WEBVTT - Virgin Birth 0:00:03.040 --> 0:00:05.840 Welcome to Stuff to Blow Your Mind from how Stuff 0:00:05.840 --> 0:00:14.520 Works dot Com. Hey, welcome to Stuff to Blow your Mind. 0:00:14.600 --> 0:00:17.279 My name is Robert Lamb and I'm Joe McCormick. You know, 0:00:17.440 --> 0:00:20.759 I realized I don't know why exactly this happened, but 0:00:20.880 --> 0:00:22.759 towards in the last couple of months, I feel like 0:00:22.800 --> 0:00:26.400 we have been really focusing on the animal kingdom that 0:00:26.520 --> 0:00:29.000 wasn't by design. I guess we just can't stop with 0:00:29.120 --> 0:00:32.240 the things with legs and blood. Well, I think maybe 0:00:32.280 --> 0:00:35.680 what's happening is that we have, without realizing it, being 0:00:35.720 --> 0:00:38.800 constructing a major and Nativity scene. Okay, and of course 0:00:38.800 --> 0:00:41.479 you have to have your various animals present, and and 0:00:41.479 --> 0:00:43.680 so we've been arranging the animal and I guess others 0:00:43.720 --> 0:00:47.839 bearing gifts of of nursery web spider style wrapped up 0:00:47.840 --> 0:00:51.519 packages of dead insect husks and sticks and stuff. I 0:00:51.560 --> 0:00:55.120 don't know who the shepherds would be. Well, whatever the 0:00:55.160 --> 0:00:57.120 shepherds are, we know that at the heart of the 0:00:57.240 --> 0:01:01.280 of the Nativity you have to have that that baby Jesus. Granted, 0:01:01.280 --> 0:01:03.720 we did an episode last year on the Baby Jesus 0:01:03.760 --> 0:01:07.440 homunculus and that is rerunning this year. But at the 0:01:07.440 --> 0:01:10.640 heart of this story of the Christmas story and Christian 0:01:10.680 --> 0:01:13.880 traditions is the story of a virgin birth. Now, the 0:01:13.920 --> 0:01:16.920 story of a miraculous birth, of course, is very common 0:01:17.000 --> 0:01:20.240 in in mythology and legend around the world. A god 0:01:20.360 --> 0:01:23.240 being the father of a famous or heroic person is 0:01:23.280 --> 0:01:26.120 a very common motif to appear wise settle for an 0:01:26.120 --> 0:01:28.839 earth dad when you can have a cosmic dad. Yeah, 0:01:28.880 --> 0:01:31.319 it's a it's it's a time tested story. Right. You 0:01:31.360 --> 0:01:34.399 have your demigod heroes that are that that have have 0:01:34.680 --> 0:01:38.160 we at least one parent that is of divine lineage. Now, 0:01:38.160 --> 0:01:39.520 before we go any further, I do want to just 0:01:39.560 --> 0:01:44.240 summarize the Christmas story as it's presented in Christmas Christian traditions, 0:01:44.280 --> 0:01:47.360 just really quickly here, so it's probably familiar to a 0:01:47.360 --> 0:01:49.880 lot of you. You have a first century BC woman 0:01:50.000 --> 0:01:52.440 by the name of Mary, and she finds out via 0:01:52.520 --> 0:01:55.840 angelic visitation that she's destined to become a first century 0:01:55.920 --> 0:01:59.440 CE mom, and not in the way she'd plan. No, 0:01:59.520 --> 0:02:02.240 instead of using offspring via relations with her husband Joseph, 0:02:02.440 --> 0:02:05.080 she has been impregnated by the High God. She is 0:02:05.120 --> 0:02:07.680 a virgin, but will give birth to a divine son. 0:02:08.720 --> 0:02:12.080 And like you, said, this is not an anomaly in 0:02:12.160 --> 0:02:16.519 global myths, legends, and religions, we have other stories of 0:02:16.680 --> 0:02:19.440 some sort of miraculous birth taking place, right, And what 0:02:19.480 --> 0:02:21.680 we wanted to focus on today was the fact that 0:02:21.760 --> 0:02:24.840 though this may in fact be some form of miracle 0:02:24.919 --> 0:02:26.880 if it were to actually happen to a human being, 0:02:27.400 --> 0:02:30.200 in other corners of the natural world, stories like this 0:02:30.360 --> 0:02:33.880 are actually not all that miraculous. They in fact happen 0:02:33.960 --> 0:02:37.560 all the time. Right. So today we're gonna be talking 0:02:37.600 --> 0:02:42.240 about parthenogenesis. That is the the scientific term for what's 0:02:42.280 --> 0:02:46.440 occurring here. It's taken from the Greek words parthenos meaning virgin, 0:02:46.800 --> 0:02:51.320 and genesis meaning origin. So this means in the animal world, 0:02:52.080 --> 0:02:55.519 or in the world of sexually reproducing species, a female 0:02:55.639 --> 0:03:01.440 that reproduces without fertilization by male sex cells, right, And 0:03:01.560 --> 0:03:05.120 it occurs pretty commonly among lower plants and invertebrate animals, 0:03:05.120 --> 0:03:09.000 particularly rotifers, a fids, ants, wasps, and bees. I do 0:03:09.040 --> 0:03:11.839 want to hit just two of my favorite examples from 0:03:11.840 --> 0:03:15.480 the invertebrate invertebrate world. First of all, in the termite 0:03:15.480 --> 0:03:18.800 world is pointed out in a two thousand nine research 0:03:18.840 --> 0:03:23.240 paper from North Carolina State University. Certain female termite primary 0:03:23.320 --> 0:03:29.320 queens of the species Radical Attorney's Separatus reproduce both sexually 0:03:29.400 --> 0:03:33.399 and a sexually during their lifetimes, sexually with the male kings, 0:03:33.440 --> 0:03:37.960 and a sexually to essentially clone themselves to create secondary queens. 0:03:39.320 --> 0:03:42.400 And these are the successor queens that will then mate 0:03:42.440 --> 0:03:44.320 with the king, So it's important for them to have 0:03:44.400 --> 0:03:48.920 no genes in common with them. So that's just I think, 0:03:48.920 --> 0:03:50.560 a fun example. All right, Well here you can you 0:03:50.600 --> 0:03:53.240 can clearly see in this picture why it is advantageous 0:03:53.400 --> 0:03:58.600 to use a sexual reproduction alongside sexual reproduction. Of course, 0:03:58.640 --> 0:04:02.080 the greatest benefit of sexual reproduction is that you get 0:04:02.080 --> 0:04:04.320 some variety in there. You don't have the a stagnant 0:04:04.320 --> 0:04:07.560 gene pool right sexual recombination. If you were just making 0:04:07.640 --> 0:04:10.320 copies of your own genes over and over again, it 0:04:10.360 --> 0:04:14.480 becomes much easier for say, parasites to find exploits with 0:04:14.600 --> 0:04:18.960 your body. But if you're constantly randomly recombining your genes 0:04:19.000 --> 0:04:21.760 with other members of your species, then you add some 0:04:21.800 --> 0:04:24.359 diversity to the mix and give yourself more room to 0:04:24.800 --> 0:04:28.039 more genetic wiggle room. It's kind of like say Hollywood 0:04:28.080 --> 0:04:31.039 made the same movie for ten years straight, Like the same, 0:04:31.080 --> 0:04:35.600 say superhero movie, just the same one time after time, 0:04:35.760 --> 0:04:38.400 and it was a really tremendous design. Everyone loved it. 0:04:38.440 --> 0:04:40.560 But then suddenly everyone's decides, you know, not that into 0:04:40.560 --> 0:04:44.880 superhero movies anymore. Bam, an entire decade wasted. Right, that's 0:04:44.880 --> 0:04:48.440 a very loose um explanation, but but that's why you 0:04:48.480 --> 0:04:51.080 get the genre mix up. Throw some zombies in there. No, 0:04:51.160 --> 0:04:52.720 and now you got a whole new thing. Now it's 0:04:52.760 --> 0:04:55.800 fresh again. Yeah, and now people will get into it. Uh. 0:04:55.960 --> 0:04:58.919 Here's another example that I love. This is probably my 0:04:59.000 --> 0:05:03.159 absolute favorite. It's a particular type of Amazonian ant micro 0:05:03.320 --> 0:05:07.359 Capris Smithy, like Alan Smithy speaking films. Uh. This is 0:05:07.400 --> 0:05:11.279 a fungi growing species. It's not unlike the leaf cutter 0:05:11.320 --> 0:05:15.200 aunt and they've actually given up on sexual reproduction altogether 0:05:15.440 --> 0:05:18.239 and have become an all female species. It's a colony 0:05:18.240 --> 0:05:20.320 of clones, so there are a lot more efficient in 0:05:20.360 --> 0:05:23.280 some ways, but they're highly vulnerable due to their lack 0:05:23.320 --> 0:05:26.239 of gene diversity. But they're an example of a species 0:05:26.240 --> 0:05:29.719 that took a reproductive tactic that existed in balance with 0:05:29.760 --> 0:05:32.960 sexual reproduction and eventually made it their own. Means. They're 0:05:32.960 --> 0:05:36.240 only means of reproduction. Now, while this might be more 0:05:36.320 --> 0:05:40.080 common and of course a sexual reproduction is the norm 0:05:40.160 --> 0:05:43.200 amongst a like single celled organism, but while it may 0:05:43.200 --> 0:05:46.680 be more common among invertebrates and these sort of what 0:05:46.760 --> 0:05:49.200 are considered lower order animals, though I don't know if 0:05:49.240 --> 0:05:51.880 it really makes sense to consider them lower or higher. 0:05:51.920 --> 0:05:55.240 What does lower or higher means? But anyway, it is 0:05:55.240 --> 0:05:58.080 going to be more surprising to find something like this 0:05:58.600 --> 0:06:03.719 in vertebrates, which normally would expect to be sexually reproducing animals. 0:06:03.760 --> 0:06:07.720 You've got a backbone, you should be having sex, right, yeah, 0:06:07.880 --> 0:06:09.960 I mean that's why it's such a rarity. Roughly seventy 0:06:10.000 --> 0:06:15.400 backbone species have been known to engage in parthenogenesis or 0:06:15.440 --> 0:06:20.640 exhibit parthenogenesis. That's a roughly point one percent of all vertebrates. Now, 0:06:20.680 --> 0:06:24.480 just a few basic category categories of parthenogenesis before we 0:06:24.520 --> 0:06:28.440 move on to specific examples. Uh, there's accidental. This is 0:06:28.480 --> 0:06:32.200 spontaneous parthenogenesis. Uh, it's not part of the plan, not 0:06:32.200 --> 0:06:34.920 part of the plan, but it does occur. And one 0:06:34.960 --> 0:06:38.880 example we'll see that later is in sharks. There's also facultative. 0:06:39.320 --> 0:06:42.040 This is when a female can produce offspring either sexually 0:06:42.200 --> 0:06:46.640 or via a sexual reproduction. Um, this is a common example, 0:06:46.640 --> 0:06:47.920 but one that we'll look at here in a minute 0:06:48.000 --> 0:06:52.359 is komodo dragons. And then there's obligate Uh, this is 0:06:52.480 --> 0:06:55.320 exclusive a sexual reproduction. That doesn't mean that a given 0:06:55.320 --> 0:06:58.800 species can't use sexual reproduction, but it's certainly not their 0:06:58.839 --> 0:07:02.560 primary means of reproduction. So, you know, think of the 0:07:02.720 --> 0:07:05.640 various invertebrates as an example of this, including the ants 0:07:05.640 --> 0:07:09.239 that I mentioned earlier. Single sex species, yes, especially especially 0:07:09.279 --> 0:07:11.360 single sex species. Well, let's take a look at those 0:07:11.400 --> 0:07:15.360 komodo dragons. Yeah, so the komodo dragon, which is Verona's 0:07:15.440 --> 0:07:19.360 komodo insists, is of course the largest lizard species in 0:07:19.400 --> 0:07:21.400 the world. And Robert, I don't know about you, but 0:07:21.480 --> 0:07:23.720 this was one of my favorite animals when I was 0:07:23.760 --> 0:07:26.160 a kid. I could not get enough of them. I 0:07:26.200 --> 0:07:29.200 love pictures of them. I think I would actually if 0:07:29.240 --> 0:07:31.840 I could get like a national geographic with a picture 0:07:31.920 --> 0:07:33.800 of one, I would cut it out. I seem to 0:07:33.800 --> 0:07:36.480 have some memories of that. Oh yeah, because it's the 0:07:36.600 --> 0:07:39.200 really it's the closest thing you can get to to 0:07:39.320 --> 0:07:42.840 a storybook dinosaur, like not counting not getting into like, 0:07:42.880 --> 0:07:46.000 you know, the the evolution of avian species and all that, 0:07:46.320 --> 0:07:48.840 But just in terms of like, I want a giant 0:07:49.000 --> 0:07:52.560 lizard creature like I see in my children's books. This 0:07:52.640 --> 0:07:54.760 is the closest you're gonna get. So yeah, I remember 0:07:54.800 --> 0:07:58.280 being super into it. I remember being like weirdly excited 0:07:58.320 --> 0:08:01.440 when I think was it Kim not Kim Baysinger, Sharon 0:08:01.480 --> 0:08:04.200 Stone's husband was bitten by one. I just remember being 0:08:04.240 --> 0:08:07.960 in thee and yeah, not to make light of that, 0:08:08.000 --> 0:08:10.120 I mean, I'm thinking that now it's probably horrific, but 0:08:10.120 --> 0:08:11.720 I remember the time it was like, oh my goodness, 0:08:11.760 --> 0:08:15.160 the Komodo dragons are coming after our celebrities, Like there 0:08:15.240 --> 0:08:17.880 was something weirdly exciting about that. And yet at the 0:08:17.920 --> 0:08:20.920 same what if they get Richard Gear. No, not Richard Gear. 0:08:21.000 --> 0:08:25.040 He's a national treasure. But in terms of seeing them 0:08:25.040 --> 0:08:28.000 in zoos, though, this is one of those animals it 0:08:28.080 --> 0:08:31.160 is both impressive and boring to see in most zoos 0:08:31.200 --> 0:08:34.600 because it's a it's a cold boded creature. It's it's 0:08:34.640 --> 0:08:36.440 just going to be sitting there most of the time. 0:08:36.920 --> 0:08:42.199 An impressive organism, but very little movement unless you're lucky. 0:08:42.440 --> 0:08:44.960 At the same time, there's there's some tremendous footage of 0:08:45.000 --> 0:08:48.559 them in the wild. If you've watched any of the 0:08:48.559 --> 0:08:52.520 the BBC Earth documentaries, you've seen some of this footage 0:08:52.559 --> 0:08:55.960 of of the active Komodo dragon. And there's nothing, there's 0:08:55.960 --> 0:08:58.440 nothing more terrifying than watching them, say, move in on 0:08:58.559 --> 0:09:02.400 a on a a vulnar horble cow that is trapped 0:09:02.400 --> 0:09:06.880 in the mud. Have you ever watched them doing acrobatic barfing? Oh, 0:09:06.960 --> 0:09:10.360 they're quite They are quite adept at barfing, aren't they 0:09:10.480 --> 0:09:14.040 unbelievable barfing? Like there, I've seen footage of them barfing 0:09:14.200 --> 0:09:16.920 where it looks like they barf up more than their 0:09:16.960 --> 0:09:21.480 own body mass. They are also Remember one of the 0:09:21.480 --> 0:09:25.760 notable things about them is that they will sling intestines 0:09:25.800 --> 0:09:28.360 around to remove the fecal matter from them so they 0:09:28.360 --> 0:09:30.960 can eat the intestines. Okay, I don't think i've read that, 0:09:30.960 --> 0:09:33.839 but I think maybe i've heard you mentioned that before. Yeah, yeah, 0:09:33.920 --> 0:09:37.200 they're they're voracious eaters. So the young commodo dragons have 0:09:37.200 --> 0:09:38.719 to hide from the adults so they don't get eating. 0:09:38.720 --> 0:09:41.600 I believe they climb trees, and of course the grown 0:09:41.640 --> 0:09:43.880 ups cannot really go after them. Yes, they can be 0:09:43.960 --> 0:09:47.640 quite aggressive, even to one another. So this species. They 0:09:47.640 --> 0:09:50.040 live on a number of islands in Indonesia, and as 0:09:50.080 --> 0:09:52.559 adults they get huge. They can grow up to about 0:09:52.600 --> 0:09:55.440 three meters or tin feet in length. Actually, I think 0:09:55.480 --> 0:09:58.920 the UH the largest one ever I read was even 0:09:58.920 --> 0:10:01.079 bigger than that. It was like tin point three feet 0:10:01.120 --> 0:10:03.079 in length, and they can weigh over a hundred and 0:10:03.120 --> 0:10:06.280 thirty kg or about three hundred pounds. Again, I think 0:10:06.440 --> 0:10:09.559 I read that the biggest one ever measured was something 0:10:09.559 --> 0:10:14.080 like three hundred and sixty pounds. They are venomous. They 0:10:14.120 --> 0:10:18.000 deliver a bite that prevents the praise blood from clotting. However, 0:10:18.120 --> 0:10:21.480 they do not primarily hunt live prey, because the majority 0:10:21.520 --> 0:10:24.760 of their diet from scavenging dead or dying animals, though 0:10:24.760 --> 0:10:27.480 of course they do also hunt, and when they hunt 0:10:27.520 --> 0:10:30.360 live prey. Those prey species can be all kinds of things, 0:10:30.679 --> 0:10:33.040 mainly dear, I think dear is the biggest one, but 0:10:33.120 --> 0:10:38.199 also bovines, pigs, rodents, monkeys, goats, and they have on occasion, 0:10:38.360 --> 0:10:41.080 as we said, attacked and killed humans. But this does 0:10:41.120 --> 0:10:45.400 not make them our enemy. These are magnificent scaly beasts, 0:10:45.480 --> 0:10:49.520 and they themselves are threatened in conservation status terms, you know, 0:10:49.600 --> 0:10:52.719 like you got the UH the i u c N classifications, 0:10:52.760 --> 0:10:56.040 they are not yet considered endangered, but they are considered 0:10:56.120 --> 0:10:59.640 vulnerable according to the w WF. They're only about six 0:10:59.679 --> 0:11:03.520 thousand and left on Earth and only about three fifty 0:11:03.640 --> 0:11:07.600 breeding females, and for that reason there are these conservation 0:11:07.679 --> 0:11:10.680 and captivity breeding efforts going on around the world. But 0:11:10.920 --> 0:11:13.960 so I want to tell a komodo dragon story. In 0:11:14.000 --> 0:11:17.880 two thousand five, a female komodo dragon named Sung Guy 0:11:18.280 --> 0:11:21.440 was living at the London Zoo and that year she 0:11:21.640 --> 0:11:24.880 produced a clutch of twenty two eggs, four of which 0:11:24.880 --> 0:11:28.760 were viable. But there was a problem. It had been 0:11:28.800 --> 0:11:31.719 two and a half years since Sung Guy had been 0:11:31.760 --> 0:11:35.280 anywhere near a male komodo dragon, so in order in 0:11:35.400 --> 0:11:38.120 order to explain her laying these eggs, it would seem 0:11:38.200 --> 0:11:42.400 she either had to somehow store sperm from a male 0:11:42.600 --> 0:11:46.560 for over two years, which is technically possible sometimes in 0:11:46.600 --> 0:11:50.960 reptiles there are like sperm storage methods that sometimes happen, 0:11:51.920 --> 0:11:56.360 or she had performed parthenogenesis and her eggs hatch seven 0:11:56.400 --> 0:11:58.319 and a half months after she laid them, and her 0:11:58.360 --> 0:12:02.040 offspring seemed healthy. Uh. In two thousand six, a female 0:12:02.080 --> 0:12:06.240 komodo dragon named Flora was living at the Chester Zoo 0:12:06.360 --> 0:12:08.680 in the UK, and she was at the time one 0:12:08.720 --> 0:12:11.960 of only two sexually mature female komotos in the whole 0:12:12.000 --> 0:12:14.679 continent of Europe. As I said, you know, many zoos 0:12:14.679 --> 0:12:17.560 around the world do these komodo dragon breeding programs to 0:12:17.640 --> 0:12:20.280 try to help get the numbers back up, and at 0:12:20.280 --> 0:12:23.080 the time Flora had not been breeding. In fact, she 0:12:23.200 --> 0:12:26.040 had never even once been kept in an enclosure with 0:12:26.040 --> 0:12:29.840 a male. Nevertheless, in two thousand six she produced a 0:12:29.840 --> 0:12:33.400 clutch of twenty five eggs and eleven seemed viable at first. 0:12:33.920 --> 0:12:37.439 So what could explain this? I mean, you have to wonder, 0:12:37.559 --> 0:12:40.800 was there like a male komodo dragon running loose in England, 0:12:40.960 --> 0:12:45.080 secretly getting into the pins when nobody's watching. And if 0:12:45.120 --> 0:12:48.360 we do entertain that possibility, we have to name that 0:12:48.440 --> 0:12:52.000 English komodo dragon. What was his name? Oh, I don't know, 0:12:52.360 --> 0:12:56.640 a rogue English komodo dragon. Uh, that'd be Rupert, right, 0:12:56.800 --> 0:12:59.079 Rupert May or maybe kind of it's kind of a 0:12:59.160 --> 0:13:02.360 Robin Hood type figure. It could be a Komoto Hood. 0:13:02.600 --> 0:13:08.480 Robin Koma's not Clive, He's Clive, Okay, So Clive? Did 0:13:08.480 --> 0:13:11.560 Clive get in there or did something else happen. Turns 0:13:11.559 --> 0:13:14.440 out it was not clive. So there was a paper 0:13:14.440 --> 0:13:20.559 published in Nature in two thousand and six by Watts, Bully, Sanderson, Boardman, CPI, 0:13:20.679 --> 0:13:24.840 and Gibson called parthenogenesis and Komodo Dragons, and the authors 0:13:24.880 --> 0:13:29.559 here performed genetic fingerprinting tests on the eggs of these dragons, 0:13:29.880 --> 0:13:32.760 and they found that in both cases the offspring were 0:13:33.000 --> 0:13:36.880 what are known as parthenogens, which are made entirely out 0:13:36.920 --> 0:13:41.000 of their own mother's DNA, rather than through sexual recombination 0:13:41.040 --> 0:13:43.640 with a mail. And in the case of Flora, this 0:13:43.840 --> 0:13:46.800 was true virgin birth. But in both cases they had 0:13:46.880 --> 0:13:49.840 created baby komodo dragons without the help of a mail. 0:13:50.640 --> 0:13:53.520 So the author's note that the offspring were homozy guess 0:13:53.520 --> 0:13:56.840 at all loci on on their genome, but that they 0:13:56.840 --> 0:14:00.560 were not identical clones of their mothers. So how would 0:14:00.559 --> 0:14:02.920 that work? Well, you've got to think about what happens 0:14:03.000 --> 0:14:06.560 in sexual recombination of an animal like this. So the 0:14:06.679 --> 0:14:10.680 mother contributes half of her genome and the father contributes 0:14:10.720 --> 0:14:13.800 half of his genome, and they combine to produce a 0:14:13.840 --> 0:14:15.920 mix of the two. And in this case the mother 0:14:16.080 --> 0:14:19.680 still only contributed half of her genome. So in order 0:14:19.720 --> 0:14:22.440 to produce an entire genome in the offspring without any 0:14:22.480 --> 0:14:27.680 mail input, the mother's half set of chromosome simply doubled itself. 0:14:28.000 --> 0:14:30.600 So the offspring are not clones of the mother, their 0:14:30.640 --> 0:14:34.520 homozygous at all loci. So everywhere you look on their genome, 0:14:34.520 --> 0:14:37.720 there's a double copy of the same allele, all made 0:14:37.760 --> 0:14:40.880 from half of the mother's genes. But so, how does 0:14:40.960 --> 0:14:42.800 this happen? You know, I was wondering, what are the 0:14:42.840 --> 0:14:45.560 actual mechanics here? Uh, there's a there's a pretty good 0:14:45.560 --> 0:14:48.240 summary in a Scientific American article from the time by 0:14:48.240 --> 0:14:51.840 Philip y am Uh and yam rights quote. Evidently, in 0:14:51.840 --> 0:14:54.520 the case of these komotos, the doubling of the egg 0:14:54.600 --> 0:14:59.360 genes occurred when, in essence, another egg, rather than sperm, 0:14:59.560 --> 0:15:04.080 did the job of fertilization. Oh genesis, the biological process 0:15:04.120 --> 0:15:09.000 of making an egg cell typically also yields a polar body, 0:15:09.560 --> 0:15:13.000 a mini ovum of sorts containing a duplicate copy of 0:15:13.080 --> 0:15:17.360 egg d NA. Normally, this polar body shrivels up and disappears. 0:15:17.680 --> 0:15:20.960 In the case of the komodos, though, polar bodies evidently 0:15:21.000 --> 0:15:25.880 acted as sperm and turned over into embryos. So it's 0:15:25.920 --> 0:15:28.600 like the eggs cell had a little copy of itself 0:15:28.640 --> 0:15:31.040 there with it that would normally shrivel up and go away, 0:15:31.320 --> 0:15:34.920 but instead it pretended it was sperm and then fertilized 0:15:34.960 --> 0:15:40.760 its own copy another thing. After producing some offspring parthenogenically, 0:15:41.200 --> 0:15:44.320 the one Komodo dragon, Sun Guy went on to produce 0:15:44.360 --> 0:15:47.160 a normal clutch of eggs with a male named Raja. 0:15:47.480 --> 0:15:51.320 So the researchers also concluded that parthenogenesis is not a 0:15:51.360 --> 0:15:55.560 fixed reproductive trait that lasts forever. In the Komodo dragons, 0:15:55.600 --> 0:15:58.400 you can go back and forth. So, in fact, the 0:15:58.440 --> 0:16:00.800 findings suggests that this is probably probably a form of 0:16:00.880 --> 0:16:06.200 reproductive plasticity. It's the ability to switch between sexual reproduction 0:16:06.280 --> 0:16:11.120 and asexual reproduction when mates are not available. Amazing. Yeah, 0:16:11.160 --> 0:16:12.720 I mean you can see why this would be a 0:16:12.760 --> 0:16:16.120 tremendous survival advantage. I mean, in particular, when you have 0:16:16.400 --> 0:16:19.920 a case where a female is not exposed to males 0:16:19.960 --> 0:16:22.760 at all for an extended period of time and yet 0:16:23.000 --> 0:16:26.800 is capable of producing viable eggs. Like if there's no 0:16:26.840 --> 0:16:29.400 mail around this, this show still has to start one 0:16:29.400 --> 0:16:31.480 way or another. Yeah, Now there are some reasons you 0:16:31.560 --> 0:16:34.400 might think that there are genetic drawbacks to that. In fact, 0:16:34.480 --> 0:16:36.800 the author is right that there is a downside to 0:16:36.880 --> 0:16:41.960 this discovery. Quote, parthenogenesis presents a previously unrecognized problem for 0:16:42.000 --> 0:16:46.440 the genetic management of threatened populations. Why would this be well, 0:16:46.800 --> 0:16:50.880 in captive breeding programs designed to help commodo dragons build 0:16:50.880 --> 0:16:55.120 their numbers back up, females are often kept isolated from males, 0:16:55.240 --> 0:16:58.160 and males are only brought in occasionally for the obvious 0:16:58.200 --> 0:17:01.080 reason there are good sense to do it like this, 0:17:01.200 --> 0:17:03.960 like sometimes these animals are aggressive toward one another, and 0:17:04.000 --> 0:17:06.920 you don't want them unnecessarily fighting or injuring one another, 0:17:07.480 --> 0:17:10.159 that kind of thing. But this means that if you 0:17:10.240 --> 0:17:13.880 keep females in all female environments with no mates, they 0:17:13.960 --> 0:17:18.560 may spontaneously give birth to parthenogens. Now what's wrong with that? 0:17:18.640 --> 0:17:22.639 Why Why wouldn't that just help increase their numbers even more? Well, 0:17:22.720 --> 0:17:26.600 it doesn't quite work like that. The problem is parthenogenesis 0:17:26.640 --> 0:17:30.359 reduces the fitness of the komodo dragon gene pool. The 0:17:30.400 --> 0:17:36.479 author's right quote oppressing concern with parthenogenesis is instantaneous homozygosity 0:17:36.480 --> 0:17:40.600 of the entire genome, as this inbreeding carries an associated 0:17:40.720 --> 0:17:45.800 risk of reduced fitness and an increased probability of extinction. Uh. 0:17:45.800 --> 0:17:48.880 And then there's another problem with the parthenogenesis, and it's 0:17:48.920 --> 0:17:53.080 that it biases the sex ratio of the offspring. Uh. 0:17:53.160 --> 0:17:57.960 The author's right quote. In Verona species, females have dissimilar 0:17:58.040 --> 0:18:01.840 chromosomes Z and double you sort of like human chromosomes 0:18:01.840 --> 0:18:05.800 sex chromosomes X and Y, uh, continuing with their quote. 0:18:06.000 --> 0:18:10.760 Whereas the combination Z Z produces males, so the parthenogenic 0:18:10.840 --> 0:18:16.200 mechanism can produce only homozygous ZZ or w W individuals 0:18:16.240 --> 0:18:21.120 and therefore no females. So the parthenogenesis in the Komodo dragons, 0:18:21.160 --> 0:18:23.720 because of the way their sex cells work, they can 0:18:23.800 --> 0:18:27.639 only make male offspring. Uh. It's sort of the opposite 0:18:27.640 --> 0:18:30.320 of the way like human sex chromosomes work, that males 0:18:30.400 --> 0:18:34.280 have an x Y chromosome and females in humans have 0:18:34.320 --> 0:18:37.239 an x X chromosome. In the dragons, it's the other 0:18:37.280 --> 0:18:41.679 way around. The males have the same two sex chromosomes 0:18:41.680 --> 0:18:43.919 and the females have the two different sex chromosomes. If 0:18:43.960 --> 0:18:46.119 you can only make a duplicate copy, you can only 0:18:46.160 --> 0:18:48.760 make new male dragons. Yeah, and this is important to 0:18:48.800 --> 0:18:50.480 keep in mind as we move forward, because we're going 0:18:50.560 --> 0:18:55.000 to see, um, you know, the exact chromosome. All situation 0:18:55.160 --> 0:18:57.239 is going to play into what kind of offspring are 0:18:57.280 --> 0:19:03.199 produced by a given species density for parthenogenesis. Yes, so 0:19:03.240 --> 0:19:05.840 back to that question about whether this is uh, this 0:19:05.920 --> 0:19:08.000 is useful in the wild. It does seem like it's 0:19:08.040 --> 0:19:11.199 probably an adaptation right for the reason you mentioned earlier. 0:19:11.560 --> 0:19:16.560 Assume a wild female Kommoto dragon finds herself isolated on 0:19:16.600 --> 0:19:19.320 an island environment. Maybe she gets washed up somewhere after 0:19:19.359 --> 0:19:24.240 a storm. She could help her genes survive by parthenogenetically 0:19:24.359 --> 0:19:27.639 producing a clutch of males with which to mate and 0:19:27.800 --> 0:19:31.520 establish a new colony genetically. This is not ideal, but 0:19:31.640 --> 0:19:35.000 it's better than nothing, But it's not good for the 0:19:35.080 --> 0:19:38.720 dragon populations that are you know, trying to be sustained 0:19:38.800 --> 0:19:42.119 right now, for the females to be laying clutches exclusively 0:19:42.359 --> 0:19:46.040 of essentially inbred males. This may be better than nothing 0:19:46.119 --> 0:19:48.159 in the wild when there are no males present, like 0:19:48.200 --> 0:19:51.119 we said, but it actually interferes with the breeding programs 0:19:51.160 --> 0:19:55.480 that conservationists are using to help like replenish the species. 0:19:56.119 --> 0:19:58.800 So this leads to the idea that hey, maybe we 0:19:58.840 --> 0:20:02.159 should be careful about keeping female dragons in isolation in 0:20:02.240 --> 0:20:05.320 captivity because when there's no mail around, this can happen 0:20:05.680 --> 0:20:08.520 and it's not actually what's best for the species if 0:20:08.560 --> 0:20:11.000 we can help it. Yeah, that's fascinating because it's easy 0:20:11.080 --> 0:20:12.840 to just on the surface of things think, yeah, I 0:20:12.880 --> 0:20:16.360 go way to go. Commoto dragons just reproduce whether there's 0:20:16.359 --> 0:20:18.200 a mail around or not. But well, it is better 0:20:18.200 --> 0:20:20.760 than nothing probably. I mean, if there literally is no 0:20:20.880 --> 0:20:24.080 mail to reproduce with, this makes sense to do. But 0:20:24.119 --> 0:20:26.280 the problem is in these cases it's not actually that 0:20:26.359 --> 0:20:28.520 there's no male, it's just there's no mail right now. 0:20:29.280 --> 0:20:31.439 And by the way, it does appear that other female 0:20:31.480 --> 0:20:35.439 Commodo dragons in captivity have shown this same same phenomenon 0:20:36.119 --> 0:20:39.320 since the initial batch of observations. For example, it was 0:20:39.359 --> 0:20:42.879 reported in two thousand and eight that healthy male dragons 0:20:42.920 --> 0:20:46.400 hatched at the Sedgewick County Zoo in Wichita, Kansas from 0:20:46.400 --> 0:20:48.320 a female who had not made it with a male. 0:20:48.960 --> 0:20:51.639 But Commodo dragons are certainly not the only reptiles that 0:20:51.720 --> 0:20:56.760 exhibit parthenogenesis. Some lizards are even obligate parthenogens that you 0:20:56.760 --> 0:20:59.159 mentioned earlier, the ones that have no choice, like the 0:20:59.280 --> 0:21:02.640 hybrid new male Mexico whiptail lizard. Uh, this is an 0:21:02.680 --> 0:21:07.360 all female species and there's no sexual reproduction whatsoever. Or well, actually, 0:21:07.400 --> 0:21:10.400 what is true is that there is no sexual fertilization 0:21:11.000 --> 0:21:14.160 there uh, because in fact, these lizards have been observed 0:21:14.400 --> 0:21:17.800 to perform a series of same sex female courtship and 0:21:17.840 --> 0:21:21.000 mating rituals, the biological function of which is an interesting 0:21:21.040 --> 0:21:23.840 subject that we could return to in the future. Uh. 0:21:23.880 --> 0:21:25.840 And I guess it's just a reminder that even in 0:21:25.880 --> 0:21:28.639 the animal world, the fact that you don't have to 0:21:28.680 --> 0:21:32.240 have sexual fertilization doesn't mean that there's not sexual behavior. 0:21:32.280 --> 0:21:33.640 All right. On that note, we're gonna take a quick 0:21:33.680 --> 0:21:35.919 break and we come back. We'll get into another reptilian 0:21:35.960 --> 0:21:42.800 species that exhibits virgin birth. Thank alright, we're back. So 0:21:42.920 --> 0:21:46.520 we've been talking about komodo dragons. We mentioned lizards reptiles 0:21:46.520 --> 0:21:51.040 that exhibit parthenogenesis. Snakes are another great source of examples 0:21:51.240 --> 0:21:54.720 of parthenogenesis. There is at least one species of snake 0:21:55.040 --> 0:21:58.560 called Indo tie flops brahminus, also known as the Brahminy 0:21:58.680 --> 0:22:02.880 blind snake, which appears to be an obligate parthenogen. It's 0:22:02.920 --> 0:22:05.560 a burrowing blind snake, so you'll find it, you know, 0:22:05.680 --> 0:22:09.320 down underneath the soil and rotten wood and leaf litter 0:22:09.400 --> 0:22:12.240 and stuff like that. It's found naturally in parts of 0:22:12.280 --> 0:22:15.400 Africa and Asia, though it has been introduced in other places, 0:22:15.680 --> 0:22:17.720 and as far as we know, all members of this 0:22:17.800 --> 0:22:22.080 species are female and they reproduce completely without sex. However, 0:22:22.440 --> 0:22:25.400 plenty of other snake species have been shown to exhibit 0:22:25.480 --> 0:22:29.280 facultative parthenogenesis, like the Komodo dragons. It appears to be 0:22:29.320 --> 0:22:33.040 some kind of adaptation. Now, apparently, for a while this 0:22:33.119 --> 0:22:36.920 had only been observed in captive snakes that we're living in, 0:22:37.080 --> 0:22:39.520 you know, in tanks or in zoos or something like that, 0:22:39.600 --> 0:22:43.320 so it was believed to be some sort of captive syndrome. 0:22:43.440 --> 0:22:47.720 But more recently it appears that facultative parthenogenesis has been 0:22:47.720 --> 0:22:51.199 observed in wild snakes, sometimes even when males are present. 0:22:52.080 --> 0:22:57.120 Just to cite one example by Booth, Smith, Eskridge, Hass, Mendelssohn, 0:22:57.160 --> 0:23:02.400 and Shoit, facultative parthenogenesis discovered in wild vertebrates in Biology 0:23:02.440 --> 0:23:05.760