Charles Darwin: the pioneering theory of the origin of life that the biologist scribbled in a letter 150 years ago

But Darwin’s key contribution was outlining a mechanism of evolution: natural selection.

The idea is that animals of one species compete with each other for food, shelter, and the ability to reproduce. Only the most suitable, that is, those who adapt best to their environment will be able to reproduce, therefore its traits will be passed on to the next generation and they will become more common.

So, while having a long neck is beneficial for giraffes, giraffes with longer necks will proliferate to their optimal neck length over the generations. Darwin expounded this in his 1859 work “On the Origin of Species”.

The fact of evolution implies something about how life began.

Evolution tells us apparently distinct species are distant relatives, both descendants of a single shared ancestor. For example, our closest living relatives are chimpanzees – the common ancestor we share lived at least seven million years ago.

Furthermore, every living organism ultimately descends from a single ancestral population: the Last universal common ancestor (LUCA, for its acronym in English), who lived more than 3.5 billion years ago when the planet was formed.

However, the theory of evolution tells us nothing about how the first life was formed: it only tells us how and why existing life changes.

Research into the origin of life didn’t really begin until the 1950s.

At that point, many scientists they suspected that life had begun in the oceans. The idea was that many carbon-based chemicals formed on Earth dissolve in the ocean, which became thick: the so-called “primordial soup”.

This was proposed in the 1920s by a Soviet biologist named Alexander Oparin. In 1953, a young American student named Stanley Miller showed that amino acids, the building blocks of proteins, could be formed in a simple apparatus that mimicked the primordial ocean and atmosphere.

The idea that life began in the ocean has prevailed for decades, but there was an obvious problem: oceans are huge, so unless they occur carbon-based chemicals in staggering quantitiesThey would have been adrift for years and never met.

“It would have too much water and too few molecules,” says Claudia Bonfio of the MRC Molecular Biology Laboratory in Cambridge, UK.

A much discussed alternative is that life may have begun alkaline vents like those of Lost City in the middle of the Atlantic.

There, the warm, mineral-rich water from the sea floor seeps through the rocks and forms mysterious white needles. Vents are a rich source of chemical energy that could have fed early organisms.

But according to a new study published last May, “the direct synthesis of amino acids or nitrogenous bases”, which are essential for life as we know it, “has not yet been demonstrated” under alkaline ventilation conditions.

This brings us back to Darwin.

Darwin never wrote in his books about how life began, but he speculated on this in private.

The key document is a dated letter 1 February 1871 which he wrote to a close friend, the naturalist Joseph Dalton Hooker. This letter is now nearly 150 years old.

It’s short, only four paragraphs, and difficult to read due to Darwin’s handwriting. After a brief discussion of some recent mold experiments, Darwin outlined the beginning of a hypothesis:

“It is often said that all the conditions for the first production of a living being are now present, that they might have been there once. But if (and oh, what a great if) we could conceive in some hot little pond with all kinds of ammonia and phosphoric salts, light, heat, electricity present, that a protein compound is chemically formed, ready to undergo even more complex changes, in the present, such matter would be instantly eaten or absorbed, which previously would not have been other than living creatures were formed “.

This requires a bit of unraveling, in part because several ideas are stuck: it reads as if Darwin was thinking about his hypothesis even when he wrote it. But the central idea is simple enough.

Darwin was proposing that life could begin not in the open ocean, but in a smaller body of water on land, which was rich in chemicals.

This is, in essence, the whole soup idea, but with one advantage: in a swimming pool, any dissolved chemical is concentrated as the water evaporates in the heat of the day.

The initial synthesis of the chemicals of life would be led by some combination of light, heat and chemical energy.

In many ways, Darwin’s idea is hopelessly incomplete, but he cannot be blamed for it. I was writing before the discovery of nucleic acids like DNA, before biologists understood how genes work and when the inner workings of living cells were very mysterious.

Darwin imagined that life began with a protein, but no one really knew what proteins wereIt was only in 1902 that proteins were intended as chains of amino acids.

But the same basic pattern is still followed today and many researchers are convinced that this is the best explanation we have of the origin of life.

Lena Vincent of the University of Wisconsin-Madison is a researcher whose work is compatible with the environment of a pond, although she prefers to keep an open mind.

You’re trying to create sets of chemicals that copy themselves as a group.

The simplest example would be a pair of chemicals A and B, where each has the ability to produce the other, so A produces B and B produces A. A pair of those chemicals could they reproduce on their own, although neither could do it alone.

In practice, chemical assemblies are more complicated than that, but the principle is the same.

There is also much evidence that ultraviolet radiation from sunlight can drive the formation of key biological chemicals, most notably RNA, a DNA-like nucleic acid believed to be a crucial component in the creation of early life.

Such processes could only occur in well-lit places, which again indicates a small body of water rather than the depths of the sea.

A protagonist in this was John Sutherland of the MRC Molecular Biology Laboratory in Cambridge, UK.

In 2009 he showed that two of the four building blocks of RNA are made up of simple carbon-based chemicals when subjected to simple treatments such as being immersed in ultraviolet radiation.

Since then, it has shown the same starting chemicals, even with slightly different treatments they can become bricks of proteins or fatty lipids that form the outer membranes of cells.

Finally, bodies of water on earth can dry out almost completely in hot weather and then fill up again when it rains. These wet-dry cycles may seem harmless, but they have profound effects on the chemicals of life.

Deamer argues that “floating volcanic hot springs” are the most likely environment for life to begin.

Sutherland has an alternative: a meteor crater, with streams running down the sides and meeting in a pool at the bottom.

It is not clear which of these scenarios is more plausible. Furthermore, many younger researchers make sure not to engage in one scenario or another, arguing that we still don’t know enough about the processes that can lead to life.

In particular, many researchers still take the alkaline vent hypothesis seriously, despite its problems.

What is clear, however, is this Darwin’s idea was far-sighted. He envisioned the need to concentrate a variety of chemicals in a small space and the need for an energy source that could drive chemical reactions.

“Like many of Darwin’s ideas,” says Vincent, the small hot pool hypothesis was “very prescient.”

Darwin pointed out another fact in his letter, which is “underestimated,” says Vincent.

“The processes that take place in that hot little pool it can happen so easily that it would happen all time“, he argues.

We may not see this simply because whenever a new protein or similar form naturally forms, it is eaten by hungry bacteria.

“We talk about the origin of life as if it were something that happened in the deep past,” says Vincent. “But it is something that could also happen At this time“.

* Michael Marshall is a science writer living in Devon, UK. He wrote a book about the origins of life, The Genesis Quest.

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