We’re a strange bunch, us humans. Having spent the last sixty years devouring the resources of our solar system’s only habitable planet, we’ve made the ice age we’re supposed to be in feel more like a sauna. Like the fluffy blue muppet, we’re insatiable — we eat everything. As a result, our natural resources have been depleted at a speed so fast, it’s threatening our survival. With ongoing droughts, the future of our food is uncertain; the soil we’ve used to grow our crops for centuries is now so dry that little can be sustained from it. Our summers are much hotter, heatwaves longer, and our once natural wildfires are burning out of control. Freezing winters come with severe blizzards, destructive storms, and a rising sea that’s eroding our shorelines, threatening to engulf our homes. And that’s just a bunch of our concerns — there’s also the many threats faced by the millions of species we share the planet with.
There’s no doubt about it — we’ve kinda screwed up. Still, beyond the fear and basic debate about whether climate change is real or what has caused it, an interesting history shows past climate events have had some major benefits; cataclysmic shifts have happened before, with many creating the conditions necessary for evolutionary leaps.
Going by the Big Bang theory, our universe first came onto the scene some 13–14 billion years ago. For an incomprehensible amount of time, it was dark, hot, and in-conducive to life; just try to wrap your head around one billion degrees… Yet in this blistering climate, nature’s four fundamental particles thrived and forces emerged. Protons and neutrons formed, coming together to create the first simple elements; hydrogen and helium.
The universe continued to expand, experiencing its first climate shift and subsequent growth spurt. Things cooled down, and our friend gravity helped make the humble gases a duo, bringing them together to create stars. Through the process of nuclear fusion, these original stars created the ‘heavy’ elements like carbon, nitrogen and oxygen. In a constant cycle of death and rebirth, elements were passed from old star to new, becoming part of each other like DNA, fresh ones created each time.
At the end of their lives, stars fall into themselves and ‘explode’ in what’s called a Supernova. It was the shock wave of a Supernova that collapsed a nearby nebula containing the ingredients of our solar system. With time, nebula particles floated through space, colliding until they formed the eight planet bodies and stabilised into their own orbits; held in place by the gravitational pull of a newborn star — the Sun. If it weren’t for stars, our entire solar system could have stayed a floating disk of gas and space dust.
Earth’s eons are more evidence that life’s greatest evolutionary leaps occurred during times of great climate fluctuations. Looking at our blue pearl, it’s hard to believe she started without her water, but a young Earth was much different to the one we inhabit today. During the Hadeon Eon, instead of the lush mix of green and blue, the entire planet began as a volcanic sea of molten rock. Hit by billions of tonnes of comets, asteroids and storms, early Earth had no sign of visible life. Yet, single-celled microscopic organisms not seen by the naked eye existed deep inside volcanoes.
It wasn’t until Earth’s crust cooled that molten rock solidified and atmospheric water vapour condensed, raining down on the planet to create Earth’s oceans. During this time, known as the Archaean Eon, these single-celled creatures flourished. Underwater, in a literal sea of churning chemicals and organic compounds, bacteria and archaea proliferated. With the atmosphere full of carbon dioxide, these microscopic blobs survived without oxygen for billions of years. When Cyanobacteria, better known as blue-green algae, began to photosynthesise, enormous amounts of oxygen was released into the ocean and atmosphere. With a decrease in carbon dioxide, Earth’s temperature plummeted; from pole to pole, ice sheets covered the planet.
To survive these conditions, bacteria and archaea fused together, creating the first multicellular organisms and third domain of life; Eukaryotes. Biology’s equivalent of the Big Bang then moved life from the Earth’s oceans onto land, beginning the Proterozoric Eon. The planet warmed up again, now with higher levels of oxygen, and The Cambrian Explosion occurred. Though there are still competing theories on the exact cause of the explosion, this event opened the door for many of our modern creatures to form. Previously, life had only existed on the ocean floor as ‘soft’ creatures without skeletons. Since then, starting as simple vertebrates and invertebrates, reptiles and dinosaurs, the Eukaryote kingdom has developed over billions of years to become the plants, animals and ecosystems we see today.
In a dark and unexpected twist, the Paleozoic era ended in The Great Dying; a mass extinction event in which most life on Earth was destroyed; 70% of land animals and 96% of marine life disappeared from our fossil records, suggesting that they perished. While scientists are still unclear on what caused the event, popular theories propose a meteorite impact or massive volcanic eruptions that occurred around the same time. Whatever the case, this climate shift paved way for the next era and leap.
The Mesozoic era, associated with the rise of Dinosaurs and reptiles, also gave rise to mammals, frogs, bees and flowering plants. Similar to the Paleozoic, the Mesozoic era ended in cataclysm; a giant asteroid impact in the Gulf of Mexico resulted in a second mass extinction. This was the end of non-avian dinosaurs and many terrestrial plants and marine species. Though, with many reptiles gone, small mammals could shine; it was during this new era — the Cenozoic, that whales, rodents and primates thrived. The global climate during this time was even warmer than today, and most environments were tropical. Though in line with the pattern of the planet, the Earth underwent yet another climate fluctuation; this time cooling and entering an Ice Age. These climatic shifts led to cooler and drier environments, turning many tropical forests into dry grasslands.
Flash forward to more recent history, 5–7 million years ago, when human ancestors the early Hominids were still tree-dwellers with divergent thumbs, moving on all fours to support their tree-to-land lifestyle. The Savannah Theory proposes that Hominids started walking on two legs because of these ice age-induced climate shifts that shrank forests and expanded grassland. Following their discovery of bipedalism, the Hominid species continued to grow during these shifts; Homo Habilis, the earliest known and now extinct species of human, made simple stone tools. With so much ice, migration was easier, and Homo Erectus travelled across the globe; from Africa to Eurasia, where they discovered fresh material to advance their tool kit, used bone to sew warm clothes, and learned how to harness fire.
History has shown a fluctuating climate is as natural and spontaneous as life itself. From the very moment of our universe’s conception, things have either been boiling, or freezing, and during these extreme times, the most pivotal moments of life’s evolution have occurred. In the heat of a billion degrees, tiny particles formed to create energy itself. Only after a massive cooling did gases coalesce to form stars, leading to the heavy elements that make up our galaxy and solar system. Violent comet bombardments and underwater volcanic eruptions created the perfect conditions for the planet’s first living cells. Global freeze overs moved simple life from the bottom of the ocean to complex life on land. Asteroids paved the way for bees and flowering plants to create the ecosystems central to the small mammals that became the species we are today.
In our own short time as modern human beings, ice ages and land changes have brought us up onto two feet, enlarged our brains and led to the discovery of tools, clothing, fire, farming, agriculture, trade and every other discovery we have continued to make. We begin a new era in an eon that has experienced its fair share of destruction. Yet, equipped with the knowledge of our symbiotic relationship with our environment, we engage in behaviour that might cause our own mass extinction.
Though the Earth has always fluctuated between climate extremes, our activities have sped up the warming of our planet far before its time. What will our world look like in a severe greenhouse period? It’s scary to think about reverting to the beginning, where our home was an uninhabitable fiery ball of molten rock. Whether or not our actions will have devastating affects for our species is yet to be determined — however one thing is for sure, the Earth will survive. She’s been through worse than what we can throw at her. Like every living species throughout life’s 14 billion year history, it will be us who will have to adapt to her conditions, or face our extinction.