When Mammals Only Went Out At Night
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- Опубликовано: 6 окт 2021
- For decades, scientists believed dinosaurs were diurnal and tiny mammals were nocturnal. But as researchers have uncovered more mammalian fossils and studied the biology of different dinosaur species, they’ve found some surprising results.
Thanks to Ceri Thomas ( / alphynix , Julio Lacerda ( / juliotheartist , and Nobu Tamura (spinops.blogspot.com/) for their excellent reconstructions featured in this video.
Produced by Complexly for PBS Digital Studios
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References: docs.google.com/document/d/1d... 
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It's also worth noting how many insect species are more active at night, like crickets, and especially on warmer nights. Perhaps mammals were adapted for nocturnality to go after the wide selection of nocturnal insects.
That makes sense. Then some of the dinosaurs evolved toward nocturnal to feast on the night-feasting mammals.
@Mullerornis who knows how big the insects were? could have been larger insects around that never made it into the fossil record.
@@keith3761 maximum size of insects in any era is tied to the availability of oxygen in their environment.
and more interestingly the _minimum_ size is too for any specific body plan: turns out they actually have a lot of systems that are hard-tied to ambient oxygen that *_need_* to stay in balance throughout their life cycle and their bodies have a lot of control mechanisms in them that adjust their growth to match (stick a modern insect in a high oxygen environment and it will just plain die, _grow_ a modern insect in a high/low oxygen environment and it will grow up proportionately larger/smaller with notably different proportions and internal organ balances)
@@evernewb2073 nerd.
@@JamesThomas-pj2lx 😂 And what obscure path brought you here?
There's one other biological factor about modern mammals that appears to be a leftover from the nocturnal bottleneck hypothesis: the inability to produce gadusol. Gadusol is a cellular metabolite in plants, fungi, and most animals that enables uv light absorption without leaving any distinct pigmentation. This is incredibly useful for any organism that spends significant amounts of time in full sun to protect dna from uv damage, and the only large collective animal taxa that can't naturally make this compound is mammals. This is highly implicative that ancient basal mammals spent so little time in daylight that producing natural sunscreen was no longer selective for long term survival by evolutionary standards and the genetic process accumulated so many deleterious mutations that mammals stop producing this staple cell product even if they began spending time out in the sun (unfortunately). This is one of the strongest points of nocturnal bottleneck for Mesozoic mammals and implies that even large species like Repanomamus couldn't live fully diurnal lifestyles even if they could directly compete with dinosaurs. Mesozoic mammals were likely most active at dawn, dusk, and night, and any species that did venture out by day still likely lived in habitats with plenty of shade or were semiaquatic like Castoracauda (please make a video about that Eons) and didn't start fully adapting to full sun niches until after the K-PG Extinction, without natural sunscreen and relying fully on melanin and dust bathing to protect against uv rays.
it could also be evidence that fur is strong uv protection reducing the selective need for alternative methods of protection like gadusol.
Thank you, interesting
@@braxon fair
What a great read
@@larry5289 braxon wrecked it in half a sentence tho.
If dinosaurs are responsible for the tiny panther that lives in my house then that's just one more thing to love them for
I want a tiny panther but my hubby won't get me a baby one 😢😢
@@Rhiannonganon you will never get a little panther Hoohoohahahaahaa 😈😈👹👹😜😜
humans are mammals so dinosaurs are also responsible for you
Velociraptors hunting at night. Now there’s a scary thought.
I know, that's some ral movie material right there, forget Jurassic Park
Bring back Utah raptors!!!
As a kid the scariest part of the Lost World for me was the Raptors hunting in the long grass.
why would you be worried about a chicken sized predator?
@@sebastian114 Utahraptors are much larger than humans.
Ah, finally I found somebody to blame for me being night owl, lol🤣
Owl's aren't mammals though.
EDIT: I am being intentionally obtuse :P
@@ZedaZ80 find alligators in the night
So you found yourself, many people dream on doing just that. 😂
*Night shrew.
You can't blame anyone living at night as that is the natural way. We need to find someone to blame for everyone else unnaturally working during the day.
Well there is more than just eye anatomy to suggest a nocturnal bottleneck; even diurnal mammals today are a lot more sensitive to UV radiation than birds or reptiles, suggesting UV resistance genes were lost in mammals due to the nocturnal bottleneck limiting the amount of daylight they were exposed to.
Another thing is that the vast majority of mammals, both diurnal and nocturnal, are what we would classify as colour-blind, having rather limited ability to distinguish different colours from eachother, which would make sense in a nocturnal environment where distinguishing colours isn't as important.
Primates (including us) are an exception to this because we evolved from Frugivorous animals, and distinguishing colours well is rather important when searching for fruit amongst tree canopies
Your profile pic is a bisexual PokéBall - you're my hero man
@@roadhigher That is correct, but I was trying to avoid eye anatomy as evidence since it is the main topic of the video.
@@roadhigher m
I was shouting the same while watching lol
If I could only watch one show, it would be Eons.
69th like
Fun fact: Apes are what happened when we started evolving back in the opposite direction. The reason why human can see more colors than other mammals is because we took on a diurnal fruit eating niche, so seeing more colors at the expense of worse night vision was actually an advantage. Also, that's why apes don't have wet noses, unlike other mammals. We can see our food, so we don't have to rely so much on smell.
We all are evolving backwards look how stupid some people are getting.
@@oliverwilliams1086 Yeah, for example some people will fall for dumb eugenicist rhetoric about reverse evolution just because they saw someone be stupid on the internet
Not just apes, monkeys too.
@@oliverwilliams1086 It’s because humans have eliminated natural selection with modern society, and there’s no evolutionary pressure for intelligence to be favored anymore. In fact, lower intelligence people are reproducing far more than intelligent people nowadays…
@@Jacob-yg7lz
Both elegant and mature way of saying "yeah, look at how stupid you are", I love it!
Great response!
I'm a complete rube, but I'd have thought the conditions post-meteor impact would be more suitable for noctournally adapted animals than diurnal ones. Doesn't seem particularly surprising that they're the ones that survived, thrived and radiated out into all the niches post-meteor and resulted in what we have now.
Maybe that makes two rubes. It's an interesting idea. Creatures who needed sun and light to hunt would have been very disadvantaged. Warm fuzzies would have adapted to see better anyway. It might explain the reduction in size of land invertebrates such as flying bugs - a post-meteor winter (
Immediately post-Impact, you're correct.
However, the dust and ash would have cleared out a year or two after the impact (according to simulations). That wouldn't really account for the lag in adaptations.
@@VelociraptorsOfSkyrim I'm confused. The video said the adaptation was surprisingly fast. What lag are you referring to?
@@Merennulli Surprisingly fast as in 200k years instead of 200m years, not 1 year
I think it's more that our nocturnal ancestors were borrowers and thus out of acid rain most of the time
Is it possible that the nocturnal bottleneck effect has more to do with which mammals survived the Chicxulub impact rather than the characteristics of mammals before this extinction event?
The Chicxulub Impact had worldwide effects, and had a fairly homogenous "kill rate" among all other groups of animals - it is more parsimonious to presume that mammals were similarly fairly homogenously affected than to presume that its just a coincidence that the more nocturnally adapted mammals survived, while thebmore diurnially adapted ones "just happened" to die off at the same time.
@@geodkyt I dont think OP is suggesting anything coincidental. Maybe nocturnal animals were better to suited to the dark, cold environment caused by the extinction event. And... I don't think you've used the word 'parsimonious' correctly here
@@RS-kt5po "Parsimony" in science generally is simply that the simplest explanation that fits the facts is most likely the correct one. You may be thinking of phylogenic parsimony, which is the related concept that the proposed phylogenic relationship that has the least number of branching and fits the known facts is most likely to be true.
And given that diurnally adapted mammal lines survived the Chicxulub Impact, yet even nocturnally adapted nonavian dinosaurs were entirely wiped out suggests that the difference is less whether or not a specific genus was nocturnal or diurnal, and more a common ancestral trait for the large collection of lineages.
@@RS-kt5po in this context I actually think OP is saying that the majority of mammals that survived the KPG would've been nocturnal and thus underground or otherwise sheltered during the impact (which implies we know what time of day the Asteroid impact happened, something I'm almost certain is impossible to know this far removed from the event.) And after the impact were indeed better suited for darker colder environments, then diversifying as they filled niches left behind by the now dead dinosaurs. I also think it's a little disingenuous to assert (not that you are or anyone else here has just generalizing for this one bit) that dinosaurs just all of a sudden all died during the impact when I find it far more likely that dinosaurs possibly could've lasted up to another couple million years after the impact and volcanism finally dying out after there was literally nothing left for them.
@@sorrenblitz805 simulations conducted of the KPG event has shown that vast majority died within a decade and the longest evidence of dinosaur survival is only 500.000 years and even that evidence is doubted by many experts
Ah, so this is why we all stay up til 4am, It's Science!
...I'm watching this at 3:13
Naw, that's just you being young. I suspect that's an adaptation for family group survival. Young folks staying up late (I use my experience as a teenager as justification for my hypothesis), banging around making plans and babies, then going to bed just before the grumpy old foks respond to their aches and bladders - and the 5 year old kids finding the teens and mid-adults, and saying, 'What are you doing?'
@@sealyoness how far into my 40's until I'm no longer young, dad? 🥺
What about burrowing? For sure that has to matter to those dark-adapted eyes!
Not necessarily. Lots of modern burrowing mammals have very poor eyesight and rely mostly on touch and smell, e.g. moles.
The mammals just found it more fun to join the dark side
*The darkside of the force is a pathway to many traits, some considered to be very important.*
come join me on the dark side, we have cookies!
Fancy how the nocturnal mammals after the dinosaur extinction might have felt excited to stay up late into the morning light instead of just going sleep at the first morning rays, just as we are excited to stay up late past sunset, in our artificially lighted nights...
I decided to join the shark side.
Alas, for I have only one DISlike to give. :P
these videos have changed my life, i was on the wrong track, getting into the wrong crowds and activities so with the execution of educating people with talented hosts and breaking down complex topics, forever grateful thankyou
I wonder if the huge amounts of ash and debris in the atmosphere immediately following the KpG extinction event also selected for nocturnal mammals? I mean, if the earth was significantly darker during that time, animals adapted to hunting at night probably had a better chance of survival.
IIRC it was only a few percent darker at worst. Enough to seriously mess with the climate and plants but not a problem for daylight vision.
Then why don’t we see the same selection pressure on other classes of animals, such as birds or reptiles?
Every Eons presenter has such clear diction, really aids in recalling the information. Thanks and kudos.
I love how you show the time period with the tectonic movements right after the intro!! I wish all your vids had the exact animation
That's why I prefer. Dark theme for every app I install
I would like to see a video about the time India was an Island from 100-50 million years ago, how the animals adapted to their isolation and how different was the fauna after the Kpg extinction event during the last 15 million years of its isolation.
i used to take care of chickens and i learned that the best time to hunt down strays that wanted to roost outside of the coop was twilight, before the night predators came out. the fifteen minutes before full dark i could see just fine, but the chickens were practically blind... i guess i had more in common with those foxes than i thought
Hey, that's not bad! I wish I'd known that when I would be sent out to find the old lady hens who were feeling crowded.
Mammal eyes: still adapted for the dark
Humans: legendarily terrible night vision
Yeah, that's something that I've been thinking about ever since I saw this. I struggle very hard in low light conditions. What kind of mutation would cause that kind of thing?
@@assassinsden7478 not growing up in the dark. Being shaped by it
@@daltonv5206 I didn’t see the light until I was already a man. By then it was nothing to me but blinding
@@assassinsden7478 umm, I think you need to get your eyes checked, mate...
Assassin's Den all humans (and most primates) have poor night vision. Mostly because our monkey like ancestors evolved for great depth perception and colour vision, to navigate in trees and find fruit. This came at the expense of our night vision, and sense of smell.
10:52 glad to see indigenous people getting a cameo
I've heard that tribes in Nebraska helped early paleontologist search for fossils from the miocene in the badlands of Nebraska
Did they know that they were finding evidence of prehistoric animals from ancient times or did they think the fossils were something different? I hope that question doesn't sound ignorant. I just mean it that way that all cultures have their own creation myths, and prehistoric animals from millions of years ago usually don't fit in those myths, which is why Romans and Christians at first thought that the bones came from cyclopses or animals that didn't make it onto the Arche Noah or stuff like that. Well, enough Christians still believe in that... So I'm just curious how much the natives knew about this topic at that point.
@@solar0wind If I had to guess, it’s likely that the fossils that humans around the world found were not interpreted necessarily as prehistoric animals. They may have been interpreted as mythical creatures. Or maybe they were used as the basis of myths. This channel did do a video on several fossils that scientists Think I might’ve been the the inspiration behind monsters such as the cyclops or dragons.
7:17 someone finally puts the dinosaur eyes in the right place! That is rare because then you have an ordinary-looking bird or reptile.
The classic model is to put the eyeball in the temple of the skull. That puts the eyeball back behind the jaw (which NEVER happens in ANY species) and gives the face the strange shape associated with "dinosaurs".
When you think about it if Dinosaurs had been cold blooded and diurnal a day and night split wouldn't lead to one group being tiny. Being awake and alert when the gigantic dinosaurs were nearly blind and extremely slow due to a combination of darkness and cold would leave a huge set of niches open for dinosaur hunters. It also would leave a ton of room for niche sharing based on differing schedules. But we don't see gigantic saber tooth tigers hunting sleeping herds of Triceratops. Nor do we see night dwelling counterparts to all the different dinosaur species.
I know this wasn't the point of this video, but my mind grabbed onto the idea that mammals are older than beans. Wild
To think all the mammals still kept traits that helped them survive the entire Mesozoic to today.
This was a really fascinating episode! I had no real conception of how different avian and reptilian eyes could be from mammalian ones - the differences are not well explained in the level of anatomy that I took, and most of my patients are mammals. I'd love to learn more details about the specific adaptations for diurnal avian eyes, for instance.
Please also tell Michelle that I enjoyed listening to their voice! It's very soothing and calming. They are a very clear presenter.
still missing Steve
did he leave or something
Thank you for a great video, Michelle! I love learning about the evolutionary history of the senses like eyesight and hearing!
47 kilos is pretty big a beast, larger than most modern dogs.
THE NIGHT TIME IS THE RIGHT TIME, THE NIGHT TIME IS THE RIGHT TIME...
😂🤣😂🤣😂🤣
I have all his albums
This our ancestors
Sing ya song margie
It was the only way to save him...
You finally got 2 Mil. subscribers. You guys definately deserved it!
Love this channel and the topics are super interesting ❤️
one the things I learned from watching Eons is that almost every animal had a shot on rulling the earth or the sea but we are the ones who did it best
Many animals are crepulscular (active at dawn and dusk). It wouldn't be surprising if the same went for earlier animal species 🤷♀️
Agreed, particularly since, even if dinosaurs were warm blooded, many other prey animals (reptiles and amphibians) would be sluggish at these times and small mamals could quite happily made a living on these prey animals
Fascinating detective work as always. Thank you!
hey eons almost got 2 Million subs. Glad to see such a high quallity channel grow and thrive
Not almost anymore. 2M+ now
Fantastic video 🤩 Thank you so much! Really eye opening 😉
I’d love a video about wood eaters personally. Though I’m sure there’s more I can only think of termites and beavers. Given that wood is such a plentiful resource why haven’t more creatures adapted to eat wood? Cheers!
You forgot fungi & bacteria
I'd say there's too much happening at first.
If u think about it.
It was plants/fungi that made its first leap out of the ocean.
Then came animals.
From a plants 🪴 perspective
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It just wants to chill and vibe but this 🐚🐛🐟🦭🐬🦎🐊🦕🐍🦋🐛🪲🦟🕴🪰
Thing just won't leave it alone.
.
So it did a thing or two
🍄🌴🌲🌵🍁🌾🌿🌷🍂🥥🌶🥦🫒🍍🍋
But people can't seem to see past this
🍔🍟
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I remember a simpler time
🦀🍦🏺🔪🧋
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Used to do this all the time before I was human
💥
🦀
Wood/cellulose requires special microbes to break down for energy. So it's only certain animals that managed to acquire and form symbiotic relationships with those microbes that can take advantage of this resource.
I guess its just like today
Most of birds are day time birds, but there are exceptions like Owls for example
Mammals probably were more adapted in nocturnal niches, but this doesnt mean all the mammal and mammaliaformes species at the time were exclusively nocturnal
Maybe our mammal linneages that survived the Cretaceous extinction were all nocturnal at some point during the Cretaceous or before
Most birds also have pathetic night vision, because they are not adapted to night at all. My parakeets couldn't see my hand in the dark, if it was placed 2 cm in front of them, while I could see them clearly
Always awesome when yall upload a video. Keep it up
Great ! Thank you people for making these awesome material
Great stuff! I would love to learn more about early mammals!
Oh that opening shot makes my heart happy
Would love if you made a video about how some reptiles have evolved to lose and grow back their tails when threatened!
Huh, actually was wondering about this the other day. Awesome to see a vid on the topic
You are welcome.
Additionally, the night sky would have been a lot brighter without light pollution I'm assuming.
Since most dinosaurs were so big, if there were ones that weren't endothermic, wouldn't they still be gigantotherms?
Makes nocturnal birds more interesting.
Fascinating as always!
No wonder I can spot an ant crossing my living room in total darkness at three in the morning
Between nocturnal, subterranean, twilight, deep canopy, tree hollows, and a number of other low light environments that would definitely have existed in abundance there likely would have been a wide range of niches and behaviors for small creatures that could see well in relative darkness to inhabit. It makes sense that it would have developed First in one or more nocturnal species of early mammalian ancestors, but mammals of their time would still have had ample opportunity to diversify and specialize and occupy many roles in their relative food webs, as most organisms do today, even before the end of the non-avian dinosaurs... but realistically, at their relative size, staying in darkness could only help. Maybe early fur even helped make them even harder to see, and distinguish in the shadows... whether they were scurrying away or stalking towards, if it works it works.
One interesting thing is that the vertical pupils of cats and foxes is considered actually a better adaptation to daylight than nighttime: they open round when it's dark, and they close when it's bright to protect the higher sensitivity from the sun. Being vertical also allows for more color perception in brighter conditions regarding the position of the color sensitive cells: in closed round pupils some color receptors at the edge get muffled until it opens again.
dude even nocturnal animals pupils constrict when exposed to a lot of light. it's not some special diurnal ability. you can go to a bathroom right now and flip the light switch on and off while looking in the mirror and you will see your own pupils constrict and expand. the main reason why a lot of ground dwelling predatory creatures have vertical pupils is because it helps improve their depth perception while they are hunting prey that is on the ground
Very detailed and informative video!
Just a heads-up, the dinosaur shown at 1:24 is Thespesius, nowadays a likely synonym of Edmontosaurus
To quote The Greatest Rock And Roll Band In The World: "The sunshine bores the daylight out of me."
RIP dinosaurs. You had a hell of a run
Wow!
The advance of mammals may be linked to the appearance of the legume?
If I had known this 20 years ago I might have convinced my daughter to eat her peas.
We really got shafted on our eyes huh? Poor color vision AND poor night vision 😭
Life finds a way,....even though there are a thousand ways.
Some form of vision at night seems like a good thing to have for diurnal mammals when there are nocturnal predators around who might wake you up for an unsolicited midnight snack.
Only an enthusiast since immemorial but unfailingly learn new things whenever I tune in to your vids. Can’t thank you enough. More 🔌 to you all.
This video focuses on diurnal and nocturnal patterns.
Some creatures are crepuscular, meaning they are most active at dusk and dawn.
These videos are just super good 👌🏼
The freaks come out at night, the freaks come out at night lol
The days are much too bright
We only come out at night
That's a lot of information about early mammals I never have encountered until now. I also used to believe in the "nocturnal bottleneck" until now... I guess I haven't been paying attention to the latest research.
Competition for the nighttime niche ... aaanndd then along came a giant meteor. Game over. Winner: mammals.
Inse cts
I would love to see an episode about what we know about how birds survived the end-Cretaceous extinction.
They did that already.
"They mostly come out at night. . . Mostly."
Probably the earliest I’ll ever get with pbs eons. Cheers! 🍻
Thank you for the acknowledgement at the end of the video...
great analysis leading to new ideas, for me at least. thanks
I remember that...good times
I know this is a tiny part of the video, but I want prints of the infrared pics of the endothermic/exothermic animals. Or maybe a bizarre beasts pin in that style? It’s so cool!
Edit: 🤦🏽♀️ unintentional pun…
Nice detail of comparing the Repenomamus sizes to more basal mammals (i.e. marsupials). Whoever wrote that - it wasn't lost on me!
I would love to see a video on how the par-avian dinosaurs became birds 🥰
Hi PBS I was wondering if you could make a video about the first million years after the astéroide impact like that’s to say the begining of the Paleocene I think. It’s hard to found informations about this era but watching one of your videos would be interesting
Great video, very cool to see a new host ❤️❤️ She's good!!
thank you for this
Also probably to do with direct mammal ancestors being burrowing animals - poor light conditions and also development of whiskers (and hair) to feel the tunnel walls.
Thanks I always wanted to know about Mesozoic mammals
PBS EONS is very nice at teaching things that in school looks boring
Last time I was this early, mammals could still see in the dark.
There are still vastly more mammal species todaywith nocturnal vision rather than full diurnal vision. Just saying.
@@Xnaut314 ok
They can still see...
love y'all's content
Could u please do a video on dinocrocuta or pachycrocuta (or just hyenas in general)
side note, im curious to know, when did mammals start developing fleshy ears?
It's a petty detail, I know, but I love that you pronounce 'niche' as 'neesh' rather than 'nitch'.
Almost at 2M Subs, Congrats!
What a fitting video to wake up to at 11pm.
Wait, you guys go outside - DURING THE DAY?!
Have you guys ever considered a video on the evolution of lagomorphs v rodents? My house rabbits often throw into sharp relief the essential differences between them and rodents, beyond just a couple extra incisors and a more herbivorous diet. And yet a lot of people think rabbits ARE rodents. (Of course, a lot of people will say ferrets are rodents, so I don't take it *too* seriously...)
SECONDED! Oh, please please please do lagomorphs! Rabbits are SO unique. I have access to a full skeleton and dozens of radiographs if you need some reference shots.
Thirded! so to speak. Would absolutely love to see this!
I enjoy learning from Eons. 😃
Great videos
You could also mention how mammalian ear is quite developed in comparison, which would be more useful in low-light conditions :)
since evolution is about fitting a niche the theory of an ever changing balance between day and night time animals makes sense to me.
Great episode. Have you guys done a T-Rex episode?
I come here for the illustrations. Lovely cat at the end.
Good video 👍🏼
Lovely video as always, and with my favorite host! Michelle's voice just goes so well with this dino talk.
feeling less weird to be a nocturnal human