Earth’s biological history stretches far beyond the age of dinosaurs. Hundreds of millions of years ago, prehistoric seas and rivers were full of strange fish with armor, fins, lungs, slime, and jawless mouths. Most of those ancient lineages disappeared during mass extinctions. A few, however, survived.
Today, scientists often call them “living fossils.” It’s a catchy phrase, but it’s not entirely accurate. These six ancient fish lineages aren’t exactly unchanged, because evolution never really stops. But they retain body plans, lifestyles, or genetic features that reach astonishingly far back in evolutionary history. This makes them scientific treasures.
But how did they survive dramatic shifts in climate, and what can they teach us about our own biology? Recent genomic breakthroughs and anatomical studies reveal that these ancient survivors hold the secrets to the evolution of limbs, lungs, and even human brains.
The earliest definitive dinosaurs appear in rocks about 230 million years old. The fish lineages listed below go back far deeper.
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