When Mammals Were Reptiles - The Synapsid Story ~ with JULIEN BENOIT
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- Опубліковано 22 лип 2024
- Were mammals once reptile-like? When did 'mammalness' begin? What are the origins of hair, lactation and warm-bloodedness?
It all began with a group of animals called the SYNAPSIDS.
JULIEN BENOIT is a paleontologist based at the Evolutionary Studies Institute, University of the Witwatersrand. His research explores the origins of mammals, going right back to the Permian, over three hundred million years ago.
MARK from Evolution Soup takes a deep dive with Julien into the world of pelycosaurs, therapsids, and cynodonts - the ancient cousins of all mammals (including ourselves).
* Any reference to early synapsids being 'reptiles' in this presentation is basically shorthand for reptile-like. This is a complex story and we want it to be accessible to the curious as well as to academics. 🙂
#evolution #synapsids #mammals
00:00 START
01:28 Julien's Background
06:44 Synapsids
19:17 When Do Mammals Appear?
28:30 Cold- to Warm-Blooded
36:55 Origin of Hair
47:14 Origin of Lactation
1:10:14 Upcoming Projects
LINKS FOR JULIEN BENOIT
Twitter: / paleonewsfrance
Researchgate: www.researchgate.net/profile/...
UA-cam: bit.ly/3CpatwY
French language: / stopscience
University of the Witwatersrand
SITE: www.wits.ac.za/
TWITTER: / witsuniversity
Animatronic synapsids shown are from 'Permian Monsters: Life Before the Dinosaurs' travelling exhibition produced by Gondwana Studios. Filmed by Evolution Soup at the Horniman Museum, London, UK. www.horniman.ac.uk
ARTWORK
Inostrancevia thumbnail art by PALEOREX @paleorex (Instagram)
/ paleorex
Synapsid depictions by JULIO LACERDA:
Twitter / juliotheartist
@JuliotheArtist
www.deviantart.com/julio-lace...
/ art.julio.lacerda
Insta: @lacerda.julio
Huge thank you to these titans of paleo art for their kind permission to use their work!
Interviews powered by streamyard.com/
#evolutionsoup #evolution #paleo #paleontology #paleoartist #Homosapiens #hominid #artwork #Darwin #cave #bone #fossils #Neanderthal #australopithecus #hominin #extinct #animals #science #anthropology #paleoanthropology #genus #species #africa #skull #skulls #naturalselection #lucy #paleontology
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Always so happy when a new Evolution Soup video shows up. These are always the best most up to date information out there. And with the best scientist, researchers and speakers. EDIT _:_ Also, now having watched the whole thing, want to add what an excellent speaker this man is -- explaining his research in such a clear and interesting and even entertaining way -- so that a layman like me has no difficulty following along. Also the whole reptile bones responsible for jaw articulation being selected and adapted by evolution into our inner ear bones (anvil and hammer) thing blew me away a little. Learned something new there about evolution I really hadn't fully realized or understood before.
Thanks for your encouraging words. Julien was great to work with.
Right!
This is what I use UTube for constantly learning a free university.
The fact that is occurred independently in different groups of mammals is also why there are different inner ear joints between therians (marsupials and placentals) and monotremes, the jaw joint was slightly different, and the different joints remained as they migrated back to form the inner ear
It's sad that humanity's (and most researchers) obsession with Dinosauria overshadows the utterly fascinating Permian. I still haven't found a decent documentary about gorgonopsian or a book dedicated to it. Thank you for this episode!
Worst is when you consider anything outside vertebrates....
Most people think Dimetordon is a dinosaur.
@@stanhry
Or, worse yet, confuse it with Spinosaurus
@@stanhry Both dimetrodon and smilodon been included in packs of dinosaurs for decades. While these toys can spark a child's interest in prehistoric life, they are sorely lacking in nuance.
Also included in some of the older packs of toy ”dinosaurs” were some bizarre creatures that managed to make it into Dungeons and Dragons. The oversized bug creature became the inspiration for the rust monster, while the bipedal oddity became the basis for the owl bear hybrid.
Other prehistoric media also muddied the waters, quite literally when it came to ichthyosaur and plesiosaur, and figuratively when it came to the sheer geological time span difference between certain organisms.
Tell me about it! I am always looking for Paleo content & I cannot wait for future docs on all my favorite extinct fauna 💕
Speaking about something very complex in a simple way requires deep knowledge about the topic - Julien shows he has truly this ability. Thank you for your great lecture!
One can possess deep knowledge without communication skills.
This was the best lecture I've heard in ages! Julien was fantastic! His explanations were so clear and understandable. I've studied the Therapsids and know a fair amount about them. Thanks for filling in the gaps.
If you understand a little bit of french, you can go on his channel, it's a real gold mine.
I enjoyed it to. I listen to a podcast called PALEOCAST and not long ago they had a long episode with the author of a book on synapsids. The book was BEASTS BEFORE US
Love your user name!
If I had a time machine and could only check out one era of prehistory I would choose the Permian. Land animals were just so bizarrely different back then and I have a feeling they looked a lot weirder than artist reconstruction. There are some scientists that believe dimetrodon actually had whiskers!
I need more synapsid content in my life
I'm fascinated by this part of our lineage and the Permian-Triassic times, and it seems like a very productive part of palaeontology in recent years. Thanks for the great talk Julien.
THIS BLEW MY MIND SO MANY TIMES!!!
This has been one of the most interesting and exciting videos I have seen in a long time, (and that's saying something, because this channel has so many fascinating talks)
Jillian's enthusiasm for this is infectious!
Please Please Please ask him to give us another talk, and thank you for another great video.
I’m a great fan of Julien Benoit, and i discovered your Channel with his post on youtube. I’m subcribin right now ! 😁
I first heard of Julien's work from Ben Thomas, and seeing him speak about his field of expertise he's more than lived up to my expectations. Superb video!
Fantastic speaker, so clear and easy to follow.
I love learning about gorgonopsids
Delightful interview. I drew upon a lot of Benoit's work for my book "Evolution Slam Dunk: Why the Reptile-Mammal Transition Proves Macroevolution & How Antievolutionists Ignore It."
Oh,where is the book aviable?
The history of mammals is really incredible. I hope fossils of the first hairy synapsids are found so that the evolution of this group of animals can be better understood.
Best channel out there don't miss out on this priceless information.
Agreed!
What an incredible video this is! Being able to cover that much ground about evolution in a single show really brings it all to life. I gasped when I heard that all mammals derive from a single species that somehow managed to survive extinction - WOW! What good luck for us that was! I thank Julien Benoit for his excellent presentation and look forward to hearing him talk about his knowledge again.
Having taught in French schools for almost 30 years in France, I remember that the scientific branches in the lycées were better than most secondary schools elsewhere in his day. English was/is not taught so well but Julien's magnificent mind and wonderful, cheerful and engaging character not only underline his brilliant mind and personality but his spontaneous sharing of his knowledge is so, so enthralling. I think we can expect many more great things from Julien in the years to come. Merci!
I deeply appreciate the trend for the sciences to acknowledge that "this is the best we got at the moment and we're all going to tentatively agree on this theory for now, but there's a high probability that all this will change as we learn more." Back when I studied physical anthropology, the latest theories were taught as truth. Any challenge to the agreed upon truth was almost viewed as heresy unless the physical evidence was seriously strong. Shaking up old paradigms was extraordinarily difficult.
Nice to see that everybody has come back to earth and decided to be a little more open minded. I think that the incredible trove of new information that's been discovered over the last few decades has forced people to pry themselves off their high horses a little bit. When I think about what we 'knew' of hominid evolution back in the 80's vs what we know now, I'm astonished. Back then, Lucy and Neanderthals were the best we had. The very *idea* that there were so many hominids running around at certain times was unimaginable.
Thank you very much for sharing this - made my evening! Having all these images inserted into the interview was very helpful in understanding and envisioning.
Gorgonopsids and Dimetrodon are two of my favorite ancient types of animals.
Brilliant and fascinating. Thanks for bringing us up to date on our ancestry and evolution. The pathways that lead to current mammalian life, and the many subtle and gradual changes, are most interesting. I wish I could go back in time and see those first creatures in life. Thanks to Dr Benoit and Evolution Soup. I am subscribed.
Very glad I found your channel. Exceptionally good. Hope the channel grows quickly.
Hey, my old uni!
Thanks for the aerial shot, showing the jacarandas! I was a Palaeoclimatologist in the mid 90s.
So good to see the therapsids getting some attention.
Just found this today and new to your channel in general. Well structured with some straightforward diagrams explain things. I have seen several documentaries and videos covering these same steps in evolution but I think this was much better presented. Julien has a strong accent but his English is very clear, he is knowledgeable, enthusiastic and expressive. You really had great chemistry and rhythm. I really enjoyed this.
Great to hear everyone is enjoying this :-)
@@EvolutionSoup It's important to say why a video is good so that you can keep your productions well balanced. And as long as criticism is constructive most content creators react positively too it. Too long, too short, too many edits, not enough visuals. But this was really engaging. Thank you.
I was reading a book about early synapsids which was saying that mammals never were "reptiles" synapsids and reptiles are branches coming from the same branch, but not reptiles generating us. Did I understand the video wrong?
Thanks for the video! I love it!
A most interesting master class, thank you both Evoluton Soup and Julien Benoît.
Wildly interesting conversation! Thank you Julien Benoit and Mark!
19:18
This question is difficult to answer because evolution is not linear but more layered.
The Pelychasaurs are Synapsids, and Therapsids are a modification of their ancestors. Cynodonts add another layer to the evolution of Mammals, with Mammalia being the current body plan of Synapsids.
Reptile is paraphylletic term, and today it applies to Diapsids rather than Synapsids.
Correct! Even the term 'Reptilia' is misleading and is only correct if we include birds and dinosaurs and exclude chelonians and rhynchocephalians.
Let's not even discuss the socalled Class Amphibia!
@@carlfrost3368
A.K.A. Lissamphibia,
Temnospondyls
@@carlfrost3368 ...or the term fish!
Great presentation on synapsids. Knowledgeable and articulated well. 👍
Enjoyed the video, well set out and reasoned. Thank you.
Although in reality Synapsids and Reptiles are two entirely seperate lineages (Prothero et al.)that emerged in the Carboniferous However I understand the usage of the term 'mammal like reptiles' in conveying to laypersons and even experts in other fields. Pelycosaurs are now considered a paraphyletic 'waste basket'.
Well the two lineages had a common ancestor that was scaled and probably looked like a lizard.
@@wendydomino The evidence demonstrates that earl synapsids had a smooth 'glandular' skin like naked mammals In my opinion Dimetrodon looks nothing like a lizard and if I turned over a board and caught a lizard with a head like Dimetrodon I would jump out of my skin lol
And I was raised on movies like "Journey to the Centre of the Earth" (1959) in which they torture poor Iguana lizards into sporting rubber sails on their backs. The other movie of the day "The Lost World" (1960) had a finbacked alligator battling (against it's will) a monitor lizard festooned with plates and a frill Unfortunately these films along with popular books et al fostered the false notion that all these prehistoric animals were giant dinosaurs or lizards or both! I will admit we were hungry to see these creatures depicted in film and often turned a blind eye to the inaccuracies not to mention the inhumane cruelty these animals were subjected to.
@@lester9330 Agreed! I totally loved those movies as a child and now they upset me because of the things they did to those unfortunate creatures. Give me a battle between two rubber suited monsters (from the 1950's) any day!!!
@@lester9330 Dimetrodon looks like a reptile though, and it is indeed a (mammal like) reptile. And earlier synapsids looked more like lizards too
My favorite part is when Mr. Benoit said 'there are too many transitional fossils' to tell the difference between reptile to mammal.
There is a book dealing with this subject, called Evolution Slam Dunk by R. J. Downard.
Great show. Very informative. Thaanks.
Thank you for this video. It was extremely interesting.
Great video
Exceptionnel! Amazing conversation, research and presentation. Merci Julien 🥰
Brilliant talk, thank you for this!
Outstanding presentation! I have heard some of this before but never so well summarized and in such depth of coverage. I will definitely come back to this site at a later date to make sure I have caught all the main points. Thanks so much for giving us such an informative presentation about this little known journey to "mammalress."
Welcome to the channel!
@@EvolutionSoup Thank you! Subscribed!!!
Absolutely fascinating and educational show. Thank you so much!
Brilliant presentation!
Although birds and insects would probably agree that mammals are all color blind, being sensitive to no more than three wavelengths, while the birds and insects can frequently see into the ultraviolet frequencies.
I have read that at least the production of immunogloblulin secretion (pre-lactation) for progeny could have occured as early as our most amphibian-like anscestor. It could go back as far as late Devonioan.
Where was this excreted?
Very cool - Excellent lecture, Julien!
Wow that was absolutely fascinating! I had to watch it in three installments as so much to take in.
I wonder if and how the idea of dinosaurs being warm blooded as theorized by Jack Horner impacts on mammalian evolution?
I also wonder at the parallels between angiosperm evolution and mammalian? They seem to have happened on about the same time scale. Maybe you could get a paleobotanist to do such a superb exposition of the subject as you have done with Julien Benoit ?
Thanks for putting this together!
When Wikipedia is your e-book and Doctor Benoit is your lecturer, all this give good understanding of synapsid which is very amazing.
This guy's French.
And his explanation is the best in English I have heard from anyone .
French is the mother of English.
That was sooooo great!
Learned a lot! Thanks
Excellent explanations thanks for the entertainment, cheers
Very cool, thank you!
Fascinating video.
very clear talk. Thanks!
Oh I really enjoyed this,what an intelligent young man
He's young but not *that* young. He's in his mid-30's. I believe he was born circa 1987. He's definitely intelligent. (And cute, too.)
Wonderful. Thank you
Amazing! I have just learned so much ! We are so old.
I've learnt a new meaning for the verb to whisk - love it!
Hair, pycnofibers, feathers: They're all excretions of a high metabolism. From what I gather, their existence came about as a byproduct of high metabolic rates, in an effort to rid the organism of materials in the form of excess keratin. This was later useful as insulation and for heat dissipation - hence there is no contradiction, per se: A high metabolism could be ectothermic, initially, leading to the sprouting of hair, which in turn could have acted as the bedrock for mammalian endothermy as we know it (Thus hair might have been a byproduct of high ectothermic metabolisms that kickstarted endothermy in mammals). Correct me If I've understood wrong, just a layman.
What advantage does shedding keratin from the skin give to the organism? You are describing it as a type of excretion. I can't deduce the benefit. Gaining scales, scutes, hair and feathers has obvious benefit. Sweat glands help cool and send pheromones, leading to mammaries.
@@2degucitas Nature doesn’t operate by design. An organism doesn't acquire hair because it "needs" it. Features that happen to exist are repurposed over time and not built to order. Same thing with flight feathers - they weren't originally for flight. There are academic papers concerning the matter, so feel free to look it up!
@@barc0deblankblank The topic wasn't design or natural evolution having sentience! I'm not a complete idiot! I quote you "in an effort to rid the organism of materials in the form of excess keratin". I just don't see a logical benefit.
@@2degucitas I understand. Yet, this (the excretion of materials) is not a suggestion I thought of myself - I am but a layman. Perhaps some quick research on your behalf would clarify any questions you might have.
👏🙂
very interesting
Thank you thank you thank you for this excellent video
Thanks!
Thank you very much.
Truly fascinating. Especially that tiny mammal bottleneck transition.
@23:16 apropos the Probainognathis fossil, that critter’s transitional double-jaw layout was predicted by Robert Broom in 1912 (about a decade before he became more famed concerning early Australopithecine finds). Diararthrognathus mentioned a few minutes later was found in the 1930s, and was named D. boomii in his honor of his prediction.
His paper:
Broom, Robert. 1912. “On the Structure of the Internal Ear and the Relations of the Basieranial Nerves in Dicynodon, and on the Homology of the Mammalian Auditory Ossicles.” Proceedings of the Zoological Society of London (March publication): 419-425.
I'm happy to learn more scientific facts-- but I had a summer home in France for twenty years, and his accent making me so homesick!
Its crazy how long life has been around and that humans have only been here a very short time in comparison
Julien has a UA-cam channel with lecture you guys should check it out.im at the beginning of the vid, don't know if he mentions it.
Interesting
Magnificient.
I was sold on these things after my Zool professor said he wasn't sure whether to call some of them scaly mice or hairy lizards.
At 40:40 he's talking about intermediately between scaly impressions and hairy impressions, there were skin impressions similar to a human's but with no hair follicles... I'd say the mouse with an extra foramen and no hair had that kind of skin. At the time some forms were losing that foramen and developing whiskers, those particular forms may have been located in polar regions, necessitating an alternate warming method to basking, thus creating the vacuum Mother Nature abhors and when these advantageous mutations arrived, they were able to thrive along with the polar protomammals.
Son Anglais est tellement par-fais! X^D
Mdr 😂😂😂
Me Anglish iz perfect !
@@StopScience tu as un vocabulaire extraordinaire ! Vraiment ! Je suis impressionné ! D’un autre côté, l’accent, on le sent, n’était pas ta priorité… néanmoins on te comprend très clairement ! C’est beau ! J’adore tes vidéos
Hairs are also associated with sweat glands, which is what mammary glands are.
@53:00 Benoit’s paper summarizing the MSX2 impact:
Benoit, J., P. R. Manger, & B. S. Rubidge. 2016. “Palaeoneurological clues to the evolution of defining mammalian soft tissue traits.” Scientific Reports 6 (9 May): 25604.
"Dreadlocks of milk" is the new band name.
Did undergound cyconodonts maintain the basking "eye?"
I'm so glad I found this channel! Here's a comment and like for the Almighty Algorithm. 👋🏼🙂👍🏼
I got a lot out of this video, and thank you, but I'm not too happy that everyone kept referring to synasids as reptiles. Yes, very reptile looking. But aren't mammals themselves technically just modern synapsids? I've seen people call them STEM mammals but that isn't clear. The best is to say "primitive animals of the mammal lineage" although that is VERY wordy. I lean towards mammal-like reptile-like animals. EDIT: Now I hear the French scientist saying "reptile-looking animals" and I am good with that.
Yes any reference to them being 'reptiles' is really shorthand for reptile-like.
Yes, mammals are synapsids. Stem or proto-mammals works fine when you know it's application.
I came upon some of his classes elsewhere, really like Julian.
Mammalia were after Reptiliomorpha before Amniota, but Reptiliomorpha is before Eureptilia ("true reptiles"), not all Reptiliomorpha ("reptile like") are "reptiles" (Reptilia and Eureptilia)
Reptilia was before Eureptilia, both past Sauropsida, after the Sauropsida/Synapsida spit, after Amniota. But I guess somehow Reptilia specifically is considered paraphyletic.
Mammals were never reptiles in any monophyletic sense, they were merely reptile like and formed further down the road past the Eupelycosauria line of Synapsida.
@Leda Alexopoulos
Sometimes I just write comments incase someone else is confused because I remember how confused I got when I was trying to first learn this stuff, 😂 I'm still always confused about something. All the back and forth in the clades gets dizzying.
@@whatabouttheearth Reptiliomorpha were a clade of tetrapods more closely related to amniots than lets say temnospodils or lysamphybia. Amniots were within that clade(Reptiliomopha). The first Amniots split between Sauropsids and Synapsids. Sauropsids is an other way to say ''Reptiles''. A reptiliomorph sister clade to Amniots was the Diadectomorphs
@@brawlholic9960
Correct. That is essentially what I said.
The suffix -morpha essentially implies before. All "reptiles" are Reptiliomorpha and Amniota but not all Reptiliomorpha and Amniota become "reptiles", the Synapsida line does not, "reptiles" are down the Sauropsida line at the Sauropsida/Synapsida split after Amniota
@@whatabouttheearth If it were up to me, I would choose the word "reptile" to be synonymous with Amniotes rather than Sauropsids, because the first Amniotes and Synapsids were very reptilian in appearance. Also if you think about it logically the clade reptiliomorpha to which the Amniote group belongs means "reptile-like"
@@brawlholic9960
I see what you're saying but the suffix Morpha is always used as a sign post meaning that the prefix is is on one of those divergent lines ahead.
So that would be like saying we should refer to Eotetropodoformes as "Tetrapods'" because Tetrapodamorpha is the clade before it, even thought the order of the clades are Tetrapodamorpha, Eotetropodoformes, Elpistostegalia, Stegocephalia THAN Tetrapoda (right before Reptiliomorpha, Amniota.)
To call Amniota a reptile is to look at it all in reverse since "reptile" came after Sauropsida. It's better to call Synapsida 'Proto mammal amniotes' or 'reptile LIKE proto mammals' .... or better yet, simply Synapsids.
50:48 maybe that has something to do with axillary and pubic hair in humans?
Sweat glands and hair, and lactation are linked. Maybe something derived?
You're actually demonstrating the futility of using terms like 'mammal like reptiles' instead of referring to the entire lineage from when it divurges from the tetrapod branch back in the Carboniferous These are only terms of convenience!
'Reptile-like mammals' is a bit better, but also inaccurate and misleading. I use 'synapsids', since we're synapsids all the way down to the split.
@@bjnslc I use the term 'Synapsids' but still use the term 'mammal like reptiles, with a qualifier, when speaking with laypeople, but I always mention the correct term. The classic literature, of course, uses the old term so wecannot completely eradicate the usage. The same thing applies to our feathered friends. There is nothing to seperate 'birds' phylogenetically from dinosauria or reptilia proper but do we start referring to the Field Guide to the Theropoda of Eastern North America?
Synapsida parareptilia.
Very nice, but what are mammals evolving into? What will the NEXT step in our evolution look like? All this fascination for the past is okay-ish, but has anybody been thinking about the future?
Evolution has no target so we simply don't know. A lot will depend on the future environmental conditions and which species has which ecological niche and how it will thrive or die out in it. There are countless pathways and branches into new pathways for the evolution of mammals in the future which just makes it impossible to identify which one is the most viable.
Perhaps there should have been slides to accompany the explanation.
Hey guys what if we can turn on the embryos of komodo dragon monitor lizards to make them there own mammals of any kind of them
T'es un chef Julien 💪🔵⚪🔴
We synapsids had the earth first.
At least along Permian coastlines. Ghost lineages abound.
Its not fair that only one group of synapsids have survived. Archosaurs got two, why couldn't we?
If Dicynodonts evolved small body size again they might have survived,the rise of the Kannemeyeriformes as large herbivores ultimately doomed them.
I believe gorgonopsid is an
american bulldog ancestor, they look a-like
Discus fish feed skinslime to there young.
Could this be considered milk?
"elephants, to whales, to humans, to monkeys, to sloths...all that weird stuff that exists today" 🤣😂🤣
🐩🐩💝❤️❤️
Por favor los videos en español :c
un chti devenu paléontologiste !
Walking with TV show was way cooler than guy with what seams to be French accent 😅
He is far more informative and knowledgable
By definition, and phylogenetically, the last common ancestor of all living mammals (Megazostrodon) is where the line between pre-mammals and mammals is. Trying to determine this transition with a certain trait, like a jaw joint, is a fool's errand. Case in point: multituberculates in which the embryonic posterior jaw bones (typical ear bones) are retained in adults. This reversal has led to great phylogenetic confusion.
(I wouldn't even try. Simply take the mammalian lineage back to when it branched off from the lineages that led to reptiles (including birds) and the various branches of the so called 'amphibia' Cladistics is elegant, truthful and not defined by life style and habit as the classical classifications from Linnaeus are.
Julien Benoit is cute ❤
We have cheeks because mammals chew their food unlike reptiles who rip chunks of meat and swallow whole.
Some reptiles interestingly convergently evolved chewing-like motions such as Hadrosauroid dinosaurs
15:15 I had to look up puppy teeth:
ua-cam.com/users/shortsarOtzSPtAhE
Why did they change?
having live birth means that soon enough you have an animal capable of fending on its own.
while egg laying animals needs to tend to the eggs longer, having higher risk that something else with eat their eggs.
so instead of laying an egg, some started retaining the egg longer until they were able to absorb the hard shell and use their own bodies as shells until the baby develops. and give birth when baby is developed enough.
some mammal babies take a lot longer to develop, days, weeks or in ape cases it takes years before they can fend for themselves.. but some mammals such as deers for example are able to run few hours after birth.
because if they cannot run they will get eaten soon
mammals can be on the move while pregnant. meaning you can run and still save your babies.
egg laying animals cannot.
they lay eggs and either leave them like turtles.
or they guard them and keep them warm until hatched.
there are snakes today that can choose to lay eggs, or they retain the egg for longer and give live birth.
@Dank Dank gravity is a theory.
music is a theory.
cells are a theory.
germs are a theory.
electromagnetism is a thoery.
etc.
evolution is foundation of modern biology, not a pseudoscience like your god hypothesis that is unfalsifiable and therefore untestable and unscientific.
@Dank Dank Ah yes, a "pseudoscience". Evolution isn't a pseudoscience because it has countless things backing it up. Creationism is a pseudoscience because the only thing backing it up is a book that was written by people 2,000 years ago, that takes ideas from other cultures and stories such as the Epic of Gilgamesh.
@@spatrk6634 Well thought out! Thanks!
If you think of it, we are the wierd ones for not laying eggs. But anyway, the word mammal alone is rooted in nursing, and behavior doesn't fossilize. If we didn't have living monothremes, we would possibly not think those mammals...
For those going by the title; 'When Mammals Were Reptiles' references...
'Mammal-like reptiles', a term from when we thought mammals evolved from a reptile lineage. Hence those 'reptiles' were thought to be diverging from others and ultimately into mammals. We don't think this anymore and that's why 'mammal-like reptile' is obsolete.
So what do we think now?
@@MKRex stem mammal I think