Meet the Eukaryote, the First Cell to Get Organized
31st October 2024
Three billion years ago, life on Earth was simple. Single-celled organisms ruled, and there wasn’t much to them. They were what we now call prokaryotic cells, which include modern-day bacteria and archaea, essentially sacks of loose molecular parts. They swirled together in shallow, primordial brews or near deep-sea ocean vents, where they extracted energy from the environment and reproduced by dividing one cell into two daughter cells. Then, one day, that wilderness of simple cells cooked up something more complex: the ancestor of all plants, animals and fungi alive today, a cell type known to us as the eukaryote.
The eukaryote’s debut transformed the planet. Today, all complex multicellular life — indeed, all life that any of us regularly see — is made of eukaryotic cells. No one knows for sure how that first eukaryote arose, but biologists believe that it took at least a billion years of interactions between bacterial and archaeal cells for it to finally come into being.
“Eukaryotes are this bananas chimera of bacteria and archaea,” said Leigh Anne Riedman (opens a new tab), a paleontologist who studies early life at the University of California, Santa Barbara. “We are still trying to sort out exactly how it happened and who was involved.”
And God said, ‘Hey, I’m standing right here.”
The eukaryotes invented organization, if we use the literal definition of “organize”: to be furnished with organs. Inside a eukaryotic cell are self-contained, membrane-bound bundles that perform special functions, called organelles. All eukaryotic cells — animal, plant, fungus or protist — have a nucleus that encloses and protects DNA. Nearly all of them have mitochondria, which produce energy to fuel biochemical reactions. (Any eukaryotic lineages that lack mitochondria used to have them and then lost them sometime in evolutionary history.) And across the evolutionary tree, different eukaryotes have evolved or procured additional organelles that assemble proteins, store water, turn sunlight into energy, digest biomolecules, get rid of waste, and more. If prokaryotes are a loose pile of papers on the floor, eukaryotes are a sophisticated filing system that binds pages into packets and labels them.
And all of this just sort of happened, you know?