Axolotl

Weird how cultural perceptions change over time. When I was a kid, axolotls were really freaky looking, almost science fiction, even scary, like aliens. As bizarre looking a creature as you could find in earth. Even the name, a Nahuatl word (they are found in lakes around Mexico City), meant water monster. A little foot long water monster, pink (a relatively rare color in the wild, they are typically brownish) and exotic and weird, especially with those bizarre juvenile gills retained in adulthood. Now in this adorable educational video, fifty years later, they are seen as positively cute. They look cute to me even. How can anyone not love that anthropomorphized smile? Ripley (distinctly not a Nahuatl word for water monster) seems to have a personality, like an anime character (though in Japan, where giant salamanders are five feet long and without the neotenic gills, salamanders are more unnerving than cute and even show up in a Godzilla movie). Somewhere over this past half century there’s been a fundamental shift in what is freakish and what is cute, a shift that even changed my own perceptions. Who knows how this works. Collective thinking. We have barely scratched the surface of the surface of the surface in understanding our brains, and not gotten anywhere at all in figuring how all our brains work together. We stumble through existence with this unparalleled device in our heads, clueless, almost, as to what it is making us think and see and do and remember.

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I’m not sure when exactly the zebra danios turned into killers.

Our zebra danios have gotten scary. Where once they’d dash about madly at the top of the tank waiting for the flakes of food, now they wake slowly from sleep, huddled together, then in a three fish column begin moving slowly (not their usual frantic dash) into the plants, moving around them, seeking meat. The flakes of fish food float down all around them but they pay no attention. They keep prowling, methodically, maybe an inch or two from the bottom of the tank. I’ve come to suspect that this was how they killed the other fish, by catching them before they were completely awake there amid the plants. I can only imagine that all three would rush in, striking, chomping, killing. In the wild they eat insects and crustaceans and worms, so they are hunters, yet in the thirty some years we’ve been stocking our aquariums with them I have never witnessed them do anything more than grab flakes of fish food drifting by. I have certainly never seen this sort of apparently coordinated behavior. It seems that almost every vertebrate has within it the predatory behavior. We are all hunters. Hell, it was predation that drove evolution itself, the whole Cambrian Explosion with all its crazy speciation was the result of the ever evolving contest between predator and prey. And here, somehow, in our little aquarium, something turned these little inch and half long fish from eaters of fish food to eaters of fish, eaters of even their own kind (as there were five of them just two weeks ago). All was peaceful until the clown loach died. That loach, though never deliberately bothering any of the other fish, was at seven inches long to them like a whale shark is to us. It ruled the floor, digging up snails. The danios stayed up several inches in the tank, away from its sudden movements. But then the loach, one day two or three weeks ago, was dead. Old age. I noticed the next morning that the danios were down zipping around at the bottom of the tank. The neon tetras calmly minded their own business, the two glass catfish scooted about. Everyone, danios included, got very excited at feeding time, like they always did. Everyone swam around excitedly, grabbing bits of tetra min flakes floating by.

I’m not sure when exactly the danios turned into killers. Within two weeks I realized that all the fish were gone but these three zebra danios. Alone in the tank, they chased each other madly about, zipping one way, then another. I was mystified. Where had all the other fish gone? I did some research, and found desperate pleas on aquarium websites. “Help, my zebra danios are eating each other!!!!” or “My zebra danios are killing my other fish!!!” I read in shock just how murderous the little beasts can be. No one seemed to know why, but there was usually a dominant fish that sets it off. A handy bit of evolution, that, where some members of the species will suddenly go rogue, turn alpha, and eat everything piscene in sight. Obviously there is a genetic advantage in there somehow. Perhaps a surge in zebra danio testosterone. But I have no idea. Looking at the tank again, one of the danios is swimming like a lunatic now, frenzied. The other two have ducked behind the leaves. Perhaps there is murder afoot.

zebra-danio2

It doesn’t look like a killer.

A shark goes for a walk

Nice bit of convergent evolution on display here when you compare this shark with the fish that evolved into all us four-limbed landlubbing tetrapods. Our own fish ancestors, though, were lobed finned with bone skeletons (like coelacanths, or an even better example, lungfish). Mudskippers, a walking ray-finned fish, are another bony fish though unlike either early tetrapods or this epaulette shark, it uses only its pectoral fins and not the pectoral and pelvic fins. Mudskippers pull themselves around by their front limbs. Tetrapods and epaulette sharks walk. Or proto-walk. They use all four limbs. Watching this little epaulette shark is eerily like watching a monitor lizard. It’s hard to think of anything strictly terrestrial that moves like a mudskipper. Yet it is conjectured that most early tetrapods like Tiktaalik lived much like mudskippers, and not much like this epaulette shark. Go further back a few million years into tetrapod evolutionary history and you can find lobed fish, such as Panderichthys, that probably lived lives much like our walking shark. Unlike mudskippers and we tetrapods, however, sharks are famously boneless. They leave lousy fossils, mostly teeth. Some really terrifying teeth, too. Megalodon has left its thirteen inch incisors scattered in fossil beds world wide.

But this shark here is maybe three feet long and quite harmless, and I watch and rewatch him perambulating across the Coral Sea floor cartilaginously, a nifty trick, but severely limiting if one is thinking about evolving into a land animal. Without the buoyancy of water, one needs the support of a bony skeleton. Gravity is a bitch. But one also needs a bony skeleton to evolve fins into limbs that all of us tetrapods use for legs, arms, feet, hands, fingers, toes, and wings (and sometimes back into fins). The jointedness of bones seems to open up a wide range of mutation possibilities–and evolution is all about mutations–that cartilage just does not seem to have. Sharks and us have been on dramatically divergent evolutionary paths since we last shared a common ancestor well over four hundred million years ago. And shark evolution, though impressive enough in its sleekness, is vastly less varied than that of those of us who spring from the homelier lobed finned fishes (and less varied than the bony ray-finned fishes, which make up well over 99% of all fish species but never left the water). Aside from our perambulating friend here, all sharks (and their cousins, the rays) swim, while nearly all of the tetrapods (i.e., four limbed creatures who live on land) walk. But the same mutational capacity that enabled the first tetrapods’ pectoral and pelvic fins to evolve into a dizzying variety of limbs continues to enable tetrapods to evolve amazing adaptations with their limbs. Vertebrate flight has evolved three times (pterosaurs, birds, bats) while frogs and kangaroos hop and snakes and legless lizards slither limblessly. There are lizards and a number of mammals who glide. Pangolins go totally post-tetrapodal and curl up into an armored ball and hurl themselves down hillsides (the sort of thing that does not show up in cladistics.) A few tetrapods have even gone back to the ocean for good to swim again, the front limbs evolving again to pectoral fins, the backs legs disappearing entirely, as if four hundred million years of terrestrial evolution had all been some terrible mistake.

Yet the simple advantages of walking along rather than swimming over a shallow sea bottom (watch the video at about 25 seconds when the shark stops to peer into a cavity, looking or smelling for possible prey) apparently led this shark along a trail of mutation that eventually allows the thing to walk with ease. And it is extremely unusual for a shark. The range of design among sharks and rays is very minimal. Very few sharks don’t look very similar to other sharks. Rays look like rays. A Greenland shark is notorious for being so old and creepy and strange looking. But it looks very similar to almost all other sharks. An aquarium with nothing but sharks would be a pretty dull looking aquarium. They look a lot alike, they act a lot alike. Then we see a video of a epaulette shark walking along the ocean floor like it’s the most natural thing in the world.

A prowler of tidal zones, an epaulette shark can survive for hours in extremely low oxygen pools. It cannot breathe air, though, as mudskippers and lungfish do and our own water’s edge ancestors once did. Rather this shark has evolved a way to reduce blood flow in critical periods to all but the brain and heart. Handy, but a no go as a terrestrial adaptation. One needs to breathe air to make it on land. So this remarkable shark is no more like us than we are like it. It’s a marine animal who sometimes can stay on the edge of land for a couple hours, just as we are terrestrial animals who sometimes can swim with the fish for short periods.

But it was the combination of using fins to lift and carry across surfaces (i.e., walking) where swimming was difficult or impossible, with getting oxygen from the air via lungs (i.e., breathing) instead of taking oxygen from the water via gills, that made vertebrate land animals possible. (Insects were already there–doubtless tetrapods were eating them–but they had evolved from marine invertebrates, and our last common ancestor was somewhere deep in the Pre-Cambrian). There are over 30,000 species of tetrapods today–7,500 amphibian, 10,000 reptile, 10,000 bird and over 5,500 mammal species–and all remarkably seem to have come from one species of lobed finned fish that managed to combine both fin walking and air breathing, and had an unusual capacity for mutation in pectoral and pelvic fins. There was a wide range of these mutated fins at first–as many as eight digits on each fin–before the final five toes/fingers was arrived at. (Perhaps the occasional six toed kitten or baby are a mutational echo of that.) There seem to have been many species that could do so and apparently the lush and swampy Devonian shore line was rich enough in food and varied enough in niches a half billion years ago to allow evolution to run riot. But apparently only one of those species led to all the four footed or two footed and two armed or winged creatures breathing air today, including us. And while this beautiful little epaulette shark has nothing to do with any of our own evolution since the Devonian, as it is only very distantly related to any of us tetrapods, watching it trundle across the ocean floor does give a brief glimpse of what our own origins looked like nearly half a billion years ago.

Cats–a forgotten draft

(an early draft of Cats, 2012)

Mockingbirds are strafing one of the neighborhood cats. A whole little mockingbird community, who spend all night and days shrieking at each other (at 3 a.m. it was a battle of car alarms) have banded together to dive on the hapless cat, who is frantically looking for cover. The birds are all fired up, having just driven off a pair of nest robbing ravens. So much violence.

I find it hard to feel sorry for Fluffy. Fluffy (not his real name) is a friendly cat, yes. Cute even, on occasion. None of the people around here have any issues with him. But mockingbirds have damn good reasons for taunting him. Cats love stalking and pouncing birds. People deny that their cat does — kitty would never kill a bird — but pet cats let outdoors have wiped out a lot of urban bird populations. They can’t help it. It’s what they do, cats. They’re hunters. And so are coyotes, and all those pet cats people let outdoors provide a steady diet for coyotes. I suspect we wouldn’t even have populations of urban coyotes if it weren’t for all the house cats people let outdoors. The more cats people have, the more cats there are outside, the more coyotes can survive living among people. You could probably graph the rise in the popularity of cats as pets with the increase in the urban coyote population. You could, but you’d have a hard time getting laid afterward.

We used to have a local population of feral cats. Some big mean toms. They’d fight all night, those eerie, annoying cries of their’s waking everybody up just in time for the burst of intense violence that followed. Sometimes you’d hear cat bodies being thrown against the side of the house with some serious force. Amazing how much energy a cat can expend in a fight. Not for very long. Cats are anatomically sprinters, not long distance runners, like dogs. All their energy has to be in astonishing bursts, since the oxygen in a cat’s blood is quickly depleted. Hence their contests are more build up than action, and size almost always wins. So the biggest, meanest cats ruled our neighborhood. Nearly all of them were feral. The pet cats would skitter home beat up and bleeding. It was getting to be a problem. Cats making a helluva racket all night. People yelling at the cats. No one getting much sleep.

Then a pack of coyotes moved into the neighborhood. End of problem. The endless war cries of cats were replaced by the occasional high pitched yelps of excited coyotes. You’d hear them running down the street on the hunt. It’s weird, a quiet neighborhood and the yelping of wild canines. Like all this civilization wasn’t even here. Like it has been stripped away for a moment and you could hear what it was once like. It’s so spooky it’s thrilling.

The coyotes ate all the stray cats. And they ate a lot of pet cats, foolishly let out by their owners. They ate a lot of little dogs, too, right in their back yards. Sad little flyers appeared on telephone poles. Rewards were offered. There’s one right outside now. I can see it from my window. The little dog is just darling. The reward is one thousand dollars. There’s a lot of money in Silver Lake.

I like cats. And I dig coyotes. And birds. Ours are indoor cats only, so off the menu, and birds are off theirs. They watch the birds from the window. My wife feeds birds. Sparrows, finches, a couple kinds of doves. Every once in a while a scrub jay drops in and scares off all the other birds. Not as often as before, though. It’s been a while since I’ve seen a lesser goldfinch, a hooded oriole, or a towhee. A long time. There were more bird species in Silver Lake when we moved here in the 80’s. Especially here near the river. The explosion in the pet cat population coincided with the disappearance of several species. Birds like the towhee which spend a lot of their time on the ground were just too easy for cats. There are far more cats now than there were twenty years ago. Everyone has a cat or three. Crazy cat ladies don’t seem so crazy anymore, merely eccentric. People leave food out everyday to feed the strays to feed the coyotes. Funny how coyotes might increase the bird population. I used to think they might. Haven’t noticed it, though. [I do now, in 2016. Even the towhees are back.] For every cat eaten there must be two more cats being brought into people’s homes. People are just mad about cats.

There are several theories about just why. The weirdest one is that cats have passed on a parasite that has altered our behavior and makes us pay lavish attention to our pet cats. Parasites can do that, nature is full of examples. The theory got lots of attention, a big story in The Atlantic, and the scientist behind it was all over television. The science is a little sketchy, though. Let’s just leave it now and agree that people are nuts about cats. And cats are nuts about killing birds.

Cats are natural killing machines, remarkable animals, though we don’t really notice. The design hasn’t changed much since it’s inception around 30 million years ago. That cat, the proailurus,or dawn cat, looks remarkably like your cat.

Proailurus

It was even about the size of your cat. Amazing how little things have changed in thirty million years. The head seems a bit larger now, which might be to make room for a larger brain. The proailurus’ jaws seem extended a bit, too, more dog-like, and the evolutionary transition to a modern cat jaw probably accounts for the larger head of the modern cat. The one pictured above has decidedly more weasel like proportions…or more kitten like. The tail of today’s house cat is maybe two thirds as long. Perhaps because modern cats use their tails to communicate and a longer tail could not be held straight up as easily. A tail straight up implies fear, for instance, and held aloft with the top few inches at a 90 degree angle shows friendliness. That larger jaw of modern cats also helps with communication, I’d guess. Small sounds resonate more inside a larger mouth, vastly increasing the cats vocabulary. House cats have an extraordinary range of sounds they make to each other. Some they make to us. Some they make for each other. They’ll call to each other and you’ll try to get their attention and they completely ignore you. Some kind of intense cat to cat thing going on, and we’re not supposed to know, like when two people break into a language you don’t know with you standing right there. When they want to talk to you they’ll let you know.

Felines have been compared to sharks as being perfect predators. Perfect hunting machines. And like sharks, once the initial design was laid out there wasn’t much alteration needed afterward. Of course sharks go back over 400 million years, but evolution in the open ocean, where conditions change very little over enormous stretches of time, can proceed much slower than on land. Things on solid ground are much more volatile. Species are under constant pressure to change or go extinct. Think of how humans have altered in just a few million years. Indeed, look at how much size variation there is even with our own species (writes the six foot five inch man). Not cats, though. All the small cats, from the cute, vicious little sand cat to the largest of the small cats, the cougar (which purrs just like the domestic short hair in your lap) come from proailurus, and all look very similar. Today’s big cats–lions, tigers, panthers, leopards, cheetahs–all descend from pseudaelurus, which itself descended from proailurus.  Weird to think about, he says, a housecat staring at him as he types.

The action outside my window has abated, for now. The mockingbirds are back up on their branches, quiet, looking for threats. Fluffy is up on the neighbor’s porch, glowering. And as the sun sets a siren wails and the coyotes come to life.

Stromatolites

The World’s Oldest Fossils Are 3.7 Billion Years Old says the headline. They were discovered in Greenland. Apparently some Aussie paleontologists went all the way to a just as uninhabitable part of the earth as the Australian Outback–just colder–to find fossils of lifeforms older than anything in their own country.  And it’s not like they were looking for them–I have no idea what they were looking for, actually, it doesn’t say–they just happened to look closely at some rocks poking out of the melting snow (you rarely hear paleontologists complaining about global warming) and immediately recognized the distinctive shapes held therein. Stromatolites!  And if there is one place on earth with rocks older than Australia, it’s Greenland. Both are mostly craton–that is big pieces of ancient land that have sort of wandered about the globe with the tectonic currents, not being ground up by continental plates and belched back up as new igneous rock formations in the mid open trenches that stitch the ocean floor. Iceland, the whole island, is part of that grinding and belching process that somehow is above sea level. As such, Iceland is about as opposite from Australia or Greenland as any place on the surface of the globe can be. There are no fossils on Iceland, it is far too new and the rock was all basically molten not long ago. Australia and Greenland, though, were in large part land that was formed maybe four billion years ago, when land was first invented, and in Australia at least there is still some of it in virgin condition (we can’t see most of Greenland yet, it’s still ice and snow covered). Both the Australian and Greenlandic cratons contain incredibly ancient rocks, and where sedimentary rock was laid down a couple billion years ago in ancient shallow seas, you will find incredibly ancient fossils. The land today is so untouched in places that in the depths of Australia there is a famous fossilized beach, you can even see the ripples left in the sand by the waves. Groovy, in an incredibly ancient kind of way.

Of course, we are not talking dinosaurs here. We are billions of years before dinosaurs fossils, before almost anything even. Fossils from that far back are few and far between. Mainly, if not exclusively, they are stromatolites. There were untold jillions of stromatolites then, vast immobile herds of stromatolites luxuriating in the young planet’s overheated waters. Indeed, Earth was a young planet full of stromatolites with no one to eat them. It was sort of a vegan paradise. Since then, though, predators were invented and stromatolites have sheltered in the less hospitable places on earth, overheated and hypersaline. There they thrive, ignored, virtually unevolving. Were we to zap one of the fossil stromatolites with a time machine gun, it wouldn’t look much different than they do today. Hence they call today’s stromatolites living fossils, like coelacanths and horseshoe crabs and cycads and the Rolling Stones.

Australia had the oldest fossilized stromatolites in the world, nearly three and a half billion years old. Or they did until the Australians I mentioned above went wandering about the ancient rocks of Greenland and found the new oldest fossils. Two hundred and twenty million years older, in fact. To give you an idea of how big a span that is, two hundred and twenty million years ago we mammals had just been invented. We were just squirmy little shrew like things, not very appealing. And birds hadn’t been invented at all. That’s how big a span of time two hundred and twenty million years is. And these Australian paleontologists found stromatolites in Greenland that were two hundred and twenty million years older (3.7 billion years old) than the celebrated 3.48 billion year old stromatolites from the Marble Bar Formation in the Pilbara region of way the hell out there Western Australia. Imagine having your oldest fossils rendered penultimate, just like that. By your own countrymen, no less. What a blow to the Australia paleontological ego, if not the body politic itself. The Government of Western Australia’s website even has a whole page boasting of “the world’s oldest known examples of fossil stromatolites (3.45 billion years old), found near Marble Bar in the Pilbara.” Ahem. Our trio of Australian paleontologists–we’ll leave them unnamed–will be a very popular bunch in the roadhouse in Marble Bar, the metropolis in the Pilbara closest to the now second oldest fossils, that’s for sure. No more free beers. Though they did push back the evolution of life on Earth even further than had been imagined. If relatively complex (by bacterial standards) stromatolites were flourishing 3.7 billion years ago, then bacteria itself must have been around much earlier than that. And the planet itself is only 4.5 billion years old. Life started here much earlier than we thought possible. I doubt, though, that would impress the locals at the roadhouse in Marble Bar. Their metropolis (population 208) was famous for one thing, and one thing only, the world’s oldest fossils. And now you’ve told everybody that they are the second oldest?

But even though the Pilbara stromatolites are a mere 3.48 billions years old, Australians can still brag (“some of the best examples of living microbialites“) that they have living stromatolites, if you call that living. Because several hundred miles to the southwest of Marble Bar, as the emu flies, is Shark Bay, and in the hottest, saltiest part of Shark Bay is a thriving stromatic metropolis. Probably the world’s most famous living stromatolites, actually, even David Attenborough paid a visit. Life forms just like this, he said with breathless and beautifully enunciated excitement, came to be in the Pre-Cambrian. He didn’t touch one. They’d feel like a slimy lichen. Which is sort of what they are, big stacks of slimy lichens, mostly made of cyanobacteria, and nowhere near as cuddly as the wallaby Attenborough had doubtless been cavorting with a day or two before.

However, despite their sliminess, these living stromatolites mean that Australia has had conceivably the longest continuous stretch of communal living on the planet. Even as the Australian craton wandered about the earth, bumping into other cratons and slowly bouncing off again, it had stromatolites. Even when the planet was wrapped in ice–the Snowball Earth hypothesis, a scary one if correct–some Australian stromatolites clung to some little saline hotspot. And they are still there, building up into stromatolites a couple feet high mat by microbial mat, like those layers of lichen you see on rocks but with little grains of sand worked in and held fast by slimy bacterial excretions to provide the structure the way we use girders to build our skyscrapers. Though to a cyanobacteria a two foot high stromatolite would be millions of times taller than the Empire State Building. They link their little flagella together somehow too, like holding tiny bacterial hands, and then they sit there and metabolize. That’s about it. That is what stromatolites so. No scurrying about like in an ant colony or a beaver dam or Los Angeles. Just four billion years of stromatolites doing essentially nothing, but doing it together. There are so many possible jokes here I can’t decide on just one so never mind.

Meanwhile, Greenland gave up on stromatolites permanently (or at least until the next super continent congeals in a half billion years or so) when Pangaea broke up and Greenland scooted pole-ward. Way too cold for stromatolites up there–they like their water hot–and not enough hypersalinity. So while Greenland has the oldest stromatolites, if Greenlanders want to see their living equivalents they have to go nearer the equator–Mexico, Brazil, the Bahamas. Or about as far away as a Greenlander can go, Western Australia, which is where those Aussie paleontologists are now, being yelled at by drunken Pilbarrans angry about being the second oldest. There goes all that tourist money.

Anyway, many years ago, back in my own personal Pre-Cambrian era, I decided that one day I’d write something about stromatolites. Now I did. I thought then that there would be more of a sense of achievement, of completion. Instead I feel empty and stromatoloid. Some bucket list this is.

stromatolites

Shark Bay stromatolites. Feel the drama.

Say it with slaughter

So Genghis Khan has 35 million male descendants. Not bad for a little guy with stupefying body odor.

It also gives an idea just how many conquered males the Mongols would slaughter, and how they took control of a land and its people by propagating their genes which meant propagating their power structure. Something similar happened in Mexico after the conquest–the Mexican national genome has markers from indigenous females and male Spaniards, with far more varied female markers present than male, meaning that Mexico was repopulated after its sixteenth century population crash (population reduced by up to 90% from its 1491 level) by a small population of Spanish males who kept themselves quite busy. Denying the conquered males the chance to propagate is something right out of the great ape playbook, and indeed goes back further, with so many mammals and birds and even fish following the same strategy. As for body odor, Genghis–and indeed the whole rank Mongol army who you smelled, they say, before you ever saw them–would have been potent androstadienone cocktails. Hubba hubba. It’s all about romance. Say it with slaughter.

Wombats

A video gone viral of a lady scrubbing a wombat.

Adorable. I imagine wombats are a little light on the smarts, though. Apparently in the early days of mammalian evolution mammals got by on cutes alone. The world was full of birds, a few big and deadly, sure, but most not, and the genuinely dangerous dinosaurs were all long gone, and the surviving reptiles never much of a threat. So you could be cute and roly poly and it worked in some odd evolutionary way. It was a step up on the monotremes, at least, who were just weird. Spikey, duck billed, egg laying, poison toed. Pretty ladies do not hold spiny echidnas in their laps and scrub them, at least not twice. Nowadays, though, anywhere outside of Australia you have to be a lean mean killing machine ball of kitten fluffiness to be considered cute. Placental mammals play rough. Slaughtering birds by the billions and melting people’s hearts. Imagine that, how humans were preyed on by leopards for our entire existence–there are million year old hominid fossil bones that million year old leopards had scraped the meat from–and now we think that little tiny scale models of leopards are the cutest things ever. Disturbing. Doubtless the distant end to humanity can be found in hardwired psychology like that. Wombats, though, are from a dumber time, when human genes were still trapped in annoying little prosimian genomes, while off in placenta-free Australia marsupial wombats were all dumb as little dorks, lolling in the sun and never getting jokes, but laughing anyway.

wombat

One wet wombat.