Defining Species

One thing about Species that I keep stressing, but which is easy to forget even for me, is that the simulation is random. It’s easy to say that a species “decides” to splinter from the main population and speciate, or to say that they’re “trying” to develop eyes and legs. But all of that is pure personification on our part: it’s like saying the ocean “decides” to have tides, or the clouds are “trying” to rain.

The ‘species’ category is a perfect example of this. I was showing a friend the game and caught myself saying that “once it comes back down from the population explosion, the simulation will make them speciate”. But that’s not how it works at all: the simulation doesn’t make them do anything. They don’t have to speciate any more than a million proverbial monkeys bashing on typewriters have to produce the Twilight series. The simulation simply detects speciation/vampire-romance after it occurs.

I could have adopted the top down approach, and made speciation something that the game makes happen after a certain amount of time or in response to certain events. That would probably have been much lighter on performance, and easier to code to boot.

But it would also have been cheating. Real life approaches things from the bottom up.*

So the speciation routine has no influence on the simulation. It’s completely passive, an exercise in analysis and display: computer-generated taxonomy. The creatures don’t know or care what species the game thinks they belong to, and the simulation would play out exactly the same with or without speciation detection. Whether or not creatures can mate is determined on an individual basis, not based on species.

This has allowed for some fascinating and unexpected effects. Quite often, a ‘speciation’ of a single creature will happen, appearing as a pixel-wide line on the population history. This is the result of a creature being born sterile (ie. mutated heavily enough that it is unable to mate with anyone else in the population). Since the creatures can reproduce without mating this creature can still have descendants, and may well become a stable species in it’s own right.

(Worth noting: a creature cannot be born into a new species, because a speciation test isn’t done for births: a newborn is simply given it’s parents species. If it is born sterile, it will speciate when the parent dies and breaks it’s link to the main population)

This system also makes for an interesting design challenge. See, two things that would make the simulation more interesting are an increased mating frequency (increasing the gene sharing and making things like sexual selection more apparent) and more speciation (making lots of small species rather than one large one). But in the current system, these two features are diametrically opposed: expanding the genetic compatibility range and allowing the creatures a wider variety of mates means populations have to distinguish themselves more before the game will detect a speciation.

One solution to this, suggested here by Icefire, is a ‘soft’ definition of species, not reliant on breeding compatibility. My problem with this is that it makes the ‘species’ category less well defined: rather than being “a collection of creatures capable of interbreeding” it becomes “a collection of creatures with an arbitrary amount of genetic similarity”.

But after some thought I decided I’m okay with exposing it for a future version. I think the default should always be the “Hard” definition of species (the game is called Species, after all) but using the softer options will allow you to make interspecies breeding possible.


*footnote: this top-down bottom-up discrepancy is an interesting spanner in the works of the Intelligent Design crowd. Design is an inherently top-down process: a designer starts with a goal and works out the simplest, most efficient method to achieve it. So designed objects tend to be mathematical and precise: straight lines and square corners. Natural objects, on the other hand, take a bottom-up approach: this molecule on that molecule, this rock on that rock, this gene on that gene, all clumping together to make up an object.

A designed room can be represented abstractly as a set of numbers: width, height and breadth for a simple rectangular prism. 3 numbers. A natural cave, on the other hand, can never be represented in full detail, because you’ll never have enough numbers. The unecessary complexity is evidence that it’s natural, not that it’s designed.

Which only makes it more jarring when denialists argue that the incomprehensible complexity of life is evidence of design. It seems like quite the opposite, from my perspective at least.

“Twilight Jokes. Statistically inaccurate Twilight Jokes. Wow, I didn’t think we could sink any lower.

The chances of pure randomness producing a particular work of fiction the length of one of Stephanie Meyer’s novels are quite significant**, and more importantly, are completely incomparible to a force like evolution, which is cumulatively influenced by forces like survival, gene-sharing and reproduction.


115362 words in Twilight * (5.10 (average number of characters per word) + 1.5 (rough guess for spaces and punctuation)) = ~761,000 characters.
1 in 49 = Odds of random key on typewriter being correct.
Odds of producing novel of this length in a single trial: 1 in 49^761000

Size of the universe = 3.1e84 (cm^3) / 4.22e-99 (planck cube volume) = 7.3e+182
Age of the universe in Plank time: 3.3 x 10^60
If trials could be condensed to the size of a cube 1 planck length on the side, and run once every plank time frame, a computer the size of the current observable universe would have performed 2.4 x 10^243 trials.

2.4*10^243 < 49^761000.

Ergo, if you want monkeys typing vampire romance novels, you're better off going into neuroscience or biology than mathematics. They've got better odds in the long run."

  1. #1 by Skylimit on August 2, 2012 - 9:26 pm

    My best guess would be that 2 critters cannot mate if their genetic distance is too far (i.e. their number of generations apart) That would be a soft distinction, and interbreeding would be possible to some extent. But then there is also no hard line between related species, which brings us back to the question : what is a species ? :o)

  1. Detecting Design « Species Development Blog

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