The Earth is a box of surprises that has seen millions of living organisms appear and disappear, but of all of them, which is the oldest species on the planet? Researchers are trying to solve this mystery, and it seems there is no clear answer.
When we think of the oldest species, perhaps the first thing that comes to mind is the indomitable dinosaurs that walked the planet millions of years ago. But the truth is that these were only a part of the biodiversity that inhabited the planet, there are even some species that shared with the dinosaurs and are still alive today, such as turtles or crocodiles, although they have undergone some changes in their evolution.
The oldest species still alive
Researchers have wondered if any species is preserved as a “living fossil,” i.e., one that retains its appearance as it was eons ago. But this is a complicated task, since the Earth is a place of constant change and everything on it evolves, from the temperature of the ocean waters to the levels of oxygen in the atmosphere.
Despite this, in November 2010, the Guinness World Record gave special recognition as the ‘oldest species’ to the tadpole shrimp whose scientific name is Triops cancriformis. The title came for one simple reason, and that is that fossils of armored crustaceans show that shrimp like these have lived since the Triassic period spanning from 251.0 million years ago to 201.3 million years ago.
Tadpole shrimp are considered the oldest species on Earth, animals whose shovel-like shape allows them to burrow into the seafloor. Their physiological design is so well suited to their habitat that it has allowed them to survive for many millions of years. However, although they look the same as they did in the Triassic when dinosaurs still lived on Earth, researchers have discovered that there are small signs of evolution in their genome that have created new species whose differences are not perceptible to the human eye.
Studies show that the tadpole shrimp is a descendant of very ancient ancestors, according to research published in the scientific journal Peerj, the species as it exists today is only 25 million years old. With this, the title of oldest species is shaken, so many will wonder if there are other contenders, and there are.
One more contender for the title
There is a group of deep-sea fish called coelacanths that are arguably like living fossils. During the 19th century, coelacanth fossils indicated that these fish were extinct at the end of the Cretaceous period 66 million years ago, just like the dinosaurs. But then everything changed when in 1938 fishermen pulled up a live coelacanth off the coast of South Africa, an astonishing fact considering that it is a species dating back 400 million years.
Since then it has been known that there are species of coelacanths still swimming freely in the deep waters of the world’s oceans, but it is exactly the same as with the tadpole shrimp, they were not immune to change. The coelacanth species alive today are not the same as they were 400 million years ago, which actually became extinct.
Horseshoe crabs dating back 480 million years are also contenders for the oldest species still alive. And while they certainly have a very striking prehistoric appearance, genome analyses of horseshoe crabs of the species Tachypleus tell us that they date back 25 million years.
In conclusion, it seems that there are no older species that have been able to escape the imminent changes of our planet. Cases such as the tadpole shrimp, coelacanths, and horseshoe crabs show us that even the most stable organisms are changing all the time, even if we do not notice it. According to fossil records, species follow a cycle in which they usually last between 500,000 years and 3,000 years before succumbing to extinction or giving in to evolution and change.
Story originally published in Spanish in Ecoosfera