The meek inherited the waters, as mass extinctions favored the small marine life hundreds of millions of years ago, which led to the species we have today.
- Researchers analyzed 1,120 fish fossils, from 323-419 million years ago
- During the Devonian period (359-419 million years ago), species gradually increased in size
- After the Hangenberg Event (360 million years ago), 97% of the large marine species were gone
- This has placed the marine animals under the Lilliput Effect, which means that they gradually decreased in size
Researchers from the University of Pennsylvania analyzed a number of 1,120 fish fossils, dating as far back as between 323 and 419 million years ago. They studied their varied body sizes, and understood their evolutionary patterns over time. For a little while, it was all going well, in link with Cope’s rule.
Named after American paleontologist, Cope’s rule states that the body size of a group of species increases over time and evolutionary path. Due to the many advantages that it could present, getting bigger was a natural course of evolution. It would make animals more fearsome predators and much more difficult to become prey. And this was precisely the case during the Devonian period (359 to 419 million years ago).
The waters were filled with large creatures, ranging from the bottom dwellers to the most vicious of predators. They roamed around the waters, and grew up in sizes larger than the average school bus. Those were the types of marine creatures that dominated and populated the waters of our planet. Smaller animals were there, but much rarer.
However, things changed. The Hangenberg Event took place around 360 million years ago, and it lead to mass extinctions where it concerned marine life. A whopping 97% of the species died-off, with the few that remained eventually disappearing as well. This has left a gap that was quickly filled by their natural prey.
According to co-author of the study, Lauren Sallan, what was once a “thriving ecosystem of large things” became a home to creatures the size of sardines. For the next 40 million years, it was the small guys that dominated over the oceans. Even more, larger species became smaller.
This was one of the examples of the Lilliput Effect, a consequence of mass die-offs that gradually leads species into decreasing their body size. It’s how many managed to survive, and how they thrived after the mass extinction. When the ecosystem is stable, marine life is able to grow up to proper sizes before they reach maturity and reproduce. However, after the mass die-off, that was a luxury they could no longer afford.
According to Sallan, that would’ve been a “bad strategy” for long-term effects. The smaller animals, however, had a much faster reproduction rate, which allowed them to populate the waters much more quickly. Soon enough, they were everywhere, with their large counterparts gone.
The researchers also bring the issue of today’s problems into the matter. They stated that that massive extinction was not caused by climate change or oxygen deprivation. This has been a widely attributed theory, including now when it’s believed our planet is heading for its 6th mass extinction due to overfishing.
Instead, it had more ecological factors coming into play. However, they claimed that the cause is less important than understanding how long it would take for these species to recover.
Image source: listverse.com