On Sticking Your Arm Into an Underwater Cavern and Hoping a Catfish Bites You

Jessica Rinaldi/Reuters/Landov

Lincoln Sadler eyes one of his favorite fishing spots, Great Rock, from a distance, but times his approach around an oncoming boat so as not to reveal the rock’s secret location. He has already hiked two miles in the boiling heat of an August North Carolina day followed by two miles of swimming and wading in the Pee Dee River.

Lincoln can wait a moment longer.

He reaches below the water and extends his arm into a dark cavern under the boulder. Enthusiastically wiggling his fingers in a dark underwater hole, Lincoln hopes a catfish bites him. Once Lincoln’s fingers are in the catfish’s mouth, he jerks the beast to the surface.

Near the Arkansas-Oklahoma border where I’m from, we call this noodling. In the Carolinas, the term is hand grabbling. Either way, it ends in a Greco-Roman grappling match where noodlers across the South, like Lincoln, wrestle very large catfish from their underwater holes. But this fishing story started long before Lincoln Sadler began his pilgrimage to Great Rock that August morning.

In the Beginning

Fifty million years ago, when bats, rodents, and elephants were also getting their start, large catfish species began diverging from their smaller brethren. Today, of the 49 catfish species in North America, 34 would not stretch across a dinner plate. Those 7 species of catfish prized by noodlers are the blue and channel catfish, and the flatheads. The latter can reach lengths of five and half feet. Work by Michael and Lotta Harman suggest these three species originated 35-40 million years after the original split between the large and small catfish, making them among the oldest of living catfishes.

Fast forward 11-15 million years and Lincoln is catching his largest catfish, 60 pounds, at Lost Rock, another of his secret locations on the Pee Dee. Lincoln’s prize catch is just 3.2 ounces light of the record largest catfish taken by Chad Lamb a few years later during the famous Okie Noodling Tournament.

Serving as human bait and wrestling catfish in the murky waters of the South may not seem efficient, but one study found that noodlers in the Tallahatchie River average catches of catfish 2.5 feet in length, nearly double that of traditional anglers. Ironically, if not for Lincoln and other noodlers, large size in catfish would prevent them from becoming dinner for a would-be predator.

In 1973, Jerry T. Krummrich, a masters student at Southern Illinois, investigated this by stocking experimental ponds with channel catfish and their predator, large-mouth bass. Krummrich determined that a channel cat must be 7-8 inches in length to avoid predation. Thus, the 49 species of catfish smaller than this would face tough times in many waters. This may be why the largest species of catfish also have the largest natural geographic ranges. The blue catfish is found from South Dakota to southern Mexico, the channel catfish from Mexico City to Manitoba, and the flathead from Mexico City to Minnesota. Compare this to one of the smallest catfish, the Ozark Matdom, measuring just over 4 inches in length. This catfish is found, as the name would suggest, exclusively in the Ozark Mountains.

There may be another reason why large catfish are geographically dispersed. Large fishes produce large clutches of eggs. While eventually yielding more offspring to geographically scatter, these large egg masses also attract predators. To protect against this, female catfish spawn in sheltered hollows with small entrances. Big underwater hollows with small openings, ideal nurseries for large catfish, are also favored by Lincoln and other noodlers. As with size itself, what would be typically evolutionarily favorable for a large catfish also makes it an easy target for a fish fry by noodlers.

You Are (Smarter Than) What You Eat

A twist of fate also produced another disadvantage for catfish. Along the Pee Dee River, Lincoln has identified a dozen rocks that are ideal for noodling. Among noodlers from the Carolinas to Oklahoma, these spots remain heavily guarded secrets. No flags or markers identify the rocks on the Pee Dee, just names, like Lost Rock and Great Rock, stored in the brains of Lincoln and his cohort.

Our large brains, that very trait that allows assessing habitat preferences for catfish or remembering locations of rocks along a river, require special nutrition. Specifically for our brain development, we need a significant amount of long-chain polyunsaturated lipids. Dr. Leigh Broadhurst does not believe it is coincidence that 3 million years ago our ancient ancestors arose in the East African Rift Valley, an area with many enormous lakes ripe with fish rich in these specific lipids.

David Braun and others found the earliest definitive evidence of this idea, a 1.95 million year old fossil site in East Turkana, Kenya, containing the butchered remains of aquatic animals. Today, fishermen benefit and catfish suffer from our million-year-old affinity for the fish course.

Increased brain size allowed not only for the development of memory and learning, but more complex communication and social interactions — and noodling is not a solitary recreational activity. As Lincoln states, “I never go by myself. Three is a minimum. If I get my arm caught in a hole, I need one person to run for help, and one person to hold my other hand.”

Sometimes, Lincoln’s group can swell to 17 people, including his brother and another Carolina noodling legend, Terry Sharp, who introduced Lincoln to noodling in 1998. Experience and social groups are key for noodlers and fishing success. For a masters thesis, Susan Baker of Mississippi State University surveyed hundreds of anglers throughout the South and found that noodlers formed stronger social connections and possessed more angling experience than traditional anglers.

But a noodler needs more than keen intellect and trustworthy friends. A noodler needs sheer bravado. Lincoln says that only about 1 in 30 men he takes out will stick their whole arm in a dark underwater hole. “They don’t cowboy up and just alligator arm it,” he says. In other words, many are too tentative, reaching in a short distance, their arms mimicking the short, squatty arms of alligators. So perhaps it's not shocking that a study found noodling is tied to masculine identity among Missouri noodlers. If, as Dr. Meghan Provost has shown, fertile women have a strong preference for men who strut in a masculine manner, imagine what landing a 100-pound catfish does for your image.

Is This Legal?

Wrestling a giant catfish to impress your friends, attract females, or simply for a large fish fry is not without controversy. Noodling is legal in just five states. In Texas, noodling is currently illegal but a bill to change this was approved by the Texas senate and house last summer. Why would noodling be illegal compared to other forms of angling? Fisheries and biologists voice concerns about the possible negative impacts on catfish populations, because noodling season in Mississippi specifically coincides with catfish spawning in the summer. Nevertheless, research indicates noodling does not negatively impact catfish populations in Mississippi or in Oklahoma due to limited success of noodlers in muddy waters and rapid currents.

And there's another reason why there may be no impact. Ultimately, few people want to “cowboy up” and shove their hands into the mouths of giant catfish.

Dr. Craig McClain is an expert on the science of body size in animals. His work has been featured in Miller-McCune, Cosmos, Science Illustrated, Wired, io9, and American Scientist. He is currently the assistant director of the National Science Foundation’s National Evolutionary Synthesis Center in Durham, North Carolina.

You can find Craig on Twitter @DrCraigMc, blogging at, or at

Live Smarter
Nervous About Asking for a Job Referral? LinkedIn Can Now Do It for You

For most people, asking for a job referral can be daunting. What if the person being approached shoots you down? What if you ask the "wrong" way? LinkedIn, which has been aggressively establishing itself as a catch-all hub for employment opportunities, has a solution, as Mashable reports.

The company recently launched "Ask for a Referral," an option that will appear to those browsing job listings. When you click on a job listed by a business that also employs one of your LinkedIn first-degree connections, you'll have the opportunity to solicit a referral from that individual.

The default message that LinkedIn creates is somewhat generic, but it hits the main topics—namely, prompting you to explain how you and your connection know one another and why you'd be a good fit for the position. If you're the one being asked for a referral, the site will direct you to the job posting and offer three prompts for a response, ranging from "Sure…" to "Sorry…".

LinkedIn says the referral option may not be available for all posts or all users, as the feature is still being rolled out. If you do see the option, it will likely pay to take advantage of it: LinkedIn reports that recruiters who receive both a referral and a job application from a prospective hire are four times more likely to contact that individual.

[h/t Mashable]

Dean Mouhtaropoulos/Getty Images
Essential Science
What Is a Scientific Theory?
Dean Mouhtaropoulos/Getty Images
Dean Mouhtaropoulos/Getty Images

In casual conversation, people often use the word theory to mean "hunch" or "guess": If you see the same man riding the northbound bus every morning, you might theorize that he has a job in the north end of the city; if you forget to put the bread in the breadbox and discover chunks have been taken out of it the next morning, you might theorize that you have mice in your kitchen.

In science, a theory is a stronger assertion. Typically, it's a claim about the relationship between various facts; a way of providing a concise explanation for what's been observed. The American Museum of Natural History puts it this way: "A theory is a well-substantiated explanation of an aspect of the natural world that can incorporate laws, hypotheses and facts."

For example, Newton's theory of gravity—also known as his law of universal gravitation—says that every object, anywhere in the universe, responds to the force of gravity in the same way. Observational data from the Moon's motion around the Earth, the motion of Jupiter's moons around Jupiter, and the downward fall of a dropped hammer are all consistent with Newton's theory. So Newton's theory provides a concise way of summarizing what we know about the motion of these objects—indeed, of any object responding to the force of gravity.

A scientific theory "organizes experience," James Robert Brown, a philosopher of science at the University of Toronto, tells Mental Floss. "It puts it into some kind of systematic form."


A theory's ability to account for already known facts lays a solid foundation for its acceptance. Let's take a closer look at Newton's theory of gravity as an example.

In the late 17th century, the planets were known to move in elliptical orbits around the Sun, but no one had a clear idea of why the orbits had to be shaped like ellipses. Similarly, the movement of falling objects had been well understood since the work of Galileo a half-century earlier; the Italian scientist had worked out a mathematical formula that describes how the speed of a falling object increases over time. Newton's great breakthrough was to tie all of this together. According to legend, his moment of insight came as he gazed upon a falling apple in his native Lincolnshire.

In Newton's theory, every object is attracted to every other object with a force that’s proportional to the masses of the objects, but inversely proportional to the square of the distance between them. This is known as an “inverse square” law. For example, if the distance between the Sun and the Earth were doubled, the gravitational attraction between the Earth and the Sun would be cut to one-quarter of its current strength. Newton, using his theories and a bit of calculus, was able to show that the gravitational force between the Sun and the planets as they move through space meant that orbits had to be elliptical.

Newton's theory is powerful because it explains so much: the falling apple, the motion of the Moon around the Earth, and the motion of all of the planets—and even comets—around the Sun. All of it now made sense.


A theory gains even more support if it predicts new, observable phenomena. The English astronomer Edmond Halley used Newton's theory of gravity to calculate the orbit of the comet that now bears his name. Taking into account the gravitational pull of the Sun, Jupiter, and Saturn, in 1705, he predicted that the comet, which had last been seen in 1682, would return in 1758. Sure enough, it did, reappearing in December of that year. (Unfortunately, Halley didn't live to see it; he died in 1742.) The predicted return of Halley's Comet, Brown says, was "a spectacular triumph" of Newton's theory.

In the early 20th century, Newton's theory of gravity would itself be superseded—as physicists put it—by Einstein's, known as general relativity. (Where Newton envisioned gravity as a force acting between objects, Einstein described gravity as the result of a curving or warping of space itself.) General relativity was able to explain certain phenomena that Newton's theory couldn't account for, such as an anomaly in the orbit of Mercury, which slowly rotates—the technical term for this is "precession"—so that while each loop the planet takes around the Sun is an ellipse, over the years Mercury traces out a spiral path similar to one you may have made as a kid on a Spirograph.

Significantly, Einstein’s theory also made predictions that differed from Newton's. One was the idea that gravity can bend starlight, which was spectacularly confirmed during a solar eclipse in 1919 (and made Einstein an overnight celebrity). Nearly 100 years later, in 2016, the discovery of gravitational waves confirmed yet another prediction. In the century between, at least eight predictions of Einstein's theory have been confirmed.


And yet physicists believe that Einstein's theory will one day give way to a new, more complete theory. It already seems to conflict with quantum mechanics, the theory that provides our best description of the subatomic world. The way the two theories describe the world is very different. General relativity describes the universe as containing particles with definite positions and speeds, moving about in response to gravitational fields that permeate all of space. Quantum mechanics, in contrast, yields only the probability that each particle will be found in some particular location at some particular time.

What would a "unified theory of physics"—one that combines quantum mechanics and Einstein's theory of gravity—look like? Presumably it would combine the explanatory power of both theories, allowing scientists to make sense of both the very large and the very small in the universe.


Let's shift from physics to biology for a moment. It is precisely because of its vast explanatory power that biologists hold Darwin's theory of evolution—which allows scientists to make sense of data from genetics, physiology, biochemistry, paleontology, biogeography, and many other fields—in such high esteem. As the biologist Theodosius Dobzhansky put it in an influential essay in 1973, "Nothing in biology makes sense except in the light of evolution."

Interestingly, the word evolution can be used to refer to both a theory and a fact—something Darwin himself realized. "Darwin, when he was talking about evolution, distinguished between the fact of evolution and the theory of evolution," Brown says. "The fact of evolution was that species had, in fact, evolved [i.e. changed over time]—and he had all sorts of evidence for this. The theory of evolution is an attempt to explain this evolutionary process." The explanation that Darwin eventually came up with was the idea of natural selection—roughly, the idea that an organism's offspring will vary, and that those offspring with more favorable traits will be more likely to survive, thus passing those traits on to the next generation.


Many theories are rock-solid: Scientists have just as much confidence in the theories of relativity, quantum mechanics, evolution, plate tectonics, and thermodynamics as they do in the statement that the Earth revolves around the Sun.

Other theories, closer to the cutting-edge of current research, are more tentative, like string theory (the idea that everything in the universe is made up of tiny, vibrating strings or loops of pure energy) or the various multiverse theories (the idea that our entire universe is just one of many). String theory and multiverse theories remain controversial because of the lack of direct experimental evidence for them, and some critics claim that multiverse theories aren't even testable in principle. They argue that there's no conceivable experiment that one could perform that would reveal the existence of these other universes.

Sometimes more than one theory is put forward to explain observations of natural phenomena; these theories might be said to "compete," with scientists judging which one provides the best explanation for the observations.

"That's how it should ideally work," Brown says. "You put forward your theory, I put forward my theory; we accumulate a lot of evidence. Eventually, one of our theories might prove to obviously be better than the other, over some period of time. At that point, the losing theory sort of falls away. And the winning theory will probably fight battles in the future."


More from mental floss studios