CATDOLL : CATDOLL: Did fish originate from marine or fresh water?

Did fish originate in sea water or fresh water?

Fish originate from freshwater.

In the Paleozoic era more than 400 million years ago, the ancestors of fish lived in shallow waters near the coast. After a long period of evolution, they spread to the deep sea and fresh water.

As the first vertebrate on Earth, fish first appeared in the Ordovician period about 480 million years ago , but fish fossils did not appear in large numbers until 420 million years ago. It was previously unclear where fish were during this gap. This study, published in the latest issue of the American journal Science, fills in this missing link in the study of evolutionary history.

The researchers examined more than 2,700 fossil records of jawed and jawless fish from the middle Paleozoic era and used data modeling to predict their habitat types. The results showed that fish have acquired a wealth of adaptations in near-shore shallow waters.

Lauren Saran, a paleontologist at the University of Pennsylvania and co-author of the paper, said that from early jawless armored fish to sharks to human ancestors, all originated near the coast, closer to the coast than coral reefs.

The study showed that soft-bodied fish were more mobile and settled in the deep sea in the next 20 million years, but armored, less mobile fish continued to live near the coast, and some migrated to fresh water, where some evolved into early tetrapod terrestrial vertebrates.