetic drift becomes a more 352 00:21:38,560 --> 00:21:43,840 Speaker 2: significant force, and the rate of fixation of deleterious mutations increases, 353 00:21:44,280 --> 00:21:48,639 Speaker 2: further reducing population size. So it is this feedback loop 354 00:21:48,760 --> 00:21:54,400 Speaker 2: between the harmful mutations making the population smaller and thus 355 00:21:54,600 --> 00:21:58,760 Speaker 2: increasing the effects of genetic drift compared to the effects 356 00:21:58,800 --> 00:22:00,200 Speaker 2: of selection forces. 357 00:22:00,560 --> 00:22:03,880 Speaker 1: Yeah, so at first you just have one wrong turn movie, 358 00:22:03,920 --> 00:22:06,160 Speaker 1: and then you have two wrong turn movies, and before 359 00:22:06,200 --> 00:22:08,000 Speaker 1: you know it, there's like twenty of them and you 360 00:22:08,200 --> 00:22:10,600 Speaker 1: haven't seen a single one, but you know that they 361 00:22:10,640 --> 00:22:14,240 Speaker 1: all have something to do with mutated hillbillies. 362 00:22:14,800 --> 00:22:18,080 Speaker 2: Yes, it's a vicious cycle of some kind. And as 363 00:22:18,119 --> 00:22:19,600 Speaker 2: a side note, by the way, that this is not 364 00:22:19,680 --> 00:22:22,120 Speaker 2: relevant to most of the species we'd be talking about, 365 00:22:22,160 --> 00:22:24,600 Speaker 2: but just because I thought it was interesting. The authors 366 00:22:24,640 --> 00:22:27,960 Speaker 2: in the context of this conservation biology book also mention 367 00:22:28,119 --> 00:22:33,000 Speaker 2: how this applies in captive populations in a conservation context. 368 00:22:33,200 --> 00:22:39,200 Speaker 2: So because captive populations of animals where you know, there's 369 00:22:39,240 --> 00:22:44,160 Speaker 2: concern for the species level survival because those might those 370 00:22:44,200 --> 00:22:48,240 Speaker 2: animals are not really competing in the wild to survive. 371 00:22:48,920 --> 00:22:52,560 Speaker 2: It is very easy, in fact, for them to accumulate 372 00:22:52,640 --> 00:22:57,080 Speaker 2: deleterious mutations in their genome because you have this genetic 373 00:22:57,119 --> 00:23:01,640 Speaker 2: drift factor. But then also the normal selection pressures are 374 00:23:01,640 --> 00:23:05,320 Speaker 2: not really applying at all. So once the population is 375 00:23:05,400 --> 00:23:09,120 Speaker 2: reintroduced into the wild, the build up of all these 376 00:23:09,160 --> 00:23:13,640 Speaker 2: deleterious mutations acquired through genetic drift can be quite harsh, 377 00:23:13,680 --> 00:23:17,320 Speaker 2: and they say that this could explain some examples of 378 00:23:17,960 --> 00:23:22,920 Speaker 2: basically poor performance of captive bread individuals of endangered species 379 00:23:22,960 --> 00:23:24,760 Speaker 2: after being released into the wild. 380 00:23:26,000 --> 00:23:28,720 Speaker 1: Yeah, there are so many factors to take into account 381 00:23:28,760 --> 00:23:31,879 Speaker 1: with captive populations, because on top of everything you just 382 00:23:31,920 --> 00:23:35,359 Speaker 1: talked about, there's also the idea that some species will 383 00:23:35,400 --> 00:23:40,679 Speaker 1: just then spontaneously asexually produce offspring, which of course is 384 00:23:40,720 --> 00:23:42,639 Speaker 1: not going to that particular offspring is not going to 385 00:23:42,640 --> 00:23:48,440 Speaker 1: be genetically diversified either, So yeah, you have this huge 386 00:23:48,480 --> 00:23:49,840 Speaker 1: bottleneck potential there. 387 00:23:50,080 --> 00:23:52,600 Speaker 2: One last thing from that book. The most common citations 388 00:23:52,640 --> 00:23:56,760 Speaker 2: I see for the theoretical work on mutational meltdown are 389 00:23:56,920 --> 00:24:01,280 Speaker 2: attributed to papers by Lynch published in the nineties, in 390 00:24:01,320 --> 00:24:05,560 Speaker 2: the nineteen nineties, but they do note also in this 391 00:24:05,600 --> 00:24:09,119 Speaker 2: book chapter that there have been some studies that looked 392 00:24:09,160 --> 00:24:11,719 Speaker 2: for so that's the theoretical work by Lynch, but there 393 00:24:11,720 --> 00:24:14,040 Speaker 2: were some studies that looked to try to find evidence 394 00:24:14,760 --> 00:24:18,840 Speaker 2: of what they call greater genetic loads, these accumulations of 395 00:24:18,960 --> 00:24:25,920 Speaker 2: mutations in small fruitfly populations. This was cited to Giligan 396 00:24:26,000 --> 00:24:28,760 Speaker 2: at all in two thousand and five, and they didn't 397 00:24:28,760 --> 00:24:32,200 Speaker 2: find it. They didn't find evidence of these of these 398 00:24:32,280 --> 00:24:36,600 Speaker 2: loads they expected. So I guess some questions about how 399 00:24:36,640 --> 00:24:39,879 Speaker 2: the theory of mutational meltdown actually applies to populations in 400 00:24:39,920 --> 00:24:40,399 Speaker 2: the wild. 401 00:24:40,760 --> 00:24:44,159 Speaker 1: Yeah, yeah, it's my understanding that, Yeah, we are dealing 402 00:24:44,160 --> 00:24:48,720 Speaker 1: with theories here, and there is a continued challenge for 403 00:24:49,080 --> 00:24:53,160 Speaker 1: evolutionary biologies to find examples and potential examples of all 404 00:24:53,200 --> 00:24:55,720 Speaker 1: of this and to define these breakthrough examples. It will 405 00:24:55,760 --> 00:25:00,080 Speaker 1: help us better understand not only this whole question of 406 00:25:00,160 --> 00:25:03,040 Speaker 1: potential mutational meltdown, but also just sort of the larger 407 00:25:03,160 --> 00:25:08,159 Speaker 1: question again of like why is sexual reproduction more beneficial 408 00:25:08,600 --> 00:25:11,480 Speaker 1: or seemingly more beneficial, like why sexual reproduction at all? 409 00:25:11,640 --> 00:25:14,960 Speaker 1: But anyway, as I understand it, based on what we're 410 00:25:15,000 --> 00:25:18,600 Speaker 1: looking at here, we have Mueller's ratchet, which is the 411 00:25:18,600 --> 00:25:24,640 Speaker 1: theoretical process that then could bring us to this end 412 00:25:24,680 --> 00:25:29,520 Speaker 1: game of mutational meltdown. Mutational meltdown in this regard would 413 00:25:29,520 --> 00:25:34,240 Speaker 1: be considered a subclass of an extinction vortex. Extinction vortex 414 00:25:34,359 --> 00:25:40,359 Speaker 1: is a larger classification, entailing different environmental, genetic, and demographic factors. 415 00:25:41,240 --> 00:25:44,880 Speaker 1: It's also worth noting and perhaps inflating the obvious here, 416 00:25:45,080 --> 00:25:48,120 Speaker 1: and that is that extinction is in the long term inevitable. 417 00:25:48,240 --> 00:25:51,959 Speaker 1: All species eventually face extinction, and I've read that something 418 00:25:52,080 --> 00:25:54,399 Speaker 1: like more than ninety nine percent of all species to 419 00:25:54,440 --> 00:25:58,040 Speaker 1: ever exist have gone extinct. Again, this is stuff that 420 00:25:58,359 --> 00:26:00,480 Speaker 1: makes perfect sense when you spell it out, but also 421 00:26:00,480 --> 00:26:03,680 Speaker 1: it can it can sort of mess with your short 422 00:26:03,840 --> 00:26:07,879 Speaker 1: term of short, short lived human brain when you start 423 00:26:07,920 --> 00:26:12,520 Speaker 1: again thinking about the really long term history of life 424 00:26:12,520 --> 00:26:15,600 Speaker 1: on Earth. So, of course, one of the big obvious 425 00:26:15,720 --> 00:26:18,399 Speaker 1: challenges to exploring all of this is that humans have 426 00:26:18,440 --> 00:26:21,280 Speaker 1: only been around on Earth and in a position to 427 00:26:21,359 --> 00:26:25,359 Speaker 1: look for examples of things like mutational meltdown for a 428 00:26:25,480 --> 00:26:30,560 Speaker 1: very short period of time. And if most asexual species 429 00:26:30,760 --> 00:26:35,040 Speaker 1: or populations don't last very long, do you know, theoretically 430 00:26:35,119 --> 00:26:38,480 Speaker 1: to Muller's ratchet or to you know, the stability of 431 00:26:38,760 --> 00:26:42,600 Speaker 1: sexual reproduction outline and things like the red queen hypothesis. 432 00:26:42,880 --> 00:26:46,879 Speaker 1: Then the various examples of ancient asexual species that we 433 00:26:46,960 --> 00:26:50,400 Speaker 1: have that are more easy to you know, to look to, 434 00:26:50,480 --> 00:26:52,840 Speaker 1: those are going to be exceptions to the rule. And 435 00:26:52,880 --> 00:26:56,680 Speaker 1: then this creates additional additional questions arise, well, how has 436 00:26:56,720 --> 00:27:02,040 Speaker 1: this asexual species been able to revive these challenges, these 437 00:27:02,119 --> 00:27:05,760 Speaker 1: rigors that we're identifying in the data here. And you know, 438 00:27:05,800 --> 00:27:08,320 Speaker 1: one of the sources I was looking at two thousand 439 00:27:08,320 --> 00:27:11,280 Speaker 1: and eights quantifying the threat of extinction from Mueller's ratchet 440 00:27:11,560 --> 00:27:15,200 Speaker 1: in the diploid Amazon molli. This is from Low and Lamach. 441 00:27:16,280 --> 00:27:18,720 Speaker 1: They point out that, yeah, these species are of considerable 442 00:27:18,720 --> 00:27:22,000 Speaker 1: interest to researchers for these very reasons. 443 00:27:22,640 --> 00:27:24,200 Speaker 2: That would be the Amazon molli. 444 00:27:25,680 --> 00:27:29,000 Speaker 1: Well, just in general these sorts of species species that. 445 00:27:29,280 --> 00:27:32,160 Speaker 2: Oh I see, yeah, ancient asexual species. 446 00:27:32,200 --> 00:27:35,320 Speaker 1: Sorry, right, in this particular paper, this particular paper that 447 00:27:35,480 --> 00:27:38,400 Speaker 1: the main focus the Amazon Mollie, though, is also really interesting. 448 00:27:38,480 --> 00:27:42,840 Speaker 1: This is a small asexual fish species that seems just 449 00:27:42,960 --> 00:27:47,520 Speaker 1: prime for mutational meltdown. However, in modeling out the rate 450 00:27:47,560 --> 00:27:51,560 Speaker 1: of harmful mutations in the species, they ran into what 451 00:27:51,640 --> 00:27:54,640 Speaker 1: they referred to in the paper as a genomic decay paradox. 452 00:27:55,119 --> 00:27:58,439 Speaker 1: So in most of the models they ran, the expected 453 00:27:58,520 --> 00:28:02,440 Speaker 1: time to extinction for them species was less than previous 454 00:28:02,560 --> 00:28:05,399 Speaker 1: estimates on the age of the species, So it would 455 00:28:05,400 --> 00:28:10,800 Speaker 1: seem that the species has outlived its genomic expiration date 456 00:28:11,800 --> 00:28:18,840 Speaker 1: if Mueller's ratchet and mutational meltdown is indeed a factor 457 00:28:19,280 --> 00:28:23,399 Speaker 1: the author's right quote, several biological processes can individually or 458 00:28:23,400 --> 00:28:27,960 Speaker 1: in combination solve this genomic decay paradox, including paternal leakage 459 00:28:28,000 --> 00:28:32,919 Speaker 1: of undamaged DNA from sexual sister species, compensatory mutations, and 460 00:28:33,000 --> 00:28:35,960 Speaker 1: many others, and they of course conclude that more research 461 00:28:36,080 --> 00:28:40,240 Speaker 1: is ultimately required. Another paper that looks into all this 462 00:28:40,320 --> 00:28:44,720 Speaker 1: that I found quite interesting was Deleterious mutation Accumulation in 463 00:28:44,800 --> 00:28:49,160 Speaker 1: asexual tymema stick Insects by Henry at All, published in 464 00:28:49,240 --> 00:28:53,680 Speaker 1: twenty twelve in Molecular Biology and Evolution. In this paper, 465 00:28:53,720 --> 00:28:59,360 Speaker 1: the researchers look at six independently derived asexual lineages and 466 00:28:59,440 --> 00:29:04,680 Speaker 1: related sexual species of the temma stick insects. So we're 467 00:29:04,680 --> 00:29:09,160 Speaker 1: talking about closely related species, some that reproduce sexually and 468 00:29:09,240 --> 00:29:12,680 Speaker 1: others that reproduce asexually. The idea here, of course, is 469 00:29:12,720 --> 00:29:16,120 Speaker 1: the closeness. They're the related closely related to each other, 470 00:29:16,360 --> 00:29:20,760 Speaker 1: so this would make the accumulation of deletarious mutations stand 471 00:29:20,760 --> 00:29:25,240 Speaker 1: out more in the asexual species versus the sexual species, 472 00:29:25,720 --> 00:29:28,840 Speaker 1: and that seems to be what they found. Quote we 473 00:29:28,920 --> 00:29:32,880 Speaker 1: found signatures of increased coding mutation accumulation in all six 474 00:29:33,320 --> 00:29:37,560 Speaker 1: asexual tymema and for each of the three analyzed genes, 475 00:29:38,040 --> 00:29:41,200 Speaker 1: with three point six to thirteen point four fold higher 476 00:29:41,280 --> 00:29:45,640 Speaker 1: rates in the asexuals as compared with the sexuals. They 477 00:29:45,680 --> 00:29:48,760 Speaker 1: also point out that the coding mutations and the asexuals 478 00:29:48,800 --> 00:29:53,160 Speaker 1: are likely associated with more strongly deletarious effects than the 479 00:29:53,200 --> 00:29:57,440 Speaker 1: sexuals due to some specific molecular reasons that they outline 480 00:29:57,440 --> 00:30:02,120 Speaker 1: in the article. They conclude that quote deletarious mutation accumulation 481 00:30:02,360 --> 00:30:07,239 Speaker 1: can differentially affect sexual and asexual lineages and support the 482 00:30:07,280 --> 00:30:11,600 Speaker 1: idea that deletarious mutation accumulation plays an important role in 483 00:30:11,680 --> 00:30:15,160 Speaker 1: limiting the long term persistence of all female lineages. 484 00:30:15,640 --> 00:30:18,720 Speaker 2: So, according to this, as we were alluding to earlier, 485 00:30:19,360 --> 00:30:24,000 Speaker 2: a species that's mainly reproducing or totally reproducing asexually and 486 00:30:24,080 --> 00:30:28,440 Speaker 2: just making clonal copies will will tend to one of 487 00:30:28,480 --> 00:30:32,320 Speaker 2: the pressures acting against it will be the tendency to 488 00:30:32,520 --> 00:30:36,760 Speaker 2: build up loads of mutations that are not helpful to survival. 489 00:30:37,200 --> 00:30:40,760 Speaker 1: Yeah, so, over time, worse mutations accumulate in the asexual 490 00:30:40,760 --> 00:30:44,480 Speaker 1: species who do not diversify via sexual recombination. They don't 491 00:30:44,520 --> 00:30:50,200 Speaker 1: purify through purging harmful mutations via sexual reproduction either, And 492 00:30:50,520 --> 00:30:53,880 Speaker 1: in fact, the authors here specifically mentioned that sexual reproduction 493 00:30:54,080 --> 00:30:59,520 Speaker 1: enhances the efficiency of purifying selection. This is fascinating. I'm 494 00:30:59,600 --> 00:31:01,760 Speaker 1: in certain the authors are not arguing that this is 495 00:31:01,800 --> 00:31:03,280 Speaker 1: the case, but it's obviously this is not like a 496 00:31:03,280 --> 00:31:07,040 Speaker 1: smoking gun for the whole idea here, but it does 497 00:31:07,080 --> 00:31:11,680 Speaker 1: seem to to give us some some some interesting evidence 498 00:31:11,760 --> 00:31:14,240 Speaker 1: to back up some of these ideas, though of course 499 00:31:14,280 --> 00:31:17,440 Speaker 1: also raising additional questions about you know, what exactly is 500 00:31:17,480 --> 00:31:30,040 Speaker 1: going on. Now, there's a I've mentioned ted Ad before. 501 00:31:30,080 --> 00:31:33,920 Speaker 1: There's a great ted AD video titled no Sex, No Problem, 502 00:31:34,400 --> 00:31:37,560 Speaker 1: and I highly recommend checking that out. It does a 503 00:31:37,640 --> 00:31:41,560 Speaker 1: nice overview of sort of the different the different strategies 504 00:31:41,560 --> 00:31:45,760 Speaker 1: of asexual versus sexual reproduction, and and and briefly mentioned 505 00:31:45,760 --> 00:31:48,680 Speaker 1: some of the concepts we're talking about here. Uh. One 506 00:31:48,720 --> 00:31:50,760 Speaker 1: thing that I thought I thought was interesting in this 507 00:31:50,920 --> 00:31:53,240 Speaker 1: videos it points out that pa fits are a great 508 00:31:53,280 --> 00:31:58,840 Speaker 1: example of an organism that utilizes both sexual reproduction and 509 00:31:58,880 --> 00:32:04,920 Speaker 1: asexual reproduction. Uh Uh, but depending on what the circumstances are. 510 00:32:05,440 --> 00:32:09,880 Speaker 1: So with these particular eight, it's when it's springtime. They 511 00:32:09,920 --> 00:32:13,240 Speaker 1: are a sexual reproducers. So it's like it's this is 512 00:32:13,320 --> 00:32:16,560 Speaker 1: the these are the fat times, Like it's it's time to feed, 513 00:32:16,640 --> 00:32:18,800 Speaker 1: it's time to reproduce. It's not time to worry too 514 00:32:18,880 --> 00:32:23,040 Speaker 1: much about, you know, differentiating your product. It's about just 515 00:32:23,080 --> 00:32:26,040 Speaker 1: getting product on the shelves. And so that's what they do. 516 00:32:27,160 --> 00:32:29,640 Speaker 1: But then when autumn rolls around, then it's time for 517 00:32:29,720 --> 00:32:32,320 Speaker 1: sexual reproduction. So it's like, Okay, this is our time 518 00:32:32,400 --> 00:32:34,960 Speaker 1: to to think about the product. This is our time 519 00:32:35,040 --> 00:32:38,400 Speaker 1: to to get experimental and see what we can do 520 00:32:38,760 --> 00:32:42,280 Speaker 1: to change up our offering for the next season. So 521 00:32:42,440 --> 00:32:45,600 Speaker 1: I thought that was just a really really interesting, like 522 00:32:45,680 --> 00:32:50,520 Speaker 1: single species example that kind of sums up some of 523 00:32:50,560 --> 00:32:54,200 Speaker 1: the benefits and some of the costs involved with asexual 524 00:32:54,320 --> 00:32:57,719 Speaker 1: versus sexual reproduction, Like this is not the It's kind 525 00:32:57,760 --> 00:32:59,800 Speaker 1: of like when you think about films in a series, 526 00:32:59,840 --> 00:33:02,360 Speaker 1: for example, when it's time to make Wrong Turn two, 527 00:33:02,800 --> 00:33:04,800 Speaker 1: you're not necessarily thinking about, well, how am I going 528 00:33:04,880 --> 00:33:07,160 Speaker 1: to recreate? No, you don't recreate. You just do what 529 00:33:07,320 --> 00:33:10,560 Speaker 1: worked the first time, accept more of it. This is 530 00:33:10,600 --> 00:33:14,360 Speaker 1: the springtime of the Wrong Term franchise. Much later, when 531 00:33:14,400 --> 00:33:16,400 Speaker 1: it's run out of gas, that's when you can you 532 00:33:16,440 --> 00:33:18,520 Speaker 1: can sit down and think, Yeah, that's when you can 533 00:33:18,560 --> 00:33:20,840 Speaker 1: be like, how do we reanalyze this, how do we 534 00:33:21,240 --> 00:33:25,000 Speaker 1: reconceptualize Wrong Turn for a new audience? And maybe we 535 00:33:25,000 --> 00:33:26,600 Speaker 1: can hire Matthew Modine to be in. 536 00:33:26,560 --> 00:33:29,200 Speaker 2: It too, And it makes sense they both be part 537 00:33:29,200 --> 00:33:32,000 Speaker 2: of your content strategy, you know. Sometimes you do reruns, 538 00:33:32,000 --> 00:33:33,640 Speaker 2: sometimes you do a crossover event. 539 00:33:34,200 --> 00:33:37,400 Speaker 1: Yeah, no, I haven't actually seen a Wrong Turn movie, 540 00:33:37,440 --> 00:33:40,160 Speaker 1: so please don't go out and see these movies just 541 00:33:40,200 --> 00:33:41,920 Speaker 1: based on me casually mentioning them. 542 00:33:41,960 --> 00:33:46,400 Speaker 2: Here Rob wrongly recommends the Wrong Turn franchise. I can't 543 00:33:46,440 --> 00:33:48,360 Speaker 2: remember if I have or not. Is it is that 544 00:33:48,480 --> 00:33:50,680 Speaker 2: the one there's like a guy in a muscle car 545 00:33:50,720 --> 00:33:52,960 Speaker 2: who drives into the woods and then they meets some 546 00:33:53,440 --> 00:33:55,280 Speaker 2: I don't know, some people and they get chased by 547 00:33:55,680 --> 00:33:56,640 Speaker 2: dudes with hatchets. 548 00:33:57,240 --> 00:33:59,840 Speaker 1: That sounds likely. I think that it's basically it's the 549 00:34:00,040 --> 00:34:02,560 Speaker 1: Hills have Eyes except in the woods. And there's like 550 00:34:02,600 --> 00:34:05,520 Speaker 1: a million of these films. It's one of there's something 551 00:34:05,520 --> 00:34:07,560 Speaker 1: always kind of alarming to me when I realized there's 552 00:34:07,640 --> 00:34:11,680 Speaker 1: like a whole franchise that has been around for years 553 00:34:11,680 --> 00:34:14,040 Speaker 1: and years and I just not only have I not 554 00:34:14,120 --> 00:34:15,960 Speaker 1: seen them, but I just have just a very surface 555 00:34:16,040 --> 00:34:19,280 Speaker 1: level understanding of what they're about, you know, like I've 556 00:34:19,360 --> 00:34:22,239 Speaker 1: maybe never even seen a trailer for one of them. 557 00:34:22,680 --> 00:34:24,440 Speaker 2: Yeah, there are a lot of series like that, and 558 00:34:25,680 --> 00:34:28,120 Speaker 2: I understand what you mean, like it can be alarming, Like, oh, 559 00:34:28,160 --> 00:34:31,760 Speaker 2: I didn't even see the first Purge. We're Unpurged nine 560 00:34:31,920 --> 00:34:34,160 Speaker 2: now this is Yeah, I don't know what's going on. 561 00:34:35,120 --> 00:34:37,400 Speaker 2: I kind of can't start at this point. I'm not 562 00:34:37,440 --> 00:34:38,480 Speaker 2: going to see these movies. 563 00:34:38,960 --> 00:34:42,239 Speaker 1: Yeah, the Purge franchise, which I haven't seen any of 564 00:34:42,280 --> 00:34:45,160 Speaker 1: those either, but I've read a bit more about them, 565 00:34:45,200 --> 00:34:48,239 Speaker 1: so I'm kind of intrigued by the way it has 566 00:34:48,440 --> 00:34:51,600 Speaker 1: survived thus far. It seems like it is a franchise 567 00:34:51,640 --> 00:34:55,520 Speaker 1: that definitely has its springtime and autumn cycles of how 568 00:34:55,600 --> 00:34:58,359 Speaker 1: it puts out new content. Like some of these seem 569 00:34:58,440 --> 00:35:00,960 Speaker 1: like definite, like okay, it's time for their Purge, and 570 00:35:00,960 --> 00:35:03,080 Speaker 1: then other times it's like, what can we do different 571 00:35:03,160 --> 00:35:05,359 Speaker 1: with the Purge this time? And then it's like cut 572 00:35:05,360 --> 00:35:07,879 Speaker 1: that we're doing a TV series, so just like tend 573 00:35:07,920 --> 00:35:11,160 Speaker 1: the Purges and then we'll work about innovating after that. 574 00:35:11,880 --> 00:35:15,680 Speaker 2: I like that you have read about the Purge. I 575 00:35:15,760 --> 00:35:18,360 Speaker 2: haven't seen it, but you've done some research. 576 00:35:19,040 --> 00:35:21,520 Speaker 1: Well, you know, it feels like it has more of 577 00:35:21,560 --> 00:35:24,600 Speaker 1: a you know, you got to stay on top of culture, 578 00:35:24,960 --> 00:35:26,880 Speaker 1: so you got to read about the Purge, whereas somehow 579 00:35:27,200 --> 00:35:31,440 Speaker 1: Wrong Turn movies maybe were less important culturally, or so 580 00:35:31,520 --> 00:35:32,120 Speaker 1: it seems to me. 581 00:35:32,520 --> 00:35:35,160 Speaker 2: Wrong Turn movies, i'd say, are less high concept because 582 00:35:35,239 --> 00:35:39,200 Speaker 2: Purge has an elevator pitch right there, unless I misunderstand 583 00:35:39,400 --> 00:35:41,960 Speaker 2: the idea is all crime is legal on one night. 584 00:35:42,320 --> 00:35:45,760 Speaker 1: Yeah yeah, okay, so, and I think it lends itself 585 00:35:46,040 --> 00:35:48,680 Speaker 1: well to referencing. You can be like, oh wow, I 586 00:35:48,800 --> 00:35:50,920 Speaker 1: tried to drive across town the other day and it 587 00:35:50,960 --> 00:35:52,759 Speaker 1: was like the Purge out there. You know, that makes 588 00:35:52,960 --> 00:35:55,319 Speaker 1: sense It's like you're saying something about how bad traffic was. 589 00:35:55,360 --> 00:35:58,400 Speaker 1: But I don't know, wrong turn franchises maybe just a 590 00:35:58,480 --> 00:36:02,080 Speaker 1: little harder to, you know, bring into your daily life. 591 00:36:02,480 --> 00:36:05,120 Speaker 2: I guess some organisms also have more of an elevator 592 00:36:05,160 --> 00:36:08,879 Speaker 2: pitch quality to them, though, you know, like the platypus. 593 00:36:09,280 --> 00:36:11,800 Speaker 2: It is, it is a furry, poisonous. 594 00:36:11,360 --> 00:36:15,120 Speaker 1: Duck, but it's also kind of high concept. 595 00:36:16,280 --> 00:36:18,760 Speaker 2: Yeah, that's what I'm saying. Yeah, it's high concept. 596 00:36:19,160 --> 00:36:21,399 Speaker 1: Yeah, good creature. Have we ever done an episode on 597 00:36:21,480 --> 00:36:24,919 Speaker 1: the platypus? I can't recall. Of course, it's diversified enough 598 00:36:24,960 --> 00:36:28,920 Speaker 1: that it's inevitably come up, at least in passing in 599 00:36:28,960 --> 00:36:30,120 Speaker 1: any number of episodes. 600 00:36:30,400 --> 00:36:32,240 Speaker 2: I don't know if we have. I just really I said, 601 00:36:32,360 --> 00:36:35,560 Speaker 2: I said poisonous, but I think the correct word would 602 00:36:35,560 --> 00:36:36,400 Speaker 2: be venomous. 603 00:36:37,800 --> 00:36:38,160 Speaker 1: I don't know. 604 00:36:38,160 --> 00:36:39,399 Speaker 2: We'll have to sort that out later. 605 00:36:39,800 --> 00:36:41,960 Speaker 1: All right. Well, on on that note, I think we 606 00:36:42,080 --> 00:36:46,960 Speaker 1: have we have reached mutational meltdown for this episode. But 607 00:36:47,239 --> 00:36:49,040 Speaker 1: we'd love to hear from everyone out there. I mean, 608 00:36:49,160 --> 00:36:52,839 Speaker 1: especially if there's anyone out there who who is in 609 00:36:52,880 --> 00:36:57,360 Speaker 1: the field of evolutionary biology. Perhaps you have some additional feedback, 610 00:36:57,640 --> 00:37:00,880 Speaker 1: additional examples, you'd like to bring to mind. Let us know. 611 00:37:00,960 --> 00:37:04,480 Speaker 1: You know, this is a topic that that caught my attention, 612 00:37:04,760 --> 00:37:08,040 Speaker 1: but I'd love to see some more data on it. 613 00:37:08,120 --> 00:37:10,719 Speaker 1: I'd love to see some more studies of note. In 614 00:37:10,760 --> 00:37:13,359 Speaker 1: the meantime, will remind you that Stuff Blow your Mind 615 00:37:13,440 --> 00:37:16,880 Speaker 1: is primarily a science podcast, with core episodes on Tuesdays 616 00:37:16,880 --> 00:37:20,040 Speaker 1: and Thursdays. On Mondays we do listener mail, On Wednesdays 617 00:37:20,080 --> 00:37:23,040 Speaker 1: we do a short form artifact or monster fact, and 618 00:37:23,080 --> 00:37:25,480 Speaker 1: on Fridays we set aside most serious concerns to just 619 00:37:25,520 --> 00:37:27,640 Speaker 1: talk about a weird film on Weird House Cinema. That's 620 00:37:27,719 --> 00:37:31,640 Speaker 1: usually where our discussions of films about mutants would wind up, 621 00:37:32,960 --> 00:37:38,240 Speaker 1: but sometimes those mutations accumulate in the core episodes as well. 622 00:37:38,640 --> 00:37:41,920 Speaker 2: Huge thanks to our audio producer JJ Posway. If you 623 00:37:41,960 --> 00:37:44,040 Speaker 2: would like to get in touch with us with feedback 624 00:37:44,080 --> 00:37:46,440 Speaker 2: on this episode or any other, to suggest topic for 625 00:37:46,480 --> 00:37:48,680 Speaker 2: the future, or just to say hello, you can email 626 00:37:48,760 --> 00:37:59,600 Speaker 2: us at contact stuff to Blow your Mind dot com. 627 00:38:00,080 --> 00:38:02,200 Speaker 1: Blow your Mind is production of iHeartRadio. 628 00:38:02,520 --> 00:38:06,520 Speaker 2: For more podcasts from iHeartRadio, visit the iHeartRadio app, Apple Podcasts, 629 00:38:06,600 --> 00:38:22,400 Speaker 2: or wherever you're listening to your favorite shows.