Dawn life

Currently I'm working my way through Mark McMenamin's book The Garden of Ediacara, an analysis of the fossil evidence from the Vendian Period, the last bit of the Precambrian (650-543 million years ago).

The subject of McMenamin's book is undeniably fascinating -- more about that in a moment -- but it's uneven reading.  Part of it is a travelogue of his work in Namibia, Mexico, and Australia, places where there are significant outcrops of late Precambrian sedimentary rocks, but it's obvious from page one that most of what he does is write papers for scholarly journals.  As a result, it's halfway between an introduction to the topic for laypeople and an extended academic paper, and I've been glad as I worked my way through it that I have at least a passing background in paleontology.

Something that struck me right away, however, was that I've been laboring under a serious misunderstanding of the Ediacaran biota; that it overlapped significantly with the Cambrian explosion fauna, the bizarre creatures like Anomalocaris and Opabinia and the aptly-named Hallucigenia.  In reality, there was almost no overlap, and the Ediacaran organisms such as Cloudina and Dickinsonia were almost certainly driven to extinction and replaced by the large predatory forms of the early Cambrian.

A fossil of Dickinsonia costata from Australia [Image licensed under the Creative Commons Verisimilus at English Wikipedia, DickinsoniaCostata, CC BY-SA 3.0]

While the early Cambrians (best known from the Burgess Shale formation of British Columbia) are clearly animals, the bizarre Ediacarans are of completely uncertain affinities.  When McMenamin wrote his book (1998) there was considerable contention about what they were, with various paleontologists arguing vehemently that they were early animals, fungi, algae, or even giant protists (or protist colonies).  Despite the passage of twenty-five years, the issue is still far from settled.  Some make persuasive arguments that the Vendian biota doesn't belong to any of the five modern kingdoms of life (animals, plants, fungi, bacteria, and archaea), but are representatives of a completely different lineage, or more than one, that left no descendants at all.

So I'm grateful to McMenamin and his book for clearing up something I'd misunderstood for years.

I was in the middle of reading The Garden of Ediacara when, coincidentally, a friend and frequent contributor of topics for Skeptophilia sent me a link to an article in Smithsonian magazine about the evolutionary origin of animals.  Another point of contention amongst biologists is determining, out of the entire kingdom Animalia, which group branched off first.  (This is sometimes phrased as which is the "oldest" or "most primitive" -- both terminology I don't like, because every living animal on Earth has an exactly equal length of evolutionary history.  It's just that during that time, some branches have changed a great deal faster than others, and some groups share more recent common ancestry than others do.)

In any case, the argument is about which group of modern animals is the outgroup -- the one that split off first, and therefore is the most distantly related to all other animals.  When I took zoology (many, many years ago) the conventional wisdom was that it was sponges (Phylum Porifera).  And there's certainly a good case to be made there; sponges are weird animals, with no differentiated organs, skeletons made of either protein fibers, bits of calcium carbonate, or slivers of glass, and no nerves, muscles, or digestive tracts.  But genetic analysis has shown unequivocally that there's an even more distantly-related group -- the comb jellies (Phylum Ctenophora).

They look superficially like jellyfish, and that similarity led scientists to put them on the same branch as Phylum Cnidaria (which not only contains jellyfish, but sea anemones and corals).  The genetic studies, though, show that there's only a distant relationship between comb jellies and jellyfish.  The comb jellies, in fact, show more of a genetic similarity to certain species of protists than they do to other animals.

"That was the smoking gun," said Daniel Rokhsar, of the University of California - Berkeley, who co-authored the paper.

So this goes to show that there's a lot we still have to learn about the earliest life on our planet.  And I'm sure that as definitive as this study seems to be, it won't be the last word.  As more evidence surfaces, expect the arrangement to change.  This, after all, is how science works; it has a mechanism for self-correcting.  And far from the reaction I've seen people have -- that the shifting understanding means "it could all be proven wrong tomorrow" -- that capacity for change is science's main strength.

After all, isn't it a good thing to have your model shift to accommodate new information?  Seems like standing firm on what you believe despite strong evidence to the contrary is the cause of a lot of the problems in the world.

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No butts about it

The early Cambrian Period was known for having some weird-looking animals, but even by Cambrian standards, Saccorhytus coronarius was pretty bizarre.

The name is a Greek and Latin composite that means, more or less, "wrinkled bag with a crown," and as disparaging as it sounds I have to admit it's pretty accurate.  The reconstruction of it from various fossils makes it look like a design for a new Pokémon that was rejected on the basis of being too outlandish:

One thing you'll notice about it is that it has no anus.  This, by itself, isn't as odd as it sounds; whole phyla of animals, notably Cnidaria (which includes jellyfish and sea anemones) and Platyhelminthes (flatworms) only have one opening in their digestive tract, meaning once they finish digesting their dinner, they spit the undigested bits out of their mouths.  This lack of a nether orifice has made poor Saccorhytus the butt of many jokes, and in fact I was going to title this post "Assless chaps" but was informed that the more prudish members of my readership might take that the wrong way.

Be that as it may, the spikes combined with its other weird features made it hard to classify.  The first Saccorhytus fossils seemed to have additional holes near the mouth, which initially were thought to be openings for gills but later turned out to be  places where spines had broken off during fossilization.  This has altered our understanding of where it fits on the animal family tree; initially, the supposed gill slits suggested it might be related to deuterostomes (including starfish, sea urchins, sand dollars, and vertebrates).  The fact that this was an artifact of fossilization, coupled with some new research, has placed it instead amongst the Ecdysozoa.  Ecdysozoa is Greek for "animals that get undressed" (speaking of undignified scientific names) because of their ability to shed and regrow their exoskeletons, and includes the familiar phyla Arthropoda, Nematoda, and Tardigrada, as well as less-well-known groups like Priapulida ("penis worms"), which takes "undignified names" to the next level.

Here's the current best-supported arrangement for known animal groups, with the Saccorhytus's branch shown in red:

So that's today's news from the No Ifs, Ands, or Butts department.  (Sorry, I'll stop with the middle-school humor.  Probably.)  Saccorhytus isn't a close relative of ours, but more allied to insects and roundworms.  Still, the lack of a hind end means it's not exactly a comfortable fit in that group either.  Of course, "if you haven’t got an anus," said study lead author Philip Donoghue of the University of Bristol, "you’re not going to be very comfortable anywhere."

Okay, look, that one wasn't my fault.  The scientist himself said it.

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Living crystals

Starfish are odd creatures in just about every respect.

They belong to a phylum called Echinodermata, which is Greek for "spiny skin" and also includes such weird animals as sea urchins, sand dollars, brittle stars, sea cucumbers, and crinoids (also called "sea lilies" or "stone lilies" because they look more like some kind of weird undersea plant than they do animals).  One of the big surprises for my AP Biology students, during the unit on zoology, was that echinoderms are our closest non-vertebrate relatives.  The old distinction of vertebrate versus invertebrate turns out to reflect less of a real genetic and evolutionary split than the distinction between protostome and deuterostome; the former includes insects, crustaceans, arachnids, mollusks, annelids (e.g. earthworms), and nematodes (roundworms), while the latter is just the echinoderms and vertebrates such as ourselves.

The names protostome and deuterostome, if you're curious, are also Greek; they mean (respectively) "first mouth" and "second mouth," referring to the order in which the openings of the digestive tract form.  In protostomes, when the beachball-shaped early embryo forms an inpocket that will lead to the formation of the gut, that first opening will eventually become the mouth; the anus forms when the inpocket tunnels its way through and comes out of the other side.  In deuterostome, it happens the other way around, but early embryologists evidently thought that "mouth second" sounded more genteel than "ass first," and that's how we ended up called "deuterostomes."  (I remember the shocked look on one of my students' faces when I told the class about this fun feature of embryonic development.  She said, wide-eyed, "So, at some point, all humans are just... a butthole?"  I deadpanned back, "Yup.  Unfortunately, some people never get past that stage.")

You might wonder how echinoderms can look so different from vertebrates if we're actually on the same branch of the animal family tree.  In fact, echinoderm larva are clearly bilaterally symmetric, just like vertebrates are; they largely lose that symmetry as they mature, although the apparent pentaradial symmetry of a starfish is kind of an illusion, because they do have organs (like the water intake organ, or sieve plate) that are offset to one side.  But they lose more than their symmetry; the adults have no true circulatory system (all they end up with is a set of what are essentially water pipes), no central nervous system (just a nerve ring and branched peripheral nerves), and the simplest of digestive tracts.  This despecialization seems to underlie their wild ability to regenerate lost or damaged limbs -- a capacity that has been under intensive study because of the possible applications to medical science.

[Image licensed under the Creative Commons Copyright (c) 2004 Richard Ling, Blue Linckia Starfish, CC BY-SA 3.0]

The reason all this comes up is because of yet another bizarre and beautiful feature of starfish, just discovered at MIT.  When they're still very early in embryonic development, and resemble spherical glass beads, they exhibit a peculiar behavior -- they spin, creating tiny vortices in the water and drawing other nearby embryos in.  Eventually they self-assemble into a living crystal -- a regular, tightly-packed lattice of embryos all spinning in the same direction.  They undergo peculiar ripples that the researchers call "odd elasticity" -- odd because the oscillations aren't damped down by the water's drag, but continue to propagate through the entire crystal, like some sort of biological standing wave pattern.

"The spontaneous, long-lasting ripples may be the result of interactions between the individual embryos, which spin against each other like interlocking gears," said Alexander Mietke, who co-authored the paper on the phenomenon that appeared last week in Nature.  "With thousands of gears spinning in crystal formation, the many individual spins could set off a larger, collective motion across the entire structure."

The benefit to this behavior isn't known.  One possibility is that the formation of these crystals makes it less likely that the embryos will be eaten by predators, but that's just speculation.  At the moment, though, it's enough to wonder at the intricacy and beauty of these odd creatures, our distant cousins on the evolutionary family tree.

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Pet warp

In recent posts we have dealt with sending a binary message to extraterrestrial intelligence, helicopters in ancient Egypt, and a creature in southern Africa that looks like some bizarre three-way cross between a human, a bat, and a pig.  So I'm sure that what you're all thinking is, "Yes, Gordon, but what about pet teleportation?"

At this point, I should stop being surprised at the things that show up on websites such as the one in the link above, from the site Mysterious Universe.  In this particular article, by Brent Swancer (this is not his first appearance here at Skeptophilia, as you might imagine), we hear about times that Fido and Mr. Fluffums evidently took advantage of nearby wormholes to leap instantaneously across spacetime.

In one such instance, Swancer tells us, a woman had been taking a nap with her kitty, and got up, leaving the cat sleeping in bed.  Ten minutes later, she went back into the bedroom, and the cat was gone.  At that point, the phone began ringing.  It was a friend who lived across town -- calling to tell her that the cat had just showed up on their doorstep.

Another person describes having his cat teleporting from one room in the house to another, after which the cat "seemed terrified:"

All the fur on his back was standing up and he was crouched low to the ground.  He looked like he had no idea what just happened, either.  That was about 10 minutes ago.  He won’t leave my side now, which is strange in itself, because he likes independence, but he is still very unsettled and so am I.

And Swancer tells us that it's not just cats.  He recounts a tale by "the great biologist... Ivan T. Sanderson," wherein he was working with leafcutter ants and found sometimes the queen mysteriously disappears from the ant nest.   "Further digging in some cities within hours," Sanderson tells us, "brought to light, to the dumbfoundment of everybody, apparently the same queen, all duly dyed with intricate identifying marks, dozens of feet away in another super-concrete-hard cell, happily eating, excreting and producing eggs!"

However, in the interest of honesty it must be said that Sanderson might not be the most credible witness in the world.  He did a good bit of writing about nature and biology, but is best known for his work in cryptozoology.  According to the Wikipedia article on him (linked above), he gave "special attention to the search for lake monsters, sea serpents, Mokèlé-mbèmbé, giant penguins, Yeti, and Sasquatch."  And amongst his publications are Abominable Snowman: Legend Come to Life and the rather vaguely named Things, which the cover tells us is about "monsters, mysteries, and marvels uncanny, strange, but true."

So I'm inclined to view Sanderson's teleporting ants with a bit of a wry eye.

What strikes me about all of this is the usual problem of believing anecdotal evidence.  It's not that I'm accusing anyone of lying (although that possibility does have to be admitted); it's easy enough, given our faulty sensory processing equipment and plastic, inaccurate memory, to be absolutely convinced of something that actually didn't happen that way.  A study by New York University psychological researcher Elizabeth Phelps showed that people's memories of 9/11 -- surely a big enough event to recall accurately -- only got 63% of the details right, despite study participants' certainty they were remembering what actually happened.  Worse, a study by Joyce W. Lacy (Azusa Pacific University) and Craig E. L. Stark (University of California-Irvine) showed that even how a question is asked by an interviewer can alter a person's memory -- and scariest of all, the person has no idea it's happened.  They remain convinced that what they "recall" is accurate.

Plus, there's a little problem with lack of a mechanism.  How, exactly, could anything, much less your pet kitty, vanish from one place and simultaneously reappear somewhere else?  I have a hard time getting my dog even to move at sub-light speeds sometimes, especially when he's walking in front of me up the stairs at a pace I can only describe as a cross between a "plod" and a "waddle."  In fact, most days his favorite speed seems to be "motionless."

Given all that, it's hard to imagine he'd have the motivation to accomplish going anywhere instantaneously.

As intriguing as those stories are, I'm inclined to be a bit dubious.  Which I'm sure you predicted. So you don't need to spend time worrying about how you'll deal with it when Rex and Tigger take a trip through warped space.  If they mysteriously vanish only to show up elsewhere, chances are they were traveling in some completely ordinary fashion, and the only thing that's awry is your memory of what happened.

Branches on the Tree of Life

Sometimes I think I spend too much time railing against specious, unscientific thinking, and not enough time celebrating the wonderful discoveries humanity has made through science.

It's amazing, when you think about it, how our lives have changed in the past fifty years.  When I was little, there were not only no personal computers, there were no pocket calculators.  Many of us still had slide rules.  There were no CDs, only vinyl records and cassette tapes.  Most kitchens didn't have microwave ovens.  Phones had rotary dials, and you got really pissed off if the person you were calling had lots of 9s in his telephone number because it took so long for the dial to spin back from a 9.  Our television was black-and-white, got four channels, and to make the reception better you wrapped the antenna in aluminum foil.

Seems pretty quaint, doesn't it?  Our lives today would seem like The Jetsons to a typical adult in the 1960s.

But the pragmatic stuff isn't all there is, and I would contend that it's not even the most important part of what science does.  There's a broadening of vision, and an increased sense of wonder and beauty, that comes from understanding the intricacies of the workings of the universe.  My life is immeasurably enriched by having an idea of the basics of physics, chemistry, biology, astronomy, geology.  Science's capacity to make us stand back and say, "That is so cool!" is, to me, one of its most important functions.  All practicality aside, it's science's ability to rock us back on our heels, to take us out of the petty world of squabbling celebrities and fractious politics, that is its greatest accomplishment.

Toward that end, I'm going to throw out there two stories from just the past couple of days that had that "Wow!" factor for me.  Both come from my field, biology.  See if you have the same reaction I did -- if, just for a moment, it gave you a glimpse into the awe-inspiring nature of... Nature.

First, we have a paleontological discovery from Argentina of a newly-named species of dinosaur called... Dreadnoughtus.  I kid you not.  And when you hear about this beast, you'll see that the name is apt.  Dreadnoughtus was a titanosaur, a relative of the huge Brachiosaurus and huger Argentinosaurus, but Dreadnoughtus put both of these species to shame, size-wise.  The familiar Brachiosaurus, often mentioned when the subject of enormous land animals comes up, topped the scale at an estimated 75,000 pounds.

Dreadnoughtus was three times heavier.

The specimen from Argentina included a left thigh bone six feet long, and neck vertebra three feet across.  That's one spinal bone, folks.  This dinosaur was an estimated 85 feet long, and weighed more than a fully-loaded Boeing 737-900.

That, my friends, is a bigass dinosaur.

Of course, this prompts our imagination to try to picture what this thing must have been like when it was alive.  "(Dreadnoughtus was) probably a pretty surly beast,” the leader of the study team, Dr. Kenneth Lacovara of Drexel University, said.  "I wouldn’t want to get anywhere near this guy.  If he leaned against you, you’re dead."

Then we have a paper on an animal collected from deep marine regions off the coast of Tasmania.  Called Dendrogramma, this animal looks a little like a translucent mushroom, only the stalk ends in a mouth.  The digestive tract runs up the stalk, repeatedly bifurcating as it goes, and branches out into the "cap."

Why is this interesting?  Because thus far, Dendrogramma has defied classification.  It seems likely that Dendrogramma represents a whole new phylum of Kingdom Animalia -- making it further removed from all other animal species than we are from jellyfish.

Dendrogramma, Phylum incertae sedis [image courtesy of Just, Kristensen, and Olesen, and PLOS-One]

That such an animal can still frustrate taxonomists, given all of our understanding of evolutionary genetics, taxonomy, and cladistics, is just an indication of how much more there is out there to learn.  If Dendrogramma does turn out, upon analysis, to be the earliest branch of the animal kingdom, "(It will) completely reshape the tree of life, and even our understanding of how animals evolved, how neurosystems evolved, how different tissues evolved," said Leonid Moroz, neurobiologist at the University of Florida's Whitney Laboratory for Marine Bioscience in St. Augustine.  "It can rewrite whole textbooks in zoology."

I find the whole thing tremendously exciting.  This, really, is the cutting edge of science, illustrating Neil deGrasse Tyson's statement "Scientists have to be comfortable with ignorance, because we live at the boundary between what is known and unknown in the universe...  Journalists write articles about science and they always begin, 'Scientists now have to go back to the drawing board!'  As if we're sitting up in our offices, masters of the universe, and then go, 'Oops!  Somebody discovered something!'  No, we're always at the drawing board.  If you're not at the drawing board, you're not making discoveries.  You're not doing science."