Here’s an appropriate post for Darwin Day: a new discovery of some very old fossils.
You remember the Burgess Shale fauna, right? The whole story, although it’s since been revised, is given in Steve Gould’s excellent book Wonderful Life (1989). Discovered by Charles Wolcott in the Canadian Rockies in 1909, the site’s shale-preserved fossils were largely neglected until students Simon Conway Morris and Derek Briggs analyzed them decades later. They’re from the Cambrian, a bit more than 500 million years ago.
The first analysis suggested that they belonged to many groups (perhaps phyla) no longer living, suggesting that there had been a luxuriant explosion of life that was subsequently pruned away by extinction. The assemblage also contained a fossil chordate, Pikaia gracilens, perhaps a relative of our ancestors, although it wasn’t a vertebrate:
The diversity of weird, un-placeable fossils led to the message of Gould’s book: had the “tape of life” been rewound, and had extinction not removed most of the Burgess Shale fauna, life today might have descended from those creatures and would be very different from what we see on Earth today. Gould’s message was one of contingency: evolution is unpredictable because of the vagaries of the environment. (Of course, while I see evolution as unpredictable by humans, I see it largely as deterministic, since environmental perturbations must themselves obey the laws of physics. Evolution is only non-deterministic insofar as mutations might be the result of completely indeterministic processes involving quantum-level events.)
At any rate, a closer examination of the fauna by Briggs and Conway Morris showed that most of the anomalous beasts were actually members of extant groups, like arthropods, annelids, and sponges, so the fauna really wasn’t as much of an outlier as Gould suggested. That somewhat overturned his idea that the types of life on Earth today were purely the result of contingencies.
Nevertheless, there are still animals in the original Burgess fauna that defy identification; one of them is the bizarre Opabinia regalis, which looks like a shrimp with a vacuum-cleaner hose attached to its head. Here’s a specimen from the nice Smithsonian site on the Burgess shale (first link in this post):
Another weird one was the six-foot predator Anomalocaris canadensis (the genus name means “abnormal shrimp”) a large predator that may be closely related to ancient arthropods. Here’s a reconstruction and a fossil of its two forelimbs:
Later comparable fauna, also remarkably well preserved, were found in the Chengjiang biota of Yunnan, China, a series of Cambrian shale fossils about 525 million years old. They’re notable for containing what may be the first known jawless fish (“agnath,” a group that comprised the ancestral vertebrates), Myllokunmingia. Here’s a fossil of that species and then a reconstruction (it’s somewhat speculative; we don’t know whether it had eyes). Myllokunmingia was about 1.1 inches (2.8 cm) long:
Which brings me to the point of this post: a new paper in Nature Communications by Jean-Bernard Caron et al. It describes a site 50 km from the Burgess Shale site (and not too far from where I’m speaking in Kamloops this spring), that, like the original Walcott site, contains a remarkable array of wonderfully-preserved invertebrate (and one chordate) species, 22% of which are new to science. It also contains many fossils known from the Chengjiana fauna, showing that some species had a broad distribution.
The specimens haven’t yet been worked up and many aren’t yet identified as to group, but some are known as identical species from other places. When the new ones are identified, however, we may see some severe revision of the early history of life.
The paper is not much more than a description of the site (called “Marble Canyon”) and a brief description of the fauna, with some pictures, so I’ll show both. A nice article in the Globe and Mail (be sure to watch the one-minute video showing the beautiful location) gives some of these photos; my captions are lifted that article:
The fossil bed was discovered in 2012, in a section of Kootenay National Park in British Columbia that cannot be accessed by trails. Although the team is not sharing the site’s precise location – to protect it from pillaging by would-be fossil hunters – Dr. Caron said it was near a scenic feature called Marble Canyon.
“It’s on the side of a mountain like any other mountain,” said Alex Kolesch, a manager with Parks Canada. “To be able to discern what’s there, you would really need to know what you’re looking for.”
The team first stumbled upon the site while looking for exposed sections of rock similar to that found in the Burgess Shale. One evening, they came to a place where it seemed that fossils were littering the ground. Upon closer inspection, they realized it was no fluke, but the eroding edge of a significant deposit that previous expeditions had missed. Within days, there were pulling out high-quality specimens of ancient marine life in stunning numbers.
First the site and some excavations:
(Jean-Bernard Caron)
The animals. If you think you know your groups, guess which phyla these belong to. The paper, which unfortunately is not free, gives some answers. For example, the third photo below shows a new species of arthropod:
(Jean-Bernard Caron/ROM)
(Jean-Bernard Caron/ROM)
Here are two pictures from the Nature Communications paper. The first shows another chordate, Metaspriggina, which has remarkable preservation of the internal organs, including the heart and liver, and, especially, the eyes (“ey” in figure), so we know that eyes had already evolved by this time. The scale bar is 5 mm long (0.2 inches):
And here is something I didn’t know about, a “bivalved arthropod,” apparently with some kind of bivalve-like shell. This one is new to science and not yet named; the scale line is 10 mm (0.4 inches), so you can see that these specimens are small:
The fossils include the first preserved neural tissue from any specimen of this period, but its meaning awaits further analysis.
Happy Darwin Day: one of your ancestors might be in the pictures above!
h/t: Diana MacPherson
_________
Caron, J.-B., R. R. Gaines, C. Aria, M. G. Mángano, and M. Streng. 2014. A new phyllopod bed-like assemblage from the Burgess Shale of the Canadian Rockies. Nature 2014/02/11/online
I have no idea what those are, I’m still stuck on :
“…a bit more than 500 million years ago.”
If that doesn’t fill you with awe and wonder then you’re a lost cause.
Mike.
“Of course, while I see evolution as unpredictable by humans, I see it largely as deterministic, since environmental perturbations must themselves obey the laws of physics. Evolution is only non-deterministic insofar as mutations might be the result of completely indeterministic processes involving quantum-level events.”
Well, that applies to everything. The main point is that evolution is chaotic in the mathematical sense. A game of billiards is completely deterministic, but in practice one can’t use classical physics to predict the outcome of a shot—not because of quantum effects, but because one can’t know the initial conditions precisely enough.
Of course, quantum uncertainty will eventually come into play. Imagine that one could know the initial conditions with the minimum possible uncertainty. How many collisions would be needed before the average difference between the predicted and actual position of a ball is more than the size of the table? Only a dozen.
A roll of the dice really is not deterministic, and more importantly, a roll of millions of dice at once really is not. It is not just that you can’t know the outcome, but that it is unknowable. We just have to wait and see what happens, and that’s what makes life interesting.
Rolling dice is governed by the laws of physics, most would say that is detemrinistic. Determinism aside, I think you mean that it is not predictable. And you have to wait and see how comes out, which is true, since it is not predictable.
Agree with Phillip, though he shouldn’t have said that billiards are completely deterministic, as he himself notes in his second paragraph.
Also, random things like asteroid impacts had a very large effect on the course of evolution.
But anyway, what a great Darwin’s Day announcement! This is very exciting and bound to reveal new insights into early life.
Replying to both Steve and Lou above, I suspect Jerry is using the word deterministic more in the sense of “physically determined” than in the sense of “non-random”, as this is how he usually seems to use it in the free will threads.
TJR, that’s the sense in which I am using it too.
But in that sense, asteroid impacts are non-random, being completely determined by initial positions and later gravitational interactions among bodies. The only thing that’s random in an absolute sense is a quantum mechanical event.
No John, the distribution of matter in the very early universe was determined by quantum uncertainties, and this influenced the locations and sizes of later stars, planets, and asteroids.
Good try, but that all comes down to sensitive dependence on initial conditions, and in that sense everything in the universe is random, as it’s all been influenced by that initial distribution. I’m pretty sure you want to make some things random but some things not random.
No John, we don’t get to choose what’s random. If you run the tape over from the beginning, with the same physical starting state, and let it run for a few billion years, you’ll get dramatically new arrangements every time. If we just rewind the tape a little bit, things won’t vary so much (planets will mostly be in the same places, etc). The universe is not deterministic, but it can behave as if it were if we consider only short time intervals. Quantum randomness of macroscopic objects is a matter of degree, depending on your time perspective.
So then you’re saying that everything is random.
Yes, we live in a quantum universe. To speak meaningfully of the importance of randomness in a process, we have to specify a time interval. This is what Phillip did in his billiard-ball example above. Billiard balls are for all practical purposes determinate in their first bounces. If the surface is nearly frictionless and they can bounce a dozen or more times, their trajectories as determined by classical physics will usually not match the actual trajectories.
That isn’t true. Quantum events have no impact on billiard balls. It’s just that the initial conditions are more complex than the simple notion of elastic conditions of dimensionless particles can deal with. This is chaotic or contingent behavior, not randomness.
To take this back to the original topic, quantum effects can be important in evolution if and only if particular, rare mutations are important in determining its course. And that may well be. But most of the apparent randomness in life’s history, at least in my opinion, comes from chaos and contengency, which are not random, though they may certainly seem so to observers.
No, John, the calculations have actually been done, and have been published in the American Journal of Physics. (Don’t have time to look it up again right now…) Phillip is right to say that after a dozen bounces, the trajectories are highly unpredictable even if the initial state is precisely known, and if the table is an idealized frictionless perfectly flat plane.
Taking it back to our original problem, even the major features of our solar system are products of quantum events in the early universe. Just like the moment of occurrence of a (macroscopic) click of a Geiger counter cannot be predicted even from complete knowledge of the initial state of the system + radioactive atoms.
Well, who can argue with an unknown citation from a prestigious journal?
In the standard theories of cosmology, quantum variations in the density of the very early universe cause its later structure (stars, galaxies). If you prefer, argue against that.
Is evolution chaotic? I didn’t know that was tested, but it would be exciting if it was! Can you give references?
I can see how evolution fulfills 2 of the 3 putative requirements for deterministic chaos, e.g. sensitivity to initial conditions (say, Lenski’s experiments where a mutation was needed to set up the later evolution to citrate metabolic capability) and topological mixing (no directionality; convergent evolution).
But I’m totally at a loss to see how evolution is dense, whether it has periodic orbits or not. I thought it was sparse, if anything. (Say, the few possible protein sequences used out of all possible.)
[ http://en.wikipedia.org/wiki/Chaos_theory ]
I think chaotic evolution is easy to disprove. In the sense that not all possibilities are accessible to life. There are certain chemical combinations we know to be prohibited and therefore not all possibilities can be surveyed by ‘random mutations’.
However, if a small set of options are available for selection, I would think that chaotic evolution within that set would be permissible.
We are cross posting: agreed.
And thanks for the help!
Or … rather density should be a measure of darwinian small survivable steps, it is the process not the constraints that is to be measured. I’m dumb.
Still, it would be nice to have references instead of my own handwaving.
Yay for getting to meet new arthropods!
Yes!! And so nice to read about slugs other than Rob Ford in The Globe!! Kootenay is a glorious part of the world. I’ve done a number of hikes around there on one of our cross- country drives. To get to the actual Burgess Shale you hace to hike with a tour ( something like 20 km- 6 or 7 miles) and the tour is only 2 or 3 times a week. The timing didn’t work for us ladt time, but might give it another try.
In 2007 my wife and I took a 7 day cruise on a working boat,The Aurora Explorer, through the Inland Passage on the west coast of British Columbia to celebrate an anniversary. There was a full complement of passengers,12,and on the first night at dinner we found ourselves sharing a table with a retired 7th Day Adventist minister and his wife. They regaled us with tales of how they had stopped off on their way to Campbell River, the boat’s embarkation point, at The Burgess Shale Site, to see where Satan had planted all the ‘fossils’.By breakfast the next morning the had requested a move to another table. I think it’s something we must have said that pissed them off!
Unbelievable, your tablemates!! As if Satan has time to sprinkle fossils about, what with all the other shit he has to stir…;-)
Ha ha! Clearly they thought you were devilish too. I would’ve got in a big argument right away. I figure if someone brings up the devil in a context like this, I get to tell them their statement is ridiculous. They usually don’t take that so well.
That’s precisely what I inferred when I wrote
“I think it must have been something I said that pissed them off.” Both my wife and I let the other couple know that we were atheistically inclined. They were able to swap with a couple from California, with whom we still correspond 7 years later.
Actually, bivalved arthropods are alive, well, and flourishing today, in the form of Ostracod crustaceans, a group which has >10,000 extant species. It’s just that they are almost all tiny and therefore a group that few people other than specialists tend to be aware of.
Economically, one of the more important fossil groups. They’re a very good tool for figuring out where the fsck (technical term) you are in a rock succession, when you’re drilling an exploration oil well. Billions of dollars of investment rides on the back of these (and other) microscopic organisms.
Less than a ten hour drive from the headquarters of the Discovery Institute.
What I wouldn’t pay to be a field assistant at that dig! Wow. I remember vividly when I first read Gould’s book on the Burgess Shale, wishing I had a submersible and a time machine.
Luckily, some people with visual skills superior to mine have had the same dream:
http://www.youtube.com/watch?v=ice47loNmsc
Interesting, this looks to be from the Attenborough series “First Life” (from about 3 years ago) but has someone else voicing it.
Heresy!
My feelings exactly. I would sit their, prying away at the shale. Weather and hunger would go unnoticed.
Many years ago when I was about 12, I stumbled across a shale outcrop in Colorado while my family was visiting an uncle who had a cabin in the woods there. I spent every day, all day at the outcrop. I still have the fossil leaves that I found.
I have a completely untrained eye for fossils. Even with professional instruction, no paleontologist would ever want me near a fossil site. It would be a disaster. Although strangely I can find contact lenses at the bottom of a pool, even ones floating in the ocean.
I’d break stuff being too eager. I’m not the person you want around for delicate work.
Why’d I already guess that, Diana:-))
If you ever go to the Field Museum, visit the Life Through Time exhibit, and you will see a similar show of a Cambrian sea bottom that goes on for quite a bit longer and features a great many more species.
Reblogged this on Mark Solock Blog.
Uh-oh. More “kinds” to squeeze onto the ark.
Well, these would have died in the flood.
What did the trilobites do? That’s what we should ask creationists! 🙂
I don’t think YHWH liked the smell of their burning flesh.
b&
As epifaunal and/ or nektonic organisms, they’d have been entirely unconcerned by the Noachian flood.
I would have thought that being covered by thousands of feet of sediment might caused them some injury. Not so?
There’s only so much sediment that you can dump before the flow rate of dewatering the sediment becomes great enough to lift the sediment that’s trying to settle. At which point, the beasties just swim up into the water column.
Yes, organisms do get buried by sediment inrushes (I must remember to get a better photograph of my rock specimen which I call “Day in the Death of a Worm.” But the death of a small local population is a different thing to managing to make a species extinct.
Except of course that this particular sediment comes in at a sustained rate vastly greater than any observed rate — we’re talking thousands of feet in less than a year — and appears to cover pretty much all nearshore environments worldwide. Face it; a Noachian flood would have been a mass extinction greater than the end-Permian, for several reasons, this among them.
IF such a thing could happen – which is simply counterfactual. Where did the sediment come from? How did it de-water (considering that over half, possibly over two-thirds of sediment is fine-grained enough to for an effective permeability barrier to it’s own (rapid) de-watering. In which case, it remains highly mobile sludge. [SIGH] Too much flu’ for this.
You understand, don’t you, that the flood is a fantasy to which it’s impossible to fit the evidence? We have to patch its leaks with miracles in many spots. My point is that in order for benthic organisms to survive it, there would need to be another of those miracle patches.
How amazingly cool is that! Distinct, detailed traces of organisms that lived half a billion years ago, that are our cousins and yet so alien to our experience.
That many believers think that “godidit” is a more amazing and profound story than this reality is, in my opinion, one of the major indicators that something is seriously wrong with either religion or a significant percentage of the people that are susceptible to it.
I was shouting out loud when I first read about the find. Very exciting!
And thanks for fleshing out some of the early finds. I also read somewhere that this makes Pikaia as the first found notochord more firm.
No, the Chengjiang is considerably older and has several chordates in it.
This sort-of implies that there was a hiatus between the early 1970s flurry of re-examination and re-description which Gould described in “Wonderful Life“, and Brigg’s and Conway-Morris’ later work. They continued working on the biota (and other material) for decades after. SCM is still working on related fauna (IIRC, he was a co-author on either Myllokunmingia or it’s associate Haikouichthys. Or, thanks to wiki, on both.) Briggs meanwhile has moved on to some exceptionally preserved material from the Silurian a few miles outside Birmingham (UK).
But I’ll resist the temptation to repeat the story that apparently so annoyed SCM in “Wonderful Life” ; people are allowed to change their minds in the face of improving evidence. And an initial burst of “splitting” (in a taxonomic sense) seems to have had a backwash of “lumping”. But there remain oddities like Opabinia and it’s relatives. That is just one weird beast – it has very evidently been Touched by the Noodly Appendage, and is attempting to emulate the experience in it’s body form!
Here’s a weirdness for you all to ponder : the Anomalocariids JAC mentions above have a weird (Opabinia-grade “weird”) jaw structure. It was originally often found detached and was identified as a discrete organism, “Peyotia“. Due to the radial (quadrant, if not higher) symmetry of “Peyotia“, it was initially thought to be a weird calcified jellyfish. Or something. But when it was identified as the jaw structure of Anomalocaris, then that tied up several loose ends. A lot of trilobite fossils had been found over the years with “cookie cutter” like chunks missing from their flanks. And the jaws of Anomalocaris fit the bite marks!
Woo hoo! Loose ends tied up!
Except … those bite marks … some of them have healed (Hitchcock was working on the screenplay for “The Trilobite Who Got Away” in his last years!), and some haven’t, indicating death shortly after the injury. But overwhelmingly … they’re on the right side of the body. Indicating … what.
Oh darn ; this has been discussed here before. It’s still fascinating though. I think.
“Peyotia” is a great name, quite reminiscent of Hallucigenia. But unfortunately it’s Peytoia.
It was the 60s. Man.
Gravy, Booby:-)
Very, very cool… I gotsta get my butt to BC come spring. Just gotsta.
Some day for me too! Wish we’d moved there many years ago when we had the chance to.
Fantastic post! Most apropos for Darwin Day.
Simon-Conway Morris, as mentioned famous for his Burgess shale work is chair of Evolutionary Paleobiology at Cambridge. He is a Christian and outspoken against materialism/reductionism. I would say he is a theistic evolutionist and has strong thoughts with regard to a teleological component of evolution. His “Life’s Solution: Inevitable Humans in a Lonely Universe” is slowly making its way up my reading book stack.
You have misplaced his hyphen, though actually he doesn’t have one. But if he did, it would be between the last two, not the first two.
“Bivalved arthropods”, aren’t those ostracods? They’re a group of crustaceans.
http://en.wikipedia.org/wiki/Ostracod
Though ostracods are bivalved crustaceans, the bivalved arthropods of the Cambrian are not ostracods; many of them aren’t even crustaceans. The earliest ostracod fossils are Ordovician.