Once Upon a Primordial Soup: A Quirky Story About Evolution
What is evolution in its truest sense? A series of mistakes, or a string of coincidences that somehow seem well-planned? We’re here to find out.
Evolution is one of the most debated topics in science. The popularity of this topic can either be tied to general scientific curiosity or the God vs. science contentions. Pick whatever you seem comfortable with. I am not here to debate but rather here to tell you a story from a perspective you may enjoy and deduce an answer for yourself. Shall we?
From nothing to everything
Our story begins nearly 4,600–4,000 years ago during what the scientists refer to as the Hadean eon. Back then we can compare our planet to what we describe as hell today. The surface of the planet was too dynamic due to flowing molten lava, the continuous bombardment of asteroids from space and a lack of stable crust. The atmosphere was nothing but scorching toxic air composed of methane, ammonia, water vapor and carbon dioxide. There was zero free oxygen. Because of such a hellish environment there was zero biological activity during this eon.
When the Archean eon arrive 4,000 to 2,500 million years ago the planet cools down enough to form a solid rock crust and continental plates. Water vapour condensed into the first global, iron rich green oceans. Our planet can finally breathe. To reconstruct this timeline better we will also talk the four eras that makes up this eon. The Eoarchean era from 4,000–3,600 million years ago is when the first form of life finally appears. Single celled organisms, simple anaerobic bacteria and archaea appear near the deep-sea hydrothermal vents. In the second era, Paleoarchean which was 3,600–3,200 million years ago early bacteria form stromatolites by building mats of microbes trapped between sedimentary layers. This was nothing less than extraordinary. The Great Oxygenation Event started. By photosynthesizing, the ancient cyanobacteria inside stromatolites released oxygen into Earth’s primitive atmosphere, raising oxygen levels and paving the way for complex life. By the Mesoarchean era (3,200–2,800 million years ago) the ancient cratons had expanded to create stable cores of the continent.
The arrival of the Proterozoic eon 2,500 to 541 million years ago marked the transition, where microbial life laid the geochemical groundwork for complex animals. It is divided into three different eras. The first one is the Paleoproterozoic era (2,500–1,600 million years ago) is marked by the Great Oxidation Event. Due to saturation of oxygen in the ocean by cyanobacteria, the oxygen started to fill up the atmosphere. This completely wiped out the anaerobic life on Earth and triggered the Huronian Ice Age by stripping the methane from air. It led to widespread ice sheets covering the continents. The Siderian, Rhyacian, Orosirian and Statherian periods of this era presented the stabilizing of continents and formations of massive bands of iron oxides directly out of ocean and depositing them on land. This deposited iron ores are stilled being mined today. Mesoproterozoic era (1,600–1,000 million years ago) had a massive biological leap as the eukaryotes came into existence will cells developing a distinct nucleus and membrane bound organelles. Sexual reproduction begins, drastically accelerating the rate of evolutionary variation. The last era of this period, Neoproterozoic era (1,000–541 million years ago) the planet plunged into series of global glaciations known as “Snowball Earth”, where ice sheets extended nearly to the equator. (Do not imagine this as the Ice Age movie. We are still far away from that timeline!!!!).
We can see something
As the planet again warmed again, we enter the Phanerozoic eon (541 million years ago to present). This is the modern eon “visible life”, where complex plants and animals diversified. It is split into three classical eras of Paleozoic era, Mesozoic era and Cenozoic era.
In the Paleozoic era came the Cambrian period, better known as the “Cambrian Explosion”. A rapid burst of evolution introduces all the major animal phyla i.e. arthropods, mollusks, chordates, etc. The Ordovician period had the invertebrates diversifying further. Jawless armor-plated fish appear. But this all again ended via a major ice age causing a mass extinction. (The environment said ice them all. Ifykyk). The Silurian period introduced melting of glaciers and stabilizing of environment. The first vascular plants and small arthropods [scorpions, millipedes] successfully colonise dry land. With the Devonian period coming in (Also known as the Age of Fish. Yes, there was time on Earth when it was just dominated by fishes. Remember the movie, Jaws. Sharks are in fact one of the oldest species of this planet).
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And with them first tetrapods (amphibians) started occupying the land. Carboniferous period peaked with a massive 35% atmospheric oxygen saturation giving rise to vast, swampy forests that covered the planet. Reptiles evolve the amniotic egg, freeing life from needing water to lay eggs. In the Permian period the continents drift together to form the supercontinent Pangea (Remember the iconic Pangea map photos in our geography textbooks!!!). The reptiles split into two lineages: sauropsids [ancestors of dinosaurs/birds] and synapsids [mammals like reptiles]. It ended with the Permian-Triassic Mass Extinction also referred to “The Great Dying”. Volcanic eruptions in modern Siberia released immense amounts of carbon dioxide, acidifying the oceans and wiping out 96% of marine species.
Now the next period that is about to come is most likely all of our favourites and the most awaited one for this article. Drumrolls please……... Yes, the Mesozoic era (252–66 million years ago) with the rise of dinosaurs. The Triassic period (252–201 million years ago) had the life slowly recovering from the extinction. The first true dinosaurs emerge alongside small, nocturnal, primitive mammals. Also during this time, the Pangea begins to crack and split forming the modern-day continents. The rise of Jurassic period (This is where the movie gets its name) had warm, humid greenhouse climate triggering a boom in vegetation. Giant sauropods like Brachiosaurus roamed the planet. Pterosaurs ruled the sky and Archaeopteryx marked the evolution of modern-day birds. During the Cretaceous period (145–66 million years ago) the dinosaur diversity reached its peak. Flowering plants started to evolve and attract insect pollinators. The period ended with a 10km wide asteroid striking the Yucatan peninsula, creating the Chicxulub crater. The resulting dust cloud blocked out sun, collapsing food webs and driving all non-avian dinosaurs to extinction.
Our Arrival
After the extinction of dinosaurs, the Cenozoic era arrived (66 million years ago to present day). It started with the Paleogene period (66–23 million years ago) as the planet transitioned into cooler, drier phase. Small surviving mammals rapidly diversify into empty ecological niches, evolving into modern day primates, rodents and hoofed animals.
The Neogene period (23–2.5 million years ago) gave way to massive open grasslands. Mammals grow to giant sizes, and early hominids diverge from common primate ancestors in Africa. Finally, it was during the Quaternary period (2.5 million years ago to modern day) that the modern-day humans (Homo sapiens) evolve, expand globally and developed agriculture, initiating the latest chapter of life on earth.
From there to here
What all I have said above may right now sound so much simpler, but in reality, it is lot more complicates. The exact timeline and durations of these events is still very much debated. New findings everyday add new logics to this ever-growing chain of mechanism. But nonetheless what happened for life to come on Earth is nothing less than miraculous.
But now what is even more than important than ever is to save this miraculous life we around us. They were here before us and have the same right as much we do to live on this planet. Cognitive evolution does not give us the right to decide who gets to live and who does not. To be honest cognition gave us the right to think above ourselves and protect those who cannot protect himself. Our existence is the product of billions of years of evolutionary history, why do we so often behave as though the rest of that history matters less now that we’re here?
I would like to end this with a quote from the person who inspired me to become what I do today,
“The fact is that no species has ever had such wholesale control over everything on earth, living or dead, as we now have. That lays upon us, whether we like it or not, an awesome responsibility. In our hands now lies not only our own future, but that of all other living creatures with whom we share the earth.”
(A little late, but a Happy 100th Birthday Sir David Attenborough…….)
