Yasemin Saplakoglu writes:

Around 4.6 billion years ago, some 9 billion years after the birth of the universe, a cloud of gas and dust collapsed into the familiar blinding ball in our sky. Scraps of leftover material collided and accreted into the planets of the solar system, including our own. For the next few hundred million years, Earth was a hellish, molten landscape bombarded by meteorites. As it started to cool, water pooled into vast, acidic oceans. The days, half as long as today’s, passed under pink carbon dioxide skies. But life wasn’t around to sense any of it. Until it was.

Around 300 million years into the existence of our solar system, conditions on Earth were right for a great chemical experiment to begin. Molecules entangled themselves in self-sustaining, self-reproducing loops. Over time, these systems became more complex. At some point, they had come to life.

Life invented new ways to move, and to capture, store, and use energy. It began to sense, respond to, and change its environment. It communicated, ate some of its neighbors and lived inside others, and formed complex, dynamic communities. Through cycles of birth, reproduction, and death; catastrophe; and bursts of evolution, it persisted and then thrived, taking over every corner of the planet.

Then, at some point, life gained a sense of itself, a reflective intelligence with the existential curiosity to ask: Where did we come from? For tens of thousands of years, we have pondered and probed the origins of life: Monks have meditated, philosophers have argued, lovers have mused, and parents have patiently answered their kids’ questions.

“Go back in human history, go back to the Neanderthals, go back 30,000 years,” said William Schopf, a paleobiologist at the University of California, Los Angeles, “and one of the things you will see is that human beings have been wrestling with this question.”

By the mid-20th century, it became possible to probe life’s origins through chemistry, molecular biology, and genetics. Hypotheses exploded. Scientists clashed over which type of molecule — RNA, lipids, proteins, and metabolites are prime suspects — could have started it all. The arguments have gone on for so long, without resolution or unifying insight, that some experts have considered the field to be in crisis.

“There’s nothing more exciting for a scientific field than a moment of crisis,” said Betül Kaçar, an astrobiologist and evolutionary biologist at the University of Wisconsin, Madison. “That’s when I think breakthroughs happen.” [Continue reading…]