Spiders evolved, get over it

I study spiders in the family Theridiidae, which you’ve probably seen many times. Sometimes they’re called cupboard spiders, or cobweb spiders, or combfooted spiders after specialized limb structures they use to tease the silk they spin. They are also somewhat specialized to capture ground insects, making something called a gumfoot web, which is a sticky line under tension that is attached to the ground. Prey that contact the gumfoot line get snared, break the tension, and then get yanked up into the air. It’s a brilliant innovation.

Some theridiidae have taken this to an extreme: Propostira, the ballista spider, has reinforced the gumfoot line to such a degree that it snaps prey up into it’s tangle web.

Propostira sp. (Theridiidae) was found on trees close to the foraging trails of O. smaragdina, a locally abundant, arboreal, highly aggressive and territorial species5. On trees occupied by these ants, the ballista spider took refuge during the day on the underside of leaves and ventured out from their refuge 30 minutes after sunset. Upon leaving its refuge, the spider began an exploratory phase during which it descended on a silk line to substrates up to 50 cm away. When it landed on a suitable substrate, it laid down an anchor point and returned to the core web by laying a tension line. Repetition of this process resulted in a fan shaped array of 15–60 tension lines that were bundled close to the substrate (Figure 1B and Video 1 at https://bit.ly/4cKtVGT) where the lines were laid out in a scaffold in the shape of a small cone. In the final phase, the cone scaffold was densely wrapped with a thinner type of silk . The spider then retreated to a position several centimeters above the cone. Very soon after the cone was wrapped (5–55 seconds; n = 12), O. smaragdina ants were attracted to it. Within milliseconds after probing the cone with its antennae, the ant displayed aggressive behavior, elevated its gaster, and bit the silk cone. The ant’s aggressive behavior is similar to that exhibited towards non-nestmates. The biting destabilized the cone and detached it from the substrate within 42.12 ± 16.09 ms (n = 5), leading to a rapid contraction of the tension lines. While still holding the cone with its mandibles, the ant was pulled off the substrate and propelled into the core web, reaching distances of up to 28.19 cm from the substrate (mean ± s.d. = 13.37 ± 8.57 cm, n = 5), with peak accelerations of 1367 m/s2 (mean ± s.d. = 1108.96 ± 166.14 m/s2; n = 5) and maximum velocities of 4.36 m/s (mean ± s.d. = 3.83 ± 0.68 m/s, n = 5, Video 3 at https://bit.ly/4cKtVGT). The spider moved only after the ant had been hauled up and was no longer in contact with the substrate. The spider then moved upwards on the web and waited until the ant was fully entangled before approaching to wrap it in silk. In one of 12 instances, the ant triggered the snare but was not hauled up; without the added mass of the ant, the snare accelerated at 4732.89 m/s2 and reached a maximal velocity of 13.47 m/s.

That’s amazing.

But you know what else is amazing? This is plainly an evolutionary adaptation, an extension of known, familiar behavior of related species that you don’t have to live in Sri Lanka or the Cape York peninsula to witness; black widows and false widows do the same thing, with less extraordinary power. But that power is a product of combining more strands to amplify the force. It’s analogous to an actual ballista, where multiple strands of fiber are twisted to make great tension that can propel boulders, rather than ants, great distances with great force.

It’s a real evolutionary success story, in that we can see a continuum of small variations that accumulate to produce this one remarkable innovation. The ballista spider is a product of its evolutionary history.

So why is Ken Ham trumpeting this story?

But spiders spinning intricate webs to snag other insects for dinner and ants blasting formic acid at their enemies brings up a question, “Why is God’s creation filled with creatures who look designed to kill or avoid being killed?” Genesis gives us the answer!

God graciously provided for his creation, giving them what they would need to survive and thrive in a world broken because of sin.
God’s original creation was “very good” (Genesis 1:31), and humans and animals were created to be vegetarian (Genesis 1:30), though it’s unclear if insects fall into the animal category. (See this article on nephesh life and whether insects were on the menu prior to the fall. Interestingly, there’s even a vegetarian spider in today’s fallen world!) But when Adam and Eve sinned, creation fell, and now all of creation groans from the effects of sin. Some animals now eat other animals, and everything tries to avoid being eaten, and even insects are now a source of pain, difficulty, and even death for humans. It’s not the way it was designed to be—slingshot spiders and aggressive ants remind us that it’s a fallen world. God graciously provided for his creation, giving animals and even insects what they would need to survive and thrive in a world broken because of sin.

Genesis gives us no answer. He claims his god arbitrarily conjured this spider ability in response to an ape eating fruit in his garden, which is no explanation at all, while biologists see this as a consequence of natural evolutionary processes that don’t require extraordinary magical events. Ham is simply stealing scientific explanations to paper over the superstitious nonsense he peddles.

Not my VBS

I never formally attended Vacation Bible School, but my house was across the street from the Lutheran church, so sometimes I was tempted. There were kids playing outside! They were playing a beanbag game! So I wandered over a few times, and I was encouraged by the sunday school to do so. Forgive me, for I sinned.

It was mostly harmless, I think — the theme was just to have fun while under the umbrella of the church. That’s all. I guess the church has gotten more aggressive nowadays.

In a bizarre, disturbing scene that’s gone viral on TikTok, a church appeared to stage a fake execution of a man—involving realistic-looking guns and military uniforms—during Vacation Bible School. As the man is being murdered, the children are cheering in unison, “Take him out! Blow him up!” The military men then take the body outside (and out of view), where it’s suggested by the pastor they’re going to “blow him up.”

It’s disturbing that children were not only watching this scene, they were encouraged to cheer on the players machine-gunning the victim. Is this where a faith centered on the public execution of a disruptor of the status quo leads us?

The preacher at that church rationalizes the scene by saying that murdered man represented sin or satan, so it was OK to kill them. I’m sure Jesus would agree that children should be taught to kill sinners. They deserve death, after all.

I wonder if this church teaches that LGBTQ+ people are sinners?

Everything is the way it is because it got that way

My favorite quote/concept of all time is this one:

Everything is the way it is because it got that way.

D’Arcy Wentworth Thompson
(allegedly)

It affects everything I look at, and it’s the perfect sentiment for a developmental biologist/evolutionary biologist. It’s what I do for a living: see something, ask how it got that way (because that is the most important question), and try to track down the causal events that led to this outcome. It’s also the fundamental flaw in creationism, because they look at things and don’t care about the how or the process or the mechanism, it’s always explained by “god did it” with no interest in how their god did it.

But the quote always bugged me, too, because it’s not in On Growth and Form, Thompson’s awesome summary of his perspective. It’s a perfect expression of Thompson’s vision, so I continue to use it and think it, but it sure would be nice to know where it came from.

Fortunately, Glenn Branch tracked it down over a decade ago.

As far as I can tell, the line is actually due to Kenneth E. Boulding (1910–1993), whose obituary in The New York Times described him as “a much-honored but unorthodox economist, philosopher[,] and poet … renowned less for a single contribution to economics than for a large number of interesting intellectual and moral insights that both charmed and challenged his fellow social scientists.” In his 1953 “Toward a General Theory of Growth,” Boulding referred to “the D’Arcy Thomson [sic] principle … that at any moment the form of any object, organism, or organization is a result of its laws of growth up to that moment” (emphasis in original), citing On Growth and Form. (Boulding was a prolific writer, so there may be earlier statements of the principle that I missed.) By 1968, if not earlier, Boulding was using the familiar vernacular formulation, although he always credited the insight, if not the words, to Thompson.

It’s not hugely important — I’m not into hero-worship, although Thompson comes close to being a hero — but it’s nice to tidy up the record.

Muggy. Buggy.

I’ve always wanted to visit France, I guess I’m getting a taste of it today. I went for my morning walk — big mistake. It’s cloudy and gray, but temperatures are climbing into the mid-30°C range, and humidity is sky high. I walked into a coffeeshop with AC, and the windows were opaque sheets of condensation. The mosquitos realized I was loose in nature and attacked me in swarms on the way home.

Dinner tonight will be served cold: iced smoothies. That will be our reward for finally hooking up the window AC unit in our bedroom.

Tickled by a reference

Cool. As a certifiable nerd, this semi-obscure (to most people) reference provokes a lot of memories.

I’ve used the Golgi staining technique. It’s a silver stain that precipitates black deposits in a subset of neurons, producing a sample of stained cells and allowing you to visualize neuronal architecture. It is a somewhat mysterious procedure — I was treating slabs of brain tissue in an arcane series of reactions over days to get the effect, and it was so exciting when my first prep actually worked. It produces these gorgeous black-on-red-gold images, and there was a time when I’d spend hours on a microscope measuring synaptic bouton density. It’s weird to see it in a joke, though. How many people will get it?

And then, Weinersmith brings up Lucifer Yellow in the red button panel:

I’ve also used Lucifer Yellow a lot! It’s a small fluorescent probe that glows very brightly, and I’ve injected it into many neurons to visualize their arbors and also assess connectivity — it diffuses freely through gap junctions.

Again, I have to ask who this joke for? Neurobiologists and histologists and historians who recognize this guy.

You’re never going to tap into that Garfield money at this rate, Zach.

Predators at work

Cruising around the garden, which is currently swarming with flies, we found a couple of happy arthropods chowing down on the bounty.

Here’s Tetragnatha with the mangled corpse of some kind of fly:

A meadowhawk was standing on some horrible, unrecognizable mass.

There are still plenty of flies available for feasting!

You call that a fair?

I have never attended the Minnesota State Fair, which is a real shame. It has a tremendous reputation, and every year I hear raves about the weird food, the entertainment, the fun atmosphere. I’m afraid, though, that the huge crowds intimidate me. I’d struggle to get parking, would have to deal with the congestion, and it’s a 3 hour drive each way to get there.

The Great American State Fair in Washington DC has no such problem.

Photos and video of the small crowds, a lack of seating and near empty food booths were widely mocked on social media, while the Daily Beast called the event “virtually deserted” and The Atlantic noted in a headline: “The Great American State Fair isn’t very great.”

Maybe I should go? Except I don’t think there’s much to see.

The Great American State Fair is underway at the National Mall to mark the United States’ 250th birthday. But not everything is off to such a great start.

The event has quickly faced problems including power outages, melting ice cream – and a lack of representation from states that declined to send delegations.

While organizers assured visitors all parts of the nation would be represented, at least 10 states and territories refused to participate, with many citing the price tag to send staff to the 16-day event as their reason for opting out.

As usual, everything Trump touches turns to shit.

Axial Twist Theory

A reader has asked me to explain Axial Twist Theory. I don’t wanna.

OK, I dug into it a little bit. It’s a crank hypothesis promoted by a tiny number of people; it reminds me of Vortex theory and Lifecode, a couple of comprehensive theories of development proposed by obsessive individuals on the basis of biased interpretations of poor or even bogus observations. Coincidentally, my criticisms of those ideas led to serious threats of lawsuits, which is another strike against them (scientific hypotheses are not defended by lawsuits), and makes me wonder if I’m going to get sued again. No worries, those were not credible threats.

So what is it? There is a web page titled “Axial Twist Theory Explained”, and a Wikipedia page. They’re both terribly written, difficult to wade through, and I suspect both were written by the same person. The theory attempts to explain a phenomenon that doesn’t exist and doesn’t need explanation.

In short, the theory claims that the face and rostral nervous system were rotated during embryonic development and evolution, which they propose to explain the existence of decussations, like the way eyes project to contralateral regions of the central nervous system.

Schema of the proposed development of the axial twist. Developmental phases are (from top to bottom): (1) the embryo turns on its left side; (2) the anterior head grows in the same direction, but the rest of the body grows oppositely into a twist. So that ultimately (3) external bilateral symmetry is regained. Note that there is no evolutionary pressure for internal symmetry so the heart (and other organs) remain asymmetric.

We have no need of this hypothesis, and they have no evidence to support it. It’s that simple.

I’m pretty familiar with the concept of decussations in the nervous system. That’s what I studied in a previous life: my graduate work was on how the spinal cord gets wired up, and there are crossing fibers all up and down the cord. The lab I was in was focused on hindbrain neurons that crossed the midline to innervate contralateral motor outputs. If we needed to twist the whole axis to get them to cross, the whole nervous system would have to be twisted like the rubber band in a model airplane. It makes no sense.

As a post-doc I studied the development of commissural neurons in the grasshopper embryo. Axial Twist Theory confines itself to vertebrate development, so one might argue that grasshoppers are irrelevant, except that insects contain lots of crossing fibers that don’t require whole body twists to explain. It’s simply a functional consequence of needing to integrate both sides of the animal, and the mechanisms for generating it is straightforward molecular signaling that has existed since the last common ancestor of vertebrates and invertebrates.

But to be fair, let’s look at the research literature. Next problem: it’s negligible. Pubmed turns up one article: Opposite asymmetries of face and trunk and of kissing and hugging, as predicted by the axial twist hypothesis by Marc H.E. de Lussanet​. It’s incredibly silly. For instance, bilateral symmetry is imperfect, so they interpret biases as the product of incomplete rotation of the face relative to the back of the head.

Exaggerated schema of the aurofacial asymmetry as predicted by the axial twist theory. During embryology and development, the face elements (red) are predicted to move toward the center from the left, with respect to the mid-plane between the ears.

It gets sillier. Part of the data in that paper was an analysis of photographs on the internet, and an experiment in which people were photographed hugging dolls and were observed in airports. Did I say silly? This is getting creepy.

Examples of left kissing (A) and right hugging (B).
The two schemas show a top view of the opposite behavioral asymmetries.

Apparently, the asymmetry during kissing is different than the asymmetry during hugging, which suggests that there is a twist between face and body. But even that is an ambiguous mess!

The kissing results also confirm the hypothesis and reproduces the findings of airport observations, experiments with dolls, as well as with couples and questionnaires. Earlier studies have revealed clear regional cultural influences: for example in some French cities, as well as in native Palestinian and Jewish Israelis, the kissing bias is reversed, whereas in a conservative muslim country (Bangladesh) the kissing bias is as in the other studies. Also, the bias in kissing and hugging behavior is strongly reduced by emotional contexts. For example, no bias was found in a public kiss between strangers. Thirdly, the kissing bias can be influenced by a lateral head tilt. For example, when kissing a doll head that is either 5° tilted to the right or 15° to the left resulted in a bias of almost 100% to the left and right side of the face respectively. Finally, both the kissing and hugging bias seem to be reduced in left handers

How do you draw conclusions about an embryonic transition that had to have occurred in the Precambrian from a wildly variable behavior in modern humans? The author treats this noise as a solid demonstration of the Axial Twist Hypothesis.

We thus showed that humans also behave as twisted creatures, as predicted by the ATH. Asking people why they kiss or hug this way, or to try it the other way leads to responses such as “it somehow feels better, more natural like this.” We thus tend to kiss as if the ventral side of the face has not quite arrived in the centre, but is still located to the left. Correspondingly, we tend to hug as if the ventral trunk is located to the right of the sagittal plane.

The final strike for me is their gross misinterpretation of zebrafish development. They claim that there is a rotation of the two eyes that fits their model, and they show a single short timelapse.

I spent years staring in a microscope at early, developing zebrafish embryos. No, the eyes don’t rotate around the body axis. In that video, they’re showing a slightly askew perspective on the head and drawing red and blue overlays on the eyes to emphasize an asymmetry inherent in the angle.

I don’t have to explain the Axial Twist Theory because it’s an imaginary phenomenon with no good evidence for it, used to explain poor observations that don’t need a deep evolutionary/embryological foundation.

It was still a little bit entertaining to dive into some bad science.