Maps and Geography

In this post we’ll discuss how to worldbuild a tree of life, looking at the origins of life, how life begins, how life forms are classified, and creating some of our own organisms that we’ll be using moving forward.

Hey everyone, my name is Matthew, at least that’s what my fellow lifeforms call me, and this video is part of a series where I will be going through a science-adjacent worldbuilding process step-by-step. Last time we established a map and the early geography of our fictional world called Locus, including its tectonic movements, wind patterns and oceanic currents.

For today’s discussion, we’re finally going to be introducing life to our fictional world of Locus, discussing how life arises in the first place, looking at taxonomic ranks, and diving into the wonderful world of speculative evolution.

To start, I’d like you to meet someone. This is LUCA. LUCA stands for Last Universal Common Ancestor and is the point of the tree of life where all subsequent living things can trace back their origin. Despite this prestigious title, LUCA may not be the first life form on the planet. The transition from a non-living planet to one that has life is slow, and LUCA is probably not the first life form, but rather the earliest that is successful.

But where did LUCA come from? The answer, or at least the way we get to the answer, is Abiogenesis. Abiogenesis is the concept of the creation of living matter from non-living matter, usually pertaining to the origins of life, and in real-life, we have had many hypotheses across the centuries for how abiogenesis may have occurred.

Perhaps the most straightforward answer a worldbuilder can use for how abiogenesis occurred is Creationism, which is the concept that life, or more generally speaking, that EVERYTHING, was created by a deity, or group of deities. While this doesn’t really work for the world I’m building, this isn’t an uncommon selection, and many famous literary works use their own creation story to answer how things came about. One of my personal favourites is Lord of the Rings, where divine beings literally sang creation into existence.

Another hypothesis of the origins of life is called the Panspermia hypothesis, proposed by Greek philosopher Anaxagoras, which is just about the coolest name I’ve ever heard. Panspermia is the theory that life exists throughout the universe and is distributed to new planets by space travelling objects such as comets, or even by intelligent life forms themselves. Of course, the problem with panspermia as a life-origin theory is that it doesn’t actually answer the question for how life was first created; it simply moves the question off the planet and takes it elsewhere in the universe.

The final hypothesis we’ll discuss is the Primordial Soup hypothesis, which while not directly proposed by Charles Darwin, was the result of expansions on his theory of natural selection. Soviet biochemist Alexander Oparin argued that earth’s primitive surface would have had carbon, hydrogen, water vapour, and ammonia react with each other to form the first organic compounds, decidedly turning non-life into life. English scientist J.B.S. Haldane independently arrived at a similar conclusion five years later and was the first to use the term ‘soup’ to describe the collective pools of organic material in his 1929 publication, The Origins of Life.

To better understand the primordial soup hypothesis, we first have to discuss heterotrophs and autotrophs.

A heterotroph is an organism that consumes other matter in order to obtain its energy. We as humans, as well as all animals, are heterotrophs; we need to eat food in order to gain energy.

Heterotrophs are contrasted with autotrophs, which describe an organism that is able to create their own food source from raw energy and materials. The most well-known real-life autotrophs are plants, which use photosynthesis to sustain themselves.

The Primordial Soup hypothesis posits that life emerged as a result of the development of heterotrophy, where the earliest life forms fed off the mineral rich water around deep-sea hydrothermal vents. Therefore, in modern science, this concept is referred to as ‘heterotrophic theory’, and it is this theory that we’ll be using moving forward to describe the origins of life on Locus.

Yes, I know, the panspermia theory of having life evolve from the alien colony Locus had in the past would have been cool but don’t worry, I haven’t forgotten about that.

For Locus we’ll say that like on earth, life started beneath the waves within 500 million years of Locus settling into the solar system it now lives in. For the first billion years of life’s history, LUCA and organisms like LUCA would exist as relatively simple single-celled organisms, and their evolutionary journey will start out very slow.

Now that we’re going to be looking at LUCA’s evolution, it’s important to understand that organisms are grouped into biological classifications called Taxonomic ranks, of which we use eight major ranks: starting with domain and moving all the way through to individual species. All of these taxonomic ranks make up the tree of life, and the more specific we get in terms of describing an organism, the further down the chain of taxonomic ranks we need to go. For example, as humans our domain is Eukarya, the branch of the tree of life we share with all multi-cellular eukaryotic life, including plants, mushrooms, as well as all other animals including birds and insects. But calling ourselves eukaryotes is not very specific and doesn’t differentiate us clearly. So, we can move down in taxonomic ranks to further specify what we are talking about, such as referring to ourselves as mammals, which is our class, and primates, which is our order, becoming more and more specific until we arrive at our species, Homo Sapiens, which means ‘Wise Human’ or ‘Knowledgeable Human’. Without taxonomic classification, we would have no idea what kind of organism we’re talking about, and we’d end up lumped in with creatures like beetles and fish, or even with trees.

Of course, the process of determining Taxonomic rank is pretty extensive, and it’s important to note that while we’ll be discussing the evolutionary journey that LUCA and LUCA’s descendants will take, detailing the ENTIRE tree of life throughout all taxonomic ranks would be an overwhelmingly exhaustive task, and waaaay beyond the scope of this series. Instead, we’ll be discussing the primarily successful groups of organisms, only discussing an individual species if it is particularly prominent or critical to the worldbuilding process, such as the creatures that will eventually evolve intelligence. Also importantly, as we discussed in our original concepts and goals for worldbuilding, I want life to be recognisably earth-like, which means that while I won’t be creating a creature that is a cat exactly, the tree of life on Locus is likely to look and feel similar to our own tree of life on earth, so we may end up with a creature that is clearly inspired by a cat, with similar features.

This means that we can save ourselves an enormous amount of hard work by setting up the foundational kingdoms and phyla really quickly. Let’s branch LUCA off into three main domains, the Unadomus, Viatores, and Duodomus, representing organisms that are similar to bacteria, viruses, and multi-cellular eukaryotic life respectively.

For our virus analogues, the Viatores, we’re using the reduction hypothesis for their origins, which states that viruses were once small cells that evolved to parasitise larger cells, losing their own cellular structure in the process. However, there are other hypotheses on how viruses came to exist, though microbiologists have not definitively determined which is correct. There is contention in real-life whether viruses are even part of our tree of life at all, but using the reduction hypothesis we’ll say that viruses on Locus are descendants from LUCA.

From here though, we’ll be focusing on the multi-cellular Duodomorum, which will also split into three main kingdoms: Folia, Pilea, and Ambulia, representing plants, fungi, and animals respectively. Folia, like plants, have developed photosynthesis, which is the process through which an organism is able to transform light energy into chemical energy for use in their organic processes. This is the equation for photosynthesis, and we can see here that an excess amount of oxygen is produced, which means that the atmosphere of the planet is going to rapidly oxygenate as Folia become more abundant. In the early stages of Locus’ history, would form a thin blanket layer across the ocean surface, asexually reproducing to branch outwards.

Next, we have Pilea which represent fungi, forming long branching filamentous structures that reproduce asexually. The Pilea are the first saprotrophs, which are organisms that feed on non-living organic matter. In their ecosystems, they play important roles as decomposers, recycling organic matter back into the ecosystem to be re-consumed by other organisms. As primordial ocean dwellers they would settle on the ocean floor and feed off the detritus that falls from above.

Finally, we have the Ambulia kingdom, which will include all of the creature’s we’ll worldbuild moving forward. Although their name means “walkers”, obviously not all creatures will evolve to walk, though this kind of generalised misnomer is reasonably common in scientific classifications and still serves our purposes to keep things labelled and clear.

Across the course of 3 billion years, life would continue to diversify to fill all available niches. A niche in ecological terms refers to the role an organism plays in their environment, examining factors like habitat, resources, predators, parasites, and pathogens, as well as how that organism affects all those factors. A niche is an organism’s ‘job’, and whenever a new niche appears, creatures will compete to fill it, with the creature most fit for the niche emerging successful. This premise of the fittest organisms surviving is called ‘Natural Selection’.

Very quickly, let’s go over some of the Phyla and Classes that are going to be the successful emergent organisms on Locus across the ages. It’s important to note that the oxygen content of Locus’ early atmosphere is around 30%, which is close to what earth’s atmosphere included in the carboniferous and cretaceous periods, when creatures like dinosaurs grew to become absolutely massive. For reference, Argentinosaurus is perhaps the largest land animal of all time on earth, and grew to sizes of up to 35 metres, weighing up to 75 tonnes. Of course, with higher oxygen levels come more intense fires, but more on that later (FORESHADOWING). For now, we know that our organisms are going to be able to get BIG, REALLY big.

First, we have three main phyla that fall within the Folia kingdom; the Tapete, Caulis, and Pulchra, representing mosses, conifers, and flowering plants. There are also three main phyla within the Pilea kingdom; the Mendax, Candentis, and Corpus, representing psychedelic fungi, bioluminescent fungi, and fungi that feed on flesh rather than on decaying flora. These six phyla across the Folium and Pileum kingdoms will make up the flora that we will worldbuild in the future. Technically, fungi should not be included when discussing ‘flora’, as we know that they aren’t plants, however when most people discuss ‘flora’, they do include fungi like mushrooms for simplicity, and so we will too.

Among the Ambulia kingdom, the three main phyla we’ll be looking at are Comedentes, Multarma, and Concha, and it is within these phyla that all the creatures we will worldbuild will fall into. Multarma are, almost exclusively, ocean-dwelling, analogous to creatures on earth like jellyfish and squid, so we probably won’t see them around too much as we go through the continental climates. Concha includes ocean-dwelling crustacean-like creatures, such as the Duruscutis and Magnumunguis, but also the land-dwelling Planapedes, which will form the foundations for many land ecosystems and are analogous to arthropods.

Finally, we have the Comedentes, which we’ll divide further into the classes Oscauda, Frigidi, and Calidi. Oscauda fill the seas and include all manner of fish-like creatures, with innumerable different species, from bottom-dwellers, to apex swimmers, to surface plankton eaters. As the saying goes on Locus, there’s always a bigger Oscauda. Frigidi are the scaley analogues to reptiles, including the bipedal order of Duopedes, as well as the terrifying and appropriately named Formidulosus. Calidi on the other hand are covered in fur, representing mammals and include the tree-dwelling Aborascensus and the tiny Velocauda, so full of potential.

You’ll notice that despite mentioning all of these groups of organisms, we didn’t actually discuss any. Well, that’s because… they’re about to die (AWKWARD). Extinction events, also known as a mass extinction, or my personal favourite terminology, a biotic crisis, are widespread rapid decreases in the biodiversity of a planet. A planet is considered to be in an ‘extinction event’ when the rate of extinction, that is the termination of the last individual of a species, outpaces the rate of speciation, which is the evolutionary process where new species are created.

The high oxygen content of Locus’ atmosphere means fires are not only easier to start but will grow to massive sizes. After life thriving on land for a good 200 million years, a cataclysmic fire will take place. In an event that would make George R. R. Martin proud, this would be the biggest fire that Locus has ever seen. More than 80% of species across all kingdoms would become extinct, if not directly due to the fire, then due to the cataclysmic change in the atmosphere as a result. The fire would consume a significant portion of oxygen within the atmosphere, meaning that any of the larger creatures that didn’t directly die from the fire would suffer hypoxia, or oxygen deprivation, ultimately leading to the death of their species.

Extinction events are reasonably expected across geological time scales, and as worldbuilders, determining the most recent extinction event of a fictional world gives a springboard from which we can establish all of the surviving species that will still be around in modern times.

So, to recap, we discussed some of the main hypotheses for the origins of life and selected heterotrophic theory as our life origin of choice on Locus. We looked at the structure of taxonomic ranks and established that the Last Universal Common Ancestor of life on Locus developed around deep-sea hydrothermal vents, before evolving into a number of kingdoms, phyla, and classes that we can use moving forward. Finally, we established the most recent mass extinction event, a cataclysmic fire, which leaves us with a modern world ready for new life to branch out and thrive.

Join me next time where we’ll start to look at individual climate zones called biomes, discussing their geography and establishing their modern flora and fauna, starting at the equator with tropical rainforests. You can find all the information for this video and other resources for worldbuilding in general over at worldbuildingcorner.com, and if you enjoyed this video don’t forget to like and subscribe to follow the world-building journey. And until next time… stay awesome!