Sharks have evolved for almost half a billion years

Sharks have evolved for almost half a billion years

As a group, sharks have existed for at least 450 million years and survived all the major mass extinctions on Earth, so sharks are older than dinosaurs and even trees.

The earliest fossil evidence of the existence of sharks or their ancestors refers to late ordovics and amounts to about 450 million years. A few million years later, the world experienced the first major mass extinction at the borders of the Ordivian and Silorian periods.

Since then, four such events have been recorded: the Devonian extinction; nevertheless, sharks still exist; their successful evolution can be explained by several factors.

Incredible ability to adapt

One such factor may be that sharks can "rapidly" change their physiology in response to changing environmental conditions.

Remember, sharks are close relatives of the slopes, but studies of gene expression at the slopes have revealed that these animals are incredibly adapted to temperature changes. According to one study, the winter slope population has reduced its body size by 45%.

This rapid evolution suggests that these changes in the body were caused by an epigenetic reaction; in other words, it was no longer a matter of natural selection taking away smaller individuals, but of changing the expression of genes due to environmental factors.

We also know that several species of slug fish, the subclass of which are sharks, can move between fresh and salt water.

Finally, two other important points: sharks are evolving in different parts of the water column; in other words, some species are more comfortable at greater depths and others live in shallow waters or even rivers; we also believe that sharks are extremely carnivorous, but now we know that they are more diverse in food.

Therefore, if a living area or food source is threatened, shark diversity as a group means that while some species may be in trouble, others are likely to survive.

However, while sharks have survived previous extinctions, the outcome of current human-induced activities may be fatal: overfishing, pollution effects, pollutants and habitat loss have dramatically reduced the populations of many previously resilient species, but it must be remembered that sharks, as predators, play an invaluable role in the ecosystem of the world ' s oceans.