Category Archives: Evolution

Saltwater Crocs: Showing How Dinosaurs Are Evolutionary Pansies Since 200,000,000 BCE

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In the waning years of the World War II Pacific campaign, British Marines and the 36th Indian Infantry Brigade landed on the shores of Ramree Island, Burma, after hours of aggressive naval bombardment. A swampy mud-soaked coastal island housing a wide variety of deadly wildlife and diseases, Ramree was key to gaining an Allied foothold on mainland Burma and reversing the spread of Japanese aggression in the region. The few thousand Japanese forces entrenched on Ramree repelled the Allied invasion during the initial weeks of heavy fighting.

January 26th, 1945, the battle turned when a force of about 1,000 Japanese defenders was routed by Allied forces. Surrounded on three sides by enemy units and hoping to rejoin the larger Japanese battalion on the other side of the island, the retreating Japanese opted for the most direct path; a beeline through the thick mud of a dense mangrove swamp. Their retreat was marred not only by the pursuing Allies but also by starvation, dehydration, mosquitos, scorpions, snakes, and one of the most infamously prolific people-murderers outside of the human species: saltwater crocodiles.

This is the last thing I’d want to run into at night in a warzone after being shot at for the past few weeks. Image source: unknown

It doesn’t take a vivid imagination to figure out that saltwater crocodiles are nothing short of gifted killers. At up to 22 feet long and more than two tons, they’re the largest reptile alive today. Saltwater crocs inhabit salty, brackish, and some fresh waters from the Indian peninsula through northern Australia and Southeast Asia, historically spanning northward to Japan. These waters are some of the most densely-populated human areas on earth, meaning the rate at which crocs and people meet face-to-face is higher than more fear-inspiring predators like sharks, hippos, bears, lions, tigers, wolves, cheetahs, dragons, mermaids, and unicorns.

Saltwater crocs, or salties, are primarily ambush predators, meaning they lay elaborate traps (jaws) in high-traffic areas (any volume of murky water larger than 5 liters) and wait for unsuspecting prey (anyone that will be dearly missed) to wander closely by (within 6-10 miles). Saltwater crocs in particular have the widest diet variety of any living crocodile. Crocs are typically apex predators in their communities, meaning they have the ability to catch, consume, and digest pretty much any other animal species from lower levels of the food web. Their prey includes smaller animals such as fish, crustaceans, and birds, but they’ve also been documented feeding upon larger mammals like deer, antelope, domesticated livestock, and humans. Given their size and musculature, it’s a wonder that saltwater crocs are surprisingly not voracious eaters and can go for weeks between meals. Let that thought give you comfort as you’re devoured alive.

Not only do salties eat nearly anything that moves, they also strike with deadly aggression.

Their bite force is the highest ever recorded; a large Australian saltwater croc broke the record with a bite force of 36,000 newtons. By contrast, this is about 40 times the force a human exerts and almost 8 times that of lions, tigers, and  hyenas. This number even rivals that of another famous predator, breaking into the lower estimates for that of T. rex. Scientists studying the evolution of crocodiles noted that the skull took on its characteristic shape, musculature, and bite before the emergence of other croc-like traits like body size, shape, joint structure, and limb placement, indicating that the bite force of crocs was a primary driver of crocodilian evolution.

On the other hand, saltwater crocs have very poor opening strength, and according to the Wikipedia article on their bite musculature, a few layers of duct tape can hold a saltie’s jaws shut. I’m not trying that anytime soon.

Once saltwater crocs get a hold of their prey, it may perform a famous behavior called the death roll. Keeping their strong hold on their prey, the croc will spin until the animal becomes separated or until the croc no longer detects movement. Most theorize that the death roll is largely an attempt to drown terrestrial prey, making them easier to consume. Others speculate that the purpose of the behavior is to rend torso from limb and produce manageable portions for easier digestion. Either way, the death roll is something with which the retreating Japanese on Ramree Island became all too familiar.

British scouts documented the horror the Japanese experienced in their retreat across Ramree. Screaming and desperate splashing were common sounds heard by the Allies in the night, sometimes punctuated by the characteristic sound of Japanese gunfire. Many speculated what horrors befell the dehydrated, starving, mosquito-plagued Japanese. Few outsiders witnessed and documented the event. Among the British forces scouting the Japanese retreat from outside the swamp was naturalist Bruce Stanley Wright. In his 1962 book Wildlife Sketches Near and Far, Wright elaborates on the event:

“The crocodiles, alerted by the din of warfare and the smell of blood, gathered among the mangroves, lying with their eyes above water, watchfully alert for their next meal. With the ebb of the tide, the crocodiles moved in on the dead, wounded, and uninjured men who had become mired in the mud.

The scattered rifle shots in the pitch black swamp punctured by the screams of wounded men crushed in the jaws of huge reptiles, and the blurred worrying sound of spinning crocodiles made a cacophony of hell that has rarely been duplicated on earth. At dawn the vultures arrived to clean up what the crocodiles had left…Of about 1,000 Japanese soldiers that entered the swamps of Ramree, only about 20 were found alive.”

Though many admittedly doubt the accuracy of Wright’s reported number of casualties, the statistic has earned the Guinness World Record for “most fatalities in a crocodile attack”. If Wright’s numbers are accurate, Ramree would be the deadliest attack by any animal on human beings in recorded history.

Few doubt the capability for saltwater crocs to bring that degree of torture upon humans. Many attacks like these occur in remote regions among populations of humans that fail to reliably collect attack data. Much of what we know about croc attack numbers comes from Australia where news reports and eyewitness accounts are more accurately described and distributed to the public. In Australia’s Northern Territory alone, 18 lethal croc attacks have taken place since 1987. Across all of Australia, the rate of deadly attack has skyrocketed from one every two years in 1971 to seven times that number in 2013, totaling 99. Of those, 27% were fatal, a low statistic compared to the country’s neighbors. In nearby Sumatra, 107 people have been attacked since 2007, almost 50% of which were fatal.

Image source: Outbackcooking.blogspot.com

One such attack was made famous by Hugh Edwards in his book Crocodile Attacks in Australia and made even more so by Bill Bryson in his entertaining travel novel In a Sunburned Country. In 1986, many moviegoers were entranced by the release of Crocodile Dundee, inspiring droves to visit the Australian wilderness. One such traveler was 24-year-old American model Ginger Meadows. Aboard the luxury yacht Lady G, Meadows and her newly-earned Australian friend stopped for a swim near the waterfalls at the beautiful King Cascades. The two women were quickly pinned in the water between a croc and a steep cliff. The girls began shouting, throwing their shoes, and tried to wait out the croc, but nothing could deter it. Meadows, a strong swimmer, attempted to make a break for the nearby embankment but vanished in a cloud of splashing in seconds. Caught in a death roll, Meadows looked to her friends desperately, but no one could do anything to help before she vanished. Her body was found floating and armless two days later.

The King Cascade falls, the site of the vicious crocodile attack on American model Ginger meadows in 1987. The attack occurred in the alcove left of the falls. Image source: Tripadvisor.com

Cases like these are hardly solitary. In 2003, a group of three adult friends were repairing an ATV in the Northern Territory when a crocodile fatally attacked one of them and chased the other two into a tree for 22 hours. In 2009, a 5-year-old Queensland boy was eaten in his own backyard trying to protect his new boxer puppy. In 2013, a New Zealand man was trapped alone on an island for two weeks when a crocodile attacked him each time he neared his boat. Last year, a 61-year-old man was snatched from his fishing boat while his family had their backs turned.

It must be said that a majority of attacks are non-fatal. It’s a common occurrence, especially in the Northern Territory, for locals to boast about close encounters with crocs. Sometimes, bait or cleaning buckets attract crocs to wayward limbs. Campsites, public spaces, or private residences located adjacent to croc habitat also can contribute to croc encounters. Excessive alcohol has also been tied to many attacks. Other times, the crocs attack objects like boat hulls, motors, fishing gear, and other inedible objects completely without warning or agitation.

Damage to an outboard motor done by an unprovoked saltwater croc in Australia’s Northern Territory. Source: ntnews.com.au

Though it’s hard to find any heart-warming aspects of the saltwater croc’s story, such things do exist. For one, a collection of Australian laws were passed in the 1970s that outlawed the unregulated trade of saltwater croc skins, a large contributor to critically low crocodile numbers. In the first ten years, the population exploded from 4,000 to nearly 30,000 animals, and today the number may be as high as 150,000 in the Northern Territory alone. To date, the recovery of croc populations from near extinction is the most successful predator conservation program in history.

Though saltwater crocs are among the most aggressive, deadly, and fearsome species in the animal world, they have also fascinated millions. From Steve Irwin to Mick Dundee, the raw power of saltwater crocodiles appeals to man’s primal urges of dominance and aggression. Crocs remind us of a by-gone era where reptiles the size of automobiles waged war on planet Earth. Perhaps that’s why we’re so entranced by them. Perhaps that’s also why we fear them so.

Further reading:

http://shadowreports.com/2011/04/13/eaten-alive-five-killer-croc-attacks-part-one-22-hours-in-hell/

http://www.couriermail.com.au/news/queensland/crocodile-tragedy-boys-family-leaves-daintree-river-home/story-e6freoof-1225812013828

http://mysteriousuniverse.org/2014/08/the-horrific-crocodile-massacre-of-ramree-island/

Cone Snails: The reason why I won’t be sleeping tonight

TitleSometimes, when I’m camping, I dream about angry bears ripping through my tent and attacking me for that forgotten bit of food I left in my pack. A perfectly logical nightmare, all things considered, but far from my worst. In that one, I was SCUBA diving with my cat when she encountered a 6-inch long cone snail. In a sudden flash of activity, one of my best buds was murdered in a rush of sadness and a chorus of bubbly muffled screaming.

I must have been about 12 years old at the time I had the nightmare, and it keep recurring. These nightmares started the same night that I first learned about cone snails and their cat-murderingly lethal toxins from a Disvocery Channel documentary. Not once have I had a nightmare about a Badass Biology topic, let alone one that still rips at the psychological wounds 13 years later.

What about cone snails makes them so horrible? So memorable? Get comfortable, I have a lot to write.

The 6 reasons why cone snails deserve to invade my nightmares:

1) I’m convinced cone snails are heralds to the war of the end times.

Cone snails look pretty innocent. In fact, many of them, like the textile cone pictured below, have intricate colors and gorgeous patterns that would make them desirable for any unsuspecting shell-lover to snatch in an instant. Just look at this little guy here:

Textile cone. I’d would seriously be inclide to play with this shell if I saw it, then I’d remember this article and swim away in a panic. I’d likely also wet myself in fear. Image source: Wikimedia

How cute, right? I think so. I’d hold him. However, what I wouldn’t expect is for that fleeting joy to be one of the last thoughts my brain could process before I’d rapidly be dead.

Unlike the garden variety of snail, cone snails are carnivorous marine snails. They’re common in Indo-Pacific waters, though they also inhabit the temperate waters around California, the Mediterranean, and South Africa among other habitats. The smaller varieties eat benthic invertebrates, though the larger ones must be quick and deadly to capture the small fish they feed upon. This selection pressure created one of the most badass weapons in the natural world.

To catch their quick prey, cone snails possess a small harpoon-shaped structure within the snail’s radula, a feeding structure that other snails use to scrape food from surfaces. In cone snails, the harpoon carries a toxic cocktail of sometimes hundreds of lethal compounds, all stored in a venom sac that supplies the harpoon with enough venom to apply to their next murder victim. This harpoon is used blindingly quickly, leaving little chance for their prey to escape. Then, after that, the cone snails engulf them whole with a mouth so horrifying that I cannot find the guts to post a picture here, thereby I suggest you just Google it.

HarpoonPic

Pictured above is the anatomy of the venom sac and a microscopic view of the toxin-tipped harpoon. Image source: theconesnail.com

2) Take a moment today to call your mother and let you know you love her.

Cone snails produce more toxins than any genus of organisms discovered by science. In fact, there are so many that an entire database has been developed to catalogue and characterize conotoxins, the potent toxic compounds present in cone snail venom. This database, called ConoServer, presently has 8482 chemical entries from no more than 215 species within the cone snail genus, a staggering number for a single organismal group.

But what are these toxic chemical compounds? Most are peptides, short strings of amino acids chained together with a special carbon-nitrogen bond. If these chains were considerably longer, portions of the string would begin interacting with other parts and fold itself into a protein, a type of molecule I’m sure you’ve heard of. Peptides, though shorter, are still useful molecules to manufacture, forming the surfactants that keep mammalian lung tissue from sticking to itself, adding nutritional value to milk, and in the case of our nightmarish cone snails, killing stuff really really quickly.

Conotoxin peptides are mostly used defensively. Most human stings are caused by a wayward foot delivered to a cone snail hiding in the sediment. However, roughly 10% or so of classified cone snail toxins have been found to be used in foraging and hunting, paralyzing their prey.

3) I am now hoarding Morton’s salt under my pillow in case one tries to break into my home.

All of the 600-700 species of cone snails are capable to stinging and injecting their toxins into humans. Not only are there a multitude of lethal toxins in a cone snail’s sting, but their lethality is nearly unparalleled. A useful way to measure how lethal a toxin can be is to measure what’s called a LD50, or the dosage expressed in mass/kg of body weight at which 50% of a population of test animals (usually rats) are killed. Arsenic, a well-known toxic substance, has an LD50 of around 15mg/kg, meaning it would take about half a teaspoon of crystallized arsenic compounds to kill a male human weighing 83.6kg, or around 181 lbs. The LD50 for some conotoxins can be as low as 0.005mg/kg, meaning you could very well be killed by conotoxin at a volume little larger than 10 medium grains of sand.

How do these toxins kill at such small dosages? If you’re an avid reader of mine, you may remember textrodotoxin, a neurotoxin in blowfish that kills by interfering with ion channels in neurons. Ion channels allow neurons to fire, and conotoxins bind to these channels with startling specificity, prohibiting their ability to function. Conotoxins kill humans in much the same way, and like tetrodotoxin, most human deaths from conotoxins are related to the asphyxia caused by the diaphragm being unable to contract. There is no anti-venom, and in some species like the geography cone, a sting is 70% fatal.

4) I strongly suggest we flee for the mountaintops.

Diabetic or not, you’ve heard of insulin. Insulin too is a peptide, and in humans it acts a hormone to help mediate the amount of glucose present in the bloodstream. Cone snails have now added another use for insulin in the natural world.

In January of this year, researchers published a study characterizing two species of cone snails that possess the first and only recorded case of weaponized insulin in the history of the planet.

That’s right. Weaponized insulin. Used as a predatory tactic, cone snails release insulin into the surrounding water when prey are nearby. It then passes through the gills of prey fish, enters the bloodstream, and drops the blood sugar enough to prevent the fish from having enough energy to flee the encounter,  all in a matter of seconds.

5) Oh dear God, there’s more?!

Conotoxins are so potent that there are serious efforts dedicated to determine whether they can be weaponized and used on mass numbers of victims by terrorists groups. In a paper published in the Journal of Bioterrorism and Biodefense, scientists outline the probability of a terrorist attack in the form of aerosolized conotoxins or contamination of food or water. Their verdict is surprisingly reassuring, citing the difficulty to extract most conotoxins from living animals and the difficulties synthesizing conotoxins in a usable and deliverable form. However, not all varieties of conotoxins face these same issues, and the risk of three broad biochemical classifications of conotoxins are candidates for bioterrorism should those few key technical hurdles be overcome.

THIS IS WHY I KEEP HAVING THESE NIGHTMARES. GAAAAAHHH, DON’T SWALLOW MY CAT!!! Source: AquariumAdvice.com and my darkest nightmares

6) Oh hey, a fact that’s not actually all that terrible.

Remember when I mentioned ConoServer, the online database that combines efforts of dozens of biochemists seeking to catalogue the vast variety of Conotoxins? Why spend the time to catalogue them if terrorists could simply learn to replicate these peptides in vitro?

Many of today’s most common and effective pain-killers carry powerful negative consequences. For example, the narcotic pain medications like the opioids hydrocodone (Vicodin), morphine, oxycodone (Percoset), and codeine are highly addictive and can leave patients with withdrawal symptoms after their course is complete. The hunt is on for a powerful non-habit forming pain killers with few side effects that can be cheap, easy to deliver, and easy to scale up.

Conotoxins may provide the solution. Much like snake venom, most research efforts on conotoxins are geared toward repurposing the toxins to serve as pain killers. Perhaps a single toxin or a cocktail of a few or several toxins could serve as potent yet non-costly painkillers, and collaborative research efforts like ConoServer could rapidly speed progress towards a revolution in patient care and pain management.

One promising conotoxin pain drug is ziconitide, a synthetic drug identical to a toxin produced by the cone snail Conus magus. Ziconitide has been FDA-approved for treating intractable pain and has shown some promise in its effectiveness. However, the drug degrades rapidly and cannot be delivered orally. Instead, ziconitide must be injected directly to the spinal cord via a surgically-implanted pump. Not terribly convenient if you ask me, but it seems to be a good start nonetheless.

Progress is being made to develop oral conotoxins-derived pain medications. In 2014, Dr. David Craik from the University of Queensland presented new evidence at the 2014 meeting of the American Chemical Society. Craik and colleagues looped peptide chains, amplifying their stability over the long-term while preserving their potency as analgesics. The prototype drug was given orally to test animals and showed nearly a 100-fold increase in effectiveness in comparison to the common painkillers morphine and gabapentin.

Overall, I find it pretty badass that such an effective killer lurks in the oceans. It delivers death in seconds to its prey and in minutes to a fully-grown human, and with no anti-venom, its effects are second to none. Hell, these guys even weaponized insulin. On top of that, they may gift humanity with a revolution in pain management. That’s pretty badass.

Want to suggest a future topic? Write it down in the comments below. Do it. Do it do it do it doitdoitdoitdotidoit.

For further reading:

http://www.conoserver.org/?page=about_conotoxins&bpage=keyrefs (list of current review papers on conotoxins as pain killers and the difficulties faced with their use)

http://www.theconesnail.com/ (lab website of the Olivera lab group at the University of Utah)

Don Cowlione: How Cowbirds Run A Songbird Mafia

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If I were to imprint on you one main point stringing together every article I’ve ever written for Badass Biology, I hope it would be this: nature has produced no shortage of jerks. I say “jerk” like it’s a bad thing, but take the time to think about the word and you’ll realize “jerk” becomes a bit endearing when we’re talking about nature.

First, let’s review what it means to be called a “jerk” species. First, a jerk has to be abundant enough to merit some sort of attention or recognition, but not more abundant than non-jerks, otherwise the jerk strategy would be much less effective. This population size balance is very delicate, but jerks seem to manage it well.  Second, being a jerk means going against some established natural norm. Usually, jerks exploit some mutually beneficial arrangement between individuals, leaving another party to carry their weight for them. It’s a pretty clever strategy if I say so myself. Third, present a jerk with an opportunity and it’s likely to get snagged. Another admirable trait in favor of biological jerks

Back to the point, Planet Earth has lots of jerks. Consider the bluestreak cleaner wrasse. On Southeast Asian reefs, cleaner wrasse set up cleaning stations where they pick off the tiny parasites that live in the skin of larger fish. This arrangement seems to work for everyone (except the parasites, unfortunately); the wrasse get dinner while the larger fish get a good skin treatment. Some jerk wrasses, let’s call them “wrasseholes”, like to instead bite big chunks out of the mucus membranes on these fish instead, turning this mutualistic interaction into a parasitic one.

To be honest, it’s not that I find this interaction all that neat. The main reason I bring this up is to mention that it DID spawn an article in Discover Magazine with a really clever name: Cheater Cheater Mucus Eater.

Sure, jerks are great and all. My favorite? This little guy:

Awwwwww. SO PRETTYYYYYYY.

Adorable, right? What about now?

The Birdfather

Why yes, I AM proud of this joke.

Make no mistake. This stone cold killa is ruthless, even enough so that I’d put the word “killa” in an article that I’m reasonably sure a future employer will read.

So what about this little bird makes it so much of a wrassehole? To start, an introduction. This is the brown-headed cowbird, a member of the family Icteridae, which consequently means nothing at all to me but sounds pretty badass all the same. What distinguishes cowbirds is that they are notorious brood parasites. They find nests belonging to other aviary families, mostly songbirds but varying from hummingbirds to birds of prey, lay their eggs next to theirs, and let those other poor bird parents feed, raise, protect, bathe, clothe, and attend PTA meetings of cowbird babies. As of 1999, approximately 140 species of birds have been documented raising cowbird young.

Here’s what’s odd about this. I’m sure you’ve guessed that cowbirds are able to get away with this sneaky business because their eggs and young look an awful lot like the birds they’re parasitizing. They don’t. More often than not, cowbird eggs are either much larger than the eggs of their host AND a different color and pattern. Moreover, cowbird chicks are gigantic when they hatch, making little songbird chicks look tiny by comparison.

One of these eggs is a parasitic cowbird’s. Can you guess which one? Did you guess the one on the bottom left? You did!? Very good!

You may be asking yourself, “why do these other birds raise babies that aren’t their own?” Right now, I’m asking myself, “have I smelled like this all day?”, but that’s really of no consequence to anyone (except my wife, I guess).

Oddly, one theory explaining why the hosts hadn’t murdered these little guys is, and I’m serious, that the host birds don’t have the cognitive ability to recognize that these chicks are different from the others. It seems odd to me that the same birds can relocate their nests among thousands of other similar-looking forest objects with near-identical colors and patterns would not be able to recognize that one of their babies is a freakish monster.

Meanwhile, I only learned today that I live 5 minutes from a major interstate highway, but I’m confident that there’s no gigantic monster baby living in my house. One of our cats is pretty large, sure, but I’m not convinced I’m her father or anything.

No, the real reason host don’t viciously murder cowbird young is pretty sinister. In 2007, two researchers from the University of Florida set up a field experiment where they manipulated cowbird presence in predator-free nests of host birds. In “ejector” nests, the researchers removed cowbird eggs from host nests, mimicking a host that rejected a cowbird egg,  whereas “acceptor” nests saw through the raising of a strange foreign cowbird hatchling. In all, 56% of ejector nests saw some the destruction of host bird eggs, but only 6% of acceptor nests were ruined. What happened?

Cowbirds happened. Females, actually. These jerks monitored the nests of their hosts, checking in on the progress of their young from time to time. If cowbirds found that their babies weren’t receiving the star treatment (or weren’t in the nest at all), the cowbirds would lay ruin to the eggs of the host bird. Essentially, these birds were exhibiting mafia behavior, laying down some pretty severe consequences if the host rejects the parasite.

What’s equally sinister is the explanation for destruction in the 6% of acceptor nests. Why kill the young of a nest that’s satisfactorily caring for your own young? Simple: murder creates room in the nest for more cowbirds.

In summation, I quite admire cowbirds. In a group of organisms whose ability to distinguish which egg is their own is questionable, these ladies are clever. It’s pretty rare to see such a sophisticated racket exist in animals with brains the size of beans. Think about the cognitive power cowbirds need to keep track of which nests are parasitized, then decide on whether to murder or not murder depending on what they see. I gotta say I’m impressed.

So, like a Don collecting tribute from his corner of Little Italy, cowbirds command respect. They’re clever, manipulative, aggressive, greedy, and all of it is so sinisterly bundled in a package that I’d rather enjoy petting.  Plus, it’s nice to know that some species out there gives others an offer they can’t refuse.

How palindromes allowed males to exist

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If I were asked to give my two most valuable pieces of advice, they would be these: First, appreciate the near impossibility that you are alive. The atoms that make you have been through some shit; they’ve swirled as stardust, formed a hot molten planet (or crashed into one from elsewhere), boiled, compressed, and decayed to a point where they were incorporated into who-knows-what part of a who-knows-what number of a who-knows-what kind of strange prehistoric organism before they now make you, sitting comfortably at your computer marveling at my repeated usage of “who-knows-what”s. The other piece of advice? Never try to drink a beer without using your hands.

Without getting abundantly philosophical, you by all means shouldn’t exist. I ask that you, at least once daily, come to terms with this fact. Appreciate also that you can come to terms with anything at all, you big-brained multi-talented sculpture of evolution. Appreciate that other humans exist that can love you and carry out services to make you more comfortable. Appreciate pizza, because how did the universe create something so perfect?

Oh, and if you’re male, go ahead and appreciate that you exist. You theoretically should not.

In evolutionary terms, males are dispensable. The adaptive value of males is that they can mix up genes to create new combinations of traits on the off-chance that some of them can help prevent an untimely death, aid in making little ones, or allow one to be more comfortable overall. Males are gene donors. That’s basically it. Yeah, some males aid in parental care or perform tasks to aid group survival, but male uselessness is a common evolutionary motif. Male anglerfish are prime examples.

Gender in humans (along with a lot of other species) is determined by the identities of a pair of sex chromosomes contained in every cell. Both males and females possess one X chromosome, a large and gene-packed chromosome chock full of genetic goodies. Females have a pair of X chromosomes, one from the mother and one from the father. Males, however, have only one X chromosome, donated by the mother, and a shrimpy and scrawny Y chromosome donated from the father. X chromosomes contain some 2000 known genes, Y contains only 78. Bummer.

There’s a good reason why the Y chromosome is so scrawny: DNA damage is pretty common. Being so long and fragile, DNA can become knotted, coiled, unwrapped, kinked, looped, mutated, irradiated, copied wrong, fixed wrong, proofread wrong, chopped, sliced, chunked, choked, broken, inverted, doubled, misread, and misunderstood. Each of your cells possesses a SWAT team of enzymes that try to prevent these things from happening, but they’re not without error. Mistakes happen. So, because our cells possess 2 copies of each chromosome, when one becomes overly mangled, these enzymes can use the other as a template of instructions to repair the damage.

X chromosomes do this beautifully. These, in short, scan each X chromosome and check for inconsistencies, using one or the other to clear up any mismatches in DNA code. Two similar chromosomal regions can also “cross over”, exchanging segments of DNA that encode for roughly the same type of protein. Most of the time, crossing over is beneficial because it throws some genetic variety into the mix.

Crossing over is like holding hands, only after you’re done, your hands trade bodies. Good old nightmare fuel.

X and Y were once paired just as healthily as two X chromosomes are today: both were large, bountiful chromosomes that crossed over frequently and used each other as repair templates. About 300 million years ago, as reptiles and mammals diverged, a mutation caused the Y chromosome to take on more “manly” attributes, including the development of testes, sperm, different hormone production, etc. X and Y were now very different chromosomes. Crossing over ceased between them. Cellular machinery stopped using one to proofread the other. They became distinct and wary of the other. The X chromosome still had a healthy pair in females and could easily use one to keep the other functional, preserving the integrity of the chromosome.

Unfortunately, Y became a genetic desert island, left all by its lonesome with nothing to use as a spell checker in case things went very wrong with its code.

By this logic, many scientists think the Y chromosome should have been obliterated. With more and more DNA mutations accumulating, more and more of the chromosome was snipped away and discarded. To make matters worse, portions of the chromosome inverted themselves. Areas swapped information, mixing things up further. The Y chromosome was rapidly becoming giant mess. Eventually, removing all these errors caused Y to become tiny, almost biting the dust altogether and doing away with males entirely! But it’s still kicking even after 300 million years. With no partner to help proofread its DNA, how did the Y chromosome survive?

DNA and language share many things in common. Almost too many. One of them is that segments of information, called palindromes, can be read from left to right or right to left and read the same way: God, a red nugget, a fat egg under a dog! DNA contains palindromes too, and they can be long, sometimes hundreds of bases in length. The problem with DNA palindromes is that they are a liability; because bases like to chemically pair up with their counterparts, segments of independent DNA can stick together to form looped hairpins, derailing the important cellular machinery necessary for replicating, proofreading, and transcribing DNA into proteins.

Palindromes on two strands of DNA can join to form hairpin regions. These are bad. Imagine a train barreling down track shaped this way and you get the picture.

The Y chromosome in particular is full of palindromes. Normally, high palindrome density is a chromosomal death sentence. However, in the case of the Y chromosome, palindromes were a blessing. Because the Y chromosome had so much repeat information and no paired chromosome to proofread it, Y could use different segments of ITSELF to validate that the information on another segment was correct. Y chromosome palindromes kink together and use one strand to proofread the other, turning large segments of the chromosome into genetic hairpins. Because both are palindromes, one segment should read exactly the same as its folded-over counterpart. So, in a sense, the Y chromosome uses what’s normally a huge flaw as its primary means of keeping information correct.

As an added bonus, this method of palindrome proofreading can create new varieties in the DNA code akin to crossing over in X chromosomes. When one strand is damaged, the enzymes responsible for repairing it can’t distinguish the damaged strand from the undamaged one. All it can do is discriminate one from the other. Therefore, it has to guess which of the two sides needs fixing. Often, this can cause the undamaged segments of DNA to take on the information of the damaged counterpart, creating new combinations of DNA code to form. While this could possibly ruin the genetic meaning of the original, it also presents an opportunity for new traits to become expressed on the ever-changing Y chromosome.

Self-repairing Y chromosome palindromes at work. This is something I’ll surely bring up at the table come Thanksgiving.

I cannot over-emphasize how important palindromes are to the sustainability of the Y chromosome. Without this ingenious little method, human history would have played out very differently. So, while palindromes can be a fun way to parody a Bob Dylan tune, be thankful that they also keep you healthy and keep your identity in check. Add that to your list of things to appreciate.

A special thanks to Sam Kean, whose book “The Violinist’s Thumb” encouraged me to write this article. It’s a fantastic read, I highly suggest it.

For more information:
http://phylogenous.wordpress.com/2010/10/01/y-chromosome-vii-why-palindromes/

http://www.hindawi.com/journals/ijeb/2012/207958/

 

Alpine swifts’ 200-day non stop flight

Original photo credit: D. Occiato- http://www.pbase.com/dophoto

You know how damn exhausting it must be to fly? I don’t. Having never had the ability to fly without propulsion, I can’t say just exactly how hard it must be. Studying the metabolism of flying birds gives us some idea, and current evidence suggests flying is really really f**king hard.

A lot of people compare flying to swimming, which I think is a bit of a BS comparison. Water is a much more dense and heavy medium than air. Sure, it’s harder to move through water than it is to move through air, but long-distance travel through the oceans has the advantage of buoyancy to counteract the effects of gravity. Without having to spend energy from falling to the ocean bottom, all effort can be spent moving forward.

In contrast, flying truly is falling with style. Most of the forward energy generated from flight occurs because of gravity, or the downward force of the wing generating movement in the forward direction. Thus, flying animals are tasked with the mind-numbingly complex task of controlling their descent and forward travel, modifying body position as air currents change, all in an attempt to keep oneself from crashing into the ground in a puddle of crushing sadness.

Basically, it’s generally agreed that moving flying is more energetically demanding than swimming or walking. Migratory birds that choose to embark on long-distance flights typically rest for a while throughout the journey. Even the largest sea-faring gliders have to rest every few days to recover from their grueling haul.

Unless you’re the alpine swift. These aviary ass-kickers don’t stop for jack shit.

“But don’t birds have to land on the ground to eat, rest, or sleep?”. F**king nope, not the Alpine swift.

These birds are built for ass-kickery. They have a body design that’s conducive for long-distance travel, mixing flapping and gliding to travel long distances using little energy. And their yearly migration is a long one, beginning in the mountains of Western Europe across the Mediterranean and Sahara to their wintering sites in the African interior and back, a journey spanning some 2500 miles round-trip.

Migration routes and non-breeding range of three Alpine swifts breeding in Switzerland.

Migratory behavior of the three birds assessed in the study published by Leichti et al. Each bird is a different color, and the arrows represent periods of non-stop flight (Figure 1 in Leichti et al 2013, link below).

There have been rumors for decades that some swifts never land for any reason, which honestly sounds ridiculous and stupid. So, to resolve the stupidity, a group of Swiss researchers placed sensors on six Alpine swifts, seeking outline their migration from the Swiss Alps to western Africa for the winter. What they found, described in a paper published in the October 2013 issue of the journal Nature Communcations, ended up being so mind-blowingly balls out that I myself can hardly believe they didn’t just make it the f**k up.

The transmitters they used collected only two parameters: light level to extrapolate position, and acceleration to determine other metrics like pitch (a measure of body position, indicating whether the animal was in flight and where it was traveling), flapping rate, metabolic activity, and a few others. They were also able to tell when and where birds were breeding, wintering, or migrating based on how the birds behaved and where they were located.

This is the tiny transmitter used by the authors to collect data over an entire year. Science! Source: https://www.sciencenews.org/sites/default/files/images/js_tiny-data-logger_free.jpg

Based on the distinct difference in activity between roosting and migrating metabolic activity and pitch, the researchers observed that the three birds they recaptured in Switzerland the following year had been on the wing for at least 200 days. Every bit of food they ate over the trip was snagged in the air during migration. And sleep? Well, the authors aren’t really sure whether swifts feel the harmful effects of sleep deprivation:

“In Alpine swifts there seems to be no necessity for physical inactivity to maintain any of the relevant physiological processes. However, our data indicate that there are distinct periods of increased and decreased activity, which could go along with some kind of sleep in flight.”

Such periods of decreased activity suggest swifts spend several nighttime hours gliding to conserve energy or perform other physiological functions. The researchers’ data backs this up too; swifts were most active and had highest flapping rates near sunrise and sunset, probably because they need to ascent to great heights to avoid gliding into the ground overnight, and probably had to work to recover this altitude at sunrise. How do they control their flight if they’re asleep? Nobody really knows, but they may only sleep one brain hemisphere at a time.

So, despite hours of grueling physical activity, swifts seem to recover without having to land on the ground or water. They travel huge distances over impossibly barren terrain, hauling ass with more long-term gusto than any land creature ever documented. They’re masters of endurance and champions of travel with a purpose.  Also, never challenge one to a “lets’s see who can fly the longest” contest. Literally every other organism on the planet will lose.

Want to suggest a topic? Write it  in the comments below!

Further reading:
https://www.sciencenews.org/article/alpine-swifts-fly-nonstop-more-six-months

http://www.livescience.com/40268-alpine-swifts-fly-nonstop.html

 

 

 

 

 

 

Humanity’s Most Badass Adaptation II: Sucks to be small

Why Ant-man is the worst superhero ever.
What if we were much smaller? Well, there’s good and bad news. The good news is that we could adopt simpler body forms, but that’s about it. The bad news? Pfft.

First. we would probably be much dumber than we are. Zoom in closely on the brain of every animal and you’ll find neurons, cells that communicate to one another using electrical or chemical signals. Hundreds to thousands of these neurons form dense and complicated circuits with one another in the vertebrate brain. Such circuits form pathways that tend to perform specific functions in the body. For instance, there are specific regions of the brain designated for movement, for regulating sleep, for hunger, for balance, for typing “guns and missiles”, and for interpreting the sights, sounds, and smells from the world. Our bodies may be able to shrink in size and still function to some degree, but our neurons cannot only be miniaturized and still function with such complex synchrony and elegance. As we grow significantly smaller, we run out of room for neurons very rapidly.

“But Kevin, I’ve always heard that a big head doesn’t mean make you smarter”. Don’t you sass me. But you are right, anonymous naysayer. There is admittedly weak evidence that intelligence correlates with head volume, yes, but that’s among humans of relatively the same size [3]. For example, my fiancée is tiny and adorable, though she’s likely smarter than I am (Fiancée et al, 2014). However, when we’re talking about a difference in scale between us and a mouse, size matters. We have nearly half the number of neurons as the U.S. military has guns and missiles, something around 86 billion neurons [5]. Mice have around 10 million. Ants have around 200,000. To put this into perspective, if each neuron were a person, our brains would outnumber earth’s human population 12 times over. A mouse’s would be constrained to the size of North Carolina. An ant’s would be Laredo, Texas. It’s hard to grow intellectually when you’re Laredo, Texas.

I apologize to anyone from or living in the city limits of Laredo. I did not mean to say your city is dumb. However, it certainly looks that way. I’ve visited your website. It looks terrible.

Come to Laredo and visit our…moon.

Being the size of an insect would present a number of other challenges. The interactions we have with things in our environment (like the water we drink and the food we eat) conform to the laws of physics. As we shrink in scale, these interactions change. To an ant, water seems as viscous as maple syrup. Gravity takes a backseat to air turbulence. As Steven Jay Gould writes, “An ant-sized man might don some clothing, but surface adhesion would preclude its removal. The lower limit of drop size would make showering impossible; each drop would hit with the force of a large boulder. If our homunculus managed to get wet and tried to dry off with a towel, he would be stuck to it for life. He could pour no liquid, light no fire…” [2].

Could an ant-sized version of early man have developed civilization even if intelligence were not a factor? Probably not, at least not at the same rate or with the same level of success. I imagine cultivating agricultural crops, one of the supposed precursors for civilization, would have been near impossible, not to mention cross-breeding them for good yield. Our meat-based diet would be replaced with who knows what, but I suppose it would include plant material and any nearby organism that decides to die. For that matter, hunting would be folly; spears and bows would be completely ineffective because we probably couldn’t put enough force behind the blow. Guns and missiles wouldn’t exist. Our predators would vastly rise in number, distancing us from the top of the food web. We’d be stomped into submission by the elements, by other creatures, and by our own ineffectiveness. Switzerland would be near impossible to get to. So long, Mürren.

What about food? Shouldn’t food be more abundant since, you know, one kernel of corn could feed an entire village of people? That’s true, but there’s a much bigger caveat to this than you’d think. The world’s food is spatially patchy. I don’t just mean that bananas only grow in the tropics or that rice grows best in silty soil. I mean that, when you’re the size of an ant, getting a bug from the ground nearby is a marathon. Food sources are really f**king far apart, but plentiful once they’re found. Many animals that live upon such food sources adopt life strategies to cope with smorgasbord-style resources. Some insects that exploit huge but infrequent foods, including flies like the gall midge, have adaptations that allow them to exploit them quickly. Gall midges typically reproduce sexually, though it takes a long time for larvae to develop this way. When midges find a mushroom, a gold mine on their scale, females reproduce without a male through a process called parthenogenesis. These offspring are formed more quickly than doing things via the sexual route, though it comes at a cost to the mother. Instead of developing externally, the larvae grow inside the mother, eventually liquefying her insides and bursting from her lifeless husk [4]. However, immature as they may be, they are ready to start chomping away on some sweet sweet mushroom bits and rotting parts of their mommah. D’awww. Overall, the flies have more successful babies this way, thus the need for bursting out of their moms and such.

Will humans do that? I dunno. That sounds desperate. But food would likely be lacking for most humans on earth. Maybe we’d be as successful as ants and develop complex chemical signals to communicate the locations of food, bypassing any other weird adaptations like the ones midges have . Maybe we wouldn’t, and we’d fill just another tiny niche in the complex world which we inhabit.

So, I hope you now understand how important our size is for our survival. We are big and scary creatures, and that’s allowed us to hunt and kill and eat meats and make pizzas and build guns and missiles. But we’re not so large that joint damage, eating entire herds of cattle per day, and toppling over and breaking bones would be a daily norm. We’re also not so small either that we can’t take showers or cultivate food. So, here we stand, results of the goal-less, powerful, yet delicate hands of natural selection. Just right.

Nobody comments on my stuff. You should comment on my stuff. Get your friends to comment on my stuff. I will then comment. We can all comment. It will be a great world full of comments.

WE HAVE GUN AND MISSILE CONFERENCES!!! HUMANITY, BITCHES!!!

 

Literature Sources:

[1] http://en.wikipedia.org/wiki/Kleiber’s_law

[2] “Ever Since Darwin” by Steven Jay Gould, Norton & Co. 1977

[3] http://science.howstuffworks.com/life/inside-the-mind/human-brain/brain-size2.htm

[4]http://www.sjgarchive.org/library/text/ontogeny/p0306.htm

[5] http://journal.frontiersin.org/Journal/10.3389/neuro.09.031.2009/full#B24

Humanity’s most badass adaptation, pt I: Bigger is Better

Picture2

At some point, modern humans started believing that we are somehow special, that we are the center of creation and of the universe and that God loves us most. My point isn’t to argue against such divine egocentricity; we are indeed very special. Hell, no other species has made guns and missiles and stuff. And we are special even from a biological perspective. The reason we’ve done so well as a species is because we have adaptations that have allowed us to do so. So what are they?

We have many. Vertical skeletal structure, opposable thumbs, massive frontal cortexes, and unlimited salad and breadsticks are all commonly cited as being necessary for our species to thrive and dominate. These are all important morphologies. I believe, however, that there is one very overlooked adaptation in our evolution, one thing that, if it weren’t just right, would negate all of the benefits from these other lesser adaptations. So if it’s not our massive brain or our dexterous hands, what is it? Turns out it’s guns and missiles.

Guns and missiles have allowed humanity to reach far beyond our former niche. We now own the planet with such unchecked power that one person can say “I want to blow up that bit of the surface right there”, and his buddy thousands of miles away can instantly reply, “done!”. This adaptation has caused an evolutionary cascade of intermittent……………..ok, I can’t keep this up. I’m full of it. Our most important adaptation is actually our size.

I guarantee that human size was not the first adaptation that would have popped into your brain, but it is arguably the most important. Am I suggesting that all animals our size are evolutionarily successful? Of course not. Am I saying that tiny or huge people are somehow inferior biologically? Nope. However, if we were, on average, significantly larger or smaller, like ten times as large or small, the course of earth’s history probably would have played out very differently.

Much like the famous fairytale porridge, we benefit from being “just right”. Being the right size means there’s space for a brain that prioritizes and categorizes and tells the body to act judiciously. We stand vertically because we’re small enough not to battle gravity as ferociously as we would if we were the size of elephants. We can offer unlimited salad and breadsticks because we’re large enough to farm yet small enough to be incapable of eating the planet’s supply of breadsticks in one sitting. In this article of Badass Biology, I hope to convince you that our dominance stems from our ideal size. Had we been much larger or smaller, the evolution of our intelligence would have played out much differently, meaning no guns and missiles.

Bigger is better, unless you’re Godzilla
What does size have to do with anything? As animals grow larger in size, they tend to become more metabolically efficient. A cornerstone of evolutionary theory lies in Kleiber’s “3/4ths power rule”, stating that for every added unit of mass, metabolic rate only increases as a rate of mass^(3/4) [1]. While the value of the exponent and its real-world meaning is debated, one thing is clear: grow larger, and you’ll use less energy for your size, a comment you also hear regularly from your disappointed girlfriend.

Humans are damn gigantic; 99% of all animal species on earth are smaller than we are [2]. Does the power rule work to our advantage? Yep. Because math. The average human male (7700g) weighs roughly 457 times that of a typical field mouse (15g). Raise both to the ¾ power, divide one by the other, and you’ll find that the human has only about 100 times the metabolic demand of a field mouse despite the 457 fold increase in mass. I’d say that gives us a pretty big advantage in terms of having to spend less time and energy feeding, replacing tissues, respiring, etc. More time for guns!

ENDOTHERMS!! WOOOOO!!!

This sounds great, but if bigger is better, why isn’t every animal huge? Again, because math. Think back to high school geometry. Among the suppressed memories of sitting behind that brunette you thought was cute but wouldn’t pay attention to you unless you were captain of a team sport but that you later reconciled with because she ended up being a relatively heartless and shallow person despite her extreme self-professed piety, or that guy across the room you thought was an asshole to other people because he had a giant triangular face and douchey long blonde hair and a name not unlike “Brittney” until he confirmed his assholiness by being an asshole directly to you about something that absolutely did not matter at all, surely you must remember the formulas for surface area and volume. Basically, a shape that grows larger and keeps its form expands its volume in three dimensions (side x side x side), whereas surface area expands only into two (side x side). Big objects, like animals or guns or missiles, have relatively low surface area compared to their volume because volume mathematically outpaces surface area as objects grow bigger.

This is a really big deal. Think about every process that keeps you alive. Breathing, eating, sensing your environment, playing Civilization 5. All of these processes rely on tissues with some kind of exposure to the outside environment. Oxygen is absorbed as air rushes across alveoli in the lungs. Nutrients are absorbed through countless tiny folds of the small intestine. Tastants and odorants absorb through fluid media in the mouth or nose to trigger sensory receptors. Civilization 5 enters your brain through tiny refractive holes in the middle of your face. These are all parts of your surface area.

The point is this: if we were a lot bigger, like Godzilla-sized, we’d have a lot of trouble performing these same basic functions given our current body shape. This would suck for the most part. We’re already pretty specialized as is; a lot of animals don’t have folds in the lungs or intestines like we do because they’re small enough (thus having enough surface area for their volume) not to need them. But not absorbing things would be only one of our many worries if we were larger.

The earth’s gravity is not all that strong in a cosmic sense, but its impact on surface-dwelling body forms is huge. Let me put it simply: stuff caint grow too big because aint no way they caint get strong enough to stand up. Fighting gravity is hard unless you’re a gun or missile, especially when you’re giantic. Our skeletons would have to be quite different in order to support our huge stature. Bones would need to be thicker yet more pliable.To be Godzilla-sized would be risky, not only because of the inevitable bone weakness and joint decay, but because of imbalance and falling. Even at twice our current size, tripping over a gun or missile would cause a tumble with 16 to 32 times more kinetic energy than it would now.
This all sounds like a recipe for disaster.

Suppose that our bodies do adjust. We grow to Godzilla size, have super-efficient perforated lungs, guts that absorb enough to get by, and bones capable of supporting a small skyscraper that can walk and build guns and missiles.  Imagine the caloric demand a body like that would require. How many hamburgers would we need to eat in a day?

Godzilla is, at lowest estimates over his career, 164 feet tall, or about 50m. A quick foray into ideal body weight calculations yields that a 25-year old male this height should weigh around 8106.8 pounds, or 3676ish kg. Plug that into the ¾ power formula, and the daily metabolic demand of our gargantuan is around 84,000 calories per day. The power rule certainly works into this huge person’s favor, because I certainly was disappointed by how low that caloric count was. So what does 84,000 calories look like? Imagine 81 quarter pound hamburgers with white wheat buns, ketchup, and a tomato slice. And that’s only just breakfast; imagine eating that three times per day. BIG PEOPLE PROBLEMS. I’m sure I’ve made my point. The earth would strain to support life of that magnitude. Here’s the kicker: I didn’t even account for added bone mass and musculature necessary to become that tall. Let’s add another 100,000 hamburgers per meal to the calculation just to be safe.

The worst part of being tall would be this: it would be really hard to fit as many people onto airplanes. The airline industry wouldn’t see as much profit from airfares, thus flying would be a privilege only for the super-rich, limiting my ability to go to places like Switzerland. And I really want to go to Switzerland.

I am convinced that Mürren is one of the most beautiful places ever. I encourage my rich philanthropist readers to take note. Did I mention how starving I am?