PS: I'd love for actual biologists to correct any misunderstandings I might have! That's all fine, but with definitions like that, apparent contradictions shouldn't be a surprise, and formulations like 'breaking the tree of life' are clear hyperbole.

In addition, paleontologists use the concept of the chronospecies since fossil reproduction cannot be examined.' Other ways of defining species include their karyotype, DNA sequence, morphology, behaviour or ecological niche. * We also want to use the term 'species' for organisms that don't sexually breed at all, necessitating different definitions for these cases.Īll of this leads to Wikipedia defining the word 'species' in this hilarious way: 'A species is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. For a counter-example, the physics community at some point went 'fuck historical precedent, we need a precise definition of 'planet'' and excluded Pluto. This seems similar to people really wanting to classify Europe as a continent, regardless of plate tectonics or land masses or any other objective criterion. For example, we really seem to want to classify dogs as a species distinct from wolves, whether that logically make sense or not. * There are some cultural expectations around the term 'species' that seem to thwart attempts at coming up with a clear definition.

This makes any attempt at building tree arrangement of species inherently logically suspect, purely from a data structure point of view. Examples are observed in nature today, and must have existed many many times historically.

* The 'interbreeds with' relation isn't transitive: population A may interbreed with B, B with C, but A not with C. So there seem to be three separate issues with the concept of 'species' as used in (pop?) biology, speaking as a non-biologist CS type of person:

Platypus evolution pluto