Systematics of living organisms


Systematics is organizing a large multitude of “objects” into subsets, for convenience or solving some task. There are many ways to achieve this: a lot of them can be found in mathematics and programming.Two basic systematic methods:

1) “Head-on” systematics.
AKA systematizing manually. This method is limited in use, but at the same time is the most versatile and unambiguous. Say, we have a set of numbers from 1 to 15. Our task is to organize them into two subsets: happy numbers and unhappy numbers. What we do: we simply iterate over the numbers and assign each of them to one of two categories – simple as that. “Let 1, 5, 6, 9, 13″ be unhappy numbers, and 2, 3, 4, 7, 8, 10, 11, 12 will be happy ones”. Our system in this case are lists of all objects in each category.

2) Criteria-based systematics.
Another approach to systematics is to select some characteristic, that is intrinsic to some objects but is absent in the rest. It is very popular in maths and programming. Say, we need to separate numbers from 1 to 20 into “odd” and “even” categories. The easiest way to do so is to describe the criterion of systematics: if a number divides into two without remainder, it is even, else – uneven. A typical IF-THEN-ELSE expression known in most programming languages. Such a method is more compact, especially for large sets of objects (no need to list all categories manually), and is as precise and flexible as the “head-on” method. Although, it is less flexible, obviously.

Both methods are mathematical only. The problem is that in the “real world” neither of them cannot be applied. E.g., those are some tasks that cannot be solved with them:

  1. Animal and plant systematics.
  2. Systematizing movies into genres.
  3. Systematizing human traits into “positive” and “negative”.
    And so on…

The reason is simple: in the real world, we normally deal with unlimited multitudes with infinite intermediate forms. How many gunshots exactly must be shown in a movie to consider it an “action movie”? Twenty? If so, then what about nineteen – not an action movie anymore? Does the weapon used matter?

Or another example: where is the exact difference between a handwritten “C” and a “G”. How large that “tail” must be to consider a letter a “G”, not a “C”? This question is almost philosophical.

Where exactly does G becomes C? What if they were part of some word, not alone? What if I added more intermediates between each pair?

Where exactly does G becomes C? What if they were part of some word, not alone? What if I added more intermediates between each pair?

How does biological systematics work?

The method currently in use in biology can more or less be applied to systematize any natural phenomenon of the real, infinite world. There is a separate article on biodiversity that I suggest to read, which explains in detail what we are about to systematize, but let me tell in brief that biodiversity is an infinite continuum of organisms, in which there are no two same individuals and each organism slowly “flows” into another one through infinite number of intermediate forms.

How to systematize such a mess? To a non-fundamentalist, it might seem that animal systematics is based on criteria: long legs and no tail – a frog, short legs and tail in place – a salamander. Animal key guides are based on that – they are books that allow telling the species of an individual animal by following a series of yes/no questions about its appearance. But in fact, the “key” method is merely an instrument to tell species apart with acceptable level of certainty while sitting in the field. It’s not systematics per se. I personally have come to wrong species using one of such key guidebooks at least several times; not because I am a pathetic biologist, but because individuals in question happened be with “artifacts”. Sometimes, it’s even worse that artifacts: a key says that a species is supposed to have five fingers. But my specimen has no legs: maybe it was born special, or lost them to predator. What do I do?

Q: If animals are systematized not by criteria, then by what?
To answer that one, I’ll tell how “creation” of new species happens. Say, once upon a time I went into a forest, saw a mouse, looked carefully, and voila! – it’s a new species. What to do? Firstly, I describe the individual in as much detail as I can: place of capture, its size, colour, anatomy etc. Secondly, I give it a name, while the mouse will normally be taken away from nature and included with the description, unfortunately for the poor animal. And become the type specimen, or the holotype, of newly created species. Each species has the holotype it is based on. Usually, there is one holotype per species, but occasionally, there are several: say, in case when males and females are strikingly different.
Thus, the entire diversity of species is summarized by a single (occasionally, several) individual specimen. And when I described the new mouse species, I had no idea if there are other individuals like it in the forest, and how different could they be from each other. The whole species is a dot in a huge continuum of animals, one little mouse.

It’s true for all animals. Five panther species are five individuals taken from infinite multitude of large cats. Five dots, and the rest is around them: thousands unnamed lions, tigers, that trot savannas and forest and fill unnamed area of animal space. They have no name. One could only compare them to one of the five holotypes and decide, which one does it remind more.

Phrase: The cat is a tiger.
Meaning: The cat looks like tiger holotype more than any other holotype.

animal continuum

There are five panther species – five exact named points. Infinite qty of cats is around them – they’re in that light-blue space around. They acquire name through comparison only. Like that black point close to the bottom. It is closer to leopard than to any other point, or, it has more similarities with it in terms of physiology, anatomy and behaviour. And thus it is considered a leopard. By the way, that’s what it is:


As you can see, an individual can be quite different from the holotype: in colour (albino), qty of legs (a trauma or innate condition), behaviour (psychological deviation) etc, and yet be part of the species. Because it’s even more different from the rest of holotypes.

Разнообразие лис. Все они считаются одним видом, именуемым Vulpes vulpes на "кесаревом" языке.

The diversity of foxes. All are one species known as Vulpes vulpes in Caesarean language.

But what if an animal is somewhere in between two type specimen? That’s a tricky one. Perhaps you could just… guess. Say, two similar frog species are in the forest: Pelophylax esculentus and Pelophylax lessonae. Now someone brings an unknown green frog to me. What’s it? P. esculentus. Or maybe, not esculentus…

Sometimes people name a new species when they can’t tell, and that unknown animal becomes a new type specimen. You could do anything you like. It’s all subjective.

By the way, other things of the natural world are as subjective. Colours, say. Not RGB computer colours, but the real ones. Some time in our early childhood our parents show us a tomato and say “red”, then a carrot saying “orange”. From now on, any time we need to tell the colour of something, we refer to those type specimen – our basic “red” and “orange”. Colours are all about comparing.

And when we encounter an intermediate colour, then… a problem…

colours red orange

Can you tell what are those? Orange or red?

Our brain is most comfortable when dealing with extremes. When it encounters something of a mixed shade, it is not so different from a computer. A computer will crush instantly, a person will crush slowly.

It helps that the type specimen of colours renew throughout the lifetime. Most of us have lots of “red” colours wired into our brains. Paler, darker, brighter etc. Also, all of us make mistakes sometimes. If one day I mistaken red for orange, people will correct me, and that mistake will immediately print into my brain as a new type specimen. We learn from our mistakes – it is literally true.

From all that, it’s obvious that colour perception varies from person to person: to someone, my dark orange is indeed red. They simply have different type specimen for red and orange, that’s all (perhaps, also different eyesight quality – who knows).

Systematics in real life is all about comparing and referring to your previous experience. Have written a book, but can’t tell its genre? Try to remember an existing book that is most similar to yours, and look its genre up Potentially, there is an infinite qty of movies and books (most of them won’t ever be written). Yet each of the existing ones is a type specimen for its genre, and thus it’s not that hard to tell what’s a new book is.

Type specimen are intrinsic to our cognition, and our language. They are our only option when we want to name and communicate the world around us. But… the nature doesn’t give a damn how you call animals and colours around. All animals are just a bunch of organics, and all colours are the same electromagnetic waves; neither absolute species nor colours actually exist. Only a sith deals in absolutes Keep that in mind.


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