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THE idea about the origin of life known as “metabolism first” – that you must first look for its source of energy – was championed in the late 1980s by Günter Wächtershäuser, a German chemist turned patent lawyer. Wächtershäuser envisioned a series of chemical reactions taking place on crystals of iron pyrite, or fool’s gold, in volcanic hydrothermal flows at high pressure and high temperature. This scheme was dubbed the “iron-sulphur world”. However, nowadays, this has been largely supplanted by an idea that originated with Mike Russell, who was then at NASA’s Jet Propulsion Laboratory in Pasadena, California. He began exploring the possibility that the first life was powered by currents of electrically charged protons within alkaline vents on the seabed. This geochemical idea is counter-intuitive, and initially didn’t go…

Most life on Earth is microscopic and single-celled. The origins of these life forms probably lie in Earth’s first billion years. For most of our planet’s history, they were all that existed. But in developing tricks such as photosynthesis to extract energy from their environment, they fundamentally changed the planet and created the conditions for more complex life forms to evolve. Even now, they have a diversity and a range of lifestyles that puts us lumbering multicellular lumps to shame, and that sets the tone for life on Earth today.…

THE vast majority of viruses are little more than strands of genetic material packaged up in a protein container called a capsid. Around a quarter are also surrounded by an envelope, which is usually made of a lipid membrane stolen from its host plus some virus-encoded proteins. A single virus is called a virion. Most are around 100 nanometres across. Their sole aim in (quasi-)life is to invade the cells of their host, release their genetic material and hijack the cell’s biochemistry to make more copies of themselves. The new virions then burst out of the cell, killing it, and begin the cycle anew. Viruses are genetic parasites. That leads to the question of whether they are truly alive, to which there is no simple answer. On the one hand,…

True multicellular organisms aren’t just clumps of cells stuck together. Different cells can evolve specialised functions, so they share the labour of maintaining the organism, creating distinct tissues and organs. A tiny organism that lived a billion years ago may have been one of the first life forms built that way. It had two different cell types, one forming its core and another its outer “skin”. making it a crucial step towards modern organisms like animals that also have a skin that is distinct from the cells inside the body. Evidence for this species, dubbed Bicellum brasieri, comes from microfossils preserved in rocks that formed in an ancient freshwater lake in north-west Scotland, found by Charles Wellman at the University of Sheffield, UK, and his colleagues. Each instance was a…

GIVEN how important we now know mass extinctions are to understanding the history of life, it may seem surprising that no one was much interested in the idea until the 1970s. Of course, the great Victorian palaeontologists, such as Richard Owen and Thomas Huxley, were aware that dinosaurs and other ancient creatures were extinct, but they didn’t see any role for sudden, dramatic events. Following Charles Darwin, they argued that extinction was a normal process: species originated at some point by splitting from existing species, and at some point they died out. Extinction certainly is a normal part of evolution. Species come and go continually – around 99.9 per cent of all those that have ever existed are now extinct. The cause is usually local. For example, a lake might…

WHEN biologist J. B. S. Haldane was asked by a theologian back in the 1940s what we could infer about the mind of the creator from the works of creation, he supposedly replied, “an inordinate fondness for beetles”. The story is almost certainly apocryphal, but it reveals both an undeniable truth and an open question. Judging by their sheer numbers, God is certainly fond of beetles. But just how fond? The number of beetle species is just one lacuna in our knowledge of these extraordinarily successful creatures. Another is what makes them quite so successful. As we slowly fill in the gaps, we are beginning to appreciate the unique insights these insects can give us. Whether we want to understand evolution, the workings of the biosphere or how plate tectonics…

Life on Earth has come a long way. In its 3 or perhaps 4 billion years on this tiny blue dot, it has weathered many storms. Now the fear is that it is facing its greatest threat yet – us. More than 70 per cent of ice-free land is now under human control and increasingly degraded. The mass of human-made infrastructure exceeds all biomass. Humans and domesticated animals make up more than 90 per cent of the mammalian mass on the planet. Our actions now threaten about a million species – 1 in 8 – with extinction. All this has happened in a blink of an eye, geologically speaking.…

THE original concept of rewilding is attributed to ecologist Michael Soulé at the University of California, Santa Cruz. In 1998, he published an essay outlining a new approach to conservation in North America. He advocated creating wildlife corridors between existing reserves, linking them up to create wildernesses large enough to support native carnivores such as wolves and bears, or even introduced ones such as lions. The idea was underpinned by cutting-edge ecology, and specifically the concept of trophic cascades. This holds that ecosystems are principally shaped by the feeding behaviour of large herbivores and carnivores, the “apex consumers” largely absent from today’s human-dominated ecosystems. Put them back in, so the logic went, and the ecosystem would automatically be restored to a healthier, more biodiverse state. When Soulé proposed rewilding, the…

FORESTS Degraders: Clearance for infrastructure, agriculture and grazing; logging for firewood; pollution, invasive pests and wildfires Restorers: Replanting native trees; conservation of plants and animals; rewilding FRESH WATER Degraders: Water extraction for irrigation, industry and homes; sand and gravel mining; dams, canalisation and drainage for agriculture; pollution from chemicals, plastics and sewage Restorers: Controls on water extraction, fishing and mining; dam removal or redesign, restoring water flows to wetlands; wastewater treatment OCEANS AND COASTS Degraders: Overfishing and coastal clearance for aquaculture; plastic and nutrient pollution; wastewater discharge Restorers: Sustainable fishing; wastewater treatment; pollution control; management and restoration of coral reefs; mangroves and seagrasses GRASSLANDS AND SAVANNAH Degraders: Conversion to cropland and pasture; overgrazing and soil erosion; unsustainable resource extraction; invasive species Restorers: Active clearance of woody vegetation; reseeding native grasses…

Earth is lush with thriving life. When it first formed, however, it was a sterile rock. How did life first get started on our planet – and where? These questions are among the most profound in science, and although many theories exist, scientists still can’t agree on the answers. Which of life’s key components – its proteins, its genes, its cell walls or its driving metabolism – came first? Did life emerge at a bubbling marine hydrothermal vent, in a warm pool on land or even in a dry or cold desert? Getting to grips with the answers would help us grasp our place in the universe, and could even guide our search for life elsewhere.…

PROTEINS FIRST ONE of the earliest ideas about the first step on the road to life was popularised by biochemist Sidney Fox in the wake of the seminal Miller-Urey experiment. He suggested that these amino acids then assembled themselves into simple proteins. In modern organisms, proteins perform a huge range of functions, including acting as enzymes that speed up essential chemical reactions. From the 1950s onwards, Fox’s team produced evidence that protein-like molecules could indeed form from amino acids. These “proteinoids” formed spherical structures that superficially looked like living cells. They could even divide into two, as real cells do, and speed up chemical reactions. Similar experiments are still being conducted today. Stefan Schiller at the Albert Ludwig University of Freiburg in Germany and his colleagues have made simple proteins…

THE alkaline vent hypothesis is often described as a metabolism-first scenario, because it emphasises the energetics of life. But this is only part of the picture. In fact, Russell’s scenario also includes compartmentalisation from the very beginning – just not in the form of cell membranes. What if we go further? It has long been thought that the ingredients for life came together slowly, bit by bit, because cells are too complex to have formed all at once. That is why scenarios like protein first and the RNA world have been so prominent. But some researchers argue this entire approach is misguided. It is a bit like trying to build a car by making a chassis and hoping wheels and an engine will spontaneously appear. Instead, recent experiments suggest that…

THE oldest confirmed fossil organisms are single-celled microorganisms. They were found in 3.5 billion-year-old rocks in an extinct volcano in the Dresser Formation in the hot, dry, remote Pilbara region of Western Australia. The fossils include stromatolites – layered rock structures created by microorganisms – and circular holes left in the rock by gas bubbles that look like they were once trapped by sticky microbial substances. Both types of structures are preserved in geyserite, a type of rock that is only found in and around freshwater hot springs in volcanic areas on land. In a 2019 study, Raphael Baumgartner at the University of New South Wales in Australia and his colleagues drilled into the rocks to get the best-preserved samples. They found many layers that looked like stromatolites. These contained…

The origin of viruses is contentious, with broadly three competing ideas. One is that viruses predate cells. In this view, viruses emerged from the primordial soup as free-living, self-replicating entities in a precellular “virus world”. Only later did they become parasitic, once cells had evolved. A second possibility is that some cells evolved simpler forms and became viruses. In this scenario, cells came first and viruses have only ever existed alongside cells. A third notion, related to the second, is that cells came first and that viruses were cellular components that “escaped” to become autonomous parasites. It may be that certain genes escaped from cells and became viruses. Conceivably, all these ideas are true. There is evidence that viruses don’t have a single common ancestor, but instead originated several times.…

In the past few hundred million years, our planet has been transformed. Today, the lands, oceans and air are teeming with animals and plants. How did we get to this point? Even now, there are many gaps in our understanding, about how and when animals and plants evolved, and when they came to colonise not just Earth’s oceans, but its land masses. What we do know is that it was far from a smooth, linear evolution. Periodic disasters known as mass extinctions have occurred at least five times since animals first evolved, each time paving the way for new species to arrive and dominate.…

BY THE end of the Cambrian Period, animals and plants were still confined to the sea. Only microbes lived on the land and it took a long time for their larger cousins to join them. Different groups moved onto the land at different times, so there was no single colonisation event. Plants seem to have reached the land first, with animals following later. Insects probably led the way. The oldest insect fossil is some 410 million years old, but it is an elaborate creature, indicating that insects evolved much earlier. Their ancestors were once thought to be myriapods – land animals including millipedes and centipedes – but Björn Marcus von Reumont, an evolutionary biologist at the University of Giessen in Germany, and others had different ideas. In 2010, he published…

THE fossil record indicates that apes started out in Africa about 26 million years ago, and were firmly settled there 4 million years or so later in the form of Proconsul africanus. A close relative that lived 18 million years ago paints an extraordinary picture of these early apes. Remains of Ekembo were found preserved, Pompeii-like, in layers of volcanic ash on Rusinga Island, Kenya. What we have is an animal with arms and legs of equal length, a horizontally oriented backbone and a brain about the size of a modern baboon’s. In other words, Ekembo looks like a largish monkey, but with a key difference – no tail. Tails allow many monkeys to balance, but Ekembo compensated with more limber wrists and hips and more powerful hands and feet…

GEORGES-LOUIS LECLERC, the Comte de Buffon, was the most famous naturalist on the planet in the middle of the 18th century, and he didn’t think much of the New World. He proclaimed the Americas “degenerate”, a sodden, miserable land filled with weak and inferior species. But Buffon reserved his most biting contempt for one creature in particular. He wrote of their “too short” and “badly terminated” legs, of their “slowness, stupidity… and even habitual sadness”. “These sloths,” he continued, “are the lowest term of existence in the order of animals with flesh and blood. One more defect would have made their existence impossible.” Buffon couldn’t have been more wrong. What he saw as shortcomings we now realise are exquisite adaptations that have allowed sloths to thrive in an exceedingly austere…

THE capabilities of bees are often put down to swarm intelligence, but over the past few years, findings have been trickling in suggesting that individuals deserve more credit. Bees can follow intricate rules, distinguish between patterns in nature, sort sensory stimuli by shape and colour and even have a rudimental ability for mathematics. To test the limits of bee abilities, Olli Loukola at Queen Mary University of London and his colleagues taught bumblebees to roll small plastic balls into holes to win slurps of sugary water. Soon, the bees were devotedly operating the miniature vending machines, frequently finding shortcuts to the sweet prize – some even walked backwards, a behaviour that isn’t natural to them. In another experiment, bees were trained to pull strings to release tasty rewards. The string…

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WHEN oxygen first started accumulating in the air 2.4 billion years ago, it plunged the planet into crisis. The stench of death was everywhere as whole branches of the tree of life were pruned almost to oblivion – all because of the waste gas pumped into the atmosphere by one incredibly successful species. This was arguably the most tumultuous episode in life’s history. Life had been thriving for well over a billion years when a new kind of cell appeared on the scene, one that harvested the sun’s energy using a process that generates a highly toxic by-product – oxygen. These cells were soon growing in such unimaginable numbers in the primordial oceans that they transformed Earth’s atmosphere. At the time, this was a catastrophe. The rise of oxygen may…

Complex, macroscopic life forms – animals, plants, fungi – shape our perception of life on Earth. They have one crucial trait in common: they are built on complex, diversified, “eukaryotic” cells that allow for a far richer biochemistry than is seen in single-celled organisms. This diversification paved the way for another evolutionary leap – multicellularity, in which specific types of cells perform different functions within an organism, developing different tissues and organs. How and when both these leaps occurred are subjects of intense research and debate.…

SPINOSAURUS LOOK at the jaws of Spinosaurus and you might conclude it was like a crocodile. Examine its gigantic claws and it is like a bear. Its broad, flat toe bones are like those of a wading bird. What could the life of a creature with such apparently conflicting features have been like? Making sense of this fantastic beast would pay dividends, because Spinosaurus might explain one of the biggest mysteries of dinosaur evolution. Everyone agrees that Spinosaurus was a giant. We don’t have a complete skeleton, but estimates suggest it was about 15 metres long, making it the largest carnivorous dinosaur yet found. It belonged to a dinosaur family called the spinosaurids that appeared roughly 150 million years ago. These animals had crocodile-like jaws and teeth, but lacked the…

The world around us is full of extraordinary, complex organisms living in extraordinary, complex ecosystems. Understanding their individual traits, and how they compete and cooperate, is a never-ending task. In this chapter, we explore some of the most extraordinary insights into the animal, plant and fungal kingdoms of recent years, from what makes sharks so tenacious to the extraordinary success of beetles and the hidden lives of trees – evolution’s wonders in action.…

What have you discovered about the secret lives of trees? The key finding is that trees are in a connected society, and that it’s a physical network and that they trade and collaborate and interact in really sophisticated ways as a cohesive, holistic society. From my training, and from the way we viewed forests or any plant community prior to that – at least in Western thinking – we didn’t see plants as collaborative and linking. We thought that plants are solitary and compete to acquire as many resources as they can to increase their fitness. That idea isn’t necessarily wrong. It’s just that the way plants grow isn’t simply by competition. They also collaborate, and there are synergies. You have called it a “wood wide web” that consists of…

OUR relationship with nature started to sour around the start of the industrial revolution, but only really veered off the rails as the Great Acceleration kicked in after the second world war. In this period, booming population and trade and higher levels of prosperity led to an exponential growth of pretty much every measure of humanity’s planetary impact: resource extraction, agricultural production, infrastructure development, pollution and habitat and biodiversity loss. This plundering was a gamble that has long since ceased paying out. Degraded land already adversely affects the well-being of 3.2 billion people and costs more than 10 per cent of annual GDP in lost yields, poorer health and other negative impacts. Those are only going to increase. In a 2021 paper in the journal Frontiers in Conservation Science, an…