Feels like there was a lot more megafauna in prehistoric earth than there are today
In: 20
The atmosphere contained more oxygen.
All of life began underwater, in the oceans. Plants spread across the land eons before animals were able to, because they form the base of the food chain. It took millions upon millions of years for plants to evolve from forms like simple mosses and algae into more complex structures with roots and stems and leaves.
During photosynthesis, plants “inhale” CO2 and “exhale” a mixture of water and oxygen. They use the carbon to build their trunks, then expel the remaining O2. Without any oxygen-breathing animals around, this saturated the atmosphere with more and more oxygen while removing more and more carbon from the air (“scrubbing” it, essentially) and packing it into the ground.
When insects and animals did evolve on land, they were able to grow larger because there was more oxygen available for them to breathe. Insects especially don’t usually “breathe” like we do, with lungs – instead they absorb oxygen through their “skin” and are thus limited in size relative to the oxygen content of the atmosphere around them.
Additionally, more megafauna existed before human development thinned their numbers through hunting or by environmental destruction, or both. As there are more people using more lands in more spaces, there is less space for megafauna to live. Large animals usually require massive territories filled with resources for them to thrive, and we’re systemically removing that to make way for more cattle farms, yum yum.
Please note this is an extremely skimmed down simplification of a lot of complex processes that played out together over literal eons of time.
FUN FACTS:
* Sharks are older than trees!
* The dinosaurs went extinct before the first flowers evolved! (BIRDS EXCLUDED)
* You live closer in time to the last living t-rex than that t-rex did to the last living stegosaurus!
* Coal is just really old squished trees that died and fell and laid there forever because no bacteria/organism yet existed that could eat lignum (wood)!
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