It is thought that “living fossils” like Triops tadpole shrimps once coexisted with dinosaurs, but which species has inhabited Earth for the longest?
The climate of the oceans and the quantity of oxygen in the atmosphere are both continuously shifting, making Earth a difficult and unpredictable environment. Every living thing is scurrying, swimming, slithering, or soaring in this world of change in order to adjust and survive — or perishes.
But which species has endured the longest in this evolving world?
Triops cancriformis, or tadpole shrimp, received the honor of being the “oldest living creature” in November 2010 from Guinness World Records(opens in new page). And with good reason: fossil evidence indicates that crabs with protection resembling shrimp have existed since the Triassic era. (251.9 million to 201.3 million years ago).
The bodies of tadpole crustaceans are shaped like spades, making them ideal for preparing the floor of the impermanent ponds they live in. They’ve maintained the system for hundreds of millions of years because it functions so well. However, despite maintaining their uniform appearance, tadpole shrimp have continuously evolved beneath their armor since at least 2010, according to DNA study released since 2010. This has led to variations between species over time that are sometimes difficult for human eyes to detect.
For instance, the tadpole shrimp T. cancriformis is merely a descendent of similar-looking Triassic ancestors and is actually no more than 25 million years old, a 2013 study published in the journal PeerJ(opens in new tab) found, and may be as young as 2.6 million years old, according to a 2012 study published in the journal PLOS One.
What about the other potential candidates for the distinction of longest-surviving mammal on Earth? Like tadpole shrimp, there are a number of species that have persisted unaltered for many millions of years and are still living today. These so-called “living fossils” include a variety of deep-sea fish known as coelacanths, which may be the most well-known. When coelacanth remains were first found in the 1800s, scientists believed they perished 66 million years ago at the end of the Cretaceous era. A alive coelacanth was then discovered in 1938 by fishermen off the shore of South Africa. There is a limit, despite the fact that these fish are more than 400 million years old.
The fossilized coelacanth species, which truly went extinct, is not the same as the coelacanth species that are currently found moving in our seas. According to a 2010 research that was released in the journal Marine Biology(opens in new tab), the existence of living things dates back between 20 and 30 million years. The same holds true for the roughly 480 million year old horseshoe crab bloodline, which is also extremely archaic. The oldest surviving species of Asian horseshoe crabs, known as Tachypleus, only appeared about 25 million years ago, according to a 2012 research that was published in the journal Molecular Phylogenetics and Evolution(opens in new tab). This is despite the fact that they resemble fossils that are hundreds of millions of years old.
There won’t be a conclusive solution to this riddle until biologists have completed unraveling the genetic histories of all living creatures. Horseshoe crabs, coelacanths, and tadpole shrimp all demonstrate that even the most apparently steady of creatures are constantly undergoing change.
According to Africa Gómez, an evolutionary biologist at the University of Hull and the study’s lead author, there isn’t enough proof to support the existence of any one species for longer than a few million years, Live Science reported.
According to an article in the journal American Scientist, studies of the fossil record indicate that species usually last between 500,000 years and 3 million years before they perish or are supplanted by a descendant.
For example, DNA alterations can occur in living things and can be handed down from one generation to the next. Additionally, it is possible for two genetically related species to marry and create a successful new hybrid species. Competition drives organisms to change as well. Animals occupying the same area with predators and prey engage in competition for sustenance and resources.
“Predators evolve, prey evolve, predators evolve, prey evolve, competitors evolve, other competitors evolve,” Scott Lidgard(opens in new tab), senior keeper of fossil invertebrates at the Field Museum in Chicago, told Live Science.
Furthermore, the surroundings can affect how long a species lives. Lidgard said, “Let’s say a taxon [group] is well suited to a specific kind of habitat and the climate shifts drastically. “It goes extinct if it can’t migrate to another place with that kind of habitat.”
Gómez believes that no animal is a living fossil because change is continuous and the word implies that animals cease developing. Lidgard claimed that the word “living fossil” can be used to research creatures with specific characteristics, like a sluggish rate of evolutionary change.
