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DNA analysis reveals there are four distinct giraffe species, not one
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Re: DNA analysis reveals there are four distinct giraffe species, not one
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Re: DNA analysis reveals there are four distinct giraffe species, not one
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Re: DNA analysis reveals there are four distinct giraffe species, not one
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Re: DNA analysis reveals there are four distinct giraffe species, not one
#105The classic operational definition of different species, as far as I remember, is that cross-breading between species is not possible.
If only it was! But then we discovered "ring species" ( https://en.wikipedia.org/wiki/Ring_species ) which threw a monkey wrench into what was once a simple definition. Basically, there are populations of animals A, B and C, where A and B can inter-breed, B and C can inter-breed, but A and C can't. So our definition of species no longer satisfies the transitive property, and it all falls apart. As far as I know, this…
> then we discovered "ring species" (https://en.wikipedia.org/wiki/Ring_species) which threw a monkey wrench into what was once a simple definition
Well, ok, we documented some ring species. That had no effect on the biological species concept, though. It never satisfied the transitive property.
Re: DNA analysis reveals there are four distinct giraffe species, not one
#106Earlier quoted context omitted.
Presumably a "species" should be an equivalence class, right? So the relation "A and B are of the same species" should be transitive, symmetric, and reflexive. Symmetry is easy (an organism shares 100% of its genome with itself) as is reflexivity (A shares n% with B iff B shares n% with A). However, transitivity does not follow obviously: for example, A and B could share 98%, B and C could share 98%, but A and C coul…
Unfortunately, speciation is mostly a continuous process, so there's no way to define species by some kind of "degree of similarity/dissimilarity" metric and have it be a transitive relationship. Any species definition that is completely transitive will necessarily have edge cases where two extremely similar organisms fall on different sides of an arbitrary threshold and are declared to belong to two different specie…
A continuous process and also a human construct that we created to help us reason about how that continuous process works.
Every biology major learns about the different species concepts/definitions [0] and why different subfields of biology might prioritize one over another.