Why were animals so much bigger in prehistoric times?

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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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81 Answers

Anonymous 0 Comments

It’s important to remember that the biggest animal that has *EVER* lived is alive right now, the Blue Whale

Anonymous 0 Comments

Dinosaurs also existed for around 165 million years. In contrasts mammals have been round 65 millions years. There was a lot more time for evolution and natural selection to work out what worked best for their survival and reproduction. So in those extra 100 million years bigger was better.

Anonymous 0 Comments

The perception that dinosaurs were much, much bigger than modern animals is false. While they could be very long, most of that came from the neck and tail. The largest dinosaur to exist was the brachiosaurus, which was 20 ft at the shoulder. The largest land mammal ever was the giant rhino, which was 16 ft, only 4 ft shorter.

Anonymous 0 Comments

The perception that dinosaurs were much, much bigger than modern animals is false. While they could be very long, most of that came from the neck and tail. The largest dinosaur to exist was the brachiosaurus, which was 20 ft at the shoulder. The largest land mammal ever was the giant rhino, which was 16 ft, only 4 ft shorter.

Anonymous 0 Comments

Well to put it simply… We just don’t know.

We have a lot of evidence to support these theories but we just don’t have the concrete science to tell you exactly why.

Anonymous 0 Comments

The perception that dinosaurs were much, much bigger than modern animals is false. While they could be very long, most of that came from the neck and tail. The largest dinosaur to exist was the brachiosaurus, which was 20 ft at the shoulder. The largest land mammal ever was the giant rhino, which was 16 ft, only 4 ft shorter.

Anonymous 0 Comments

Well to put it simply… We just don’t know.

We have a lot of evidence to support these theories but we just don’t have the concrete science to tell you exactly why.

Anonymous 0 Comments

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

Anonymous 0 Comments

Well to put it simply… We just don’t know.

We have a lot of evidence to support these theories but we just don’t have the concrete science to tell you exactly why.

Anonymous 0 Comments

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