Tooth and claw

The earliest living things, way back in the Precambrian Era, were almost certainly either autotrophs (those that could produce their own nutrients from inorganic chemicals) or else scavengers.  One of the reasons for this inference is that these early life forms had few in the way of hard, fossilizable parts, of the kind you might use to protect yourself from predators.  Most of the fossils from that era are casts and impressions, and suggest soft-bodied organisms that, all things considered, had life fairly easy.

But the Cambrian Explosion saw the rather sudden evolution of exoskeletons, scales, spines... and big, nasty, pointy teeth.  There's credible evidence that one of the main reasons behind that rapid diversification was the evolution of carnivory.  Rather than waiting for your neighbor to die before you can have a snack, you hasten the process yourself -- and create strong selection for adaptations involving self-defense and speed.

After that, life became a much dicier business.  I was discussing this just a couple of days ago with the amazing paleontologist and writer Riley Black (you should definitely check out her books at the link provided).  She'd posted on Bluesky about the terrifying Cretaceous mosasaur Tylosaurus proriger, which got to be a mind-blowing twelve meters long (around the length of a school bus).  This species lived in the Western Interior Seaway, which back then covered the entire middle of the North American continent.  I commented to her what a difficult place that must have been even to survive in.  "We always describe the Western Interior Seaway as 'a warm, shallow sea,'" Riley responded.  "Ahh, soothing -- and not like 'holy shit these waters are full of TEETH!'"

What's interesting, though, is that even though we think of predators as mostly being macroscopic carnivores, this practice goes all the way down to the microscopic.  The topic comes up because of a paper this week in Science about some research at ETH Zürich about a species of predatory marine bacteria called Aureispira.  These little things are downright terrifying.  They slither about on the ocean floor looking for prey -- other bacteria, especially those of the genus Vibrio -- and when they encounter one, they throw out structures that look like grappling hooks.  The hooks get tangled in the victim's flagella, and at that point it's game over.  The prey is pulled toward the predator, and when it's close enough, it shoots the prey with a microscopic bolt gun, and then chows down.

Aureispira isn't a one-off.  The soil bacterium Myxococcus xanthus forms what have been called "wolf packs" -- biofilms of millions of bacteria that can be up to several centimeters wide, that glide along soil particles, digesting any other bacteria or fungi they happen to run across. 

A "wolf pack" of Myxococcus xanthus [Image licensed under the Creative Commons Trance Gemini, M. xanthus development, CC BY-SA 3.0]

This one immediately put me in mind of one of the most terrifying episodes of The X Files; "Field Trip."  In this freaky story, people are put into a series of powerful hallucinations after inhaling spores of a microorganism.  The hallucinations keep the victim quiet -- while (s)he is then slowly digested.

Of course, the microbe in "Field Trip" isn't real (thank heaven), but there are plenty of little horrors in the world of the tiny that are just as scary.  Take, for example, the aptly-named Vampirococcus, which is an anaerobic aquatic genus that latches onto other bacterial cells and sucks out their cytoplasm.

But the weirdest one of all is the bizarre Bdellovibrio, which is a free-swimming aquatic bacterium that launches itself at other single-celled organisms, moving at about a hundred times its own body length per second, then uses its flagella to spin at an unimaginable one hundred revolutions per second, turning itself into a living drill.  The prey's cell membrane is punctured in short order, and the Bdellovibrio burrows inside to feast on the innards.

So.  Yeah.  When Alfred, Lord Tennyson said that nature is "red in tooth and claw," I doubt he was thinking of bacteria.  But some of them are as scary as the mosasaurs I was discussing with Riley Black.  The world is a dangerous place -- even on the scale of the very, very small.

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Raw deal

A friend of mine, a veterinarian in Scotland, has proven to be a wonderful source of topics for Skeptophilia, mostly on health-related issues.  Her skeptical, evidence-based approach has given her a keen eye for nonsense -- and man, in this field, there's a lot of nonsense to choose from.

Her latest contribution was so over-the-top at first I thought it was a parody.  Sadly, it's not.  So, dear readers, allow me to introduce you to:

The Raw Meat Carnivore Diet.

Once I ruled this out as an example of Poe's Law, my next guess was that it was the creation of someone like Andrew Tate to prove to us once and for all that he's the alpha-est alpha that ever alpha-ed, but again, this seems not to be the case.  Apparently, this is being seriously suggested as a healthy way to eat.  And it's exactly what it sounds like; on this diet, you're to eat only raw meat from ruminants (beef, bison, lamb, elk, etc.), salt, and water.

[Image licensed under the Creative Commons Jellaluna, Raw beef steak, 2011, CC BY 2.0]

At the risk of stating what is (I devoutly hope) the obvious, this is a really really REALLY bad idea.  Cooking your food remains the easiest and best way to sterilize it, killing pathogens like E. coli, Salmonella, Shigella, Campylobacter, and Staphylococcus aureus, as well as other special offers like various parasitic worms I'd prefer not to even think about.  The writer of the article, one Liam McAuliffe, assures us that the acidity in our stomach is perfectly capable of killing all of the above pathogens -- which leads to the question of why, then, anyone ever becomes ill from them.

Then there's a passage about an experiment back in the 1930s showing that cats fed a raw meat diet were generally healthier, which may be true, but ignores the fact that cats are damn close to obligate carnivores, and we're not.  To convince yourself that cats and humans have evolved to thrive on different diets, all you have to do is look at the teeth.  Cats have what are called carnassial molars; narrow, with sharp shearing edges, designed to cut meat up into chunks.  Our molars are flat, with cusps, typical of -- you guessed it -- an omnivore.  Citing the cat experiment as a reason we should all eat raw meat is a little like observing that cows thrive when allowed to graze in verdant fields, and deciding that henceforth humans should eat nothing but grass.

This brings up something else that Mr. McAuliffe conveniently neglects to mention; to have our digestive systems function properly, humans (and other omnivores) need to have a good bit of plant-derived cellulose in our diets -- what dietitians call "roughage" or "fiber."  Without it, our intestines clog up like a bad drain.  Eliminating all the vegetables from your diet is a good way to end up with terminal constipation.

What a way to go.  Or not go, as the case may be.

Then, there's a bit about how cooking meat reduces the amount of nutrients it contains -- specifically the B vitamins thiamine, riboflavin, and niacin.  Once again, this may well be true; but even if it is, the next question is, how many of us are deficient enough in these nutrients that the loss from cooking is actually a problem?  Let me put it this way; how many people do you know who have had beriberi (thiamine deficiency) or pellagra (niacin deficiency)?  (Riboflavin deficiency is so rare it doesn't even have a name.)  The fact is, if you're eating a normal diet, you are almost certainly getting more of these vitamins than you need, and the small amount of loss from cooking your t-bone steak is far offset by the benefit of not dying from an E. coli infection.

Not to beat the point unto death, but McAuliffe's contention -- that we are, in his words, "hypercarnivorous apex predators" -- is nonsense.  Our closest relatives, chimps and bonobos, are thoroughgoing omnivores, who will certainly eat meat when they can get it but also love fruit, and will chow down on starch-rich roots and stems without any apparent hesitation.  What's optimal for human health, and which has been demonstrated experimentally over and over, is a varied diet including meat (or an equivalent protein source), vegetables, and fruits -- just like our jungle-dwelling cousins.

So.  Yeah.  Go easy on the moose tartare.  I'm of the opinion that a steak with a glass of fine red wine is a nice treat, but let's avoid eating it raw, okay?

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Death... with big, nasty, pointy teeth

Today I'm going to write about a piece of research that isn't controversial, or deeply thought-provoking, or politically relevant, but because it's just plain awesome.

It's from the realm of paleontology, and is about a gigantic carnivore, which is part of its appeal.  Have you noticed how the little-kid fascination with dinosaurs usually revolves around carnivorous ones like Velociraptor and Tyrannosaurus rex?  They're seldom as impressed by herbivores like Pachycephalosaurus, which also has the disadvantage of meaning "thick-headed lizard," so it's kind of unimpressive right from the get-go.  Velociraptor, though?  "Swift hunter?"  Now that's cool.  You can bet that those wicked pack-hunters would never have put up with being given a humiliating name.  I bet if the paleontologists had decided to name them Brocchodentidorkosaurus ("buck-toothed dorky lizard"), the raptors would have eaten them for lunch, and that's even considering the fact that they've been extinct for seventy million years.

The dinosaurs, not the paleontologists.

But I digress.

The subject of today's post is a mammal called Simbakubwa kutokaafrika, which means "humongous lion from Africa" in Swahili (speaking of impressive names), even though it wasn't a lion at all.  It was a hyaenodont, a predatory group of mammals that are in Order Creodonta, a group only distantly related to modern Order Carnivora (i.e., cats, dogs, bears, weasels, seals, and a few other families).  The creodonts are an interesting group, at least to evolutionary biologists, because there's still a major argument going on regarding how to assemble their family tree.  Some paleontologists believe they're monophyletic -- all descended from a single common ancestor -- while others say they're polyphyletic, with different groups of creodonts coming from different ancestors that were further apart on the mammalian clade.

Whichever it is, they've now been shown through detailed skeletal analysis to have a closer connection to the bizarre pangolins than they do to today's carnivores -- yet another example of how common sense can lead to the wrong answer.

Reconstruction of a hyaenodont by Heinrich Harder [Image is in the Public Domain]

In any case, Simbakubwa was discovered recently by Duke University paleontologist Matt Borths, who was going through some fossils in the back rooms of the Nairobi National Museum when he found something that made him sit up and take notice:

The remains of a carnivorous mammal that was an estimated 1.2 meters tall at the shoulder, 2.4 meters from tip to tail, weighed an estimated five hundred kilograms, had canine teeth the size of bananas, and had three sets of incisors, two of which were big, nasty, and pointy.

That, my friends, is one serious carnivore.  That's a carnivore that could have turned your average African lion into an African lion meatloaf.

Simbakubwa is estimated to have lived around 23 million years ago, placing it in the early Miocene, but the creodonts as a group were apex carnivores for a lot longer than that.  They originated in the Paleocene (the epoch that began with the K-T extinction, 66 million years ago), and made it to the mid-Miocene (14 million years ago).  Modern(ish) true carnivores (i.e. Order Carnivora) first showed up 42 million years ago (the mid-Eocene epoch), and only reached Africa around 22 million years ago -- right around the time Simbakubwa was lumbering around the place.  So no wonder the true carnivores only began to diversify in Africa after the hyaenodonts were safely out of the way, eight million years later.

All of this highlights two things -- first, what amazing discoveries might be lurking on dusty museum shelves, forgotten and unstudied; and second, that we honestly don't know very much about what critters were out there in prehistoric times.  The conditions required for generating a fossil are thought to be mighty uncommon -- most animals don't leave any traces at all, only a few years after they die, so it's likely that the vast majority of the living things that have ever existed aren't represented in today's fossil record.

So the number of species we know about are far outnumbered by the ones we don't know about.  Meaning that as bizarre, fascinating, and wonderful as are the prehistoric animals we've classified, if we were to time-travel back to whatever epoch you choose, we'd find ones more bizarre still.  And that's even including a banana-fanged predator the size of a polar bear.

All of which puts me in mind of the last sentence of Charles Darwin's Origin of Species, which seems a fitting way to end:

There is grandeur in this view of life, with its several powers, having been originally breathed into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved.

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Monday's post, about the institutionalized sexism in scientific research, prompted me to decide that this week's Skeptophilia book recommendation is Evelyn Fox Keller's brilliant biography of Nobel Prize-winning geneticist Barbara McClintock, A Feeling for the Organism.

McClintock worked for years to prove her claim that bits of genetic material that she called transposons or transposable elements could move around in the genome, with the result of switching on or switching off genes.  Her research was largely ignored, mostly because of the attitudes toward female scientists back in the 1940s and 1950s, the decades during which she discovered transposition.  Her male colleagues laughingly labeled her claim "jumping genes" and forthwith forgot all about it.

Undeterred, McClintock kept at it, finally amassing such a mountain of evidence that she couldn't be ignored.  Other scientists, some willingly and some begrudgingly, replicated her experiments, and support finally fell in line behind her.  She was awarded the 1983 Nobel Prize in Physiology and Medicine -- and remains to this day the only woman who has received an unshared Nobel in that category.

Her biography is simultaneously infuriating and uplifting, but in the end, the uplift wins -- her work demonstrates the power of perseverance and the delightful outcome of the protagonist winning in the end.  Keller's look at McClintock's life and personal struggles, and ultimate triumph, is a must-read for anyone interested in science -- or the role that sexism has played in scientific research.

[Note: If you purchase this book using the image/link below, part of the proceeds goes to support Skeptophilia!]