What is a species, anyway?
nytimes.com
nytimes.com
I've long wondered whether abandoning the concept of "species" in favor of some continuous measure of genetic relatedness would work.
From a practical, everyday standpoint, it would obviously be unworkable. We created the idea of species because in day-to-day life it's incredibly useful and only breaks down in some pretty niche edge cases (again: from the perspective of a lay person, those edge cases are both more common and more important to the scientists working with them). But as far as scientists, and particularly phylogenists and evolutionary biologists/ecologists go, it seems like we might save, if nothing else, a ton of effort that currently goes into trying to fit the round peg of nature into the square hole of our categorical system.
That being said, phylogeny is at best only tangentially related to my own expertise so I'm sure there would be difficulties that I haven't though of.
I consider the focus on species and speciation to be a science social phenomenon more than anything else, a lot of it attributable to the prestige of being the one to "discover" the species (a.k.a. describe it in a way that sticks).
The flipside is that the science of phylogenomics is incredibly fruitful, in that as we collect more complete information about genomes and their diversity and patterns of conservation, we are able to better understand life in all of its forms. It's also very data intensive and computationally complex - some of the most sophisticated data compression, suffix tree construction, hashing, and clustering algorithms are used in this field.
An unsung group of heroes in the face of this insane complexity is the scientists at NCBI whose job it is to organize all of the taxonomic and reference genetic/genomic sequence information (they are the ones who build the GenBank, RefSeq, and NCBI Taxonomy databases). Their work is as close as it comes to the source of truth on this. While the GenBank FTP server is easily overwhelmed by modern workloads trying to ingest this data, AWS and GCP provide high throughput mirrors (https://aws.amazon.com/opendata/, s3://ncbi-blast-databases, gs://blast-db).
You just slap a topology on things and you get an effective type theory that gets mostly good results which allow you to elide most of the complexity. This in turn allows you to reason about more complex things at a loss of fidelity — what we call abstraction.
If you think being able to recognize a forest rather than be overwhelmed by the number of leaves on trees is useful, then you understand why humans do that.
The "what" of something is part and parcel of intelligibility. If reality is intelligible, and we are truly rational creatures that are able to know this reality, then this would entail that reality is divided into kinds that we can recognize. What those kinds are, and which things belong to which kinds, is a separate question, indeed the question in this article as it relates to living things.
You’d have to solve the problem that chromosome counts vary, too, though (in animals from 1 for the male jack jumper ant to over 500 in the Atlas blue butterfly. See https://en.wikipedia.org/wiki/List_of_organisms_by_chromosom...)
Also theory is much easier understood on simpler models. Just like big O notation abstracts over many things, simple models are much easier to reason about. There is a time and place for considering the memory hierarchy, how floating point division is really not the same level of speed as integer addition, but inferring the canine phylogeny under some easy-to-reason-about model of evolution is much simpler (both theoretically and practically), especially if you have already gathered data for five or six years and people are getting tired of no results.
The question of "what is a species" made me go a bit insane. I really wanted a unique identifier for each "species", but kept running into edge cases like species that changed scientific names (so you'd need name + date to resolve it). Occasionally people would refer to species by common name, but a common name can resolve to dozens of different scientific names. I don't think people realize how difficult and awkward it is to build software that deals with ambiguous entities.
This is a tangent, but the US Fish and Wildlife service has a cool tool for exploring endangered species [0]. I had a few issues with the data, but was overall impressed with how easy it was to access and how deep it goes (there are gigabytes of shapefiles representing endangered species boundaries offered in zip files). Preble's meadow jumping mouse [1] had a range so complex that its shapefile was 250 MB, the complete set of shapefiles covering all species' ranges was 2.5 GB--this single species of mouse took up 10% of this! For comparison, the Topeka Shiner's range shapefile was only 147 KB.
[0] - https://ecos.fws.gov/ecp/report/adhoc-creator?catalogId=spec...
I've had a few opportunities to build active directory from the ground up. It always starts nice and clean with Accounting, Sales, Production, etc. Then Directors, Managers, Supervisors etc.
Everything maps out nicely in the beginning but then you run into things like "well Susie is only a supervisor, but she's in account so needs access to X. And Bob is a director but shouldn't have access to Y. And Managers should only be able to access Z but only if they are in Marketing. Etc."
You end up with a bunch of custom groups and the whole idea of a big venn diagram disintegrates.
In theory everyone has a defined role on paper, but it completely falls apart when the rubber meets the road.
And this agrees with the former book, in which Oderberg distinguishes between a phylogenetic understanding of species, and an ontological understanding. The traditional ontological definition for "human" is "rational animal". It is composed of the genus "animal" and the specific difference "rational" that differentiates the human species from among the other species in the genus "animal"[2]. Under this traditional way of defining species, rational life on other planets would, therefore, qualify as human. "The aliens" would be, in some sense, "one of us", even if they were to differ phylogenetically. This becomes quite interesting in the context of an analysis along the lines of Aristotle's "De Anima", as, for example, rationality has definite entailments when it comes to anatomy and physiology.
[2] I am using the terms "genus" and "species" in the relative, ontological, intensional sense[3], not the narrow biological sense, as more or less meaning "broader category" and "narrower subcategory", respectively. Thus, we can say that the species of triangle is a plane figure that has three straight bounding sides, where "plane figure" is the genus, while having three straight bounding sides is the specific difference.
[3] https://en.wikipedia.org/wiki/Genus%E2%80%93differentia_defi...
In any case, what Maritain says is astonishing, and I fear you've just given me another reason to be suspicious of him :-). Is he claiming that the difference between (say) a shark and a dog is merely a question of accidents?
It is a discovery for people who are taught that the distinctions between species are very clear and then learn otherwise.
Saying that "humans" are capable of locomotion or movement using their legs implicitly refers to an expectation, and nobody with that intends to say that individuals who are confined to a wheelchair are not humans.
Saying that humans have 5 fingers on each hand, which is the expectation, does not imply that individuals born with a different number of fingers are not humans, but simply that is not the expectation.
This comment cannot be answered properly without knowing who the "biologists" are, which insect types we are talking about, and what is going along with the different number of something.
The fact that individuals with four or six fingers are considered to be of the same species has nothing to do with politics, but with the fact that people with "4 fingers" can reproduce (this is the expectation) with individuals with "5 fingers" and "6 fingers" and produce fertile offspring.
Politics comes into play when it comes to, for example, species conservation. Populations of the same species that have remained isolated from each other for centuries, millennia or more may accumulate due to selection processes, genetic drift or founder effect, genetic and phenotypic characteristics that do not allow individuals from the two populations to reproduce successfully. Fertilization may not occur, the progeny may show morphological abnormalities, or the offspring may not be fertile. But the above may occur in, say, 20 percent, 50 percent or 90 percent of cases, and for any of these percentages the existence of a new species, variant or subspecies can be argued. Should the two populations be protected since they are (or are not) different species?
It is clear that a human being who is sterile, or one who cannot move about, is in some sense a defective specimen, as these deficiencies impede the realization of human telos. (If you deny telos, then truly nothing is intelligible. Not only does the notion of defect no longer make sense, not only are biology and biological function impossible and anatomy made unintelligible, but even efficient causality is made unintelligible and science impossible, as the very fact that an effect follows from a cause, that is is not arbitrary, presupposes telos.)
https://www.princeton.edu/news/2020/05/07/gene-flow-between-...
https://news.ycombinator.com/newsguidelines.html
(your first sentence is good though!)
Well, then you have problems like how speciation occurs. If the ability to produce offspring is your definition, then interbreeding does not exist by definition. And then you're left with the question of how species come about. Let us suppose some member of species A produces an offspring of species B where B is not A. Then for the species B to survive, there must arise another member of that species B (i.e., one that can interbreed). So you have at least three low chance events: (1) two members of the same new species being born (2) at roughly the same time (3) meeting each other and (4?) breeding. You also could not say that A and B could interbreed, and it is only some species C arising form B that cannot interbreed with A, because you've already make interbreeding impossible; if you can breed, you are the same species. So if A and B can interbreed, and B and C can interbreed, then by transitive property, so can A and C. So interbreeding, full stop, cannot be criterion, certainly not the sole criterion.
> Its just a human word like wall or chair.
But this undermines the notion of species as objectively true. Artifacts of that sort differ from natural kinds in the sense that such artifacts have no inherent tendency to be what they are, whereas natural kinds do. A chair is not inherently to be something we sit on. That is merely a telos in the mind of the craftman, and this telos is what that determined the form he would give the artifact. The affordance and suitability of such an artifact for sitting is something that a user of that artifact may recognize in the chair and take advantage of. What qualifies as a chair is at least in part subject to convention for practical reasons. But a bird is not like that. It is not a matter of perspective that a bird is "birdy" and does birdy things and realizes objective ends in birdy ways that are not merely observer relative. Sure, we can categorize animals for practical purposes, and we may do so according to various ends for practical rather than theoretical reasons (like classifying beaver as a fish, and fish as not meat, for Lent), but that sort of practical classification is merely practical and secondary to the question of what something actually is.
And we cannot avoid saying what a thing is as that is inherent to the notion that reality is intelligible. If you were to reduce "birdiness" to mere convention, then you would indeed be characterizing birds in the same manner as artifacts (this is called mechanism, and it has severe problems). But even a mechanist would still need to classify the things that go into making this object of merely conventional identity, at some level, or else be left to conclude that reality is unintelligible, though strangely conventions manage to magically escape this problem, as mental entities would remain intelligible. One who denies the intelligibility of the world would be left with the task of explaining how he can even make the distinction between his intelligible "mental world" and "the world out there" without some intelligibility in the first place.
Ideas have consequences, consequences greater than many realize.