Remember the snail darter? It's a tiny endangered fish discovered in 1973 that stopped construction of the Tellico Dam in Tennessee for a while in the late '70s. Yesterday the New York Times wrote about a new study which suggests the snail darter was never a new species at all. It was just the eastern population of the stargazing darter found largely in Missouri.
This has provoked an avalanche of commentary on Twitter about how the whole thing was a hoax from the start, an example of a scientist "finding" a species solely as a way to stop a construction project he opposed. Thomas Near, who led the new study, helped this meme along by telling the Times the original researchers “squinted their eyes a bit” when they declared the snail darter a new species.
That might well be the case, but it got me curious about what Near actually says in his journal article. The initial motivation for the study appears to be his discovery that there's little genetic difference between the stargazing and snail darters, but that's historically meaningless since this kind of genomic analysis wasn't available in 1973. Rather, species were identified by morphological analysis. That is, by their form and shape.
It may seem as though it should be obvious if two things are truly different species, but it's not and never has been. Species split apart over thousands of years, and in between there may be subspecies and population segments. Deciding if something is distinct enough to qualify as a separate species is more art than science.
But Near would like to turn that around and make it more science. To that end, he has constructed a "comparative, reference-based taxonomic protocol" that reduces morphological differences to numbers. As an example, here's his analysis of three different darter pairs:
If you look at the red and blue scatterplots, it may seem like all three pairs are similar. There's a lot of overlap, and it's not clear why two of these show enough difference to be distinct species while one (snail darter/stargazing darter, far left) doesn't.
But Near performs a principal component analysis that produces a morphological distance between each pair. The snail/stargazing pair comes in at 0.15, well under the 0.31 and 0.34 of the other two. Other darter pairs have even higher MD values. Near concludes that 0.15 is much too small for the snail darter to qualify as a separate species.
So was the original classification a mistake or a deliberate fudge by a single scientist? Mistake seems most likely. As Near says:
Since its description in 1976, the Snail Darter’s distinctiveness from its most closely related species, the Stargazing Darter (Percina uranidea), has not been questioned.
It wasn't just one guy. What's more, it took 13 co-authors working with the latest tools of 2024 and aided by genomic analysis to figure out that the original conclusion was probably wrong. And Near isn't even sure it made a difference:
We will never know if this revised delimitation of the Snail Darter would have affected the outcome of one of the most significant legal and political conflicts over wildlife protection. Under the [Endangered Species Act], an imperiled “species” may be a subspecies and for vertebrates, a distinct population segment (DPS).
It is not clear if the level of distinctiveness of the Snail Darter would merit protection as either a subspecies or DPS.
So: most likely it was an honest mistake, though given a tailwind by the desire to oppose the Tellico Dam. In the end however, the dam got built and the snail darters, whatever their true status, were relocated to new habitat. In 1984 they were upgraded from endangered to threatened and in 2022 they were delisted entirely. Everybody got a happy ending.
In MAGA world, there are no "honest mistakes" in science. Nothing but conspiracies by radical leftists to bring about One World Government.
Which is funny, because science done right is nothing but honest mistakes.
Finally, some good news?
Morphological differentiation - or non-differentiation - of species can be absurd. As Darwin said, if paleontologists were given the bones of different dog breeds they might assign them to different genera, let alone species.
Species are supposed to be differentiated on the basis of (successful) interbreeding, but even this is not infallible.
I'm reading "Sapiens" by Yuval Noah Harari right now and he says that in biology animals are said to be of the same species if they tend to mate with each other and produce fertile offspring.
Not much use to a paleontologist.
That's the definition I learned in college long before he invented that brilliant concept.
But it seems like us and Neandertals are the same species along with a couple other varieties, but judging by extensive common differences you might not think so. My Biological Anthopology prof in 1990 thought we didn't interbreed, but I knew we at least tried it out. And we did. I'm around 2% and proud of it.
My preferred definition is that two populations are the same species if they CAN interbreed with each other and produce fertile offspring. Thus for instance, grizzly bears and polar bears do not "tend" to interbreed, for geographical reasons if nothing else; there is only a slight overlap between their ranges. However, they CAN and occasionally do interbreed and produce fertile offspring; hence, they're the same species.
It's also thought that Neanderthals, Denisovans, and Homo Sapiens interbred so successfully that they ceased to be distinct populations, and it appears that some fraction of the current human population carries Neanderthal and/or Denisovan genes. That means that the three formerly distinct populations were all members of the same species.
I wonder if anybody ever tried to crossbreed snail darters with stargazing darters.
Heh. It's always more complex than these right-wing know-nothings make it out to be. Google on ring species, for example, for another wrinkle of complexity.
Yeah, I was thinking of that! Like snow hares and southern marsh rabbits - they can breed with neighboring populations but not with each other.
And once that determination is made, is it presented and treated as art, or is it presented and treated as science?
An interesting paragraph from the dam's Wikipedia page:
Along with:
I'm sure there is fodder for all at that page: https://en.wikipedia.org/wiki/Tellico_Dam
I think it important that the head of the team which found an endangered species had already predicted that a number would be found. Besides the snail darter, what other endangered species were found in the basin, or was that the only one?
It was the only one. That speaks to the integrity of the study. If they were just about slowing or stopping the dam, they'd have ginned up a slew of endangered species.
In the other direction, having said he thought to find up to ten, he had to find at least one.
I make a distinction between "I will look to see if there are any endangered species." and "I expect to find up to ten endangered species."
Well, you'd have a list of possible species because you know what's already endangered and what habitats are there.
Given that Etnier was probably thoroughly familiar with previous surveys of the life-forms in the Little Tennessee River, it would not be surprising if he could predict that a really thorough survey would turn up new species, and roughly how many.
Genome sequencing has certainly redone a lot of family trees, but a lot of current discussions center on clades (groupings).
There is also a focus on functionality. Giraffes were considered a signal species, but now it looks like there are four (and more subspecies). That makes their conservation difficult. They can be bred together in captivity, but that does not happen in the wild.
https://giraffeconservation.org/giraffe-species/
During the big evolution debates the creationists used to complain that whenever they found a problem with evolutionary theory, scientists would revise the theory to deal with it. What they didn't realize is the this is what science does; it is self-correcting (given decent science and enough time).
Prior to protein and DNA sequencing, phylogenetic trees were based on physical features which were difficult to quantize and therefore inherently a bit subjective, particularly when a species in different environment may differ in its characteristics just based on things like the available food supply. While DNA sequencing was not available in the early seventies, it was a time when the first microbiological phylogenetic trees were being done based on protein sequencing (initially done with Cytochrome C, a protein found in all oxygen dependent species). Comparing the protein (or later DNA) sequence in different species allowed an objective mathematical value representing the difference to be assigned. It was still pretty cutting edge at the time of the snail darter controversy.
In science there is a tendency for researchers to "discover" new species (live or fossil) because it is an ego boost. Not conscious or even common, but it's there.
See the Cope Marsh Fossil Feud to get a taste of how wild it got in the past.
I'm a scientist, and I continue to beat my head against the wall over how politically clueless scientists are. We have to all know by now that one of the strongest pillars of right-wing propaganda -- especially in the age of Trump -- is the narrative that science and scientists are a bunch of leftist liars. So one question that comes to me is "Why do this study?" Is there nothing more important to do in your lab that would *not* feed the right-wingers who are determined to destroy your very profession, other than revisit and reopen the old snail darter "controversy"? Of course, these researchers may not have imagined, in their very tall and narrow silo, that any Trumpist trolls would be aware of their little project. Think again. They are like cicadas in a year of emergence: everywhere and ready to fuck anything that moves.
I'm a scientist, too. Indeed, I'm a PhD geneticist. I grew up in Tennessee, so I recall vividly this episode. I'm glad this study was done and was published.
There was a time when the Soviet Union was a leader in genetics. Then came Lysenko, and a lot of Soviet geneticists lost their jobs, their freedom and even their lives. Fortunately, world science didn't stop doing crop and livestock breeding for fear of its political repercussions.
The answer to right-wing propagandists is not for science to cave to their terrorism. The answer is to show how better science drives better conclusions.
Looking at the three sets of pictures, the snail darter and the stargazing darter seem to appear the most dissimilar. Maybe the pictures are not accurate or I'm not looking at it right. However, based on appearance in the pictures, I would say that this pair is much more likely to be different species than the other two. In the 1970s there wasn't much more to go on than that was there?
Correct. And with these fish, I doubt comparisons of Cytochrome C would be informative. Genomic comparisons are useful for such differences by comparing sequences that are not under purifying selection.
Why would it matter whether the snail darter is a separate species?
Suppose you have an extremely common species of fish. And a population of them lives in an inlet somewhere. And one day, the entrance to the inlet is closed through some natural landslide or the like. Something that preserves the ability of the fish to live in the inlet. Now the population within the inlet will begin to diverge from the broader population.
At what degree of variation does that isolated population acquire moral significance, such that humans must preserve it?
Suppose the landslide sealing the inlet is eroding at a predictable rate. Must we intervene to stabilise it?
In 60 million years all traces of humanity on this planet will be gone. A new intelligent species could then arise on this earth, despoil it, and vanish in turn. And this cycle could repeat tens of times before this planet becomes uninhabitable.
Species become extinct all the time. The obsession with extinction reflects little more than a displaced fear of death.
"Species become extinct all the time. The obsession with extinction reflects little more than a displaced fear of death."
Species become extinct all the time, yes, on geological timescales. Humanity is driving species extinction at a rate that vastly exceeds the pre-human background rate. Taking some steps to address that is not a "dispaced fear of death" as you seem to dismiss it.
And anyway, we decided collectively that we wanted to take steps to slow and prevent extinction of species when we, collectively, enacted the Endangered Species Act. It's perfectly valid for this country to express a preference that things like bald eagles, american alligators, and yes, snail darters continue to exist some decades from now, whether or not we can say for sure they will still exist 1 million (let alone 60 million) years from now, and to enact a law reflecting that preference.
"Species become extinct all the time, yes, on geological timescales."
The fossil record evidence demonstrates extinction occuring on geological timescales. But by its very nature, the fossil record is not going to show extinctions occurring on shorter timescales. And I suspect that speciation and extinction typically occur on smaller spatial and temporal scales than would be detectable in the fossil record.
And it is true that we collectively decided to enact the Endangered Species Act. But did we really intend to empower random professors to halt a regional development project based on questionable grounds, such that an veritable Act of Congress would be required to restart the development project?
Think carefully before you answer. Because such unforeseen consequences underly the housing crisis, the infrastructure crisis, the absence of high-speed rail.... and all other sorts of failures that Right Thinking people like you bemoan.
"Species become extinct all the time" seems like a step on the way towards "People die all the time -- so why should we (1) care if they get shot, or (2) bother with medical treatment, if they don't have the money, or (3) try to stop/prevent wars that aren't raging in our own neighborhoods?
The key being that we, as Americans, have been responsible for driving thousands of these species to extinction. Mass killing, forever, and to what purpose?
We in the "Western World" have developed a preference for biodiversity and so seek to preserve it. I am completely unfamiliar with what other parts of the world do about endangered species, so will not speak to their preferences.
We shouldn't be myopically focused on species when considering policy, it's an imperfectly constructed classification and focus on overall survival of related species should be sufficient, the policy shouldn't be different whether the snail darter is or is not deemed a different species (simpletonism).
Good points. How might the legislation be written, though? A big thing with the ESA was highlighting various charismatic species, like owls or big cats. Admittedly, the snail darter falls short there...
Howabout the Spotted Owl? I think the little guy saved some of the last old growth forests in California.
Like +25 for the spotted owl! I think there's at least one in our local Zoo.
That zoo resident owl could be the last one. Spotted Owls are being displaced by Barred Owls that have migrated slowly westward across the Great Plains by means of human planted forests. So now the US Fish & Wildlife people want to kill many thousands of barred owls to protect Spotted Owls from being overwhelmed and pushed to extinction. Owls are wonderful, and different owls are really interesting to watch. I'm not sure people are smart enough to manage animal populations to preserve against extinctions.
IF THE OWL CALLS AGAIN
at dusk
from the island in the river,
and it’s not too cold,
I’ll wait for the moon
to rise,
then take wing and glide
to meet him.
We will not speak,
but hooded against the frost
soar above
the alder flats, searching
with tawny eyes.
And then we’ll sit
in the shadowy spruce and
pick the bones of careless mice,
while the long moon drifts
toward Asia
and the river mutters
in its icy bed.
And when the morning climbs
the limbs
we’ll part without a sound,
fulfilled, floating
homeward as
the cold world awakens.
by John Haines (1924 – 2011)
Copyright © 1993 by John Haines. Reprinted from The Owl in the Mask of the Dreamer: Collected Poems, Graywolf Press, Saint Paul, Minnesota.
Well, we don't have Barred here, yet. It'll be a long time before they're truly displaced.
Something to consider, but I'm not in favor of pushing fiction as truth, if even for a "good" cause (which saving our old-growth and other forests is), though the immediate implications could be perplexing as in this case, so not saying we need to rush to change how we approach this. 😉