Hi! My name Rachel👋 I have a PhD in geoscience and I post educational videos for those interested in geoscience & related fields🌎and/or for those studing for an exam!😉
Subscribe if you want to learn about topics like:
- Earth History / Historical Geology
- Geochemistry / Stable & Radioactive Isotopes
- Paleoclimatology & Paleoceanography
- Biogeochemistry
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- Paleontology
- Mineralogy / Crystallography
- Igneous & Metamorphic Petrology
- Physical Geology
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- Depositional Environments
- Carbonate Petrology
GEO GIRL Website: Geogirlscience.com (visit my website to see all my courses, shop merch👕, learn more about me, & donate to support the channel if you'd like!)
About me: I am currently an NSF postdoctoral fellow & professor at the University of South Carolina!🐔
The books and references I use for my videos are always linked in the individual video descriptions🙂
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If you make " mega fauna of the holocene" into a t-shirt, I will buy one😉 also maybe add an arrow pointing to the wearers face like my " I'm with stoopid" t-shirt.
Prehistoric megafauna and everything else that was around during that era is some of my favorite moments in all of earth's timeline. The amount of different types of animals is crazy! We all know the most popular but there are so many different species with in these different animal groups. For example there was so many different types of saber toothed cats, big cats, giant Mustalids, crazy kinds of marsupials, giant kamodo dragon type lizards, the list goes on and on. The biodiversity was so complex and impressive back then. It's a dream to imagine what those habitats and ecosystems must have been like.
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Further evidence that in fact, Australia does not exist.
Great vid GG. I hope Texas adopts the Glyptodon as the official state prehistoric critter.
I think climate change was never the cause, the mega fauna extinctions took place over a long period from 50,000 BP (Australia) to 500 BP (New Zealand) under highly variable climatic conditions, but there is generally a close correlation with the first human arrival in an area. Naive animals with no previous predators, allow hunters to approach easily.
Thank you. You make this very easy to understand 😊. The charts are especially helpful. One of your earlier videos probably covered my question; but, how do we know what the temperatures and CO2 levels were millions of years ago ?
They didnt go extint they just shrunk
Shiiit. I couldn't absorb the information because the host is so distractingly pretty.
You make no mention of the catastrophic calamity which struck the American, Asian and Australian continents during the start of the Younger Dryas time period. Only Africa was spared bombardment, which explains why mega fauna is still alive there today 🌍
What about the giant wombats? There was also a giant platypus 5-15MYA but it had teeth so even weirder than the modern ones.
I think the current thinking with the Short faced bears, either Arctotherium or Arctodus, is that they probably weren't very carnivorous, this is supported by their large size, close relatives (Brown bears are already quite vegetarian, but Short Faced Bears's closest relatives are Spectacled Bears who's diet is over 90% plant matter, its only really Polar bears that have specialised into a large obligate predatory role), teeth morphology, lack of appearance in predator traps like the La Brea tar pits and I think some work done on the isotopes of their remains that suggest a diet where meat was rare. If that's the case they probably weren't much effected by the declines in potential prey items in contrast to Lions, Saber-tooth cats and Wolves in the environment around them.
How come we are trying to revive wholly mammoths and not giant armadillos!!??!?
Great video, always love your stuff! You said sabre-toothed tigers are big cats, but I don't think that's true. Smilodon is the genus, correct? Big cats refers specifically to the genus Panthera, which is why cheetahs and pumas are not big cats. So I don't think sabre-tooths would fall under that clade either.
Been watching a KZreadr who explores the southwest native american cliff dwelling sites -- we always thing about other hostile human tribes being predatory -- however maybe megafauna bears, wolves and cats should also be considered -- I am sure some archo-geologist have documented what animal bones are found in common with these ancient human dwellings' Maybe? Good job Doc!!!
Good point about how humans affect megafauna is more than just hunting. Humans cause many changes in environments that also can lead to extinction along with hunting.
Glad to have you back, greetings from Mexico
Stomped by Gomphotheres! 😮 Oh! Oh no!
:0 omg this show is about me
You glossed over quite a bit there. For instance, the overhunting explanation is based entirely on a coincidence of timing, and only really makes sense in the context of Clovis First. Yet almost no one believes Clovis First anymore, as there is now ample evidence of human habitation well before the Clovis culture. Moreover, there is some concrete evidence of the impact theory, which hopefully you will address in the next video. Likewise with the volcanic hypothesis. At this point the field seems to be in flux, and sure there is some controversy as there always seems to be in academia, but IMO the old overhunting explanations don't really fit all that well with the latest evidence. Looking forward to the next video.
Humans are often blamed for extremely action of mammoths & others. One thing not quite clear is in hunting scene of them. Seemingly mammoths were inhabitants of harsh, cold place, which is very tough for the early humans. Is it probably a biased view? Alternatively, mammoths could be seasonally migrants for which humans used to take an opportunistic hunting fest? It seems those wooly giants were away from ordinary human activities (hunting) ecologically. What do think?
"Mega" is probably because of downsized modern counterparts, but truly "Mega", tons way above, took place before KPg extinction. Super-Mega? Curious things are: 1) land animals underwent miniaturization, roughly speaking, 2) those giants are mainly composed of herbivorous members, while predators are way lighter, compared to the Mesozoic era, & 3) gigantism in mammals (although not presented here avian giants shared the same fate). Compare to extinction events in this site, this time around it looks as if less complex. Earlier videos demonstrated narratives ranging wide, series of geological setups etc. That may indicate this extinction event might be quite different, despite climate change, overall condition might be relatively calm without noticeable volcanic activities or receding coastlines etc. This video may need sequel! By the way, was the extinction featured here limited to landscape, no coinciding things happening in the ocean?
Mega-pleisto-faunication 🎶
And giant beaver
Human occupation of Americas goes back at least 27k yrs and likely much longer. Which may undermine the "hunted to extinction" hypothesis.
I am an (almost) retired meteorologist with a strong interest in paleoclimatology, paleontology, and archeology. For those reasons, the Younger Dryas period has been of great curiosity to me for at least a decade and a half. At the beginning of the YD, clovis spear points used by the indigenous North Americans disappear from the archeological record along with many of the megafauna they hunted. Like @georgefspicka5483, I currently favor the YDIH (Younger Dryas Impact Hypothesis) as being a large contributing factor. I say "currently", because I want to stay open-minded while more research is done. The topic remains very controversial among scientists, and I suspect there may be egos involved. What else is new? Scientists are human too LOL. As far as megafauna being hunted to extinction, I question if there were enough humans in North America to accomplish that. Also, I think extinct predators like sabertooth cats would have had access to prey smaller than megafauna, including bison, deer, and antelope. There is evidence that humans arrived in N.A. way before the YD. For example, human footprints were recently found in New Mexico with grass seeds C14 calibrated at 21K to 23K calendar years. And there are other finds that suggest earlier dates then that. "Food" for thought. Thank you @GEOGIRL for this and other KZreads. I look forward to your next one on the YD.
I'm very ok with however you pronounce the names , I still know what you're talking about.
I am skeptical of the overhunting hypothesis. If this hypothesis is true, then why are there vast herds of bison in North America? I thought maybe it might be because the megafauna had naturally very low populations, unlike the Bison. Would naturally low populations lead to more vulnerability during ecological stress events? Also, why couldn’t Smilodon snack on bison and thus survive? Again, pronghorn antelope evolved their incredible speed to evade a now extinct cheetah-like predator, or so I’ve heard. So why is that predator extinct? It’s not from lack of prey species.
Really interesting talk. When you were talking about the short face bear. I was looking at where they were in North America, and it occurred to me that maybe the meteor crater/ Berringer crater in northern Arizona played a mayor roll in their extinctions. It was about 50,000 years ago, and the effects of the meteor on the climate and habitat would have been devastating, I would think. At least shrinking their area, leading to territorial fighting. Competing for food. Idk, just a thought. Peace and Ahev
I wish we knew more about the ecological interactions of the Pleistocene megafauna with each other and their environment. I sometimes wonder if early humans might have wiped out one or two species that just happened to be keystone species or ecosystem engineers and the cascade of impacts to the rest of the species and the larger ecosystem that would have followed.
Hi Rachel, Thank you so much for featuring my game and your feedback! I hope your viewers enjoy it and that I get to make expansions for it.
what about the theory that life persisted in pools of melted ice on the surface?
By your reasoning the younger dryas must have been caused by human activity. Over hunting caused mega fauna extinctions in NA. Things change...so it must have been human activity Yah...your woke hypothesis isn't science it's a cult of self-deprecation.
Hi, I really love your work and always enjoy your videos. One small critique of this video however is that you don't point out that you are focusing on the megafauna extinction that occurred in the Americas and, to a lesser extent, in Serbia which was connected to North America by the Bering Land Bridge. A similar megafauna extinction occurred 40,000 years ago in Australia, also coincidental with the arrival of humans on the continent. Interestingly, African megafauna survived into the present age, on the continent where humans evolved. The continuing human caused mass extinction event however may overwhelm these majestic creatures in time as well.
The Dire Wolf is a common fantasy staple, i believe it comes from Dungeons and Dragons. It may be based on the real thing.
I like the anthrocothere. they are so cute.
Great lecture, but I'm also happy that you improved a lot and do not speed anymore as if you're trying to catch a bus 🚌🏃♀️ 😅
This is not a well-done video. Please write out your narrative prior to recording, and don't simply speak extemporaneously. Also look up small details that you aren't sure of, such as what the name "dryas" refers to. Your narrative sounds like an oral presentation given to an undergraduate class.
Oh a great lecture after a pause 👍 You like wolly rhinos ? Then you will like Elasmotherium, another giant rhino, but with only one horn 🦏
I found your channel a couple of years ago and I found it fun. Also I have to point out that you forgot the American Lion.
Pleistocene megafauna need to be recreated as plushies. Everyone wants to cuddle with a wooly rhino plushie, right? And how adorable would a glyptodon plushie be?
I wonder why the straight-tusked elephant Palaeoloxodon antiquus, which was alao an animal from that time, went extinct.
all of these animal family names are so outrageous, being some crazy word, but in the 80's or something someone decided they wanted to use the word "dinosaur" as one of those names, and then somehow the definition for dinosaur that existed for over 100 years just "goes extict"?? BTW english doesn't work that way, ye-old english words can still be used and their ye-old meanings still apply. I mean except dinosaur somehow. Somehow dimetrodon just isn't a dinosaur anymore, even when all of these crazy animal familia names are literally just so that there is a unique word, and have nothing to do with spoken language. A bug is still a bug, even if it's a spider, and a chicken ... is not a dinosaur. It's a fun thought experiment, and it may work out that as a descendent they can be classified in the clade dinosauria (a different word, btw) meaning that a chicken can be called a dinosauria (a different word, btw) , but a dimetrodon , regardless of its status as a synapsid, is one of the original dinosaurs, was a dinosaur for over 100 years, and remains today, a dinosaur.
One thing I've never gotten about the human over-hunting caused extinctions, is the fact that horses and camels that crossed the Bering Straight going west into Asia where human already existed and would have hunted them thrived, and did not go extinct like North America. What would account for that?
Megalania prisca a 4,500-pound 25-foot monitor lizard that was the Pleistocene apex predator of Australia.
Rangel Island Mammoth extinct 3,750 years ago, humans appeared their 500 years later (3,250 years ago). In that case it was a crisis in the food they ate and probably genetic continuity in immune system due to isolation. Human activity did play a role in the extinctions worldwide though. There was also a smaller Sicilian Mammoth extinct (I believe 9,500 years ago), miniature Paleo-Loxodonta on Flores and Komodo Island in the Lesser Sunda region of Sumatra. Although the terror bird age was really the Paleocene there were variations in South America until the Holocene, now only the Red-Legged Seriena bird exist from this lie but is the size of a roadrunner.
I think that it should be explored that "human hunting" should be divided into multiple categories, or at least two. There should be over-hunting for food / resource exploitation, and there should be pest extermination. There can be some overlap, but I do think that there is reason to believe that some animals are extinct on purpose, while others are extinct incidentally, and think it would be an interesting set of ideas to explore. For example, beavers went extinct in Europe, but was it because they build dams, and humans found these dams to be significant problems, leading them to destroy the dams and kill the beavers wherever they found them? In this case, the extinction of the beavers would be the result of pest control. In the case of Pleistocene megafauna, there may have been animals that were big problems, so were killed to prevent these problems, which would mean they were not hunted for resource exploitation (although they may have also been exploited when killed) and instead were hunted as a form of pest control.
Megafauna from around the world. Today there are North American Bison, there was a buffalo species as well as giant Bison species nearly 3 meters to the shoulder in the Pleistocene. Giant armadillos, and giant ground sloths. Giant deer in Europe (Megaceros) and in India a 4-ton tortoise that lived in the Decan Peninsula, Smilodon fatalis, but multiple other saber-tooth tiger and cat species. Many other giant species, 17-foot iguana in Equatorial West Africa, even giant beavers, a 1,500 pound (650 kg) giant Antigua Rat in the Caribbean and so forth.
Thanks Rachel. Hope the paper writing went well! Looking forward to next video on the YD. Lots of silly theories bout that.