Modern humans have been on Earth less than .01% of the planet’s existence.

The Earth has been around for a while — about one-third as long as the universe itself. By comparison, Homo sapiens are the new kids on the block. Earth’s story began at the outset of the Hadean eon, about 4.6 billion years ago. It took 600 million years just for the Earth’s crust to take shape, another 300 million years for the first signs of microbial life to pop up, and about 3.2 billion years after that for life to really get going thanks to the evolutionary burst known as the Cambrian explosion. Several mass extinction events and some 465 million years later, mammals finally took center stage, but modern humans didn’t enter the biological limelight for another 65 million years. With the first Homo sapiens appearing around 300,000 years ago, humans have only been on planet Earth for 0.0067% of its existence. 

In those 300,000 years, humans have been pretty busy. For a couple thousand years, we harnessed fire and lived a nomadic existence, until around the fourth millennium BCE, when the very first civilizations began to take shape. Since then, humans have been on a meteoric trajectory, going from hunter-gatherer to spacefarer in less than 6,000 years. Carl Sagan famously displayed the universe’s history on a 365-day calendar, with the Big Bang on January 1 and our current moment starting at 12:01 a.m. the next year. On that timeline, it’s only at 10:30 p.m. on December 31 that humans first appear, and all of recorded history is squeezed into just a few seconds — but what a few seconds it’s been.

There’s a that’s jellyfish considered biologically immortal.

Immortality is the dream of ancient mystics and futuristic transhumanists alike, but for humans and most other animals on Earth, the promise of such longevity remains out of reach — that is, unless you’re a jellyfish known scientifically as Turritopsis dohrnii, nicknamed the “immortal jellyfish.” The life cycle of most jellyfish begins with a fertilized egg that grows to a larval stage called a planula. Eventually, the planula attaches itself to a surface, and forms into a tubelike structure known as a polyp. These polyps eventually bud and break away into an ephyra, aka a young jellyfish, and these floating youngsters then develop into adult medusae capable of sexual reproduction.

Most species of jellyfish call it quits at this point, and eventually die like every other species on Earth — but not Turritopsis dohrnii. Instead, when this creature becomes damaged for whatever reason, it can revert to a blob of living tissue that eventually develops back into a polyp, and once again its developmental process repeats. Of course, this jellyfish isn’t immune to the numerous dangers of the ocean — whether from predators or climate change — but if left to their own devices, these incredible creatures can just go on living forever. 

Although the immortal jellyfish is a longevity outlier in the animal kingdom, there are a few other organisms that can pull off similar feats. Planarian worms display a limitless ability for regeneration, and can become two worms when cut in half. Additionally, the bacterium Deinococcus radiodurans is resistant to basically everything, as it can reassemble its genome and effectively return to life even after intense heat or radiation — a feat that earns the hardy bacterium the fitting nickname “Lazarus microbe.” Maybe immortality isn’t so impossible after all.