In an evolutionary sense, sharks are credited as the oldest survivors on the Earth! Sharks have been wandering in the ocean water for a long period of time. They are the only creatures who have survived 5 mass extinctions on the land. With the passage of time, they underwent many adaptations only to survive in the changing environment. Many species of sharks boast their lifespan by replacing the rows of teeth. Let’s repeat the historical background of sharks to know how old they are!
How Old are Sharks?
Sharks are often titled as living fossils, the fossil records of sharks show that they have been roaming in the oceans for about 450 million years. They are the longest lived group on the planet and thus have a longer life span than other animals such as the Great White sharks can live for more than 70 years, the Great hammerhead live for 44 years but among all the oldest known shark species the Greenland sharks lived for 272 years on an average! Unbelievable!
The Evolution of Sharks
The evolutionary history of sharks shows that they arrived on land about 400 to 450 million years ago which means they are 200 million years older than dinosaurs! Implausible! Scientists believed that sharks are the descendants of small fishes with no bones, fins and eyes. Afterwards, the fishes evolved into 2 major groups: bony fishes and cartilaginous fishes!
The fossil records of sharks depict that there are 3000 species of sharks that lived in the ocean till date but most of them vanished without any records. Sharks skeleton is made up of cartilage which doesn’t provide a clear historical background of sharks, the teeth, fins and denticles will remain preserved. According to some studies, some species of sharks that lived 150 million years ago have resemblance to the shark’s species living today.
Irradiating the historic eras to calculate the accurate age of sharks:
The Paleozoic Era (545 to 250 million years back)
This time zone shows the evolution of sharks from single cell to 2 groups: bony fishes and cartilaginous fishes. A large number of sharks came into existence in this era. Some species. Today, no species of sharks from Paleozoic are living today but many species evolved from the shark of this era.
The Mesozoic Era (250 to 65 million years back)
Studies show that some shark species from the Paleozoic had lived in this period. During the Mesozoic era, the modern sharks first evolved and their number of sharks increased rapidly. Furthermore, many of the marine reptiles disappeared in this time zone.
The Cenozoic Era (65 million years ago to present day)
Today sharks are the top predators of the food web! The Hammerhead sharks are reported to be the last species of modern sharks that underwent evolutionary changes about 50 to 35 million years ago.
Despite 5 massive extinctions on Earth, many species of sharks have been threatened today and have vanished from the land due to human activities, pollution, climate changes and of course the habitat destruction!
What does it Conclude?
This fossil history of sharks shows that they were living in the oceans for more than 400 to 450 million years ago. They are older than dinosaurs or even many trees, they are the only creatures on the planet that have survived five mass extinctions. No older shark’s species are known to exist today but many of the modern sharks have evolved from them. As they are long lived species, sharks have a long life span – the average life expectancy of modern sharks is 70 years! Similar to humans! Today sharks are being threatened due to human activities, they need to conserve otherwise they will become extinct in the upcoming years!