First dinosaurs We are very, very small compared to prehistoric creatures. Besides dinosaurs, snakes, felines and more remain a beast compared to their counterparts today.

In addition plants and insects took on unimaginable proportions. Then something happened and living beings became smaller. So what caused this huge impact?

The main reason prehistoric life forms were so large was “oxygen produced by cyanobacteria”.

Visible as a blue-green layer over lakes and seas, these microscopic organisms were able to obtain their energy through photosynthesis 2.4 billion years ago. Thanks to their photosynthesis with carbon dioxide, oxygen – waste to them – was released into the atmosphere and life forms on Earth changed drastically. The rise of oxygen in the atmosphere “The Great Oxidation Event” is called.

Oxygen-breathing organisms become more active and larger.

The amount of oxygen increased 800 million years ago and even further 500 million years ago. This one excess of oxygen It was an invaluable boon to the growth of living things. Living things, whose cells were filled with oxygen, became more agile and larger over time.

Then a mass extinction occurred as a result of the meteorite impact, and The oxygen level has dropped drastically. Only small creatures that could survive on less oxygen survived this disaster.

According to Cope’s Rule, living things will be large again in many years.

According to this idea, living beings as we evolve in time shows a growth trend. Prehistoric creatures also reached gigantic sizes over time. 66 million years have passed since the extinction of these creatures, and this period is very short for living things to once again take on gigantic proportions.

Oxygen may not be the only reason!

At that time, the land masses were larger, which more space resources. Creatures that evolved in a limited area, especially on islands, are known to be smaller. Pygmies and aborigines of the island peoples are the best examples of this.

Sources: 1, 2, 3, 4, 5, 6