Dinosaurs seemed to have generally been so much larger than animals today. Huge dragonflies that dwarf their modern counterparts, turtles 10ft long. What is the mechanism that allowed them to be so large, or conversely makes modern ones smaller? Is it about Oxygen levels, or efficiency, or something else?
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I used to work at one of America’s best tracksites! Basically supply and demand. For a long time the dinosaurs were able to grow larger and larger because there was very little competition for food, predators followed the herbivores and the herbivores followed the plants.
KT marks the shift where the meteor sent the world into a time of darkness and ash, where only the smaller, easier to feed, animals survived. The plants all died and herbivores of dinosaur size couldn’t support their bodies demands and died off, leaving nothing for predators to eat. All land animals of today are descendants of the small survivors.
Tldr: plant life thrived and allowed animals to become giant before they all got vibe checked
Well here’s the thing, although many people believe mammals have been around for 65 million years, they in fact have been on earth for at least 170 million years, possibly as long as 225 million years.
For most of this time mammals were very small, while dinosaurs evolved to fill virtually every terrestrial niche available, and other reptiles took over the seas and skies.
Yes some dinosaurs got very big, but most species did not grow to the proportions of Tyrannosaurus Rex, Triceratops or Brachiosaurus. Most species that we are aware of were well below the 5000 lbs mark. Even Allosaurus, the “Lion of the Jurassic”, a 30 ft long predator was a 3000 lbs animal.
But there is one niche that Dinosaurs were never able to claim, and that is of the very small. Think mouse or shrew size. During their 170 million year reign, dinosaurs were never able to crack that ecological niche, and that’s because the mammals dominated it and kept them out. Dinosaurs kept mammals from getting big, mammals kept dinosaurs from shrinking. Which I for one is a pretty rad fact.
Another reason animals today tend to not be as large is well, Us. Almost all Mega fauna on this planet is now gone, and the timing of these extinction evens correlates strongly with the arrival of Homo Sapiens entering the local eco system. Look at the mega fauna of Australia, where man did not arrive until relatively recently. Usually bigger animals are the first to die off and go extinct when the environment changes to drastically to quickly, and well humans are arguably the greatest shake up artists the world has ever seen.
Well here’s the thing, although many people believe mammals have been around for 65 million years, they in fact have been on earth for at least 170 million years, possibly as long as 225 million years.
For most of this time mammals were very small, while dinosaurs evolved to fill virtually every terrestrial niche available, and other reptiles took over the seas and skies.
Yes some dinosaurs got very big, but most species did not grow to the proportions of Tyrannosaurus Rex, Triceratops or Brachiosaurus. Most species that we are aware of were well below the 5000 lbs mark. Even Allosaurus, the “Lion of the Jurassic”, a 30 ft long predator was a 3000 lbs animal.
But there is one niche that Dinosaurs were never able to claim, and that is of the very small. Think mouse or shrew size. During their 170 million year reign, dinosaurs were never able to crack that ecological niche, and that’s because the mammals dominated it and kept them out. Dinosaurs kept mammals from getting big, mammals kept dinosaurs from shrinking. Which I for one is a pretty rad fact.
Another reason animals today tend to not be as large is well, Us. Almost all Mega fauna on this planet is now gone, and the timing of these extinction evens correlates strongly with the arrival of Homo Sapiens entering the local eco system. Look at the mega fauna of Australia, where man did not arrive until relatively recently. Usually bigger animals are the first to die off and go extinct when the environment changes to drastically to quickly, and well humans are arguably the greatest shake up artists the world has ever seen.
Well here’s the thing, although many people believe mammals have been around for 65 million years, they in fact have been on earth for at least 170 million years, possibly as long as 225 million years.
For most of this time mammals were very small, while dinosaurs evolved to fill virtually every terrestrial niche available, and other reptiles took over the seas and skies.
Yes some dinosaurs got very big, but most species did not grow to the proportions of Tyrannosaurus Rex, Triceratops or Brachiosaurus. Most species that we are aware of were well below the 5000 lbs mark. Even Allosaurus, the “Lion of the Jurassic”, a 30 ft long predator was a 3000 lbs animal.
But there is one niche that Dinosaurs were never able to claim, and that is of the very small. Think mouse or shrew size. During their 170 million year reign, dinosaurs were never able to crack that ecological niche, and that’s because the mammals dominated it and kept them out. Dinosaurs kept mammals from getting big, mammals kept dinosaurs from shrinking. Which I for one is a pretty rad fact.
Another reason animals today tend to not be as large is well, Us. Almost all Mega fauna on this planet is now gone, and the timing of these extinction evens correlates strongly with the arrival of Homo Sapiens entering the local eco system. Look at the mega fauna of Australia, where man did not arrive until relatively recently. Usually bigger animals are the first to die off and go extinct when the environment changes to drastically to quickly, and well humans are arguably the greatest shake up artists the world has ever seen.
Up until quite recently, they weren’t. You’ve got a case of selection bias – big animals are exciting so they get put on display more. We have all of prehistory to scour for the giant counterparts of modern animals, and even if a specific time period only had a few giants (like our modern elephants, giraffes, tigers and polar bears), we can pick up the giants of EVERY time period and put them on display together.
There were specific time periods with a lot of large animals, like the famous Jurassic and Cretaceous, but there were also time periods where most animals were smaller than today. The Triassic for example had pretty small animals overall.
That being said, there ARE fewer giant land animals NOW than there were before humans, because we killed them. Big animals are relatively easy to hunt if you have weapons and fire, provide a lot of meat, are dangerous if predatory and therefore targets, require a lot more food (so are vulnerable to humans messing with their ecosystem in other ways) and reproduce slowly. All of these traits make them prone to extinction when humans enter the picture.
Up until quite recently, they weren’t. You’ve got a case of selection bias – big animals are exciting so they get put on display more. We have all of prehistory to scour for the giant counterparts of modern animals, and even if a specific time period only had a few giants (like our modern elephants, giraffes, tigers and polar bears), we can pick up the giants of EVERY time period and put them on display together.
There were specific time periods with a lot of large animals, like the famous Jurassic and Cretaceous, but there were also time periods where most animals were smaller than today. The Triassic for example had pretty small animals overall.
That being said, there ARE fewer giant land animals NOW than there were before humans, because we killed them. Big animals are relatively easy to hunt if you have weapons and fire, provide a lot of meat, are dangerous if predatory and therefore targets, require a lot more food (so are vulnerable to humans messing with their ecosystem in other ways) and reproduce slowly. All of these traits make them prone to extinction when humans enter the picture.
Bro use the search bar this got posted a couple days ago. Also to save your time, it’s a bit like survivor bias, the reason humans assume all animals from prehistoric times are giant is because all the fossils we have found from those times are giant, but it makes sense that giant fossils are much easier to find and harder to break down, therefor our collection of prehistoric fossils will favour large animals when in reality, things like bugs and small animals did exist, we just don’t have many fossils to prove there existence, just think, the blue whale is the largest animals to ever live on earth and it’s alive right now, not a prehistoric fossil, but now
Bro use the search bar this got posted a couple days ago. Also to save your time, it’s a bit like survivor bias, the reason humans assume all animals from prehistoric times are giant is because all the fossils we have found from those times are giant, but it makes sense that giant fossils are much easier to find and harder to break down, therefor our collection of prehistoric fossils will favour large animals when in reality, things like bugs and small animals did exist, we just don’t have many fossils to prove there existence, just think, the blue whale is the largest animals to ever live on earth and it’s alive right now, not a prehistoric fossil, but now
Up until quite recently, they weren’t. You’ve got a case of selection bias – big animals are exciting so they get put on display more. We have all of prehistory to scour for the giant counterparts of modern animals, and even if a specific time period only had a few giants (like our modern elephants, giraffes, tigers and polar bears), we can pick up the giants of EVERY time period and put them on display together.
There were specific time periods with a lot of large animals, like the famous Jurassic and Cretaceous, but there were also time periods where most animals were smaller than today. The Triassic for example had pretty small animals overall.
That being said, there ARE fewer giant land animals NOW than there were before humans, because we killed them. Big animals are relatively easy to hunt if you have weapons and fire, provide a lot of meat, are dangerous if predatory and therefore targets, require a lot more food (so are vulnerable to humans messing with their ecosystem in other ways) and reproduce slowly. All of these traits make them prone to extinction when humans enter the picture.
Part of it is survivorship bias (of fossils). The bigger animals tended to have the biggest bones, and those have a better chance of surviving as fossils.
It’s also not exactly true that modern animals are a lot smaller. The blue whale is the largest animal to ever exist and is around today. In addition, the Earth was full of giant turtles, giant ground sloths, mammoths, and other huge animals until pretty recently. However it seems that when Homo sapiens arrived on the scene we tended to prefer hunting the bigger animals and quickly drove them to extinction.
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