Sara Gironi Carnevale
In 1944, Erwin Schrödinger published a book called What Is Life?. The physicist, famous for his alive-and-dead cat, clearly relished a brainteaser. Today, there is still no good definition. Life is generally agreed to require a minimum of two things: metabolism and reproduction. But the question of how chemistry morphed into biology billions of years ago is very much open to debate.
Now, a surprising contender has emerged as the catalyst for sparking the first life – and it is one we typically associate with deadly diseases.
Advances in molecular genetics have revealed that all living things on Earth are descended from a single organism dubbed the last universal common ancestor, or LUCA, which emerged around 4 billion years ago. We also know that our planet is approximately 4.5 billion years old. During those first half a billion years, simple, then more complicated, organic molecules were spontaneously synthesised and assembled in larger complexes, eventually evolving into the primitive, single-celled LUCA. How did that happen?
Biologists have long debated which key molecule of life came first. RNA – a cousin of DNA – has been a front-runner because some RNA may be able to copy itself. However, these molecules seem too unstable to develop into life. Another possibility is proteins. Here, the problem is that they can’t reproduce. Now, some researchers are suggesting a solution to these roadblocks – and it comes from an unexpected quarter.
What are prions?
Prions are weird proteins, originally fingered as agents of infectious neurodegenerative diseases such as kuru and scrapie. That’s how, as a virologist, I became interested in them. But it has become apparent that prions aren’t, in fact, a malevolent rarity, but are found in many organisms, playing a host of crucial roles, from the immune system to memory formation. Could they also be the missing piece in the puzzle of life’s origins?
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Each month, Michael Marshall unearths the latest news and ideas about ancient humans, evolution, archaeology and more.
