The Mechanics
I almost want to get immediately sentimental. But let's for a moment talk about how this tree of life was created and thus how to read it.
To explain how this is build, let's talk about what happens with a single creature. This creature will have a number that represents their species. When the creature replicates, their offspring will have a number that's either +1 or -1 from their parent's number. Using this simple scheme, over many generations different species will have numbers that drift away from each other.
By chance there will also be a lot of cross over of the numbers as species' numbers wander. To fix this I bias the probability of picking -1 or +1 based on where the other creatures are. So for example if there are 1000 creatures with the number 40 and this creature has the number 41, their offspring will likely get a +1 and be 42. This has the effect of spreading out the numbers.
Next I want to use these species numbers to see which creatures are which on the map. So I assign that number to a color. On a 0 to 255, RGB color scale I get to have 1530 different full-brightness colors; so I'll just mod the number of the species with 1530 and plot it on the color scale.
Now I have colors that represent species. How to build the tree? Every X turns I can take a census of what species there are and plot a single line where the intensity is proportional to the percentage of the population with that color. Stacking those slices on each other for tens of millions of turns gives us the full and complete tree of life.
The meaning
Now for the fun part. More accurately, now for the amazing part.
At a high level, it's the first time I've ever seen every single species ever in the tree of life. No stumpy branch or leaf in this tree is left un-turned. We don't have to rely on some spotty fossil record that we piece together by comparing physical structures. We don't even have to parse the DNA. We have a tree of life based on real heritage data. And crazier yet, this is a tree of life playing out just like all our evidence said ours did. Right in front of our eyes in a repeatable way.
Look at the long stretch of yellow and orange. Notice how the yellow is longer lived (ave age ~5000 turns vs less than 1000 turns for orange) and branching less often because replication rates are slower. If we look at the real-time video of the world we can actually see yellow being killed off by the more aggressive pink who are themselves overtaken by the more stable red species.
Look at the times when a branch fans out and then suddenly tightens. That's a small set of individuals or even a single individual which turned out to be more fit than the others and out-competed them. That property alone is what keeps the lines of the species from drifting farther from each other.
I built this system with the intention of building true causational (not correlational) studies of life. The first step of that is getting life. This looks a lot like life to me. Maybe not life just like ours. Maybe without temperature-based homeostasis and carbon. But are we so sure that's the right definition of 'life'? :)
