Evolutionary Definition of Species

2007 Oct 31

The question of what is a species has no good answer. The difficulty is that there are several definitions for species. This is generally acknowledged as a problem. There is disagreement on how organisms should be classified. In many cases it is because it is not obvious to all biologists what distinguishing factor should be used for classification.

Humans are driven to organize and classify their world. Darwinian evolutionists are driven to find cases of speciation consistent with and supporting their world view. And scientists are personally driven to carve out their own piece of the world. The result is that species divisions can become extremely fine-grained. I also think that the divisions become silly.

To illustrate this, I will apply these species definitions to humans. All humans are currently classified in one species, Homo sapiens. However, by applying common species differentiation methods, it appears there should be many species of humans!


  • A morphological species is differentiated by the morphology (the form, body shape) of the organism. Darwin's finches of the Galapagos Islands are classified this way: by beak size. In the case of these finches, the classification is very subtle. note
    • If this specific example were extended to humans the analogous indicator could be lip size. Then actress Angelina Jolie might be in a species different from most other females.
    • Another example: African Maasai (tall) and African Bushmen (small) would be different species.

    The classification level above species is genus. This scientist's article says that species is the only really important designation. In fact although Darwin's finches are currently in 4 genii, there are serious suggestions they should all be in one.

    He makes a significant point that it is hard to observe one of these finches and be certain of its species. By looking at the pictures, I would agree. In fact, he says the problem is made more difficult because they interbreed!

    I have some doubt that all these would be considered separated species if Darwin had not been the one that originally designated them so.

  • An ecological species is adapted to a particular set of resources, an environment niche.
    • If this were applied to humans, then Sherpas living up in the Himalayas would be a unique species (from humans at sea level) because of their adaptation to the altitude.
  • A mate-recognition species is differentiated from others because individuals in that group recognize each other as potential mates.
    • If this were applied to humans, then many strongly ethnic groups could be considered a separate species.
  • A phenetic species is differentiated by phenotype. Phenotype is observable characteristics of an organism that come from interaction of its genetic constitution with its environment.
    • If this were applied to humans, the fit athletes and the flabby nerds in a high school would be considered separate species.
  • A biological isolation species is one that is distinguished by organisms that naturally breed with each other. If they do not breed together in nature, then they are different species.
    • If this were applied to humans, then kids from the suburbs and kids from the inner city would be in different species.

There are some definitions that would not divide humans (e.g. biological reproductive species - able to produce fertile offspring). However, most of the definitions would carve up humans into many species. Why the inconsistency? Is it hypocrisy?

I think the big problem is that Darwinians are driving to make biology inherently support their world view. They are refining the biological classification system to mirror their view of origins of existing species and newly emerging species. (Mayr, section 3)

However, humans would be offended by such divisions. There would be "class-ification warfare" between people because of it. Inevitably some people would say their class was better, and people would then fight over the divisions and against the divisionaries. The evolutionists would not then accomplish their goals. So, yes, it is hypocrisy.

2007-10-31 updated 2021-05-31   © 2021 Larry Grove