If at all time travel was possible and you go back 200 million years, no doubt the Earth would feel like a completely different world—filled with unfamiliar giants and unusual living creatures. Yet, if you reach a swamp, there is a good chance that a familiar creature would greet you in this drastically different world.
Yes! Believe it or not, but crocodiles have remained the same for hundreds of millions of years. This fact has been brought out by a new study that sheds light on the evolutionary history of these colossal aquatic animals. The study shows that even in this incredibly long span of time—closer to the age of dinosaurs—the crocodiles have undergone only marginal changes.
Apart from crocodiles—and its close family of alligators, caimans—all other living beings like birds, lizards and land animals have transformed to form thousands of diverse species in the past millions of years. Crocodiles, however, have evolved into only 25 different species on Earth, say the researchers.
Hey crocodile, why didn’t evolve faster?
As per researchers, the secret behind the crocodile’s persistent body shape for millions of years can be decoded through an evolutionary pattern known as punctuated equilibrium. It is basically a biological theory which explains why the rate of evolution remains slow, followed by a long period of equilibrium.
Sporadically, however, a species would experience faster evolutionary change due to particular changes in environmental conditions like a warming climate. Therefore, with global warming, the crocodile’s body size is also likely to increase eventually.
Dr Max Stockdale, the lead author of this research, said: “It is fascinating to see how intricate a relationship exists between the Earth and the living things we share it with. The crocodiles landed upon a lifestyle that was versatile enough to adapt to the enormous environmental changes that have taken place since the dinosaurs were around.”
The results concluded that the presence of not many diverse species of crocodile today and less distinct traits are a prime indicator of their slow evolutionary rate. Moreover, their fewer changes also indicate that—even when other species of animals evolved—crocodiles were able to survive the changes in their surroundings easily.
The authors note that their body versatility is also a sign of how they were able to survive the catastrophic meteor impact, which killed the dinosaurs during the end of the Cretaceous period around 66 million years ago. Moreover, the crocodiles are known to adapt and habitat more easily to the warmer climatic conditions. As they do not hone the ability to control their body temperatures and therefore, crocodiles insulate from the warm environment.
The evidence also highlights a possibility that more species of crocodiles thrived and existed during the time of dinosaurs, as compared to the present. The mercury levels soared much higher during the age of dinosaurs than today. The study notes that in prehistoric times, there were also types of crocodiles that were more exotic and not yet known to science. They are deemed to be as big as dinosaurs!
How was the study conducted?
Palaeontologists often study the hypothetical tree of evolution to join the missing dots on how the animals got certain body types, features, traits and attributes that define them. This research—led by a team of scientists from the University of Bristol—specifically studied the evolution of the crocodilian body.
For this, the team studied the fossils of crocodiles found from the early Jurassic period. The study ascertains that crocodiles found today have a close resemblance to the ones that lived along with dinosaurs from the Jurassic period more than 200 million years ago. The authors refer crocodiles to be ‘living fossils’ as they have a close resemblance to those once lived on Earth millions of years ago.
The researchers also used advanced evolutionary modelling techniques to compare the body size data from fossil records. On the method, Dr Stockdale, explains: “Our analysis used a machine-learning algorithm to estimate rates of evolution. Evolutionary rate is the amount of change that has taken place over a given amount of time, which we can work out by comparing measurements from fossils and taking into account how old they are.”
The research team is planning to investigate and explore further why different types of prehistoric crocodile species became extinct while others survived.
The study was published in the journal Nature Communication Biology last week and can be accessed here.