WEBVTT - Strange Milk 0:00:03.040 --> 0:00:05.840 Welcome to Stuff to Blow your Mind from how Stuff 0:00:05.840 --> 0:00:14.400 Works dot Com. Hey you welcome to Stuff to Blow 0:00:14.440 --> 0:00:17.320 your Mind. My name is Robert Lamb and I'm Joe McCormick. 0:00:17.320 --> 0:00:20.200 And today I wanted to start with the question I'm 0:00:20.200 --> 0:00:22.439 going to try to do my best big lebowski boys. 0:00:22.600 --> 0:00:28.159 What makes some mammal? Uh? Yeah? Thinking about mammals, what 0:00:28.240 --> 0:00:30.680 are a few common features of mammals? Of course, we 0:00:30.760 --> 0:00:35.360 know that all mammals are vertebrates, along with birds, reptiles, amphibians, 0:00:35.360 --> 0:00:38.680 and fish, they get the backbone going on. Mammals, along 0:00:38.720 --> 0:00:42.520 with birds, are of course endothermic or warm blooded, which 0:00:42.520 --> 0:00:45.880 can that can sometimes be a misnomer because, as we've 0:00:45.920 --> 0:00:48.879 discussed before, there are cases where mammals can cool their 0:00:48.920 --> 0:00:53.920 bodies down quite a bit. Most mammals, excluding monotreams, have 0:00:54.160 --> 0:00:58.560 live berths rather than laying eggs. Mammals generally have hair 0:00:58.880 --> 0:01:01.840 as opposed to scales or feathers, right, unless they've lost 0:01:01.880 --> 0:01:06.039 that hair by becoming aquatic creatures or for reasons yet unknown, right, 0:01:06.160 --> 0:01:09.039 or for living underground, etceter Right, Yeah, yeah, and then 0:01:09.040 --> 0:01:10.959 we get to the big one, of course, It is 0:01:11.000 --> 0:01:14.120 that mammals nurse they're young, with milk, and this is 0:01:14.160 --> 0:01:17.760 one of the real miracles of nature. It is really, 0:01:17.840 --> 0:01:20.160 and we're not just We're not just saying that because 0:01:20.240 --> 0:01:25.200 milk has such an important role in human child rearing, 0:01:25.480 --> 0:01:28.440 or because humans have this weird thing where we drink 0:01:28.480 --> 0:01:31.840 the milk of other species, especially around the holidays. You know, 0:01:32.440 --> 0:01:36.760 this is kind of a slightly holiday themed episode because 0:01:36.920 --> 0:01:41.200 a lot of people drink eggnog boiled custard type drinks, 0:01:41.200 --> 0:01:45.959 which are more traditionally milk based. Is eggnog a dairy product. 0:01:46.000 --> 0:01:47.880 I thought it was made with eggs. I have no idea. 0:01:48.160 --> 0:01:50.200 Oh yeah, there's cream in there. I mean, obviously if 0:01:50.240 --> 0:01:54.160 you can get the soy nog, which I have memories 0:01:54.480 --> 0:01:58.120 of being tasty, and yet this year I do. Yeah, 0:01:58.080 --> 0:02:00.600 I have memories. I see like I saw it in 0:02:00.640 --> 0:02:02.280 the store. I got kind of excited. I got a 0:02:02.600 --> 0:02:05.360 particular carton of soy nog, brought it back home to 0:02:05.360 --> 0:02:08.520 share with my son, Um who is Um Who's who's 0:02:08.520 --> 0:02:11.320 six and uh and he said, oh, this is good. 0:02:11.360 --> 0:02:15.000 This tastes like wet cold sugar. And I was like, yeah, 0:02:15.200 --> 0:02:17.400 it does kind of taste like wet cold sugar. It 0:02:17.440 --> 0:02:20.440 doesn't have this particular I don't want to damn all 0:02:20.480 --> 0:02:24.040 soy nog because I have to be remembering something real. 0:02:24.480 --> 0:02:28.160 But this particular one, yeah, did not have that fatty, creamy, 0:02:28.440 --> 0:02:31.800 uh finish to it anything, but like normal full fat 0:02:31.880 --> 0:02:35.040 milk products always does have a kind of strange sweetness 0:02:35.080 --> 0:02:39.519 to it. You're noticed the odd sweetness of skim milk. 0:02:39.680 --> 0:02:42.480 There's something feels a little off about it. Yeah, I 0:02:42.480 --> 0:02:44.040 mean it's been a while since I've had skim milk. 0:02:44.160 --> 0:02:47.120 I do tend to just use um, like soy milk, 0:02:47.680 --> 0:02:50.840 almond milk, coconut milk, that kind of thing these days. Um, 0:02:51.120 --> 0:02:54.760 And thus my desire to get in the Christmas spirit 0:02:54.800 --> 0:02:57.720 by buying soy nog. Right, But so okay, it's not 0:02:57.800 --> 0:03:00.520 just the role in human culture that we use the 0:03:00.560 --> 0:03:03.640 milk of other animals in our cuisine, which is pretty 0:03:03.720 --> 0:03:06.160 much objectively weird. I think that's one of those things 0:03:06.240 --> 0:03:08.440 aliens would come to Earth and see us doing and 0:03:08.480 --> 0:03:11.120 think was weird. But it's also that it's it's a 0:03:11.120 --> 0:03:13.560 deep part of what we are as an animal. The 0:03:13.560 --> 0:03:16.480 possession of memory glands and the rearing of children with 0:03:16.560 --> 0:03:20.400 milk is uh that that's like a main morphological feature 0:03:20.440 --> 0:03:22.840 of what it means to be a mammal. The word 0:03:22.880 --> 0:03:28.280 mammal basically means like breast beast. Yeah, we are a 0:03:28.280 --> 0:03:31.720 bunch of breastbeasts really so yes, it nourishes our offspring 0:03:31.919 --> 0:03:34.800 and in doing so helps to establish immune system competence 0:03:34.840 --> 0:03:38.600 as well. Now, the exact nutrient composition of milk is 0:03:38.600 --> 0:03:41.120 going to vary across a lot across species, and it 0:03:41.200 --> 0:03:44.040 also can change quite a bit depending on the different 0:03:44.080 --> 0:03:47.800 stages of lactation, which is something that's easy to overlook. 0:03:47.880 --> 0:03:51.400 Milk is not just necessarily oh, here's the here's the 0:03:51.400 --> 0:03:53.960 formula coming out, and know the formula will change. The 0:03:54.000 --> 0:03:57.559 actual nutrient load will will vary depending on the developmental 0:03:57.600 --> 0:04:00.880 stage of the young, So milk fat content and seals, 0:04:00.920 --> 0:04:04.760 for instance, can be as high as six. Meanwhile, it's 0:04:04.800 --> 0:04:09.080 basically nothing in wallabies. And speaking of wallabies, according to 0:04:09.240 --> 0:04:13.880 the Origin and Evolution of Lactation by Capuoso and Acres 0:04:13.880 --> 0:04:17.799 Posting two thousand nine, quote milk in the tamer wallaby 0:04:17.960 --> 0:04:22.480 that's uh. Macropus eugeny changes from a very dilute secretion 0:04:22.600 --> 0:04:27.599 containing primarily carbohydrate during early lactation to a more energy 0:04:27.640 --> 0:04:31.919 dense milk that contains substantial quantities of protein and fat 0:04:32.000 --> 0:04:34.359 during late phases of that left lactation. So that's a 0:04:34.440 --> 0:04:37.919 nice example of just how the the the the exact 0:04:37.920 --> 0:04:42.200 details of the milk will change during the course of 0:04:42.240 --> 0:04:45.039 the the young's growth. Now, we could probably devote a 0:04:45.040 --> 0:04:47.680 whole episode or multiple episodes in the future to the 0:04:47.720 --> 0:04:53.320 study of milk, true biological mammal milk, because that's a 0:04:53.360 --> 0:04:56.400 fascinating subject on its own, But today we wanted to 0:04:56.440 --> 0:05:00.279 focus on something even weirder, which is all of the 0:05:00.440 --> 0:05:04.280 non mammal quote milk that's out there. There has been 0:05:04.320 --> 0:05:06.760 an astonishing amount of research that I had not kept 0:05:06.839 --> 0:05:11.080 up with until diving into it recently about all about 0:05:11.120 --> 0:05:14.000 animals you would just never expect to produce milk, producing 0:05:14.120 --> 0:05:16.600 something like milk, Yeah, I have to say this also 0:05:16.680 --> 0:05:19.960 forced me to learn about a couple of different creatures 0:05:20.000 --> 0:05:21.839 I was not familiar with then we brought to my 0:05:21.880 --> 0:05:25.800 attention solely because they produced something that one might call milk. 0:05:26.120 --> 0:05:29.119 So this will be our anomalous milk episode. But before 0:05:29.160 --> 0:05:31.640 we get into the anomalous milk, I guess it's worth 0:05:31.640 --> 0:05:34.880 a quick look at actual mammal milk itself. Right now, 0:05:34.880 --> 0:05:38.400 I know You've done some episodes on dairy products and 0:05:38.480 --> 0:05:42.120 on mammal milk in the past, right, Yeah, there's there's 0:05:42.120 --> 0:05:45.320 an older episode that I did with Julie Douglas back 0:05:45.360 --> 0:05:48.160 in the day, and then more recently did an episode 0:05:48.200 --> 0:05:53.479 with Christians Say titled Uh Holy Butter. As the name implies, 0:05:53.560 --> 0:05:56.320 it's mostly about butter and how we make butter and 0:05:56.600 --> 0:05:58.720 some of the uses we have for better Did you 0:05:58.760 --> 0:06:01.360 all talk about bog butter? Yes, we did talk about 0:06:01.360 --> 0:06:04.279 bog butter. Bog butter is so good. Yeah, but we 0:06:04.320 --> 0:06:07.000 also talked about how butter and also milk, is nothing 0:06:07.000 --> 0:06:11.040 short of solar energy transformed through a few different steps 0:06:11.320 --> 0:06:14.880 into a food. For instance, there's the of course, the 0:06:14.880 --> 0:06:18.200 the alchemy of photosynthesis to kick things off. The grass 0:06:18.240 --> 0:06:21.200 in the field converts energy in the form of sunlight 0:06:21.240 --> 0:06:24.520 into chemical energy in the form of sugars and other carbohydrates. 0:06:24.560 --> 0:06:27.800 This is essentially the first miracle of milk. And then 0:06:28.080 --> 0:06:33.400 you have a female ruminant in this case cow, sheet, camel, water, buffalo, goats, 0:06:33.440 --> 0:06:37.760 et cetera. They consume that grass and truly, as Elaine 0:06:38.480 --> 0:06:42.080 Cosa Rova explores in her tremendous book, Butter a rich 0:06:42.200 --> 0:06:45.000 history Um, you're better off thinking of it as a 0:06:45.080 --> 0:06:49.040 processed harvesting rather than a meal, because ruminants are built 0:06:49.040 --> 0:06:52.640 to transform grass into milk. Uh. Consider that they have 0:06:52.720 --> 0:06:56.080 these three or four chambered stomachs. Uh. They're upper dental 0:06:56.120 --> 0:07:00.640 pad instead of teeth from massive for massicating green. And 0:07:00.760 --> 0:07:03.440 each animal puts its own particular chemical spin on the 0:07:03.480 --> 0:07:06.120 process as well. But they crunch up the greens and 0:07:06.160 --> 0:07:10.320 they ferment them in their mini chambered guts eight hours feeding, 0:07:10.360 --> 0:07:13.520 eight hours ruminating, and then the remains of the day resting, 0:07:14.440 --> 0:07:17.679 so that that masceration, the repeated chewing of the cud 0:07:17.840 --> 0:07:21.600 helps to carry out the second miracle of milk, the 0:07:21.600 --> 0:07:24.960 transformation of a low fat diet of grass into high 0:07:25.040 --> 0:07:28.120 fat milk. Yeah. You always wonder about that, right, Like 0:07:28.200 --> 0:07:30.720 you look at the beginning product in the end product, 0:07:30.760 --> 0:07:34.840 and you're like, I don't understand exactly what's happening here. Yeah, 0:07:34.920 --> 0:07:36.920 And and part of this is just the miracle digestion. 0:07:36.920 --> 0:07:40.080 The broken down food is assaulted by microbes and the 0:07:40.120 --> 0:07:43.560 oxygen free fermentation chamber of the gut, the grassy meal 0:07:43.600 --> 0:07:46.200 is broken down to the basic elements, strings of carbon 0:07:46.240 --> 0:07:49.240 and hydrogen molecules, and then other backed here recombine the 0:07:49.280 --> 0:07:52.640 elements into volat how fatty acids. Only half the fat 0:07:52.720 --> 0:07:55.160 comes from the cow's diet. The rest comes from the 0:07:55.200 --> 0:07:59.040 cow's own body fat. Oh wow. Yeah, And so it's 0:07:59.080 --> 0:08:02.000 sort of it's not just making a product out of 0:08:02.000 --> 0:08:04.680 what it just eight, but it's giving of itself when 0:08:04.680 --> 0:08:07.080 it creates milk. And I think that's one of the reasons, 0:08:07.120 --> 0:08:09.360 like we put the human layer on milk to write 0:08:09.400 --> 0:08:13.440 like milk is this this giving of something something to 0:08:13.120 --> 0:08:15.800 uh to to bring nourishment to another. And of course 0:08:15.840 --> 0:08:18.000 we have so many metaphors related to that, including of 0:08:18.000 --> 0:08:21.720 course that the milk of human kindness. But in this 0:08:21.960 --> 0:08:26.120 example talking just about ruminate milk. Um, it's a you know, 0:08:26.240 --> 0:08:29.120 fatty liquid to ensure the survival of the animals young 0:08:30.000 --> 0:08:32.800 and um. The exact composition again is going to vary 0:08:32.800 --> 0:08:36.040 from species to feat species, with additional factors depending on 0:08:36.160 --> 0:08:40.360 environment and diet. For instance, uh a new produces twice 0:08:40.400 --> 0:08:43.360 the fat content of cow milk, Goat milk has smaller, 0:08:43.480 --> 0:08:46.920 more digestible fat molecules, yak milk has less sugar and 0:08:46.960 --> 0:08:49.840 more protein, and camel's milk has three times as much 0:08:49.920 --> 0:08:53.280 vitamin C water. Buffalo milk has twice the fat of 0:08:53.320 --> 0:08:56.280 cow milk. And then we have things that are not 0:08:56.400 --> 0:09:00.120 even um, you know, we don't traditionally think of as 0:09:00.160 --> 0:09:04.800 milk producers. But consider the whales. Oh yeah, blue whales 0:09:04.840 --> 0:09:09.040 for instance. Uh this, this always blows my mind. Uh. 0:09:09.400 --> 0:09:12.360 A newborn blue whale gainst. Two hundred pounds a day 0:09:12.440 --> 0:09:15.840 just by nursing, and the average whale produces forty times 0:09:15.840 --> 0:09:17.960 more milk than a cow. And this has even led 0:09:18.040 --> 0:09:21.480 some scientists to consider the possibility of milking whales and 0:09:21.559 --> 0:09:24.920 specially prepared milking bays and then using that milk for 0:09:25.000 --> 0:09:28.800 human consumption. Is there really any milk of any animal 0:09:28.920 --> 0:09:33.800 that has not been considered for human consumption? UM? I 0:09:33.800 --> 0:09:38.000 don't know. I mean there's some that are certainly more attractive. Um. 0:09:38.040 --> 0:09:42.440 But anytime you start reading around about different milks, I 0:09:42.440 --> 0:09:44.760 feel like there's a good chance somebody's tasted it and 0:09:44.760 --> 0:09:46.920 they will tell you what the flavor profile is. What 0:09:47.080 --> 0:09:51.880 does rat milk taste like? What what does monkey milk 0:09:52.000 --> 0:09:57.200 pair with? I don't know. I have sometimes think about 0:09:57.200 --> 0:09:59.360 cat milk, like, what like tiger milk would taste like? 0:09:59.360 --> 0:10:01.560 Would it be did you know or who did have 0:10:01.640 --> 0:10:05.319 kind of a like a meati consistency to it, probably 0:10:05.880 --> 0:10:10.720 like a nice French washed rind cat milk cheese. I also, 0:10:11.400 --> 0:10:13.760 this is a topic that I discussed in that past 0:10:13.800 --> 0:10:15.199 episode with the the jew. It was of course the the 0:10:15.320 --> 0:10:19.160 the idea that you do have certain situations that can 0:10:19.200 --> 0:10:23.439 cause males to lactaatee as well. Uh, some do to 0:10:24.040 --> 0:10:27.040 some are more like behavioral environmental, and others have to 0:10:27.080 --> 0:10:30.280 do with their regularities in the body. But you also 0:10:30.360 --> 0:10:33.120 have certain male fruit bats that lactated, and these are 0:10:33.120 --> 0:10:36.920 the only examples of male mammals lactating as a part 0:10:36.920 --> 0:10:39.880 of a regular parental activity. Yeah, and you can see 0:10:39.880 --> 0:10:42.840 already in the idea of male animal lactation that there 0:10:42.960 --> 0:10:46.240 is going to be They're gonna be some like asterisks 0:10:46.400 --> 0:10:50.760 next to the official like dictionary definition of milk, which 0:10:50.800 --> 0:10:54.719 is something like an opaque white fluid that's rich and 0:10:54.800 --> 0:10:58.160 fat and protein that's secreted by female mammals for the 0:10:58.200 --> 0:11:02.200 nourishment of their young. So obviously there's not that's not 0:11:02.280 --> 0:11:05.240 quite all cases, because in some cases males secrete it 0:11:05.280 --> 0:11:07.600 like the bats you're just talking about. And then I 0:11:07.640 --> 0:11:11.160 guess the question comes in where if you have something 0:11:11.240 --> 0:11:14.679 that meets all those qualifications but is not produced by 0:11:14.720 --> 0:11:17.720 a mammal. Is that technically milk or not? I think 0:11:17.760 --> 0:11:21.080 a lot of biologists might say no, but they might 0:11:21.120 --> 0:11:25.080 still use the term in describing whatever this other substance is. 0:11:26.120 --> 0:11:28.320 What is the substance on the Simpsons that they're drinking 0:11:28.360 --> 0:11:32.520 in the school cafeteria. I think it's rat milk now 0:11:32.559 --> 0:11:37.400 with vitamin R. Oh, my bones they feel so brittle. 0:11:37.640 --> 0:11:41.880 But I always drink plenty of malk. Well, maybe it's mack, 0:11:42.040 --> 0:11:44.880 maybe it's milk. Well, whatever you call it, milk, malk, 0:11:45.160 --> 0:11:50.479 milk analog. There are clearly strong reasons that non mammalian 0:11:50.559 --> 0:11:55.160 animals would would have an incentive to secrete milk like 0:11:55.280 --> 0:11:57.400 fluids that they used to feed their young. It's a 0:11:57.400 --> 0:12:00.640 really useful strategy and it serves quite a few dif functions. 0:12:00.679 --> 0:12:03.160 I mean, for one thing, it allows the parent to 0:12:03.200 --> 0:12:06.160 produce food for their offspring without having to like leave 0:12:06.720 --> 0:12:09.080 or hunt or forage. You don't have to go out 0:12:09.120 --> 0:12:13.000 of the nest. Another thing is that it tightly controls 0:12:13.080 --> 0:12:16.080 the nutritional content of the offsprings food, making sure they 0:12:16.120 --> 0:12:18.080 get exactly what they need. And you can see that 0:12:18.120 --> 0:12:21.560 in the very different nutritional profiles of milk, like you 0:12:21.600 --> 0:12:24.439 were talking about earlier, like with wallabies and stuff. It's 0:12:24.440 --> 0:12:26.760 also a way for the young to eat all the 0:12:26.800 --> 0:12:31.200 mother without actually eating the mother. Yes, exactly, Uh yeah, 0:12:31.240 --> 0:12:33.960 and so it can. It can include extra nutrition, lots 0:12:34.000 --> 0:12:36.720 of fat and protein, maybe more fat and protein than 0:12:36.760 --> 0:12:39.600 you could expect to get from food sources in the environment. 0:12:39.840 --> 0:12:43.200 It's like super concentrating the nutrition profile for the young, 0:12:43.400 --> 0:12:46.600 which will help them speed up and grow faster. And 0:12:46.640 --> 0:12:49.880 then it can also deliver really important additives. Earlier you 0:12:49.960 --> 0:12:53.480 mentioned immune function, and that does seem to be a 0:12:53.600 --> 0:12:56.880 very important role of of milk and animals. The idea 0:12:56.920 --> 0:13:01.880 of stimulating the immune system with antibodies or supplementing the 0:13:01.960 --> 0:13:07.160 offsprings microbiome with microbiodelic commenceled bacteria from the mother. Yeah, 0:13:07.160 --> 0:13:09.200 I feel like this should come as no surprise following 0:13:09.200 --> 0:13:12.839 our poop eating eating animals episode, because obviously, if if 0:13:13.040 --> 0:13:16.920 eating a little um parental poop is going to provide 0:13:16.960 --> 0:13:19.040 that kind of a boost, obviously that kind of boost 0:13:19.120 --> 0:13:22.400 might be available via milk. And then on top of 0:13:22.440 --> 0:13:25.520 all that, like the additives for the immune system, you 0:13:25.600 --> 0:13:28.960 also can add hormones. This can be especially useful when 0:13:28.960 --> 0:13:32.280 it's like hormones that could have something to do with 0:13:32.440 --> 0:13:35.960 cementing the psychological bond between parent and child, or things 0:13:35.960 --> 0:13:38.440 like growth hormone to help speed up the growth of 0:13:38.480 --> 0:13:40.600 the young. So with some of that in mind, it 0:13:40.679 --> 0:13:44.320 might be less surprising what I'm about to say, which 0:13:44.400 --> 0:13:49.199 is that a number of bird species secrete a substance 0:13:49.240 --> 0:13:51.880 analogous to milk. I think we should look at a few, Robert, 0:13:51.880 --> 0:13:53.920 will you look at milk birds with me? Let's do it. 0:13:54.080 --> 0:14:00.120 How about pigeons. Pigeons both male and female, regurgitate a 0:14:00.240 --> 0:14:04.640 highly nutritious substance known as crop milk into the mouths 0:14:04.640 --> 0:14:07.360 of their young, and don't let the fact that it 0:14:07.480 --> 0:14:10.520 is delivered in the form of nourishing barf throw you off. 0:14:10.600 --> 0:14:14.360 This is not regurgitated food. This is not the parent 0:14:14.440 --> 0:14:18.360 bird providing a partially digested version of what they just date. 0:14:18.720 --> 0:14:22.360 Crop milk is a separate, original substance secreted in the 0:14:22.440 --> 0:14:25.920 crop organ. It's from the parent's body itself. Now the 0:14:26.000 --> 0:14:28.360 crop organ is I don't know if you've ever seen 0:14:28.400 --> 0:14:30.280 one of these, ROBBERTI, it's sort of have not. It's 0:14:30.320 --> 0:14:34.160 like a pouch area in the esophagus that can be 0:14:34.280 --> 0:14:37.680 used to store and moisten food before it continues on 0:14:37.760 --> 0:14:41.000 down the elementary tract for digestion. And I think it's 0:14:41.040 --> 0:14:45.000 thought that um the crop organ is useful for like 0:14:45.200 --> 0:14:48.600 prey species of birds that might be trying to gobble 0:14:48.680 --> 0:14:51.200 up a bunch of food really fast while they're out 0:14:51.200 --> 0:14:53.880 somewhere exposed and then be able to fly off quickly 0:14:53.960 --> 0:14:56.320 and reduce the amount of time they're out there eating 0:14:56.360 --> 0:14:58.720 and exposed to predators. So you want to be able 0:14:58.760 --> 0:15:00.560 to just like stuff it all in, like get it 0:15:00.600 --> 0:15:02.880 all down there really fast, and then get out of there, 0:15:02.920 --> 0:15:05.400 and then you can settle down somewhere safe and try 0:15:05.400 --> 0:15:08.120 to digest. It's a it's a it's a doggy bag 0:15:08.240 --> 0:15:11.880 essentially inside the body, Yes, exactly, it's it's your it's 0:15:11.880 --> 0:15:15.520 your styrofoam clam shell inside the bird's throat, and so 0:15:15.560 --> 0:15:19.440 the crop milk, it's actually produced by pigeons and doves. 0:15:19.760 --> 0:15:21.920 This is described in a paper I'll come back to 0:15:21.960 --> 0:15:25.960 in a minute as quote an oily, yellowish cheese like 0:15:26.200 --> 0:15:31.200 substance that is formed into small seed sized rice shaped pellets. 0:15:32.000 --> 0:15:35.360 I've also seen it described as cottage cheese but yellow. Well, 0:15:35.360 --> 0:15:38.160 this sounds fine. I have no objection to any of that. Okay. 0:15:38.240 --> 0:15:42.840 So apparently crop milk is produced by the inner cells 0:15:42.920 --> 0:15:46.680 of the crop pouch becoming moist and then sort of 0:15:46.800 --> 0:15:50.600 sloughing off into the pouch and then getting regurgitated. So 0:15:50.640 --> 0:15:53.760 it's like, here's some let me barf you up some 0:15:53.840 --> 0:15:57.920 of my highly nutritious inside skin. This is my flesh, 0:15:58.760 --> 0:16:01.880 et cetera. Right now. An interesting thing in birds and 0:16:01.920 --> 0:16:05.480 pigeons is that this process in parent pigeons is apparently 0:16:05.520 --> 0:16:10.960 controlled by the hormone prolactin, which is also what stimulates 0:16:11.000 --> 0:16:15.320 milk production in mammals. That's kind of interesting because you know, 0:16:15.400 --> 0:16:18.080 they don't have memory glands. It's not you would think 0:16:18.080 --> 0:16:20.120 that it would be something completely different, but it's pro 0:16:20.240 --> 0:16:23.520 lactin in both cases that gets the parent doing this. 0:16:23.880 --> 0:16:27.240 Crop milk tends to be mostly protein and fat, about 0:16:27.240 --> 0:16:31.920 six protein maybe thirty something percent fat, and then just 0:16:31.960 --> 0:16:35.600 a little bit of carbohydrates and minerals and other things 0:16:35.640 --> 0:16:38.800 in there. A two thousand twelve study in Plos One 0:16:38.880 --> 0:16:41.400 by Megan Gillespie at All found that if you took 0:16:41.560 --> 0:16:45.960 baby chickens and fed them crop milk from pigeons. They 0:16:46.040 --> 0:16:50.160 sort of became like little minor hulk chickens. After just 0:16:50.240 --> 0:16:53.000 seven days, the pigeon milk chickens were more than twelve 0:16:53.040 --> 0:16:56.960 percent heavier than control chickens. And also they showed greater 0:16:57.000 --> 0:17:00.680 diversity of gut bacterious specifically in the seaka um, and 0:17:00.720 --> 0:17:03.480 they had higher expression of the immunoglobulin I g A, 0:17:03.560 --> 0:17:07.000 which is an antibody class that's crucial for all kinds 0:17:07.040 --> 0:17:09.840 of immune system function. Now, a side question you might 0:17:09.840 --> 0:17:12.520 be wondering is why did they test this on chickens 0:17:12.680 --> 0:17:15.320 rather than on pigeons. I think the answer is that 0:17:15.400 --> 0:17:18.440 with pigeons you couldn't really have a control group because 0:17:18.480 --> 0:17:21.679 young pigeons would just die without the crop milk. And 0:17:21.720 --> 0:17:23.879 there I've read that there have been other studies that 0:17:23.920 --> 0:17:26.520 looked into this. They're like fed pigeon crop milk two 0:17:26.640 --> 0:17:28.960 chickens to see what happened, and the chickens always really 0:17:29.040 --> 0:17:32.360 beefed up. It. It's like it's clearly something that their 0:17:32.400 --> 0:17:35.399 bodies respond well to. But there are some other birds 0:17:35.440 --> 0:17:38.920 that also produce UH and feed their young with secretions 0:17:38.960 --> 0:17:41.879 from the upper digestive tract that are crop milk or 0:17:41.960 --> 0:17:45.679 something like it. Flamingos would be an example. According I 0:17:45.720 --> 0:17:49.080 was reading about the flamingo crop milk feeding on the 0:17:49.160 --> 0:17:51.960 San Diego Zoo website. They were talking about their flamingos. 0:17:52.000 --> 0:17:54.760 Oh yeah, they have a great website, great outreach. Yeah, exactly, 0:17:54.840 --> 0:17:56.959 And so the a few things they mentioned. One is 0:17:57.000 --> 0:18:01.639 that apparently when young chicks flamingo chicks are hungry and 0:18:01.640 --> 0:18:04.959 they're calling out for feeding, it's not just their own parents. 0:18:05.080 --> 0:18:08.760 Other adults in the flock can be stimulated to act 0:18:08.800 --> 0:18:11.720 as sort of foster feeders, which is sweet, that's cool. 0:18:12.000 --> 0:18:13.959 And the way that seems to work is that they 0:18:14.200 --> 0:18:17.280 they suppose that hearing the sound of the hungry chicks 0:18:17.320 --> 0:18:21.720 calling for food stimulates the production of the milk like analog. 0:18:22.359 --> 0:18:24.520 And then also one of the things they say is 0:18:24.560 --> 0:18:28.640 that as the parent flamingos produce crop milk to feed 0:18:28.680 --> 0:18:32.159 their chicks, their feathers tend to be drained of color 0:18:32.280 --> 0:18:34.720 over time. So like if you've got an adult that's 0:18:34.760 --> 0:18:38.080 producing crop milk feeding a young one, it turns from 0:18:38.119 --> 0:18:40.399 pink to a pale pink or even to a white. 0:18:40.600 --> 0:18:43.920 And then after the they stopped producing it, they gradually 0:18:43.960 --> 0:18:47.480 get their color back. One more, of course, is emperor penguins. 0:18:47.520 --> 0:18:49.040 You may have heard about this, like, you know, the 0:18:49.320 --> 0:18:52.280 male emperor penguins guarding the the egg while the female 0:18:52.280 --> 0:18:54.719 goes off to feed. So that goes on. But what 0:18:54.800 --> 0:18:58.480 happens if the the young penguin hatches from the egg 0:18:58.520 --> 0:19:02.080 before the female returns from feeding with fish to regurgitate 0:19:02.160 --> 0:19:05.200 for it. Apparently the male penguin will do something like this, 0:19:05.240 --> 0:19:08.680 will generate some upper digestive tract milk to bar out 0:19:08.760 --> 0:19:12.080 for the little penguin, and the little penguin gets its 0:19:12.080 --> 0:19:16.000 nourishment that way. So again, it's it's certainly not milk, 0:19:16.359 --> 0:19:18.960 but it does seem to be meeting some of the 0:19:18.960 --> 0:19:22.720 criteria we've discussed. Well, it's a lot like milk nutritionally, 0:19:23.000 --> 0:19:25.440 it seems to serve a lot of the same functions 0:19:25.520 --> 0:19:28.800 and be composed in a pretty similar way. So I 0:19:28.840 --> 0:19:31.240 don't know, I don't know whether you should call it 0:19:31.320 --> 0:19:33.399 milk or not. I mean, again, I think if we 0:19:33.440 --> 0:19:36.440 go by the technical definition, milk is only produced by mammals, 0:19:36.440 --> 0:19:38.840 So it's not milk, but it looks like milk, It 0:19:38.920 --> 0:19:42.160 apparently tastes like milk, it does what milk does. Yeah, 0:19:42.200 --> 0:19:45.760 we could call it bird milk or or bird nog 0:19:46.119 --> 0:19:48.320 a holiday twist. That's good. Well, how about let let 0:19:48.400 --> 0:19:50.760 me take you to the next step. This one might 0:19:50.800 --> 0:19:53.879 seem unbelievable, but maybe just a tiny bit less. So, 0:19:53.960 --> 0:19:57.760 given that birds produce milk like secretions, what about dinohnog? 0:19:59.160 --> 0:20:03.040 So what are birds? They are the dinosaurs that survived 0:20:03.119 --> 0:20:06.280 the fifth extinction right there, the descendants of these feathered 0:20:06.320 --> 0:20:09.240 dinosaurs that survived when the thing that killed all the 0:20:09.280 --> 0:20:12.960 other dinosaurs. Now, given that modern birds exhibit a form 0:20:13.040 --> 0:20:16.639 of what might be considered lactation, is it possible that 0:20:16.800 --> 0:20:20.480 some dinosaurs also fed their young with milk like secretions. 0:20:21.200 --> 0:20:23.400 We don't know the answer to this, but exactly this 0:20:23.560 --> 0:20:28.080 question is explored by the Australian molecular biologist Paul Else 0:20:28.520 --> 0:20:33.680 in a Journal of Experimental Biology paper called Dinosaur Lactation. 0:20:34.720 --> 0:20:38.000 It's like Chariots of the Gods. You know, if you 0:20:38.080 --> 0:20:41.800 end it with a question mark, you're always safe. It's 0:20:41.840 --> 0:20:43.720 not in all caps, though, I will say that that 0:20:43.840 --> 0:20:46.080 is a good point, but no, that this is a 0:20:46.080 --> 0:20:49.080 fun question. So he says, you know, if dinosaurs did 0:20:49.080 --> 0:20:52.040 perform something analogous to lactation, we don't know, but if 0:20:52.040 --> 0:20:55.440 they did, it's another one of the many soft tissue 0:20:55.440 --> 0:20:58.400 based biological features that are just going to be extremely 0:20:58.440 --> 0:21:02.359 difficult to infer from postilized remains. The bones don't usually 0:21:02.400 --> 0:21:05.000 tell us things like that, So the only way to 0:21:05.040 --> 0:21:07.560 try to answer this kind of question is to look 0:21:07.600 --> 0:21:09.840 at the indirect evidence. And so he's got a few 0:21:09.840 --> 0:21:13.400 thoughts here. One of them is about the initial size 0:21:13.480 --> 0:21:18.399 difference between adults and hatchlings of some dinosaur species, especially 0:21:18.440 --> 0:21:21.439 the sauropods. Yeah, yeah, so he says, like, you know, 0:21:21.480 --> 0:21:24.480 it almost seems as if it would present mechanical problems 0:21:24.560 --> 0:21:27.840 and feeding. He said to I believe this was to 0:21:28.000 --> 0:21:31.639 a campus newspaper. He was speaking about his paper to quote, 0:21:31.680 --> 0:21:34.199 although I work at the molecular level, I'm basically a 0:21:34.200 --> 0:21:37.520 comparative physiologist, and one thing that always struck me as 0:21:37.640 --> 0:21:41.280 unresolved about dinosaurs was how a dinosaur parent of several 0:21:41.280 --> 0:21:44.919 tons could feed young of only a few kilograms. It 0:21:45.000 --> 0:21:48.399 seemed obvious a form of lactation similar to that present 0:21:48.480 --> 0:21:52.000 in birds. And then in his paper he writes, quote 0:21:52.080 --> 0:21:55.119 lactation might free large parents from having to feed their 0:21:55.160 --> 0:21:58.840 newly hatched young the regurgitated products of their own meals 0:21:58.880 --> 0:22:01.960 that might be unsued did for altricial young based on 0:22:02.080 --> 0:22:05.880 digestive systems unfamiliar with coarse fodder like you know, rough 0:22:05.920 --> 0:22:09.440 plant matter that adults would be eating, and essential nutrient 0:22:09.520 --> 0:22:13.440 requirements to promote rapid growth, and replace this with secret 0:22:13.600 --> 0:22:18.280 secretory products. Oh, that's a hard word. Secretary uh synthesized 0:22:18.320 --> 0:22:21.359 by the four gut that are more suited to supporting 0:22:21.480 --> 0:22:25.400 rapid development. So again there's obviously some kind of incentive 0:22:25.440 --> 0:22:27.800 there would be if they could produce something like this. 0:22:27.920 --> 0:22:29.920 We don't know if they could, and so if we 0:22:30.080 --> 0:22:33.320 entertain that possibility for a second, the dinosaurs produced milk 0:22:33.359 --> 0:22:35.679 for their young, it's likely they did it in the 0:22:35.720 --> 0:22:38.879 same way as birds rather than like mammals do. So 0:22:38.920 --> 0:22:41.879 that would probably mean nutrient rich secretions from the upper 0:22:41.880 --> 0:22:45.080