A new study says that the very first animals that burrowed deep into the ocean sparked a global warming that resulted in mass extinctions among species.

The first animals that developed skills to burrow deep into the ocean floor some 520 to 540 million years ago had also altered the organic material on the seafloor. This resulted in more carbon dioxide emission and less oxygen in the atmosphere or what people know today as global warming.

That global warming prevailed for the next 100 million years. The Earth conditions became cruel for the earliest animals and contributed to several mass extinctions thereafter.

Now, Tim Lenton, a professor from the University of Lexter and one of the researchers of the current study, saw a parallelism between the behavior of the ancient animals in the past and the behavior of "human animals" at present.

"We are creating a hotter world with expanding ocean anoxia (oxygen deficiency) which is bad for us and a lot of other creatures we share the planet with," he said in the paper published in Nature Communications on July 2.

The First Burrowing Animals

The first animals that adapted bodily functions for burrowing evolved during the Cambrian period. They closely resembled the worms, mollusks, and the arthropods at present day.

Before these animals learn to dig, the ocean floor was covered with thick and preserved mats of microbes. When the animals started penetrating deep into the seabed, they also unintentionally recycled dead organic material and mix them within the seafloor sediment. This process is called bioturbation and the changes that it brings to the seabed are similar to the changes that happen when worms dig the garden soil.

These worm-like creatures reproduced and became pervasive, eventually colonizing more and more area of the ocean floor. They continued to mix soil and organic materials. The bioturbation went on and on with the animals consuming more oxygen and releasing more carbon dioxide into the atmosphere. The process reached a point where the result was already similar to the burning of fossil fuels at present.

The Biggest Bioturbators

Simon Poulton, a professor from the University of Leeds, noted that the ancient animals that were living on the sea floor did not cause much of an impact in the ocean bed. Instead, the greater impact was brought by the animals that burrowed deeper into the soil.

"This meant that the first bioturbators had a massive impact," said Sebastiaan van de Velde from Vrije Universiteit Brussel and the lead author of the study.

These ancient burrowing animals can dig 0.4 to 1.2 inches below the surface. In comparison, their modern-day counterparts can already excavate about 10 times deeper.