As one of the marine ecosystem's top predators, the animals we know today as sharks evolved from similar creatures that roamed the seas an estimated 450 million years ago — an era when the biodiversity of marine seascapes increased exponentially and plants began colonizing land. It was a new period in which life slowly migrated from the ocean to terrestrial environments.
"sharks are older than the north star" is now the worst fact i know
— 🦋 child of earth and starry heaven 🐞 (@earthcounter) October 6, 2023
Snopes spoke with two astronomical experts who said that such claims oversimplify the history of our planet, the stars, and beyond. As such, they are not entirely factual.
The evolutionary lineage of sharks can be traced to their earliest ancestors some 450 million years ago, during the Late Ordovician Period. But here’s where the claim gets complicated: The North Star, or Polaris, is actually comprised of three stars, each of which has varying ages.
Evidence Suggests Sharks Appeared (In Some Form) 450 Million Years Ago
The earliest known fossil evidence of sharks (or their ancestors) are “shark-like scales” that date back to 450 million years ago, according to the National History Museum in London. However, whether these scales adorned "true sharks" or "shark-like animals" is an issue debated by the scientific community.
Nonetheless, scientists largely agree that, according to DNA evidence, living sharks, rays, and deep-sea fish called chimeras likely began evolving around 420 million years ago.
Let’s take a quick dive into the history of sharks:
During the Devonian Period (380 million years ago), sharks in the genus Antarctilamna took a form resembling current-day sharks.
Some 20 million years later (roughly 359 million years ago), a mass-extinction event killed three-quarters of the planet's species, sparking the Carboniferous Period. That was an era in which sharks dominated the world’s oceans and evolved into many different shapes and sizes, known as the “golden age of sharks.”
Then, about 100 million years later (about 252 million years ago), another mass extinction during the Permian Period killed nearly all marine life — 96% — except for sharks.
Later, during the Early Jurassic Period (some 195 million years ago), the oldest-known group of modern sharks began to evolve, including the sixgill bluntnose species that's still alive today.
What's Known About the Ages of Three — Yes, Three — Stars That Make Up Polaris
But where does that evolutionary history place sharks in the timeline of the North Star's formation? The answer is not so clear.
The North Star, or Polaris, is comprised of three separate stars. Among them, a yellow supergiant dubbed Polaris Aa is the biggest and brightest. It's in a binary orbit, which means it's one of two stars that orbit around one another. That smaller companion star is Polaris Ab, and the third star, Polaris B, is a small companion that orbits Polaris Aa and Ab.
“With the naked eye, we only see Polaris as a single star because Polaris Aa is so bright compared to the other two,” Susanna Kohler, an astrophysicist and science writer with the American Astronomical Society, wrote to Snopes in an email.
In the field of astronomy, determining the age of an individual star is difficult
largely because such calculations are based on estimates and assumptions.
“Most studies estimate the age of the primary component, Polaris Aa, to be somewhere around 50 million years — younger than sharks! The other two components are typically estimated to be older [than sharks],” explained Kohler. "Different studies come up with different results."
As an example of the varying estimates, a 2020 study (that has not been peer-reviewed) estimated Polaris Aa is between 45 and 67 million years old, Polaris Ab is at least 500 million years old, and Polaris B is around 1.5 billion years old.
That study was authored by Hilding Neilson, an astrophysicist and assistant professor at the Memorial University of Newfoundland. Neilson confirmed to Snopes that, while it’s probable that the Polaris makeup is less than 450 million years ago — thus, making it younger than shark-like creatures — measurements are not precise. (Again, the study was still in preprint, as if this writing, which meant it had not been reviewed by scientific peers.)
“Polaris could be anywhere from 200 to 600 million years old based on measurements of its mass, and potentially can be even younger than 200 million years,” Neilson wrote in an email. “The answer is really unclear."