NYT: How life arose?
You are here. So am I. So are the doves out back and the marigolds lining the swamps. But how did any of us come to be?
It's one of 100 unanswered questions The New York Times is chasing, and worth a deeper read.
Every living thing runs on the same basic chemistry. Most scientists agree that all cellular life traces back to LUCA, the Last Universal Common Ancestor. LUCA was likely a population, not a lone creature, and it was already complicated. What came before it is anyone's guess. What came after are three turning points that produced the variety of life on the planet.
- First, how chemistry became biology. Some think natural reactions in Earth's early waters made organic compounds that, over time, learned to copy themselves. Others look to the seafloor, where reactions could unfold around thermal vents safe from radiation above the water.
- Second, how simple cells grew complex. About two billion years ago, eukaryotic cells arrived: bigger, more intricate, with nuclei, mitochondria. Most scientists agree that symbiosis, one organism moving in with another, was central to the change. The details are still being debated.
- Third, how life got big. After a long, slow stretch, Earth went through a run of hard ice ages starting about 720 million years ago. One theory says the glaciers and the weathering that followed washed nutrients into the oceans, feeding algae and increasing oxygen levels. That may have helped complex life take off. But some lineages had already gone multicellular, so the link is far from settled.
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