Evolution of Live birth (Why do mammal not lay eggs?)

Mammals, like almost all other types of animal today, used to lay eggs, but then they adapted to give birth to live young. why did some mammals make this change and if it has been so beneficial why haven't more animals evolved to do it?
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[@99bulldog]

One of the things I find fascinating is how humans can find almost any baby mammal to be cute. I often wonder if this is a common trait across all mammals.

[@Pedrosa2541]

There are some exceptions, baby echidnas are like cold turkey with spines.

[@alecfoster5542]

There is something about the slightly disproportional large head and large eyes, right?

[@grantbartley483]

It's probably some sort of bell curve of dislike-to-like. Distributions of traits across large populations often are bell curves.

[@stephenspackman5573]

I think it's an evolved survival strategy, and a very deep one. In truly extreme circumstances, your genes benefit from preserving even extremely distant relatives, and conversely manipulating others to preserve your young is always clever. And we certainly do see animals acting kindly, across species boundaries, to babies that would make a perfectly fine lunch.

[@stephenspackman5573]

@@Pedrosa2541 We were just talking about puggles last night! I find them adorable, my wife thinks they look like creepily animated chicken breasts. One of us must be wrong!

[@DavidMcGuizz]

Echidnas might be the most underrated animal in terms of cuteness. Look at all of them running around together. Amazing

[@h4ppyp3an4buter6]

omg yes, i even stop paying attention on what he was saying because of their cuteness 😭😭

[@Gildedmuse]

Fun fact: a group of echidnas is a parade.

[@georgevan]

@@Gildedmuse based facts

[@Tobunari]

@@Gildedmuse Poor Knuckles...

[@ExtremeMadnessX]

They want to find Sonic.

[@mariastevens6406]

I love that you've been doing this for 4 years now and still use such a calming voice. Please keep doing so. It's so much easier to absorb, and to be honest, I doubt I'm the only one who plays your videos to unwind or fall asleep to.

[@Olnx]

agreed

[@ashmellow78]

fr. it's amazing honestly, it helps me learn so much more!

[@Paul_Rohde]

Yes, it's relaxing to unwind to these videos.

[@PMFCreek]

Used his videos to sleep countless times

[@pashion289]

i have a sleep playlist of moth light media and natural world facts videos. it makes me fall asleep faster than anything else

[@purple0hairstreak]

Fascinating! I’m currently 6 months pregnant and it’s absolutely delightful to learn how live birth evolved, especially the way the placenta has replaced the yoke in mammals as source of nutrition.

[@Stephen-jw8ci]

such an interesting subject. if you haven’t already i highly recommend the book “the rise and reign of the mammals” it just came out recently. starts with the first tetrapods to show mammalian traits and goes all the way to modern times

[@b.a.erlebacher1139]

I second this recommendation. It's a wonderful book.

[@rickwrites2612]

I just got this from library. It looked a bit dense I wasn't sure whether to start it yet but now I will.

[@Stephen-jw8ci]

@@rickwrites2612 you definitely should, it’s a little bit of a slow read because of all the scientific terms but also really interesting

[@maemorri]

One thing I learned that surprised me is just how many non-mammals also give birth to live young. Familiar species such as great white sharks and reptiles like garter snakes have evolved to hatch eggs internally and the baby(ies) emerges from the mother fully formed. While this may be a superficial similarity, it shows how easily varying reproductive strategies may evolve in widely separated lineages.

[@darcieclements4880]

The convergence in some boas is pretty impressive.

[@glenbe4026]

I always found it cool & interesting that the 3 great extinct marine reptile families (not actually dinosaurs); Plesiosaurs, Ichthyosaurs & Mosasaurs are all believed to have given birth to live young. Eg, The closest living relative of the Mosasaur are the Monitor Lizards which still lay eggs. It makes sense when you think about as these were fully aquatic animals that needed air to breathe, but it makes you wonder why Turtles have not transitioned to live birth.

[@empathyisonlyhuman7816]

Howdy hi hi @Maemorri, Wow, that's an astute observation. I was unaware that garter snakes did that. And certainly such snakes lack an umbilical cord. However, on thinking about this. Marsupials somewhat emulate egg laying in that they give live birth, but then shelter them in their pouch rather than inside an amniotic egg. In a way carrying their 'nest' with them. Thus freeing up the parent animal to maintain their normal routine without much interruption. Much the same as what most reptiles do when laying their eggs. Cool insight!

[@empathyisonlyhuman7816]

@@glenbe4026 On the turtle question, I would expect that there is a lack of evolutionary pressure toward making the change. And with their shells, I imagine such a shift would be exceptionally complex and costly. Besides, such changes as this. I would think are exceedingly rare regardless of the circumstances or conditions.

[@macabrecitrus2127]

Aphids have live births too

[@grayphoenix2152]

Can we just appreciate how cute & happy that animal looks in the thumbnail? Like, she be singing while singing, hey this is my baby, we went for a walk & I'm having the nicest day of my life

[@luciferbikkuangmin9528]

Fun fact: in Chinese, we call Synapsida the “Beasts”, and Sauropsida the “Dragons”, and the fight between Synapsida and Sauropsida is called “龙兽争霸 (Dragon & Beast War)”.

[@king_halcyon]

Wow. Interesting

[@abduking.]

cold🥶

[@yijhebsldiv3gyxi88]

common china W

[@tar-mairo]

Longtime subscriber, first time commenting. Congratulations on your 100th video and hopefully there are many more to come!

[@heitorsouzademoura7747]

Same here its been some good years of content

[@rat_dragon]

Same here :)

[@Chamelionroses]

Yes. Love the videos.

[@tar-mairo]

@@heitorsouzademoura7747 It really was! My favorite from the past year was probably the evolution of komodo dragons, but the most interesting would be either the evolution of spider webs or maybe the evolution of frogs. Regardless, all are awesome!

[@DM-ql6ps]

While Kayentatherium Has larger litters than any living mammal, there are 2 Modern species that sort of come close. The Tailless Tenrec with 32 and the Virginia Opossum with 22. Both of these animals descend from ancestors who had much smaller litters, evolving large litters to cope with high predator pressure.

[@carsonianthegreat4672]

3:54 that leaf in the lower right is a Tuliptree leaf-Liriodendron. Tuliptrees evolved about a hundred million years ago (back before the mass extinction that killed the dinosaurs). That means it actually lived along side the mammal group featured in the image! That’s some insane attention to detail!

[@tjarkschweizer]

That might be coincidence though. Looks like the artist just put their drawing over the picture of a random Forrest.

[@Dragrath1]

@@tjarkschweizer Its possible though it should be noted that Tuliptree fossils from the late Cretaceous fossil assemblages are known so it is a valid choice of a modern tree with Cretaceous analogs (and in fact had a far broader distribution and abundance compared to their modern counterparts). In terms of distinctiveness its one of the few angiosperms that meets this criteria and they are geographically restricted compared to their ancestors (Only survive in Eastern North America and East Asia in relatively similar climates) so the chance that this was a coincidence seems pretty low.

[@davidrosen5137]

My favorite tree!

[@FooRise]

These videos are so fascinating, i love it. Absolutely great work. Thanks a lot for uploading and for all the educational content.

[@RalfTenbrink]

Great video. All your videos are of extremely high quality. Great to see you subscriber numbers are much higher than the last time I checked. Keep up the good work.

[@torinn3618]

I just assumed it was just because of warm bloodedness allowing for longer gestation periods. learning about all the cold blooded animals that give live birth was very fascinating. I love this channel.

[@shasan2393]

Learning some scorpions independently evolved placentas blew my mind

[@kellydalstok8900]

Birds are warm blooded as well, and even (many) dinosaurs may have been.

[@masterdeetectiv9520]

@@kellydalstok8900 for birds it makes sense since they fly that transitioning to live birth would have been disadvantageous

[@leggonarm9835]

Aren't sharks warm-blooded? Scorpions and lizards live in tropical and desert conditions, so that accounts for the heat problem.

[@Racc-Kun_YT]

@@leggonarm9835 there are a few species with warm blooded capabilities but the vast majority of fish and sharks have cold blood

[@saxoman1]

You just absolutely blew my mind! Completely rocked my world with this video! This has been one of those questions I've had forever, and you're the 1st to really cover it. And now, Among other things, I know that placental mammals aren't the only ones that have placentas?!?! Freaking lizards and snakes have them too!? Mind blown! But now I can see a bit more clearly how a Complex placenta evolved (For it seemed like an impossible leap that went unexplained to me before). And somehow the fact that monotremes have the small one too was also mind blowing! This is why I subscribe to you! You cover the hard hitting stuff, thanks!

[@saxoman1]

Another thing, some sharks babies have umbilical cords?!?!?! 🤯🤯🤯

[@EliKennedy]

I really appreciate content like this where the entire focus is the subject matter at hand. It’s a refreshing oasis in a world stuffed with gimmicks.

[@heitorsouzademoura7747]

Really love your Channel bro

[@Floris_VI]

Seriously my afavorite channel, one of the only 3 I have notification on for

[@jurassic_hobbyonmyaltaccou3878]

This is one of the best paleo channels out there great content

[@domesticus2958]

You are consistently one of the best paleontology channels on KZbin. Thank you very much and keep it up!

[@pacotaco1246]

As a placental mammal, can confirm

[@monhi64]

Idk why that makes it sound gross but it kinda does 😂 Also kinda redundant we hardly recognize platypus or is it platypi

[@abelramirez7320]

​@@monhi64 it's completely justified especially if you've actually seen a real placenta lol

[@mauriciomunoz87]

Phenomenal content as always. Keep up the great work and congratulations on your 100th episode!

[@rdongart]

You seriously make some of the best animal/biology/nature videos I have seen on youtube. Not all this crazy voice over sell click bait stuff. Your videoes are just packed with interesting information from start to end covering a subject in an easy to listen to way with relevant visuals instead of the "10 (random) facts about..."-style. Pure quality!

[@markdrill2707]

Please do a video on the evolution of horns, aka herbivore head crowns. What were some of the first horned animals? And how did they arrive at such an interesting form of combat

[@TheaSvendsen]

Oh wow, I never thought about that but now that you mention it, I’m all for learning about the evolutionary process of horns. Sounds like a great and fascinating topic for a video!

[@matheussandbakk9959]

I mean horns are just keratin, just like our hair, so probably the same hair follicles specialized to make denser material, first as armor. With more fighting, they developed sturdier or pointier structures. Weirdly enough, horns, antlers and the like, basically only appear in mammals fighting between themselves, either for mates or territory. While we have examples of this being sexual selection, like with the moose, it could have started this way entirely

[@markdrill2707]

@@matheussandbakk9959 I understand how it happened. Mortis midia just has excellent skills of research and presentation and goes in depth on subjects I like to learn about but takes time or effort to find and string together in a meaningful since in the way I want, he refines and condenses it to a marketable degree when it could otherwise be tedious. I understand the process of headbutting or ramming and gaining evolutionary traits to develop weapons but I want to have a glimpse in to the real lapse of change that happened in history, the difference branches that it took, how similar are deer antlers, cow, goat and rino horns? Did they convergently evolve or is there some bassal shared ancestors they all inherited it from. I'd also love to see him present something on the physiology and evolution of the intelligence of the octopus

[@tjarkschweizer]

@@markdrill2707 When it comes to cattle and goats you may notice that cattle kinda look like big bulky goats and that goats kinda look like small cattle. That's because they are basically cousins. You may also notice that antelopes kinda look like slender cattle or tall goats. Again, that is because they are closely related. These three all have the same type of horn, which they definitely inherited from a common ancestor. All other horned mammals have different horns. I am afraid I can't help you with your questions about the evolution of antlers and rhino horns though. Oh in case you didn't know, sheep are a type of goat and gazelles are a group of antelopes.

[@golddragonette7795]

@@tjarkschweizer sheep and goats are almost impossible to tell apart in the archaeological record, so you get a lot of unidentified 'ovi-caprid bones'

[@IamNoOne-001]

THIS IS A TOPIC THAT I ALWAYS WANTED TO KNOW MORE! THANKS MOTH LIGHT MEDIA!!!!🦔🥚

[@EarthenExplorer]

Dude i just love watching your vids while I chill out and eat a meal. Makes me feel like when i was a kid watching nature documentaries so long ago.

[@cadenz7719]

If I remember correctly there’s a ancient virus that occurred in ancient mammals the helped suppress the immune system in the uterus. Even though it wouldn’t of been a driving factor it would’ve given mammals a new trait that would be eventually be selected for.

[@wyett123]

Considering viruses changed our DNA all the time, it's not a stretch.

[@lollertoaster]

I'm really glad you made that video, I was wondering for months why mammals are so weird compared to other animals when it comes to birth.

[@DanielZarate-so7cv]

This is the BEST most informative and concise video on this subject!

[@msclrawslammer]

Good video. I just wanted to mention something the author here doesn’t. Some years ago I watched a PBS NOVA video about this researcher discovery about the origins of the mammalian placenta. According to his research the special tissue of the placenta corresponds to ac ancestral viral infection that managed to become inheritable so all mammals with placenta developed from this ancient common ancestor. The researcher found the actions that produce the placenta which include fast cellular division (it was compared to cancer in that respect. Another interesting and unique feature of the lace tag is cell fusing. During the development of the placenta cells grow quickly but also fuse together making big multi nucleated cells. Apparently the genetic code that makes all of this happen was identified as originally foreign in the mammalian genetic code. It seems we humans have a lot of genes that are the remnant of ancient viral infections that our ancestors caught over millions of years. The author of this moth media video doesn’t mention any of this in his explanation of the evolution of mammals. I wonder if this theory was discarded or just hasn’t gathered sufficient evidence to be considered a step into the placental development in mammals?

[@prototropo]

This was the very best video Moth Light has done! Thank you. I'd love more on reproductive strategies!

[@yissibiiyte]

This is one of those questions creationists think is impossible for evolution to answer, because there's "no such thing as transitional steps between eggs and live birth". If only they knew that such "transitions" exist today in ovoviviparous animals.

[@joevaghn457]

Doesn’t matter. They arrogantly refuse to learn about, yet it doesn’t change the _fact_ evolution happens.

[@matheussandbakk9959]

Even in ovoviviperous organisms, while most exclusively use the egg yolk, some use a combination of egg yolk and placenta. True live birth, probably lessened the reliability of egg yolk until they exclusively used the placenta

[@darcieclements4880]

Oh you should see how much they hate snakes. No other group of animals has more transitional existing species for all different kinds of traits than snakes do. They are like a gold mine of evolutionary history with convergence with other groups.

[@Ireallyreallywishiwerenthere]

If I ever go back to believing in a god, I cannot deny that evolution is fact and that god must have made evolution just as he or she made everything else just as intricately and complex. People who deny evolution are just wild lmao it’s just fact😂

[@katyungodly]

My favorite paleo channel 🙌🏻

[@FurryDogKiller]

i love this channel so much. this was such a relaxing and informative video

[@spoonerson1103]

Love your channel- so glad I found it-thank you for what you do

[@NitroIndigo]

I've been wondering for a while: is it easier for some groups of animals to evolve live-birthing than others? It's happened numerous times among lepidosaurs, but never among archosaurs or turtles. I assume sea turtles would have a much easier time passing on their genes if they didn't have to slowly crawl onto the beach and make themselves vulnerable to lay their eggs, so I can only assume their hips are too inflexible to allow them to give live birth, but I'm not an expert.

[@masterdeetectiv9520]

Keep in mind theres a lot of lepidosaur species compared to archosaurs or testudines

[@NitroIndigo]

@@masterdeetectiv9520 True, but plesiosaurs gave live birth, and they're probably more closely related to turtles.

[@quitlife9279]

I'm not actually sure if the survival rate of hatchling turtles would be higher if they were given birth underwater, versus random delayed hatching at a beach at night. What would be there to stop large fish following a female turtle waiting for it to give birth then eating all the young? An adult turtle isn't exactly very concealed or manoeuvrable, so can't get away from predatory fish, a pregnant female turtle might end up being a dinner bell in the ocean.

[@salemsaberhagan]

There was a comment that mentioned how a viral pandemic that suppressed the immune system helped the placentals along. It happened all over the Old World i.e. AfroEurasia & spread to the Americas via the land bridge up near Russia-Canada. Madagascar was isolated. We picked up the virus' genes & repurposed those for our own use. I think I saw a video about that too back when the pandemic was still fresh.

[@monhi64]

Definitely, I mean when it comes to adopting a totally new and unique trait it’s a relatively safe bet that one of the animals most suited to it will acquire it. Of course it’s a long ass process the animal has to have chemistry between its old self and it’s new self. If turtle were to start giving birth there would be a shitload of intermediate steps between current turtles and the ones that give birth. What I always wonder about the most is like where’s the tipping point, who’s the first turtle to give birth that was born from an egg. That’s just such a massive transformation that no matter what way you cut it has to be done in one animal even if the parent was super close.

[@ineffablemars]

thank you for having a soft calming voice. I was having a panic attack and this calmed me down.

[@ingenuised]

A video on the evolution of warm bloodedness is probably a good addition to this although it probably sounds obvious as to why; like colder climates, perhaps it could be due to defence of fungus, and there's not much known about the process of switching from cold to warm blood

[@fennecishere]

This was really interesting! Could you do the evolution of external ears? If not that's fine, I'm just curious why almost all mammals has external ears

[@kellydalstok8900]

The better to hear you with, my dear.

[@Snowstar837]

I wonder if it has something to do with heat transfer and warm-bloodedness as well?

[@isaacbruner65]

Strictly speaking, there is no reason for any trait to exist. Random mutations randomly create random traits in populations. These populations are then acted upon by random environmental factors, and the members of the population that happen to have the most ideal traits for that environment survive. Placental mammals and marsupials have external ears because our ancestors had external ears, that's all, and monotremes don't have them. The question might be why the environment could have been more favorable for our ancestors who had the earliest version of external ears than their relatives.

[@b.a.erlebacher1139]

@@isaacbruner65 Platypuses could have lost their external ears secondarily, like seals, as an adaptation to an aquatic lifestyle. IIRC, echidnas are now believed to descend from a platypus lineage, so ancestral monotremes might have had perfectly good external ears. It would be interesting to know whether extant monotremes have retained some ear-moving muscles.

[@b.a.erlebacher1139]

One of the things that characterizes mammals is the reorganisation of the original jaw bones to create the bones in the ear as well as a new jaw joint. This new ear has much better hearing. A flap of skin to protect the ear from debris could have developed into a mobile structure that helps determine the direction and distance of sounds, and signal to conspecifics. It could also be used to radiate heat. I'm just handwaving here! If someone has found attachment marks for ear-moving muscles on the fossil skull of a pre-mammal or early mammal, this would help determine when external ears (pinnae) developed relative to other mammalian traits.

[@Ohboymason]

I wish this channel posted more i love the videos

[@StuermischeTage]

The brown bear mama being followed by her pups strutting through the snow is the cutest thing ever :D

[@XxPaganHeartxX]

Yo this dropped while i was at work and i screamed, i couldnt wait to get home to watch this. Love you Moth Light, one of my favorites!

[@sander258258ify]

What a great video! Very intresting as always. I realy love to learn about evolution. Keep em comming!!

[@liambroughton910]

I would love to see a video on the development of bioluminescence!

[@penneymoore6220]

This is such an interesting subject. I love this channel!

[@mg4361]

One thing that I often wonder about is what the initial push for the development of the amniotic egg was and what the transitional stages looked like. As in, do we know what structures in the amphibian egg are homologs of the three membranes and the shell? Was the drying climate the initial push or did something else push the egg to become more complex, which then placed it well for adapting to dry environments?

[@dibershai6009]

The drying climate was the initial push

[@mg4361]

@@dibershai6009 Do you have a link to a paper discussing this?

[@abelramirez7320]

I don't know of any yt channels with less than 500,000 subs that consistently get views in the hundreds of thousands. That's just amazing.

[@ryandixon8202]

just wrote an essay about the evolution of the reproductive system! interested to hear what new information you can tell me!

[@touch-fuzzy3240]

babe wake up new moth light media video dropped

[@truthsmiles]

I didn’t know I had a yolk sac when I was an embryo! That’s pretty cool and by itself seems to be strong evidence that I evolved from egg-laying ancestors :)

[@monkeywrench2800]

Brilliant piece Mate. Made it easy to teach this subject to my home schooled daughter. Thank you!

[@nexuswave1984]

There are some slight mistakes. From an evolutionary point of view, you shouldn't take echidnas as a prototype of monotrems that one day splitted from the family and "became" marsupials, and stopped laying eggs. It's well known from the fossil record and from genetic studies that platypuses are the only basal form of monotrems (as far as we know of) and that they splitted only about 20-30 millions of years ago from platypuses, hence being a recent terrestrial evolution stemming from a fully acquatic ancestor (platypus).

[@tylerball665]

These are the most relaxing videos

[@icycrusader1947]

Speaking of marsupials, could you also describe brain development across species namely the presence of the corpus callosum.

[@mirrorblue100]

Thanks for these programs on the miracle of life.

[@martykitson3442]

more interesting to me because of your comments about scorpions, i never knew they were live bearers I'll hafta research that a little🧐

[@Deacon_Blues_1984]

Love your videos. Keep them coming.

[@cro-magnoncarol4017]

I remember it being pointed out live birth has its advantages. For example, mammalian herbivores don't need to worry about finding & securing nesting sites since their young can basically run within an hour of birth. This might have been the reason why herbivorous Dinosaurs didn't under go seasonal migrations seen in mammalian herbivores, as their eggs took 6 months to hatch (For Hadrosaurs at least) so they were forced to stay in harsh conditions year around to both defend their eggs & secure the nest site from other species. Of course, laying eggs has is advantages as well. It allows you to produce more young at once, are less taxing on the mother to produce & is one of the reasons Dinosaurs were able to get so much bigger compared to Mammalian herbivores.

[@elmarko9051]

Weren't there other pressures essentially forcing dinosaurs to get bigger and bigger - namely nutrient extraction, or lack thereof from their diets? They were essentially giant reaction vessels, trying to pull out as many calories from browsing on plants that were not nutrient-dense. Curious about your thoughts.

[@cro-magnoncarol4017]

@@elmarko9051 Yes, that's why I said "One of the reasons".

[@elmarko9051]

@@cro-magnoncarol4017 Super.

[@duhsbo]

This video tought me the value of the placenta Also, baby elephants are just adorable

[@RobertGotschall]

Oviperous is laying eggs, and Viviperous is live young, but Ovoviperous, like in snakes and sharks, was described to me as having the eggs hatch internally and then live young are produced?

[@Gildedmuse]

That is what I had heard, too, and was a bit embarrassed when he said it, since I had recently corrected someone about the idea of sharks all laying eggs. I looked it up, just to make sure, and it does appear that ovoviviparous refers to eggs that develope within the body. It may have just been a slip of the tongue or slight mispronouncion. This videos are typically well researched, and the words in question sound fairly close. I'm more likely to believe they simply slipped up on the word. However, it is a fairly major distinction, as ovoviviparous do not "lay eggs" but prodice them, fertilize them, and retain them in their body, making that particular line entirely inaccurate. Perhaps the creator could pin a comment to the top with an explanation of the difference? ETA: I hadn't finished the video at the time of comment, but he does go on to differentiate between oviparous and ovoviviparous so, yes, it was entireky down to a mispronouncion/mistake.

[@matheussandbakk9959]

As far as I'm aware, the distinction comes in the form of a placenta. Viviperous always use a form of plcenta, while Ovoviperous either only use the yolk or a combination of the two (Though that's rarer).

[@daniellu8662]

Having sources in the video is a sign of a quality channel. Now I haven't checked all the sources to be fair. I personally think all channels that spread scientific content should have to include sources. Anyways I love the content on this channel!

[@Coastal_Cruzer]

I agree. Sources are like 90% of the process

[@1TakoyakiStore]

I remember hearing about placental mammal placentas actually being possible due to horizontal gene transfer from an ancient virus due to some DNA evidence that was otherwise unaccounted for. Don't know the specifics but I was surprised it wasn't mentioned.

[@argie9914]

Excellent video! I hope you make a video on the evolution of neurons some day.

[@_Solaris]

This channel is like candy 👍

[@lauravansanten7804]

I'm always so happy when I see a new upload. Great video again, thanks!

[@johnelliott7850]

Live young is just so passe. Might have had children if the wife could lay eggs - and have some left over for breakfast. Nice video, by the way. Informative.

[@RiiftApart]

Congratulations to 100 videos, MLM! Here’s to 100 more!

[@danielled8665]

Can I say, as a human woman who has gone through the whole live birth thing... I have a few suggestions for improvement. :/

[@tjarkschweizer]

I am sure you do XD At least you survived it :|

[@danielled8665]

@Tjark Schweizer true, I was blessed to have been born and had kids *after* doctors realized they should probably wash their hands between doing autopsies and delivering babies. Hurrah!

[@b.a.erlebacher1139]

Would you really want to lay an egg large enough to contain a full term baby? At least a newborn baby is elongated and has a flexible skull! And the baby would have to have some way of breaking out of the egg, teeth or claws or horns or something. And then you'd have to nurse the dangerous little monster. I think marsupials have the right idea.

[@kazkk2321]

This was a great video. I loved it and answered many questions for me. Thanks for posting

[@Wobkerer]

I smell creationists rushing to the comment section… many of them

[@akwabiwameyo230]

Nice analysis. Really wonder about the evolution of the placenta and milk production

[@jacobdarling4172]

Fuck ya I paused my workout for this

[@Ballistics_Computer]

Another moth light media video

[@rat_dragon]

It wasn't just mammals that evolved to give birth to live young. Some birds, amphibians, reptiles, even fish and invertebrates do.

[@angelalewis3645]

So well researched and presented!!

[@kimbratton9620]

Moth Light Media you rock!!

[@thunderfoxanimations]

Congratulations on making a hundred videos

[@glasslakes]

Great video. Thank you.

[@MannyEspinola-q4t]

Thank you for this video

[@sassa82]

Such a good topic!

[@davidfletcher6703]

You just answered a question I've had for years, how do manta rays reproduce

[@austinhinton3944]

It's thought milk evolved to act as a secretion to keep the proto-mammal egg moist, before it was co-opted as a way to feed the young as its used in monotremes.

[@JuicyJam]

DRINKING GAME!!! Take a sip of your drink when there is: - a time lineage - a genetic tree - a new illustration - a size comparison Take a shot when: - the narrator says "however"

[@MrTheDudeManGuy]

"cancel all my appointments Edna, there is a new moth light media video out"

[@ItzElsie]

I love watching the videos, keep up the great work! Please do evolution of Aardvarks next! They are going extinct and I would love to see the family tree.

[@finnolson4251]

Please make a video on the evolution of milk I’ve been wondering about that for years

[@LDrosophila]

May I recommend lactation? Great video

[@MikeS29]

Fascinating, thank you!

[@YellowFellow-lc2rn]

thanks for the content fam

[@jacobdarling4172]

Yaaaaaaaaaaaaaaaaaaaa NEW VIDEO WHOOOOOOOP WHOOOP

[@jameshays381]

I had to go to the emergency room when I was only a couple weeks pregnant and got an ultrasound and the baby just looked like a teeny tiny blop on top of a big yolk. I was told the yolk feeds him while the placenta is still getting established. I wonder if that's true if the placenta is originally for gas exchange

[@stax6092]

Awesome.

[@billyr2904]

The key characteristic that separates placental mammals from the other mammal groups, is that they lack epipubic bones, which are the bones in marsupials that support the pouch.

[@Dr.Ian-Plect]

I think you overlooked the blindingly clear key trait!

[@billyr2904]

@@Dr.Ian-Plect As stated in the video, the group called the placental mammals is a misnomer, because any animal that is viviparous (gives birth to live young) independently evolved a placenta. This also includes marsupials, though marsupials don't rely on there placenta to much, because they have very short gestation periods, and as a result give birth to extremely underdeveloped young. Marsupials however found a solution to this, by evolving really nutritious milk that allows there offspring to further develop. So what truly separates placental mammals, from all other mammals, is that they lack epipublic bones, which in marsupials and monotremes, support a pouch. Placental mammals instead evolved longer gestation periods, and generally larger and more developed offspring (though there are some exceptions).

[@Dr.Ian-Plect]

@@billyr2904 You still missed it; live birth of fully developed young!

[@billyr2904]

@@Dr.Ian-Plect some placental mammals give birth to not quite fully developed young, e.g. giant pandas.

[@Dr.Ian-Plect]

@@billyr2904 - A point that doesn't negate the fact that giving birth to live fully developed offspring is the major distinction between placentals and other mammal groups. - An example of one or even a few that don't are not enough to break this distinction - IN ANY CASE, it's only a few traits with a relatively small degree of development remaining. Still a LARGE degree away from the range and degree of development left in other groups! -------------- In other words; stop waffling in an attempt to refute the obvious.

[@TheElatedDwarf]

Thank you so much for your work. I was sent to a Christian school that didn’t teach this stuff. And I have so much to catch up on.

[@johnpaleontology]

Can you make a video about the evolution of anteaters?

[@nutmeg6782]

I love your videos

[@acct5910]

Interesting topic. Great video.

[@MaryAnnNytowl]

Another high quality video, thanks! You've definitely earned this like and comment for the care and feeding of your Almighty Algorithm! ❤❤

[@grokeffer6226]

This is fascinating.

[@AnkanBob]

I really enjoy watching echidnas

[@heffo67]

Very interesting, thank you.