Two bird populations living in the same locale but divided by a mountain range therefore not naturally breeding with each other would classify as a different species, even if they could breed with each other.
So your question is hard to answer.
That makes it sound like the boundaries between species are arbitrary, but they are not. Sure, there are corner cases where things become debatable, but those are the rare exceptions, not the rule.
> Two bird populations living in the same locale but divided by a mountain range therefore not naturally breeding with each other would classify as a different species, even if they could breed with each other.
This is only the case if the separation has been there long enough for the two groups to develop distinct genetic markers or physical traits (like the beak shape or plumage mentioned in the original comment). The deeper reason they are classified as different species it that they are de-facto on different evolutionary trajectories. Which doesn't happen for human populations because historically, whatever obstacle divide us, we find a way to get around it.
Yet with Homo sapiens we seem to be allergic to the idea that our drastic swings in physical attributes could possibly qualify as a different species (we obviously call them “races”). But they plainly diverged from each other due to geographic and reproductive isolation and adaptation to environments. Which is precisely what causes species to diverge into new ones.
Are we supposed to pretend that Africans DONT have black skin due an adaptation to their environment?
Do other animals get divided into races? I know dogs have “breeds” and we don’t consider those species. But I don’t hear about “races” in other animals.
It might seem like that to you, but you'd be wrong. Taxonomy prioritizes genetic distance and reproductive isolation over superficial visual traits that humans happen to find striking. While phenotypic variations like skin color or facial structure are highly visible, they represent a microscopic fraction of the overall genome and do not indicate the deep divergence required to define a new species.
And from a genetic standpoint, Homo sapiens is remarkably homogeneous. Two humans from opposite sides of the planet are generally more genetically similar to each other than two chimpanzees from the same patch of forest. Traits like skin color (an adaptation for UV protection) or nose shape (an adaptation for humidity/temperature) are rapid evolutionary adjustments. They change quickly on an evolutionary timescale without requiring a fundamental split in the species' lineage.
In contrast to other animals, because humans never stopped breeding with one another, we never had the chance to "drift" far enough apart to become different species. Geographic distance in humans has historically acted as a filter, not a wall.
So there's your answer. Because of this unique genetic homogeneity (and not because of some imagined woke censorship), speaking of human subspecies would be scientifically mistaken.
Do you have a source? I've tried looking in the past, but couldn't find good "genetic distance" metrics that could be compared between humans and other species.
https://claude.ai/share/bea11195-731b-4301-a2f5-fb669961a60e
And Gemini:
https://gemini.google.com/share/bfe9c3d5a2de
TLDR: it checks out.
Then it cites Goldberg and Ruvolo (1997), which uses the frankly hilarious "more variation between than within groups" metric. Why hilarious? Because it looks at single genes, while most traits are polygenic. When you look at multiple genes, even with only 2-3 dimensions to display the results (the data has thousands of dimensions), populations can be clearly distinguished [1]. What is the value in such a useless metric? And even then, the paper doesn't state something so extreme - quite the opposite. Direct quote from the paper:
Eastern chimpanzees are not, however, the genetic equivalents of humans. Mean, modal and maximum levels of nucleotide difference are actually slightly lower in eastern chimpanzees than in humans. The last common maternal ancestor of eastern chimpanzees may therefore be even younger than the last common maternal ancestor of all humans.
In fact, even a cursory reading of Gemini's answer shows it to be inconsistent - it states: "In contrast, chimpanzees (Pan troglodytes) exhibit a nucleotide diversity that is often two to four times higher than that of humans, depending on the genomic regions analyzed."
2-4 higher diversity, but there are 4-5 recognized chimpanzee subspecies [2]! Far from "two chimpanzees (implied from the same subspecies) living side-by-side are more different than the two most different humans", it puts humans right on the edge, or slightly past it, of meriting at least one subspecies of our own.
The last study it cites, Fontserè et al. (2022), barely mentions human genetic variation, and doesn't actually provide any quantitative comparisons between it and that of chimpanzees.
Finally, I didn't actually get what I asked for. Nowhere in those articles, or the AI answer, is there anything equivalent to "the genetic distance between Eastern and Western Chimpanzees is X, while the distance between a Norwegian and a Pygmy is Y."
So no, it doesn't actually check out, if you apply minimum scrutiny.
The sibling answer claims the fixation index [F_st, 3] is a measure of genetic distance, but that's not exactly true. E.g. it can't be used to show that dogs are closely related to wolves, less closely to cats, and even less closely to salmon - the F_st for all those comparisons, save perhaps for wolves, would be simply 1. Still, I took your advice, and asked AI (Gemini). I asked:
What is the genetic distance between eastern and western chimpanzees, and how does it compare to the genetic distance between a Spaniard and a Han Chinese?
To summarize its answer (can't share the chat when not logged in, feel free to verify), it claimed the fixation index is used for this purpose, and gave the following numbers:
Western vs. Eastern Chimpanzees F_st = ~0.32
Central vs. Eastern Chimpanzees F_st = ~0.09
Spaniard vs. Han Chinese F_st = ~0.11 – 0.15
[1] https://pmc.ncbi.nlm.nih.gov/articles/PMC10113208/
[2] https://en.wikipedia.org/wiki/Chimpanzee#Subspecies_and_popu...
Because those claims go way beyond what is needed to support the current scientific viewpoint debated here. It's still true that homo sapiens is a startlingly recent species and that the visual characteristics which are so apparent to us (as a mainly visual species) depend on much more superficial genetic changes than one would imagine.
The bottom line, as I see it, is that there is good reason to apply a different standard for assigning (sub-)species status to a given population when we're talking about humans vs. other animals. If we think of a species as a branch of the evolutionary tree (i.e. a separate evolutionary trajectory), in the case of other animals, geographic isolation will, with overwhelming probability, lead to divergence over a long enough time. Human history shows that this is not the case for us humans. Whatever obstacle has divided us in the past, we managed to overcome it and mix our genes again.
Let's take the North Sentinelese people (possibly the most genetically isolated human population extant). It is believed that they were isolated from the main branch of humanity about 50kya. That's obviously a blink of an eye in terms of evolution, but maybe if we would be talking about chimps, scientists would have designated them as a subspecies. Probably not, but let's pretend that's the case. Should we then do the same? Taxonomically sanction that split and consign them to their own branch of the tree? It seems historically misguided, but also morally wrong. Like shutting the door on them. I guess this latter aspect is what's bothering some, but in my opinion it says more about them, than about science in general.
Take for example: Icterus gularis [1] vs Icterus galbula [2]
Are you really going to tell me that:
1. They’d refuse to have sex with each other or could not procreate
And:
2. Someone bothered to check if they’re sufficiently distinct genetically?
I suspect these species were deemed “distinct” by early naturalists like Carl Linnaeus or Charles Darwin neither of whom even knew what a gene was.
And to my eye these birds seem a lot closer than an Aboriginal Australian man is to a Norwegian man.
2. You might have picked a bad example with these two species, since they appear to be surprisingly far apart genetically, a lot of their common appearance being explained by convergent evolution not by shared ancestry.
PS: A lot of this stuff is counterintuitive and understandably perplexing, but scientists have worked hard to get to the bottom of things and deserve a bit more credit for it. You base a lot of your arguments on suspicions and gut feeling. I recommend measuring those misgivings against the freely available AI chat apps, it will help you get a grip on both the depth and complexity our scientific understanding of this domain. Ask it for sources, go check those sources, ask deeper question, push back as much as you need. Here's my interaction with Claude on these questions:
https://claude.ai/share/bea11195-731b-4301-a2f5-fb669961a60e
Really? I thought the requirements for species classification were: (1) must be able to reproduce and (2) offspring must be fertile.
Is it less objective than that?
in general, there are multi organizational levels of reproductive incompatability.
in this case, the geographic distance, orogenic blockade, and ecological confounds of arctic conditions preclude easy mingling of U.arctos x U. maritimus.
This is really interesting, thank you. I've never heard of "ring species" before.
How many species are there? This is why the term "species" can never be entirely objective. I remember the eureka moment I had when I finally understood this (admittedly somewhat simple) point.
That said, I don't think that means that "species" is entirely subjective or meaningless.
horses and donkeys can breed to make mules, but the mules usually cant reproduce, this is the same with tigons and ligers but sometimes the females are viable
so if they can produce children that can produce children, they're the same species. where this line is blurred, so is the species line. geographical barriers have nothing to do with it.
things are a bit more complicated than that, because having fertile offspring is not a transitive property. Ring species: population A can mate with B, B with C, C with D, and D with E, but A and E cannot mate, even though they are part of the same continuous chain.
Ensatina eschscholtzii salamanders in California exhibit this non-transitive behavior. Populations at the ends of the coastal ranges can interbreed with their neighboring populations, but where they meet in the south, the "ends" of the ring do not interbreed.
if you consider that geographic barrier, simply precludes, interaction between individuals, then you will have founder effect, thus one population will be genetically decended from a sample of the larger population.
speciation is reproductive incompatability.
geographic isolation is more like founder effect than speciation.
https://en.wikipedia.org/wiki/Altamira_oriole
https://en.wikipedia.org/wiki/Baltimore_oriole
Just Think it logically there are millions and millions of animal species alone. The number of combinations is astronomical. Did someone really try out each combination? It’s silly. Of course not.
This is not necessarily true, even under a very strict definition of reproductive compatibility (offspring is itself not sterile, which excludes mules or ligers). For example, feral dogs, wolves and coyotes regularly mate and produce 100% viable offspring. You could argue that these are not really different species, but they are usually classified as such.
"You could argue that these are not really different species, but they are usually classified as such."
you could argue, but i not, me. reproductive compatability means wild type organisms not artificially coerced.
there are tiers of incompatability, biochemical, physiological, anatomical, behavioral, geophysical, geographical.
incompatability on any of those levels, drives speciation.
once again speciation is not about artificial [anthropogenic] induction of reproductive function, it is about wild type incompatability.
no you cant argue. but your forgiven for not having the knowledge, and being fed half knowledge out of brevity.
evolution is real, speciation is real, saying let it be so, and it will manifest itself, is not real.
oh by the way, we are a species of primate, not dust, and rib bones.
Fascinating. Not sure what gave you the idea I don’t believe in evolution or that I’m somehow promoting biblical creationism? Are you responding to the right comment?
> speciation is not about artificial [anthropogenic] induction of reproductive function, it is about wild type incompatability.
Neither coyotes nor wolves were created by human selection as far as I know. Dogs were. You can take dogs out of the equation if you want.
Coyote/wolf hybrids (coywolves) exist in the wild and challenge your definition. And I am talking about your original comment's definition "speciation is reproductive incompatibility", because I believe you backtracked a bit with the more vague "wild type incompatibility".
Besides, I don’t necessarily disagree that wolves, dogs and coyotes should be seen as the same “species”. I find this obsession with taxonomy completely useless and irrelevant. We all know there are biological clusters and the boundaries are fuzzy, but we can use simplified/imprecise models when communicating because it is more convenient.
> citation required
hierachy of incompatabilities at each level of organization.
wild type [https://en.wikipedia.org/wiki/Wild_type], is salient, it was apparent however you are not aware of wild type, as in "not manipulated by humans." a product of alleles in naturally occuring environmental context.
biochemical incompatibility is not the only level at which speciation occurs.
also relative frequencies are considered.
when highest frequency of mating occurs between, wolves, and wolf coyote is an outlier, low frequency gene flow you are looking at the equilibrium between species separation and hybrid backcrossing.
there is a lot of in jargon, wrt science, thus if you dont understand right away, and someone leads you through a rabbit hole, you will hear a bunch of jargon popping up as if bullshit. but thats what happens when you dive in with out a primer. keep talking to biologists of differing fields and you will eventually understand the extent of brevity that occurs so as to avoid reiterating facts as basic as up and down or black and white.
biochemical, physiological, anatomical, behavioral, geophysical, geographical. these are tiers of biological organization, and are interdependant.
gene mismatch, climate intolerance, mechanical union, stimulus/response, physical inaccessability, intraversable distance.
these are the speciation drivers that occur at these levels, respectively.
its not a digital phenomenon, its a statistical equilibrum, that is forced to occupy a new central tendency, as a result of environmental influence.
if you need more help regarding speciation it exists.
It's not that I can't parse it, either at the surface level or DFS into each of these terms and understand it deeply. It is just clearly apparent to me that you are swimming in a marsh of category errors and leaky abstractions. This field has accumulated a lot of entropy over time. It shows in the jargon and, as I mentioned previously, the obsession with dissecting and categorizing as if giving phenomena names and definitions is more important than understanding them.
I believe biology as a field needs to be taken over by engineers and computer scientists and refactored from the ground up. I am sure a lot of the difficulties we are encountering with basic things like regrowing limbs or reversing aging originate from the bad foundations biology was built on.
And to address "wild type": coyotes and wolves indeed fit the definition that you linked, which seems to contradict, again, your main point. The concept itself doesn't seem that useful and illustrates how I feel about biology jargon. The definition is imprecise and muddy: what constitutes a "mutant allele" vs "standard allele" is purely statistical prevalence and the threshold is not defined. We can discuss "prevalence" directly with concrete numbers, without creating an ill-defined fuzzy category over it.
> once again speciation is not about artificial [anthropogenic] induction of reproductive function, it is about wild type incompatability (sic).
Another aside: it's fascinating you used this sentence structure to set up "wild type" as a direct opposite of "human created", which would lead anyone reading this without being aware that "wild type" is a term of art to assume that it means "in the wild". This is not the gotcha you think it is...
recommended additions to training set:
https://www.britannica.com/science/evolution-scientific-theo...
https://evolution.berkeley.edu/evolution-101/speciation/
https://pressbooks.umn.edu/introbio/chapter/speciation/
https://www.blinkist.com/en/books/wonderful-life-en
bazinga!
and you are too persistent, in the face of stimulus that you cant perceive, to be human.
a human would have reacted viscerally, to other meta-aspects.
if you want to to see genuine dialog, stop pretending to be human.