WEBVTT - From the Vault: Eternal Youth, Part 2 0:00:05.840 --> 0:00:07.680 Hey, you welcome to Stuff to blow your mind. My 0:00:07.760 --> 0:00:10.600 name is Robert Lamb and I'm Joe McCormick, and it's Saturday. 0:00:10.640 --> 0:00:14.000 Time to go into the vault for Eternal Youth Part two. 0:00:14.120 --> 0:00:16.720 If you checked us out last Saturday, it was Eternal 0:00:16.760 --> 0:00:18.880 Youth Part one. This is going to be the second 0:00:18.920 --> 0:00:22.960 part of that series. This originally published January. Should we 0:00:23.000 --> 0:00:25.000 get right into it. Yeah, let's just belly right up 0:00:25.040 --> 0:00:27.360 to the bar and have a drink from the Fountain 0:00:27.360 --> 0:00:33.680 of Youth. Welcome to stuff to blow your mind from 0:00:33.680 --> 0:00:42.280 how stuff weren't dot Com? Hey, you, welcome to stuff 0:00:42.320 --> 0:00:44.599 to blow your mind. My name is Robert Lamb and 0:00:44.640 --> 0:00:46.879 I'm Joe McCormick, and we're back for part two of 0:00:46.920 --> 0:00:50.720 our discussion about where's my eternal youth? Why can't I 0:00:50.880 --> 0:00:54.680 be young and beautiful forever? Why do we age? I 0:00:54.720 --> 0:00:57.120 know that's the It's the question we've always wondered. It 0:00:57.440 --> 0:01:01.360 shows up in our philosophical writings, it shows up in 0:01:01.480 --> 0:01:05.600 our religion, our mythology. Uh. In researching this topic, I 0:01:05.680 --> 0:01:08.919 kept thinking back to Genesis six three. This is the 0:01:09.000 --> 0:01:12.200 King James version, and the Lord said, my spirit shall 0:01:12.240 --> 0:01:16.440 not always strive with man for that he is also flesh, 0:01:16.600 --> 0:01:20.160 yet his days shall be a hundred and twenty years. 0:01:20.920 --> 0:01:25.560 So there's God putting a limit on how old a 0:01:25.640 --> 0:01:29.840 human can become and saying like, here's the aging process. Uh, 0:01:29.880 --> 0:01:33.640 these are the rules. Obviously doesn't apply to Highlanders. That's right. Well, 0:01:33.680 --> 0:01:36.160 you know, maybe they're they're part of the giants in 0:01:36.160 --> 0:01:38.320 the Earth or something. I don't know, Oh that could be. Yeah, 0:01:38.319 --> 0:01:41.679 I guess they're not humans. So well, the spoiler for 0:01:41.760 --> 0:01:45.759 Highlander to certain cuts, they are not from Earth right 0:01:46.240 --> 0:01:49.200 in the good cuts from Earth. Yet again, we're just 0:01:49.240 --> 0:01:52.200 trying to throw those seeds down. Highlander two episode it's 0:01:52.240 --> 0:01:55.560 coming now. Speaking of parts one and two, this episode 0:01:55.680 --> 0:01:57.880 is a part two. Yeah, so if you haven't listened 0:01:57.880 --> 0:01:59.440 to part one yet, you should go back check that 0:01:59.480 --> 0:02:02.880 out first. And that we explored the question of why 0:02:02.920 --> 0:02:06.360 we age. We look at some animals that don't really 0:02:06.400 --> 0:02:09.080 age in the same way that humans and other similar 0:02:09.120 --> 0:02:14.000 mammals do, and we look at historical explanations people have 0:02:14.040 --> 0:02:17.040 tried to come up with for why we age, and 0:02:17.080 --> 0:02:20.000 we also explored some reasons to think that those historical 0:02:20.080 --> 0:02:22.480 explanations were not correct. Today, we're going to try to 0:02:22.480 --> 0:02:28.960 get into the modern evolutionary synthesis, take on why we age? 0:02:29.000 --> 0:02:32.080 What's happening and how do you solve this paradox of 0:02:32.200 --> 0:02:35.880 the fact that aging is a decline over time in 0:02:35.960 --> 0:02:40.280 our survival and reproduction fitness, and yet evolution should be 0:02:40.320 --> 0:02:44.440 constantly optimizing our survival and reproduction fitness. Why would it 0:02:44.480 --> 0:02:47.280 allow us to go into this period where we tend 0:02:47.320 --> 0:02:50.680 to die and tend to get worse at surviving and 0:02:50.720 --> 0:02:53.919 tend to not be able to reproduce anymore. Indeed, because 0:02:54.200 --> 0:02:57.720 I certainly don't want to deify natural selection and say 0:02:57.760 --> 0:03:02.440 that like natural selection produces perfect forms or ideal forms, 0:03:02.480 --> 0:03:05.119 But look at the forms the natural selection has produced, 0:03:05.280 --> 0:03:09.920 Look at all the various engineering problems that that that 0:03:10.000 --> 0:03:12.840 evolution has managed to solve. Why would there be this 0:03:13.120 --> 0:03:16.800 be this huge, at least from our perspective, flaw in 0:03:16.880 --> 0:03:19.440 the design. Yeah. Now, of course, today, as we often 0:03:19.480 --> 0:03:22.359 do with evolution, just for the ease of communication, we're 0:03:22.360 --> 0:03:24.600 going to be using a lot of metaphors that offer 0:03:24.639 --> 0:03:28.240 a kind of like embodied view of evolution, as if 0:03:28.320 --> 0:03:31.040 like it's making choices. What we, of course know is 0:03:31.080 --> 0:03:35.560 that evolution is a is an optimization algorithm. It's not 0:03:35.640 --> 0:03:37.960 a person. It's not a thing. It doesn't really have 0:03:38.120 --> 0:03:40.800 desires of it of its own. It has a way 0:03:40.840 --> 0:03:43.480 that it works, and the way that it works is 0:03:43.560 --> 0:03:48.160 to optimize the success of genes that survived natural selection 0:03:48.200 --> 0:03:51.080 and reproduce. Now, one of the answers we explored in 0:03:51.120 --> 0:03:54.880 the last episode is one of the most common things 0:03:54.920 --> 0:03:56.840 people are going to turn to when they're trying to 0:03:56.880 --> 0:03:59.600 explain why we age. It's the thing that my brain 0:03:59.680 --> 0:04:03.200 and immediately went to before I read anything on this subject. 0:04:03.720 --> 0:04:07.320 I started to think, well, let's see, if everybody just 0:04:07.440 --> 0:04:13.040 lived forever and nobody naturally aged out and died, then 0:04:13.160 --> 0:04:16.560 you'd have way too much competition for resources, right, You'd 0:04:16.560 --> 0:04:19.440 have way too many people trying to live on the 0:04:19.480 --> 0:04:21.880 same landscape, you have too many people trying to eat 0:04:21.960 --> 0:04:25.400 from the same food sources. You'd have overpopulation, and and 0:04:25.480 --> 0:04:28.640 everybody would suffer for it. Overpopulation ties into a number 0:04:28.680 --> 0:04:31.520 of our different dystopian views of the future, as does 0:04:31.560 --> 0:04:35.440 the possibility of immortality becoming an option at least a 0:04:35.440 --> 0:04:38.200 certain privileged people in society. You know, you get this 0:04:38.240 --> 0:04:44.400 sort of trope of the awful uh Methuselah of the future. Right, 0:04:44.480 --> 0:04:49.279 some just dreary, old, greedy individual who will not die 0:04:49.640 --> 0:04:52.279 and let go the reins of life so that others 0:04:52.320 --> 0:04:54.679 may grasp it. Right, Well, as much as we don't 0:04:54.760 --> 0:04:57.400 personally want to grow old and die, you can sort 0:04:57.400 --> 0:05:00.440 of recognize from an impartial standpoint, if you just consider 0:05:00.480 --> 0:05:03.400 it in other people, that it seems kind of unfair 0:05:03.440 --> 0:05:06.640 that people should live forever, right, Yeah, unless it's me 0:05:06.880 --> 0:05:09.960 or someone that I'm invested, and there they should put 0:05:09.960 --> 0:05:12.520 a limit on that stuff. Yeah. So, but these types 0:05:12.560 --> 0:05:15.960 of answers, while true, it is true that it's good 0:05:16.000 --> 0:05:18.720 for the species that we should age and die, and 0:05:18.760 --> 0:05:22.479 that it's good for future generations. Uh, good of the 0:05:22.560 --> 0:05:26.200 species and good of the group based explanations come under 0:05:26.240 --> 0:05:30.680 a lot of fire from evolutionary biologists. There's some biologists 0:05:30.680 --> 0:05:33.680 to endorse kind of qualified versions of of good of 0:05:33.760 --> 0:05:36.800 the group and good of the species type explanations, but 0:05:36.839 --> 0:05:39.640 there I think many more who don't. And here's an 0:05:39.680 --> 0:05:43.080 example to illustrate one of the big problems in why 0:05:43.200 --> 0:05:46.200 these good of the group explanations fail to hold up. 0:05:46.560 --> 0:05:49.279 All right, hit me with it, Okay, Let's imagine a 0:05:49.320 --> 0:05:52.719 pack of alien space wolves. Okay, and for our warhammer 0:05:52.760 --> 0:05:56.560 for fans out there. He's not talking about space marines here. Wait, 0:05:56.600 --> 0:05:58.720 I don't know what space will Is that a thing? Yeah, 0:05:58.720 --> 0:06:02.160 it's a faction of the space Marines. In the Warhammer 0:06:02.200 --> 0:06:06.120 Fort K universe, there are wolves. Well, no, they well 0:06:06.120 --> 0:06:09.360 they wear wolf skins and they're you know, genetically enhanced 0:06:09.400 --> 0:06:12.880 super soldiers. Okay, so it would really complicate them the 0:06:13.400 --> 0:06:16.000 analogy you're making here, if if we were to draw 0:06:16.040 --> 0:06:17.800 them into the discussion. Well, I was just trying to 0:06:17.839 --> 0:06:20.240 make clear that this is a hypothetical, not like real 0:06:20.279 --> 0:06:23.080 wolves on Earth. Okay, So alien space wolves living on 0:06:23.080 --> 0:06:26.719 an asteroid somewhere in hunting space here. Now, let's imagine 0:06:26.720 --> 0:06:29.680 this pack of alien space wolves has evolved genes that 0:06:29.760 --> 0:06:32.440 cause them to grow old and become infertile after about 0:06:32.480 --> 0:06:35.160 ten years of age, after which you know, they usually 0:06:35.200 --> 0:06:38.400 die within a couple of years. And let's say that 0:06:38.520 --> 0:06:42.000 each female space wolf has an average of one space 0:06:42.040 --> 0:06:46.720 wolf pup every year that she remains fertile. So, unless 0:06:46.760 --> 0:06:49.880 the space wolf is killed by injury or disease or 0:06:49.960 --> 0:06:54.640 a marauding space explorer, um, the average space wolf female 0:06:54.720 --> 0:06:58.840 has tin offspring in her life lifespan. Everybody's happy, right, 0:06:58.880 --> 0:07:00.960 because they don't eat too many of the space dear, 0:07:01.040 --> 0:07:04.640 they don't become overpopulated. It just works out pretty well. 0:07:05.200 --> 0:07:09.440 But then suddenly one of these space wolves acquires a 0:07:09.520 --> 0:07:12.960 mutation that allows her to stay fertile and survive for 0:07:13.080 --> 0:07:18.320 twelve years instead of ten, so she has twelve space 0:07:18.320 --> 0:07:21.320 wolf pups, whereas all the other females in the pack 0:07:21.400 --> 0:07:24.720 are still having ten, and half of her pups carried 0:07:24.720 --> 0:07:28.840 this extended fertility and longevity gene, so those six pups 0:07:28.880 --> 0:07:32.520 each have twelve pups, while non carriers of the gene 0:07:32.520 --> 0:07:35.040 only have ten, and so on and so on down 0:07:35.080 --> 0:07:39.600 the generations, and eventually this cheater gene for extended life 0:07:39.680 --> 0:07:43.480 and extended fertility is going to proliferate, even if it 0:07:43.560 --> 0:07:46.360 might be worse off for everybody in the long run. 0:07:46.440 --> 0:07:50.040 Even if the long living, long reproducing animals have too 0:07:50.040 --> 0:07:53.880 many offspring and consume too many resources and suffer die outs, 0:07:53.920 --> 0:07:58.040 this won't really cause a re selection towards shorter lifespans, 0:07:58.120 --> 0:08:01.480 because how would it. Instead, what it would do is 0:08:01.560 --> 0:08:05.040 optimized for whatever genes are possessed by the survivors of 0:08:05.080 --> 0:08:07.960 those die outs, and that would probably be like those 0:08:08.040 --> 0:08:11.560 that store fat better or hunt better, or can extract 0:08:11.680 --> 0:08:14.880 nutrition from space moss in addition to meat. And this 0:08:14.960 --> 0:08:17.720 is a really common type of argument against good of 0:08:17.800 --> 0:08:20.760 the group and good to the species explanations and evolution, 0:08:20.880 --> 0:08:25.640 because any mutation that cheats on the stasius you've created 0:08:25.760 --> 0:08:28.000 for the good of the group will tend to start 0:08:28.080 --> 0:08:31.440 to get an edge and then have more offspring than 0:08:31.480 --> 0:08:34.440 those who don't cheat, and eventually that new gene will 0:08:34.480 --> 0:08:36.760 become the norm. Right. Yeah, It's kind of like if 0:08:36.800 --> 0:08:40.040 you have a you know, an academic environment where everybody's 0:08:40.080 --> 0:08:42.760 cheating on the exam, the exam, the grading becomes that 0:08:42.840 --> 0:08:46.920 much harder each and every time. It's true. Yeah, it's great. 0:08:47.000 --> 0:08:49.199 So it's like you've got to grade on a curve 0:08:49.240 --> 0:08:53.760 because everybody's cheating, so everybody's grade goes down. Um. Yeah. 0:08:53.840 --> 0:08:56.640 And so I just want to remind you though, this 0:08:56.679 --> 0:08:59.160 doesn't mean that there is not such a thing as 0:08:59.200 --> 0:09:00.880 the good of the group the good of the species. 0:09:00.920 --> 0:09:03.760 Those things clearly are true. And it clearly is true 0:09:03.880 --> 0:09:07.280 that it's good for the next generation that older generations 0:09:07.320 --> 0:09:10.160 age out and die. I care about the survival of 0:09:10.160 --> 0:09:12.640 the rest of my group. I care about members of 0:09:12.679 --> 0:09:15.880 my species and about future generations. But I care because 0:09:15.920 --> 0:09:19.040 I have a brain and I can recognize what's going on. 0:09:19.520 --> 0:09:22.439 Ma genes don't care, and your genes don't care. They 0:09:22.480 --> 0:09:26.920 just chemically proliferate themselves. They don't have a sentimental attachment 0:09:27.080 --> 0:09:30.079 or or an idea that the next generation should get 0:09:30.120 --> 0:09:32.680 resources to. All right, So this just brings us back 0:09:32.760 --> 0:09:37.920 to the question, though, why have we evolved to grow old? Right, 0:09:37.960 --> 0:09:41.679 it's still unsolved. Why not live and reproduce forever, maintaining 0:09:41.760 --> 0:09:46.160 perfect youth and vigor until something extrinsic happens, until we 0:09:46.160 --> 0:09:50.040 get killed by a hemorrhagic fever or tractor accident. All right, 0:09:50.080 --> 0:09:51.680 We're gonna take a quick break and we come back. 0:09:51.800 --> 0:09:57.680 We will answer that very question. Thank alright, we're back, 0:09:57.760 --> 0:10:00.240 all right. So there are a number of modern, well 0:10:00.280 --> 0:10:04.360 accepted scientific theories trying to answer the question of why 0:10:04.520 --> 0:10:08.040 we evolved to age. And here's a starting point for 0:10:08.040 --> 0:10:10.280 several of those theories. Let's go back to the wolves 0:10:10.320 --> 0:10:14.040 for a second. Imagine the space wolves. Maybe a hypothetical 0:10:14.040 --> 0:10:16.840 wolf species could breed and stay healthy until about the 0:10:16.840 --> 0:10:20.199 age of ten, Like we said, why not twenty, Why 0:10:20.240 --> 0:10:23.840 not thirty? Why not five hundred? Well, here are a 0:10:23.840 --> 0:10:28.559 few things to consider. Wolves did not evolve in zoos 0:10:28.880 --> 0:10:33.160 or as domestic pets, where they're guaranteed meals and protection 0:10:33.240 --> 0:10:38.319 from violence and guaranteed access to veterinary care. The landscape 0:10:38.360 --> 0:10:41.600 that created the wolf as it exists is one in 0:10:41.640 --> 0:10:44.840 which there is a constant struggle to get enough meat 0:10:44.880 --> 0:10:48.080 to survive and to not get sick and die, and 0:10:48.120 --> 0:10:50.840 to not get injured and become unable to hunt, so 0:10:50.880 --> 0:10:53.520 you starve. If you are a wolf living in the 0:10:53.559 --> 0:10:56.360 wild and you survived the first year of your life, 0:10:56.559 --> 0:11:00.440 one of these things like injury or disease or star ovation, 0:11:01.240 --> 0:11:05.000 very likely will kill you before you get a chance 0:11:05.080 --> 0:11:08.560 to reach old age. These causes of death like disease 0:11:08.600 --> 0:11:12.120 and injury, or what's known as quote extrinsic causes of death, 0:11:12.200 --> 0:11:15.440 death caused by outside pressures and not by stuff that's 0:11:15.480 --> 0:11:18.480 in your genes or by old age. And so we 0:11:18.520 --> 0:11:20.679 can look at the real life example to see how 0:11:20.720 --> 0:11:24.079 common this is. The actual gray wolf canis lupus lives 0:11:24.080 --> 0:11:26.760 somewhere around an average of six years or so in 0:11:26.800 --> 0:11:29.600 the wild, but in captivity it can live for more 0:11:29.600 --> 0:11:34.280 than fifteen years. So here's the first crucial bit to use. 0:11:34.320 --> 0:11:37.720 Some more metaphorical language. If there are physical processes that 0:11:37.800 --> 0:11:42.560 tend to render a wolf progressively less fit every month 0:11:42.679 --> 0:11:46.840 after it's more than ten years old, evolution almost never 0:11:47.040 --> 0:11:50.600 sees that. To put it in another metaphor, asking why 0:11:50.640 --> 0:11:54.000 evolution allows the wolf to grow old to deteriorate with 0:11:54.040 --> 0:11:57.000 old age is kind of like asking why we don't 0:11:57.040 --> 0:12:01.040 have laws against time travel. The reason isn't that our 0:12:01.120 --> 0:12:05.079 legislative bodies have considered and debated the issue of time travel, 0:12:05.160 --> 0:12:08.000 and in the end they concluded that time travel is good, 0:12:08.040 --> 0:12:10.800 we better, we better allow it. That's not what happens. 0:12:10.880 --> 0:12:14.240 What happens is the issue doesn't come up. Yeah. It. 0:12:14.679 --> 0:12:17.240 It reminds me of some of these various programs that 0:12:18.000 --> 0:12:20.480 informs you have to do to figure out how you're 0:12:20.480 --> 0:12:23.360 saving your for your retirement, and they tend not to 0:12:23.400 --> 0:12:26.880 cover the second century of your life because it's not 0:12:26.920 --> 0:12:30.200 going to happen. That's a perfect metaphor. Yeah, how come 0:12:30.280 --> 0:12:33.040 you're not saving enough money for when you're two hundred 0:12:33.120 --> 0:12:35.880 years old. It's not that you've decided it's better to 0:12:35.960 --> 0:12:39.240 be broke when you're two hundred. It's just that the 0:12:39.240 --> 0:12:42.360 the situation of being two hundred does not tend to 0:12:42.400 --> 0:12:46.080 come up very often. Now, obviously it's not nearly that extreme, 0:12:46.120 --> 0:12:49.240 because sometimes in some cases animals do live to old 0:12:49.280 --> 0:12:53.320 age and they face biological siniscence under natural conditions. But 0:12:53.480 --> 0:12:57.480 for many species it's pretty rare. For species of animals 0:12:57.480 --> 0:13:00.520 that tend to die from one cause or another before 0:13:00.600 --> 0:13:03.840 they get the chance to grow old evolution doesn't have 0:13:03.960 --> 0:13:08.439 many opportunities to test what happens in old age, so 0:13:08.480 --> 0:13:12.359 it can't optimize the animal for old age very efficiently. 0:13:12.960 --> 0:13:16.480 And compare this to how strongly evolution tests and optimizes 0:13:16.520 --> 0:13:19.880 for the effects of genes that manifest in early life. 0:13:20.000 --> 0:13:22.840 If something affects how likely you are to survive at 0:13:22.880 --> 0:13:27.200 age twenty or at age ten, evolution is going to 0:13:27.240 --> 0:13:32.079 be very strongly selecting for or against that gene. Okay, 0:13:32.080 --> 0:13:35.000 so this is one part of the landscape of explanations today. 0:13:35.040 --> 0:13:39.000 Most species that show significant aging evolved to their anatomically 0:13:39.080 --> 0:13:42.559 modern condition in a situation where mortality was high and 0:13:42.640 --> 0:13:45.480 evolution didn't get a lot of opportunities to see what 0:13:45.600 --> 0:13:49.360 happens in old age, much less optimize it. Let's introduce 0:13:49.400 --> 0:13:52.360 another wrinkle into the explanation. Yeah, this one has a 0:13:52.360 --> 0:13:56.840 wonderful title. This is mutation accumulation, right, So we go 0:13:56.960 --> 0:14:00.600 to the British biologist Peter B. Meadair. He was one 0:14:00.600 --> 0:14:03.600 of the primary evolutionary thinkers credited with working out the 0:14:03.640 --> 0:14:06.720 implications of this model of aging, where the force of 0:14:06.800 --> 0:14:11.160 selection just declines with old age. So in several works 0:14:11.160 --> 0:14:14.040 in the middle of the nineteen forties and the nineteen fifties, 0:14:14.559 --> 0:14:18.200 uh he argued, based on similar logic, that natural selection 0:14:18.200 --> 0:14:21.080 would often be blind to the effects of mutations that 0:14:21.160 --> 0:14:25.840 cause negative effects laid in life after reproduction is mostly stopped. 0:14:25.840 --> 0:14:29.360 So let's use another analogy. Imagine a mutation called the 0:14:29.400 --> 0:14:33.880 twenty birthday surprise gene, which means that on the day 0:14:33.920 --> 0:14:37.680 you turn twenty, carriers of this gene suddenly transform into 0:14:37.680 --> 0:14:43.000 a bucket of fishheads and thus lose all ability to reproduce. Now, 0:14:43.000 --> 0:14:45.520 this would mean that in order to pass on this gene, 0:14:45.920 --> 0:14:50.000 a carrier would have to reproduce before their twentieth birthday. 0:14:50.040 --> 0:14:52.440 So kids they have before they're twenty years old could 0:14:52.440 --> 0:14:55.880 still carry this gene, but they don't get the chance 0:14:55.960 --> 0:14:58.680 to have any kids after their twenty years old, when 0:14:58.680 --> 0:15:00.880 plenty of other members of the piece these would continue 0:15:00.920 --> 0:15:05.360 having children, all potential reproduction after twenty is canceled, thus 0:15:05.400 --> 0:15:08.680 giving people with this gene significantly fewer children on average 0:15:08.680 --> 0:15:11.360 than people without it, and so the gene is unlikely 0:15:11.400 --> 0:15:15.200 to spread in the population. Now imagine a similar gene. 0:15:15.280 --> 0:15:19.840 This is the hundredth birthday surprise gene. Carriers of this gene, 0:15:20.080 --> 0:15:23.680 upon the day of their hundredth birthday, suddenly transform into 0:15:23.720 --> 0:15:27.000 a VHS copy of Highlander to the Quickening. Okay, and 0:15:27.000 --> 0:15:30.160 and and therefore becoming immortal. No, not quite No. The 0:15:30.200 --> 0:15:32.520 problem is, well, I guess you you might get to 0:15:33.320 --> 0:15:35.600 live somewhat forever on a shelf, but you don't. You 0:15:35.640 --> 0:15:38.880 definitely don't get to reproduce after that, right, there's very 0:15:38.920 --> 0:15:42.400 little sexual reproduction between copies of Highlander to the Quickening. 0:15:43.160 --> 0:15:47.200 But also it doesn't really matter, right because do carriers 0:15:47.200 --> 0:15:50.720 of this gene have any fewer children the non carriers 0:15:50.760 --> 0:15:54.200 of this gene. The answer is no, right, because who's 0:15:54.240 --> 0:15:58.440 still having children at age one hundred Almost nobody. So 0:15:58.520 --> 0:16:00.800 even if you have this very unhel helpful gene, you 0:16:00.840 --> 0:16:03.680 don't like it that you transform into a VHS tape 0:16:03.680 --> 0:16:06.560 on your hundredth birthday. That's not good for you, but 0:16:06.640 --> 0:16:09.200 it doesn't matter to how many children you have. It 0:16:09.240 --> 0:16:12.120 has no effect on that. So if you have this gene, 0:16:12.160 --> 0:16:14.720 you can spread it to all your children, and they 0:16:14.720 --> 0:16:17.840 can spread it to all of their children and so, 0:16:17.960 --> 0:16:20.360 and they'll all have just as many kids and grandkids 0:16:20.400 --> 0:16:22.720 as the neighbors who don't have it. You've already passed 0:16:22.760 --> 0:16:26.680 it on by the time it matters. So this would 0:16:26.720 --> 0:16:29.360 be the case. Though we we've we've used the Highlander 0:16:29.520 --> 0:16:32.920 to transformation as as an example here. But even if 0:16:32.920 --> 0:16:37.560 it were something seemingly beneficial, like say a gene made 0:16:37.600 --> 0:16:41.280 you suddenly really excellent and talking to members of the 0:16:41.320 --> 0:16:45.680 opposite sex at age one hundred, you know, like or 0:16:45.760 --> 0:16:48.800 the opposite it made you terrible at a speaking to 0:16:48.840 --> 0:16:52.120 the opposite sex at age one hundred, it would still 0:16:52.120 --> 0:16:55.280 be the same case, right, yeah, unless the basically the 0:16:55.320 --> 0:16:57.320 only thing that would matter would be if it's a 0:16:57.360 --> 0:17:00.840 gene that suddenly makes you able to reproduce again. I mean, 0:17:00.880 --> 0:17:03.400 if it did that, then that would probably matter. But 0:17:03.520 --> 0:17:06.600 as long as you're past the age of reproduction and 0:17:06.640 --> 0:17:11.359 you're not having any more children, mutations good or bad 0:17:11.520 --> 0:17:15.840 are just going to sort of accumulate randomly without having 0:17:15.880 --> 0:17:19.760 any effect Onesoever, natural selection just doesn't pay attention to 0:17:19.800 --> 0:17:22.440 them because it never gets to notice them. Well. But 0:17:22.720 --> 0:17:24.440 then the other thing too, is that if you're talking 0:17:24.440 --> 0:17:26.480 about something that would kick in so late in life 0:17:26.520 --> 0:17:30.320 that even people with that gene might never experience it. Right. 0:17:30.400 --> 0:17:33.200 It's like if you're playing a role playing game, video 0:17:33.280 --> 0:17:35.000 game or what have you, and there's some sort of 0:17:35.040 --> 0:17:37.639 like high level ability and you look at it. It 0:17:37.640 --> 0:17:39.280 looks great, but you know you're never going to play 0:17:39.320 --> 0:17:41.880 the game long enough to get it. Yeah, so what's 0:17:41.920 --> 0:17:44.400 the point. Yeah, the game might as well for you 0:17:44.680 --> 0:17:48.400 not even have that thing in it. And apparently there 0:17:48.400 --> 0:17:50.840 are going to be genetic mutations like that. And this 0:17:50.960 --> 0:17:53.280 was Meta WIRs insight. It came to be known, as 0:17:53.280 --> 0:17:58.439 you said, as the mutation accumulation hypothesis. Whether reproduction stops 0:17:58.480 --> 0:18:01.080 because you die of extra ends it causes. This was 0:18:01.119 --> 0:18:02.680 a big thing Meta or had in mind. It's like 0:18:02.720 --> 0:18:05.040 we talked about, you know, the wolf gets injured and 0:18:05.119 --> 0:18:08.040 can't hunt, the wolf gets sick and dies, the wolf 0:18:08.080 --> 0:18:12.119 gets killed by something, whether that happens or because you 0:18:12.240 --> 0:18:14.760 age out of your reproductive stage of life for some 0:18:14.840 --> 0:18:18.680 other biological reasons. Genes that have negative effects that show 0:18:18.800 --> 0:18:23.600 up mostly after reproduction has stopped, are not subject to 0:18:23.640 --> 0:18:26.040 the full force of natural selection. So there's not much 0:18:26.119 --> 0:18:29.240 preventing the proliferation of genes that harm you in old 0:18:29.240 --> 0:18:32.040 age because there's nothing to weed them out, and they 0:18:32.080 --> 0:18:35.159 accumulate in the genome over generations by what's known as 0:18:35.240 --> 0:18:39.120 genetic drift. And the genetic drift is just the random 0:18:39.200 --> 0:18:42.240 dispersing of genes that don't appear to have a very 0:18:42.240 --> 0:18:45.359 strong positive or negative effect. So if you've got a 0:18:45.440 --> 0:18:49.600 mutation that you acquire for a nasty surprise in old age, 0:18:49.640 --> 0:18:51.800 something bad that happens to your body, and you could 0:18:51.840 --> 0:18:54.399 look at the process of aging like this, it's just 0:18:54.480 --> 0:18:58.600 a large plethora of genetic mutations that cause bad things 0:18:58.720 --> 0:19:01.760 to happen to your body. Later on, you can still 0:19:01.800 --> 0:19:04.280 pass it on to your kids because you're you've had 0:19:04.320 --> 0:19:06.920 all your kids by the time it starts affecting you. 0:19:07.400 --> 0:19:10.280 And so these genes can become common in the gene 0:19:10.280 --> 0:19:13.760 pool of your species simply because there's nothing stopping them. 0:19:14.160 --> 0:19:17.240 So simply put it, the force of selection declines with age. 0:19:17.560 --> 0:19:21.000 Mutations that are neutral early in life when selection is strong, 0:19:21.080 --> 0:19:25.000 but negative later on, they could accumulate in the population. 0:19:25.760 --> 0:19:27.480 I like to think of this as the sack of 0:19:27.520 --> 0:19:31.600 kitty litter scoopings in the closet scenario. Okay, explain. But 0:19:31.920 --> 0:19:33.800 a friend of mine, when I first met her, she 0:19:34.280 --> 0:19:37.520 had a cat box, and then she would scoop the 0:19:37.560 --> 0:19:40.400 cat box and it would accumulate in a garbage bag 0:19:40.480 --> 0:19:44.040 in the closet. Accumulate me, you mean accumulate as and 0:19:44.119 --> 0:19:46.080 she would dump it, yes, in a garbage bag in 0:19:46.119 --> 0:19:48.000 the close. And it was. It was a lot cleaner 0:19:48.040 --> 0:19:49.800 than this makes it sound, but it was. It was 0:19:49.880 --> 0:19:51.440 very much a sort of kicking the can down a 0:19:51.520 --> 0:19:54.199 road scenario, like eventually you're gonna have to take that 0:19:54.240 --> 0:19:59.080 bag of of of of litter scoopings out, but you're not. 0:20:00.200 --> 0:20:02.240 The whole situation is not built on what you're going 0:20:02.320 --> 0:20:05.000 to have to do tomorrow. It's about what's happening to today. 0:20:05.040 --> 0:20:07.280 But what if you're looking at that closet and you're saying, oh, 0:20:07.320 --> 0:20:09.600 there's enough space in here that I could keep scooping 0:20:09.600 --> 0:20:11.760 it into the closet until I die of some of 0:20:11.760 --> 0:20:14.320 their cause, and then I would never have to take 0:20:14.359 --> 0:20:17.040 it out. It would be completely irrelevant. So it can 0:20:17.080 --> 0:20:21.159 accumulate forever, just like these deleterious genes can. Okay, So 0:20:21.200 --> 0:20:23.959 that's clearly one part of the answer. One part is 0:20:24.000 --> 0:20:26.720 that stuff that affects you late in life is just 0:20:26.880 --> 0:20:29.439 less likely to get weeded out by natural selection. But 0:20:29.920 --> 0:20:33.680 what if there's something more than that. What if maladaptive 0:20:33.720 --> 0:20:36.679 genes that manifest in old age aren't just allowed to 0:20:36.800 --> 0:20:39.399 roam wild by sort of the careless shepherd of a 0:20:39.480 --> 0:20:44.919 natural selection. What if they're positively selected four in some way. 0:20:45.080 --> 0:20:47.200 And that's what we'll explore when we come back from 0:20:47.200 --> 0:20:52.000 this break than all right, we're back, So now it's 0:20:52.000 --> 0:20:56.240 time to talk about antagonistic pleotropy. In a paper in 0:20:57.119 --> 0:21:00.399 seven and the journal Evolution, the American Evolutionary by alllogist 0:21:00.440 --> 0:21:04.400 George C. Williams had a breakthrough that made metoirs original 0:21:04.520 --> 0:21:08.399 hypothesis even stronger and sort of complimented it. And so 0:21:08.440 --> 0:21:10.400 this was a paper that I mentioned in part one. 0:21:10.440 --> 0:21:13.760 Actually it's the paper called pleotropy, Natural Selection and the 0:21:13.840 --> 0:21:18.960 Evolution of sinescence. Williams hypothesis for the evolution of aging 0:21:19.040 --> 0:21:22.560 came to be known, as I said, as antagonistic pleotropy. 0:21:22.560 --> 0:21:25.919 And what this means is that well. Pleotropy. The word 0:21:26.440 --> 0:21:31.480 comes from the Greek roots meaning multiple turns or many effects. 0:21:32.320 --> 0:21:37.680 Pleotropy happens when a single gene codes for multiple different 0:21:37.800 --> 0:21:41.240 phenotypic effects, meaning effects on the body or effects on 0:21:41.280 --> 0:21:44.520 the behavior. So if you had one gene that both 0:21:44.880 --> 0:21:48.800 gave you black hair and gave you an extremely long, 0:21:49.480 --> 0:21:52.719 pinky fingernail, that would be pleotropy. Or if you had 0:21:52.760 --> 0:21:56.720 a gene that made you really tall and also made 0:21:56.800 --> 0:22:01.399 you better at learning multiple languages, that would be pleotropy. 0:22:01.440 --> 0:22:03.840 And there are lots of examples of this in animals 0:22:03.840 --> 0:22:07.600 in the real world. Here's one in chickens. Robert, have 0:22:07.640 --> 0:22:10.040 you ever seen the frizzle chickens? Who? I don't know. 0:22:10.080 --> 0:22:13.920 I've seen some pretty funny looking chickens before. I've seen 0:22:13.960 --> 0:22:16.159 a frizzle chicken. I mean the ones that have like 0:22:16.240 --> 0:22:19.639 the curly vegas outfits. Uh yeah, well yeah, I have 0:22:19.720 --> 0:22:22.520 seen some of these. These these chickens that have like 0:22:22.520 --> 0:22:25.280 a lot of extra feathers around their their talons and all. 0:22:25.680 --> 0:22:28.560 The frizzle gene is is a gene in chickens that 0:22:28.600 --> 0:22:31.840 causes the feathers to curl up instead of lying flat, 0:22:31.920 --> 0:22:36.120 so you get these crazy looking like awesome, beautiful, regal 0:22:36.240 --> 0:22:39.640 puffy chickens and they look really cool. But it turns 0:22:39.640 --> 0:22:43.080 out this gene also controls several other phenotypic effects. So 0:22:43.240 --> 0:22:46.000