In March 2020 a special paper was published in the Proceedings of the National Academy of Sciences (PNAS). Pieced together by experts from Rutgers, The State University of New Jersey, this work could ultimately influence our understanding of life and its beginnings. You see, its authors believe that they’ve identified the building blocks of life that were present during Earth’s earlier days.
The group of Rutgers scientists involved in this study are part of a project known as Evolution of Nanomachines in Geospheres and Microbial Ancestors (ENIGMA). The team is closely associated with NASA and even receives funding from the agency. In essence, ENIGMA seeks to learn about early life and how it came about.
It’s broadly accepted within the scientific community that simple forms of life must initially have come into being from something that had not previously been living. This process is called abiogenesis, though the specifics behind it have not yet been fully grasped. In fact, as one of the ENIGMA scientists themselves put it to Rutgers Today in March 2020, “We know very little about how life started on our planet.”
Of course, many people have dedicated their lives to the study of life and its obscure origins. Perhaps the most famous person to have done so is Charles Darwin, an English biologist and naturalist who many consider to be one of the most influential people in history.
Before his theories revolutionized our understanding of evolution, however, Darwin was a student. In 1825 – when he was just 16 years old – he started studying medicine at the University of Edinburgh in Scotland. But after his first year had been completed, the teenager took an interest in the study of animals.
When it became clear that Darwin wasn’t going to practise medicine, his father moved him to the University of Cambridge. Here, the elder Darwin hoped, his son would go on to eventually join the clergy. That, of course, didn’t happen, and across three years Darwin scored quite well and picked up an a Bachelor of Arts degree.
Throughout his Cambridge years, Darwin’s passion for the natural world grew. He took to collecting beetles of varying kinds, but the young man ultimately sought a greater deal of adventure. Darwin eventually moved into the realm of geology, and as a graduate he went on a mapping excursion in Wales.
In 1831 Darwin took up a job as a naturalist aboard the HMS Beagle – a British survey vessel set to cross the Atlantic and reach South America. From there, it would pass Australia and head home to Britain. The trip lasted five years, and it greatly influenced Darwin. The things he saw – such as animals, plants, landforms and fossils – had a tremendous bearing on his thinking. And in particular, he was astonished by the particularly distinctive species which lived on the Galapagos Islands.
By the time that he’d returned to Britain in 1836, Darwin had collected a huge array of samples from his voyage. His excursion and the notes he made on it had thrust him into the center of the scientific community, and so Darwin’s father decided to finance his work. The naturalist also picked up funding from the British government.
Among Darwin’s many discoveries from his voyage was the fact that the South American landmass was incrementally rising from the ocean. He also took note of a dozen new kinds of finch. But vitally, on top of everything else, the journey focused Darwin’s mind onto the notion of how different species came to be.
By the year 1837 Darwin was noting the differences exhibited by different species of creature and plants. You see, he had come to realize that living things “transmute.” Or, to use another term, he grasped that they evolve. His idea gained traction the following year after he read the works of the English cleric Thomas Robert Malthus. The latter had argued that populations continue to grow until food disappears and what follows is a struggle for survival.
Writing in his autobiography in 1876, Darwin himself elaborated on his thoughts in those earlier days. Reflecting on Malthus’ theory, the naturalist wrote, “It at once struck me that under these circumstances, favorable variations would tend to be preserved, and unfavorable ones [would] be destroyed. The result of this would be the formation of new species. Here, then, I had at last got a theory by which to work.”
In 1838 Darwin began thinking about how farmers breeded animals with the most beneficial attributes. In this scenario, the farmer selects the livestock that should reproduce. But within the context of the wild, Darwin realized, the environment undertakes this process. In other words, the animals or plants that have adapted best to their surroundings can continue to live and reproduce. This is known as natural selection.
It wasn’t until 1859, however, that Darwin’s most important publication first went into circulation. This was On the Origin of Species, a pivotal text widely considered to be the most vital work ever written on the subject of biology. It was in this book that Darwin wrote, “… Probably all the organic beings which have ever lived on this Earth have descended from some one primordial form, into which life was first breathed.”
Following its initial publication, Darwin revised On the Origin of Species six times over the years. By the final edition, the concept of evolution was recognized by most serious scientists. Natural selection, on the other hand, continued to face resistance. It was only in the 1930s – decades after Darwin’s death – that the theory started to really take hold.
Nowadays, Darwin’s thoughts on species and evolution are thought of as central to the study of biology. Broadly speaking, it’s accepted that everything which lives today has descended from common ancestors which came before. But that’s by no means to say that questions don’t remain. For instance, it’s not at all clear how the initial forms of life on Earth came to be in the first place.
Human beings have speculated that non-living matter at some point became animate since the time of ancient Greece. Aristotle, in fact, wrote about this very subject around the fourth century B.C. But in 1924 a more reasoned and scientific theory was formulated. This focused on the hypothetical condition of the Earth billions of years ago – a state referred to as the “primordial soup.”
Writing in his book The Origin of Life that year, the Soviet scientist Alexander Oparin posited that conditions on Earth had allowed inorganic matter to become living. However, since that time, the planet had changed; oxygen now prevents such a thing from happening. But even if it could occur, organisms already here would quickly kill any newly created ones.
Oparin, naturally enough, was writing in Russian. Yet around the same time, a Briton named John Burdon Sanderson Haldane had been working on similar subjects in English. And he ultimately gave this line of thinking the term by which we know it today. That is, he wrote of a “soup” made up of living matter and water which was found on Earth long ago.
Haldane wrote in The Origin of Life, “When ultra-violet light acts on a mixture of water, carbon dioxide and ammonia, a vast variety of organic substances are made, including sugars and apparently some of the materials from which proteins are built up.” He added,“… Before the origin of life they must have accumulated till the primitive oceans reached the consistency of hot dilute soup.”
Haldane and Oparin’s ideas are now referred to as the Heterotrophic theory, though other names have also been used. For instance, it might also be called the Heterotrophic origin of life theory or the Oparin-Haldane hypothesis. In any case, one might extrapolate a number of basic tenets from the arguments contained within.
Put simply, the Heterotrophic theory suggests that so-called organic compounds combined with water in the early days of the Earth. The resulting mixture was something we can now term as primordial soup. It was within this matter that the initial lifeforms of Earth came to be and started to reproduce.
But the notion of primordial soup and the wider Heterotrophic theory are by no means a sure thing. Today, scientists are still trying to figure out how life got started on Earth, with different people considering varying factors in pursuit of an answer. The ENIGMA scientists, for example, have focused on the subject of protein.
Proteins are sizable biomolecules that are crucial for allowing living things to undertake in a variety of actions. Broadly speaking, the ability to grow and to restore damaged cells is down to proteins. And they are an essential aspect for the effective functioning of all living cells.
Proteins are a vital part of life as we know it, with different kinds serving a variety of specific functions. Muscle proteins allow creatures to move, and antibodies are utilized for the sake of overcoming infection. Enzymes, meanwhile, help to break down food that’s ingested by an organism.
And enzymes are of particular interest to the ENIGMA scientists hoping to learn more about the beginnings of life on Earth. You see, it’s believed that enzymes came into being on the planet before cellular life ever did. These early enzymes would have caused electrons to move and thus allow food to become energy.
Food being converted into energy is vital for life, so the ENIGMA researchers took a look at contemporary enzymes. The team wanted to discover whether they had more basic elements, so they looked at different proteins which had been gathered in a global database. They then split them into the smallest size that they could be while still functioning.
Each of these enzymes had a specific purpose; one, for instance, might hold iron together, whereas another would deal with copper. Yet the scientists were interested in recognizing smaller parts which were common throughout every enzyme.
The researchers then started to recognize a pattern. It seemed that a pair of particular enzyme parts were linked to all others. In other words, they were central to the functionality of all the other components. These parts were specifically responsible for joining DNA and holding iron together.
The researchers could then infer that the two aforementioned enzyme parts were likely the first to ever crop up on Earth. Because they were the first enzymes to generate chemical reactions, they in turn created the conditions for subsequent enzymes to function independently.
The experts believe that these two enzyme pieces created the so-called building blocks of life, and they are still present in contemporary times. They are able to work on their own, but the fragments also serve a wider purpose, too; they’re the basis for more complex protein formations that we can see nowadays.
The co-author of the ENIGMA study is professor of Biochemistry and Molecular Biology at Rutgers Robert Wood Johnson Medical School Vikas Nanda. And in March 2020 he talked about the project’s significance in an interview with Rutgers Today. He said, “This work allowed us to glimpse deep in time and propose the earliest metabolic proteins.”
Nanda went on to explain how he and his colleagues intend to move forward. He explained, “Our predictions will be tested in the laboratory to better understand the origins of life on Earth and to inform how life may originate elsewhere. We are building models of proteins in the lab and testing whether they can trigger reactions critical for early metabolism.”
Nanda also spoke to Discover magazine about ENIGMA’s findings that same month. And he explained that any conclusions drawn by their research are based on mathematical projections, rather than physical evidence. After all, it’s hardly likely that any fossils will ever be found from the beginning of the Earth 3.5 billion into the past.
As Nanda himself put it to the publication, “That’s the scientific challenge. How can we infer from what we have now what these [enzyme parts] looked like?” Hopefully, though, further research will shed light on the subject down the line. The implications, after all, could be immense.
Despite the lack of physical evidence, theories about the earlier days of Earth would appear to back up the ENIGMA research. You see, it’s thought that the planet’s seas likely contained lots of iron. And given that one of the enzyme parts was linked specifically to the element, this would add credence to the argument.
Throughout the course of their investigations, the ENIGMA scientists tested the two enzyme parts on their own to see if they could function. Nanda told Discover, “I was skeptical at the beginning that this would work. I thought we’d make enzymes and have to coddle them to get them to work.”
Yet in spite of Nanda’s reservations, it seems that the enzymes worked fine alone. But as he later acknowledged, that actually shouldn’t have come as too much of a surprise. He told the publication “If you’re a small peptide on a rocky surface in the early ocean, and you have no cell to protect you, [you] have to be tough to survive.”
If the research is correct and these two enzyme parts are essential for life, then perhaps they might be found further afield. Indeed, they may be at the heart of extraterrestrial life, too. If experts keep an eye out for these components throughout the Solar System, it could lead to significant discoveries further down the line.
Here on Earth, however, Nanda and his ENIGMA colleagues will continue to study the components of enzymes and how they relate to one another. The expert told Discover, “Each connection represents something that had to evolve for a new function, and each one is a choice nature made. There’s lots of data to mine.”