Why were prehistoric era animals so gigantic in comparison to animals from the “modern era”
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While there are many causes almost every one can be traced back to extreme levels of oxygen in the air. You can’t grow very large if your cells start dying due to lack of oxygen, when there’s more oxygen in the air it’s easier to get bigger
There are a few different answers. But the most relevant (aka during prehistory like you asked, while humans were around but before documentation) is that *we* drove them to extinction. There’s a reason only Africa and the oceans still have megafauna. African animals evolved with us and knew us as predators while other continents didn’t, and we couldn’t effectively scour the oceans. Until now, that is, and you can see the extinction of the ocean’s megafauna happening in real time.
Source: my education, but *Sapiens: A Brief History of Mankind* by Yuval Noah Harari also outlines it fantastically.
What, you mean like why aren’t there mammoths and massive tigers and suchlike? Because humans killed them.
If you mean like dinosaurs – it’s because air was more oxygen rich back then. Nowadays you just aren’t going to get enough oxygen into your lungs to be that big
One huge consideration about mass extinction events: When one happens, food becomes incredibly scarce. Smaller animals are able to scrape by with the little food that is left. Megafauna that require literal tons of vegetation to survive starve quickly. Predators that prey on huge herbivores run out of herbivores to feed on.
Little critters manage to eke out a living long enough to arise the undisputed underdog champs of evolution. So multiple mass extinction events lead to adaptable, small, and low maintenance as the biggest factors in long term survival as a species.
After coming out on top from mass extinction events, the lucky megafauna survivors historically encountered something very unfortunate. The little monkeys with sharp sticks.
Edit: grammar
What are you specifically referring to? Dinosaurs?
Dinosaurs got big because of their special bodies that were made to better handle mass on land, such as having hollow bones and air sacs
Mammals haven’t been much bigger than as they are today. There was more variety in the ‘big’ animals but the sizes themselves weren’t too different. On land there were some bigger than the modern African elephant, but not by much
In the ocean the blue whale is the largest known animal to ever live
I think we are the reason. Giant sloths, mammoths, mastodons and sabber-toothed tigers all died out, arguably, because of human predation. Look up Irish Elk.
No humans.
We kill everything bigger than us. That’s why all the giant mammals are endangered.
It is explained pretty well in Sapiens book. Basically, instead of asking why they existed back then, you should ask why they do not exist now. In prehistoric era all kinds of animals existed, gigantic and small. However, most superfauna has been exterminated by… humans. The more we developed our means, the farther we started to travel and our population grew. The bigger the animal is, the easier it is to hunt it down, so humans prioritized them. It is said that Australia used to have 90 species of megafauna which was limited to ~5 within decades after homosapiens arrival.
From what I understand, prehistoric animals were so large because there was much more oxygen in the atmosphere, more oxygen means larger animals. As for the blue whale which is considered the largest animal on the planet to date, they’re large because they have a slower metabolism, they don’t use energy as quickly and the cooler waters provide more oxygen for them. Paramount Plus did a great documentary on this exact topic and it would answer a lot of your questions.
The ocean is filled with massive animals, sharks, mackerels, dolphins, tuna, billfish, squid, octopus, whales, etc.
Land was also filled with massive animals like that until one large predator showed up and literally killed them all. Why? I dunno… so they could waste time on Reddit I guess.
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