I have many thoughts here. First I would say that I totally agree that the species concept stops making any sense as a strict, discrete category the second horizontal gene transfer / true asexual reproduction enter the picture. I should probably have said this at the beginning of the post so that people who work in viruses and bacteria (as you seem to!) knew that my argument didn’t apply to organisms capable of that.
In my experience, however, microbiologists are too quick to generalize from their part of the field to all parts of it. It is 100% true and defensible that “everything is a bag of genes, and genes constantly flow between them; species aren’t real and are just useful lines to draw in a continuum of gene flow, which constantly changes over time” if you’re talking about bacteria. But genes do not constantly flow between humans and chimpanzees via HGT. When you’re talking about most of the animals that the IUCN cares about (for better or worse), you’re talking about sexually reproducing organisms that (imo, once they SPECIATE) stop sharing genes. You cannot treat them the same way you would a virus.
I also totally agree with this statement: “We form these categories not because they carve reality at the phylogenetic joints but because these categories are useful. Fish are fish. Trees are trees.” I don’t mean to propose that everyone stop using the words fish, or tree, even though they’re not monophyletic. But there is (and should be!) a different between technical scientific vocabulary and common usage. I don’t insist people call bananas “berries” because, in common usage, they’re not. But botanically speaking, we have a definition for “berry” that we apply consistently, no matter what the common usage is, and this definition makes bananas a berry. I believe that the technical definition of “species” should be similarly transparent and consistent. I agree that “there are multiple joints at which you can carve reality, and which joints you choose to carve depends on why you are carving reality in the first place.” But as I hope the essay above illustrates, the Biological Species Concept as it is usually formulated cannot hope to be consistently applied to relevant organisms (ie. sexually reproducing macroorganisms incapable of HGT etc)
In terms of this question asking about all human populations being able to reproduce: ”But can you verify it? Do you have experimental evidence that a human from location A can form fertile offspring with a human from remote location B?” There have been many many recorded instances of human populations that have been long isolated being perfectly capable of being able to reproduce with other populations. To this day, there has NEVER been a recorded instance of the opposite. We know that Homo Sapiens could produce fertile offspring with Neenderthals, MUCH more different from us than any modern humans.
It would be very strange to lend much credence to the idea that not all human populations could produce fertile offspring. The burden of proof would clearly be on the person trying to say otherwise.
In terms of your philosophical problems with conservation: “(I also have philosophical issues with “conservation”—what, exactly, are you conserving and why is that time more worth conserving than any other time?)” These are all worthy questions that bear consideration. But noting that a practitioner in any given field will be required to make contestable value judgements is not really an argument against that field. The same could be said of doctors, politicians, lawyers, journalists, etc.
Hey Eniteris!
I have many thoughts here. First I would say that I totally agree that the species concept stops making any sense as a strict, discrete category the second horizontal gene transfer / true asexual reproduction enter the picture. I should probably have said this at the beginning of the post so that people who work in viruses and bacteria (as you seem to!) knew that my argument didn’t apply to organisms capable of that.
In my experience, however, microbiologists are too quick to generalize from their part of the field to all parts of it. It is 100% true and defensible that “everything is a bag of genes, and genes constantly flow between them; species aren’t real and are just useful lines to draw in a continuum of gene flow, which constantly changes over time” if you’re talking about bacteria. But genes do not constantly flow between humans and chimpanzees via HGT. When you’re talking about most of the animals that the IUCN cares about (for better or worse), you’re talking about sexually reproducing organisms that (imo, once they SPECIATE) stop sharing genes. You cannot treat them the same way you would a virus.
I also totally agree with this statement: “We form these categories not because they carve reality at the phylogenetic joints but because these categories are useful. Fish are fish. Trees are trees.” I don’t mean to propose that everyone stop using the words fish, or tree, even though they’re not monophyletic. But there is (and should be!) a different between technical scientific vocabulary and common usage. I don’t insist people call bananas “berries” because, in common usage, they’re not. But botanically speaking, we have a definition for “berry” that we apply consistently, no matter what the common usage is, and this definition makes bananas a berry. I believe that the technical definition of “species” should be similarly transparent and consistent. I agree that “there are multiple joints at which you can carve reality, and which joints you choose to carve depends on why you are carving reality in the first place.” But as I hope the essay above illustrates, the Biological Species Concept as it is usually formulated cannot hope to be consistently applied to relevant organisms (ie. sexually reproducing macroorganisms incapable of HGT etc)
In terms of this question asking about all human populations being able to reproduce:
”But can you verify it? Do you have experimental evidence that a human from location A can form fertile offspring with a human from remote location B?”
There have been many many recorded instances of human populations that have been long isolated being perfectly capable of being able to reproduce with other populations. To this day, there has NEVER been a recorded instance of the opposite. We know that Homo Sapiens could produce fertile offspring with Neenderthals, MUCH more different from us than any modern humans.
It would be very strange to lend much credence to the idea that not all human populations could produce fertile offspring. The burden of proof would clearly be on the person trying to say otherwise.
In terms of your philosophical problems with conservation: “(I also have philosophical issues with “conservation”—what, exactly, are you conserving and why is that time more worth conserving than any other time?)” These are all worthy questions that bear consideration. But noting that a practitioner in any given field will be required to make contestable value judgements is not really an argument against that field. The same could be said of doctors, politicians, lawyers, journalists, etc.