Glimpse of the dawn

A pair of words biologists (and interested laypeople) have to be careful with are primitive and advanced.

They're often used in place of the generally more appropriate simple and complex.  By that usage, an amoeba is primitive and an aardvark is advanced.  But where it gets confusing is that primitive and advanced are also sometimes used to mean "like something that evolved earlier" and "like something that evolved more recently," respectively -- so they use primitive to describe a stegosaurus and advanced to describe a spider monkey, when in fact both of those are about equally complex.  (It gets even murkier when you throw in questions of relative intelligence.)

It bears keeping in mind that while modern organisms vary greatly on the simple/complex spectrum, they all have lineages that have been around exactly the same amount of time -- 4.3 billion years, give or take a day or two.  All known lineages of terrestrial life converge on a single life form nicknamed LUCA -- the Last Universal Common Ancestor -- around four billion years ago.  To our eyes, LUCA probably wouldn't have looked like much.  It probably resembled species we now classify as bacteria.

But all life on Earth descends from it.  And as far as the primitive/advanced bit, the only difference is in that time, some of the lineages changed a great deal more than others did.

The reason this comes up is because of a link sent to me by a friend and frequent contributor of topics for Skeptophilia, about a species of fairly modern-looking jellyfish that was found in rock strata that are 505 million years old.

The species, named Burgessomedua phasmiformis, was a free-swimming, tentacle-laden predator with a bell on the order of twenty centimeters in diameter.  It, like many of the Cambrian explosion fauna, were found in the exceptionally well-preserved Burgess Shale Formation of the Canadian Rockies in British Columbia.

Artist's impression of live Burgessomedusa in the Cambrian seas [courtesy of artist Christian McCall]

Jellyfish and most of the other members of Phylum Cnidaria are generally scarce in the fossil record, because their bodies are primarily water.  If you've ever seen a dried-up jellyfish on the beach, you know what I'm talking about; there's barely anything left.  (Don't assume that this means they're harmless, though.  Even the dried tentacles of a Portuguese man-o'-war can pack a dangerous sting.)  But you can see how astonishing it is not only to have one create an impression in sedimentary rocks, but to have that impression last for 505 million years.

So the exceptional preservation of this extremely rare fossil animal is amazing enough.  But what I find even more mind-boggling when I think about the life back then is the bigger picture of what the Cambrian Period was like.  At that point, all life was in the water.  There was (more or less) the same amount of land as there is now, albeit configured completely differently -- but on that land was not a single living thing.  No plants, no fungi, no animals.  Nothing.  It was a vast expanse of empty rock, sand, and dust.

At this point, the first terrestrial plants wouldn't make their appearance for another fifty million years, and even then, they were highly water-dependent and very likely clustered along shorelines.  The first vascular plant -- one with the internal plumbing most plants have today -- that appears in the fossil record is Cooksonia, which appeared during the mid-Silurian Period (about 430 million years ago).  It was a strange, rather Dr. Seussian thing:

[Image licensed under the Creative Commons Smith609 Ground texture from Image:Mud closeup.jpg, Cooksonia pertoni, CC BY 3.0]

But when Burgessomedusa was swimming in the Cambrian oceans, all that lay millions of years in the future.  This glimpse of the dawn of time gives us a picture so alien to our current mental image of the Earth it's hard to believe it's the same planet.

What this tells paleontologists, though, is that even in the early Cambrian, there were relatively modern-looking jellyfish -- and that even though today's cnidarians are advanced in the sense of "length of their lineage on Earth," they haven't changed much at all during all those hundreds of millions of years.  The general reason for such stability is that the body plan works; there's little selective pressure to favor alterations in a system that does fine as is, however "primitive" it may look to us.

As a writer friend of mine posted yesterday:

The details might be off a little, but the gist is accurate enough.

****************************************

An explosion of understanding

One of the reasons I love science is its capacity for inducing wonder.

Albert Einstein said it best: "Joy in looking and comprehending is nature’s most beautiful gift."  Being able to look around you and think, "Okay, now I understand a little bit more of the universe" is nothing short of a thrill.

I recall having that feeling when I first learned about the Cambrian Explosion, a sudden increase in biodiversity that occurred about 540 million years ago, and which produced virtually all the animal phyla we currently have today.  I think it struck me that way because it was so contrary to the picture I'd had, of evolution slowly plodding along, from something like a jellyfish to something like a worm to something like a fish, through amphibians and reptiles and mammals, finally leading to us as (of course) the Pinnacle of Creation.  That view, it seems, is substantially wrong.  While there has been great change on many branches of the family tree of life, all of the basic branches diverged right about the same time.

Fascinating, too, that there were also a variety of branches that left no living descendants, that are so bizarre to our eyes that they look more like something from a science fiction movie.  There's Dickinsonia:

[Image is licensed under the Creative Commons Verisimilus at English Wikipedia, DickinsoniaCostata, CC BY-SA 3.0]

... and Anomalocaris, shown here as a model of what it might have looked like when alive:

[Image is in the Public Domain]

... and the aptly named Hallucigenia, which could be straight out of a fever-dream:

[Image is licensed under the Creative Commons Scorpion451, Hallucigenia Reconstruction Current 2015, CC BY-SA 4.0]

... and my personal favorite, five-eyed, vacuum-cleaner-hose-equipped Opabinia:

[Image is licensed under the Creative Commons Nobu Tamura (http://spinops.blogspot.com), Opabinia BW, CC BY 3.0]

If you'd like to find out more, I encourage you to read Stephen Jay Gould's awesome book Wonderful Life, which will tell you about these four creatures and a great many more besides.

The reason I bring this up is that some research out of Oxford University has elucidated not only the structure of these odd creatures, but the environment in which they lived.  Having fossils from 540 million years ago that were sufficiently intact to determine what they'd looked like while alive is amazing enough; but being able to determine anything about the conditions under which they lived is downright astonishing.  But that's just what Ross Anderson and Nicholas Tosca, of the Department of Sedimentary Geology at Oxford, and their team have done.

Their paper, which appeared in the journal Geology, described microscopic mineralogical analysis of the Burgess Shale of Canada and the Ediacaran Assemblage of Australia, two of the finest deposits of Cambrian Explosion fossils in the world.  And what the geologists found allowed them to make a guess at where the likes of Opabinia and the rest lived: warm, shallow ocean ecosystems that had water rich in iron.

The iron content allowed the formation of the mineral berthierine, which is not only distinctive in its origins, but has an anti-bacterial effect that halted decomposition and prevented decomposition.  This resulted in the phenomenally well-preserved fossils both sites are known for.

"Berthierine is an interesting mineral because it forms in tropical settings when the sediments contain elevated concentrations of iron," Anderson said.  "This means that Burgess Shale-type fossils are likely confined to rocks which were formed at tropical latitudes and which come from locations or time periods that have enhanced iron.  This observation is exciting because it means for the first time we can more accurately interpret the geographic and temporal distribution of these iconic fossils, crucial if we want to understand their biology and ecology."

The whole thing is tremendously exciting.  To not only have an idea of the appearance of these animals, but to be able to picture them in something like their actual habitat, gives us a glimpse of a world five times older than it was during the heyday of the dinosaurs.  It's breathtaking to think about.

I'll end with a quote from another scientist -- Brian Greene, the physicist whose lucid writing about modern physics in his book The Fabric of the Cosmos inspired an equally brilliant NOVA series.  Greene says: "Science is a way of life.  Science is a perspective.  Science is the process that takes us from confusion to understanding in a manner that's precise, predictive and reliable -- a transformation, for those lucky enough to experience it, that is empowering and emotional."

****************************************

An explosion of understanding

One of the reasons I love science is its capacity for inducing wonder.

Albert Einstein said it best: "Joy in looking and comprehending is nature’s most beautiful gift."  Being able to look around you and think, "Okay, now I understand a little bit more of the universe" is nothing short of a thrill.

I recall having that feeling when I first learned about the Cambrian Explosion, a sudden increase in biodiversity that occurred about 540 million years ago, and which produced virtually all the animal phyla we currently have today.  I think it struck me that way because it was so contrary to the picture I'd had, of evolution slowly plodding along, from something like a jellyfish to something like a worm to something like a fish, through amphibians and reptiles and mammals, finally leading to us as (of course) the Pinnacle of Creation.  That view, it seems, is substantially wrong.  While there has been great change on many branches of the family tree of life, all of the basic branches diverged right about the same time.

Fascinating, too, that there were also a variety of branches that left no living descendants, that are so bizarre to our eyes that they look more like something from a science fiction movie.  There's Dickinsonia:

[Image courtesy of the Wikimedia Commons]

... and Anomalocaris, shown here as a model of what it might have looked like when alive:

[Image is in the Public Domain]

... and the aptly named Hallucigenia, which could be straight out of a fever-dream:

[Image courtesy of the Wikimedia Commons]

... and my personal favorite, five-eyed, vacuum-cleaner-hose-equipped Opabinia:

[Image courtesy of the Wikimedia Commons]

If you'd like to find out more, I encourage you to read Stephen Jay Gould's awesome book Wonderful Life, which will tell you about these four creatures and a great many more besides.

The reason I bring this up is that some new research out of Oxford University has elucidated not only the structure of these odd creatures, but the environment in which they lived.  Having fossils from 540 million years ago that were sufficiently intact to determine what they'd looked like while alive is amazing enough; but being able to determine anything about the conditions under which they lived is downright astonishing.  But that's just what Ross Anderson and Nicholas Tosca, of the Department of Sedimentary Geology at Oxford, and their team have done.

Their paper, which appeared in the journal Geology last week, described microscopic mineralogical analysis of the Burgess Shale of Canada and the Ediacaran Assemblage of Australia, two of the finest deposits of Cambrian Explosion fossils in the world.  And what the geologists found allowed them to make a guess at where the likes of Opabinia and the rest lived: warm, shallow ocean ecosystems that had water rich in iron.

The iron content allowed the formation of the mineral berthierine, which is not only distinctive in its origins, but has an anti-bacterial effect that halted decomposition and prevented decomposition.  This resulted in the phenomenally well-preserved fossils both sites are known for.

"Berthierine is an interesting mineral because it forms in tropical settings when the sediments contain elevated concentrations of iron," Anderson said.  "This means that Burgess Shale-type fossils are likely confined to rocks which were formed at tropical latitudes and which come from locations or time periods that have enhanced iron.  This observation is exciting because it means for the first time we can more accurately interpret the geographic and temporal distribution of these iconic fossils, crucial if we want to understand their biology and ecology."

The whole thing is tremendously exciting.  To not only have an idea of the appearance of these animals, but to be able to picture them in something like their actual habitat, gives us a glimpse of a world five times older than it was during the heyday of the dinosaurs.  It's breathtaking to think about.  

I'll end with a quote from another scientist -- Brian Greene, the physicist whose lucid writing about modern physics in his book The Fabric of the Cosmos inspired an equally brilliant NOVA series.  Greene says: "Science is a way of life.  Science is a perspective.  Science is the process that takes us from confusion to understanding in a manner that's precise, predictive and reliable - a transformation, for those lucky enough to experience it, that is empowering and emotional."