Category Archives: The Liminal Times

The Woke Sea

Oysters can change their gender multiple times in their lifespans.

Within 12 hours of their birth, oysters begin pulling calcium out of the water to create their signature shells. For the first few weeks of their lives, these newborn bivalves zoom around in a current until they eventually settle on some hard substrate, whether it’s a rock, pier, or another oyster. This place of protection is where the oysters will spend the rest of their lives (which can be as long as 20 years). Eventually, usually a year after birth, it’ll be time for the oysters to breed, and that’s where things get interesting. 

Although born male, oysters have the impressive ability to switch their sex, seemingly at will. Every season, females can release up to 100 million eggs, and the amount of sperm released is so high it’s essentially incalculable. Once the egg and sperm are released, the oysters rely on pure chance for fertilization to take place, as the egg and sperm meet in the open water. Because any resulting larvae are extremely vulnerable to predators (especially filter feeders), oysters have evolutionarily compensated by being one of the most virile and sexually flexible species in the world — meaning that their ability to change sex likely evolved as a matter of survival. This impressive fecundity means that natural oyster reefs can grow to tremendous size; as little as 10 square feet of reef can house up to 500 oysters. Scientists theorize that water temperature could play a role in triggering whatever causes an oyster to change its sex, but many aspects of the process remain a mystery. 

The 99th Percentile

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.