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The oldest proof that life existed comes from special rock samples. These rocks have organic stuff in them with a specific "chemical fingerprint"—basically, they don't have as much Carbon-13 as you'd usually expect. Since living things prefer using lighter carbon, finding this in old rocks tells scientists that something was alive back then -
Stromatolites are lumpy, layered rocks made by tiny colonies of germs over a long time. Scientists have found fossils of these mounds that are about 3.4 billion years old! Because they were built by living microbes, these fossils are basically the oldest proof we have that life existed on Earth way back then. -
After Earth formed, it cooled down enough for the surface to harden into a solid crust about 4.5 billion years ago. Once things were even cooler, volcanic steam and ice from space comets turned into rain, filling up the low spots to create the oceans by about 4.4 billion years ago. -
The Cambrian Explosion happened about 541 million years ago, and it was basically a massive growth spurt for life on Earth. Before this, most living things were just tiny, simple blobs, but suddenly, evolution went crazy and created tons of complex animals with eyes, legs, and hard shells. It’s called an "explosion" because, in terms of Earth's history, all these new species showed up really fast. -
Around 2.4 billion years ago, tiny germs called cyanobacteria took over the world. They were the first to use photosynthesis, which meant they sucked up sunlight and pumped out massive amounts of oxygen. Before them, the air was actually toxic to us! They multiplied so fast that they completely changed the atmosphere, eventually making it possible for oxygen-breathing animals to exist. -
Around 600 million years ago, life finally leveled up from single cells to multicellular organisms. Instead of living alone, cells started sticking together and working as a team. By splitting up jobs—like some cells handling food and others handling movement—they could grow much bigger and more complex. This "squad" approach is what eventually led to all the plants and animals we see today! -
The very first living things appeared: prokaryotic cells. These are super simple, single-celled organisms like bacteria. They don't have a nucleus (a "brain" to hold their DNA) or any fancy internal parts; they’re basically just tiny bags of chemicals that figured out how to copy themselves. Even though they’re basic, they were the "OG" life forms that ruled the Earth for billions of years before anything else showed up! -
Around 2 billion years ago, life got a major upgrade with eukaryotic cells. These were much fancier than the simple prokaryotes because they actually had a nucleus which is like a protected "control center" for their DNA. They also had tiny "engines" called organelles that helped them process energy way more efficiently. This was a huge deal because it allowed cells to get bigger, more complex, and eventually work together to build everything from trees to people -
Dinosaurs ruled the Earth for a massive chunk of time, from about 230 million years ago until they were wiped out 66 million years ago. They weren't just big lizards; they were a huge variety of animals that lived all over the world, from the tiny, bird-like ones to the massive long-necks that were taller than buildings. Even though most of them went extinct when a giant asteroid hit the planet, they didn't totally disappear, birds are actually their direct descendants. -
Around 470 million years ago, the first plants finally crawled out of the water and onto land. Before this, all the greenery was basically just seaweed or algae stuck in the ocean. These "pioneer" plants were super small and simple, sort of like the moss you see on rocks today, because they hadn't figured out how to grow tall or stay hydrated without being soaked in water. Once they took over the land, they started pumping out oxygen and creating soil.
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