HBM118: Mountain Seabed

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Life on earth began in the oceans.  And it used to be simpler. For the first few billion years, life consisted of microbes that didn’t really swim or hunt; they mostly floated and, if they were lucky, bumped into something they could engulf and digest. But that changed during the Cambrian period.

Over a relatively short period of time known as the Cambrian Explosion, organisms started becoming larger and more complex. For the first time they grew limbs and exoskeletons; intestines and eyes. Animals from this period developed strange body plans that look almost alien to the modern eye. It was an unprecedented surge of biodiversity.  But many of the animal groups that emerged during the Cambrian Period died soon after during an extinction event, their bizarre body plans perishing along with them. To paraphrase the evolutionary biologist and paleontologist Stephen Jay Gould, these were “early experiments in life’s history.” Among the survivors of the Cambrian extinction event was metaspriggina, a tiny fish the size of a human thumb. This tiny fish is one of the oldest ancestors of all vertebrate life on earth - including us.

Over millions of years and tectonic shifts, Cambrian-era seabeds became modern-day mountains. Today, one of the best places in the world to study fossils from the Cambrian period is at the Burgess Shale fossil deposit, high in the Canadian Rockies. The animals fossilized in the rock were buried quickly in mud that had the right conditions to preserve the soft tissues like brains, organs, and muscles, giving paleontologists a detailed glimpse at some of the first complex life on earth. Scientists have been mulling over the Burgess Shale fossils since they were first excavated in 1909.

A metaspriggina fossil. Metaspriggina is an ancient relative to all vertebrate life on earth. Photo by Molly Segal

Stephen Jay Gould was one of those scientists fascinated by the Burgess fossils. He paid attention to the research coming out about them and started wondering what life would look like if a different set of animals had survived and our ancestors had died out. Would humans - or something like us - have ever evolved?  Gould thought not. In his 1989 book Wonderful Life, he came up with the ‘tape of life’ thought experiment. Gould wrote, “Wind back the tape of life to the early days of the Burgess Shale; let it play again from an identical starting point, and the chance becomes vanishingly small that anything like human intelligence would grace the replay.” This idea is called Evolutionary Contingency.

Animation of a metaspriggina swimming, via Royal Ontario Museum.

Not everyone agreed with Gould. Most notably, his contemporary Simon Conway Morris, another evolutionary biologist and paleontologist. Morris spent years studying the Burgess Shale, and it was his work that Gould had cited for his book about Evolutionary Contingency. Conway Morris disagreed with Gould’s interpretation that human intelligence was a fluke. He wrote his own book in 1998 called The Crucible of Creation and posited that, while life may have looked very different after a replay of the ‘tape of life’, consciousness may still have emerged in other forms. He wrote, “There are not an unlimited number of ways of doing something. For all its exuberance, the forms of life are restricted and channeled.” (p. 13) This idea is called Evolutionary Convergence.

In August 2018, producer Molly Segal joined a group of paleontologists, including Jean-Bernard Caron of the Royal Ontario Museum for their biennial dig at the Burgess Shale.  Caron believes that Contingency and Convergence both play a role in evolution, their debate has informed discussions about evolution ever since.

Producer: Molly Segal
Editors: Bethany Denton and Jeff Emtman
Music: The Black Spot

HBM090: Two Small Creatures with Human Eyes

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Ian Tattersall, Curator Emeritus of Human Origins, Division of Anthropology, American Museum of Natural History.

Ian Tattersall, Curator Emeritus of Human Origins, Division of Anthropology, American Museum of Natural History.

Natural history museums are art galleries.  Scientifically focussed art galleries, but art galleries nonetheless.  

Ian Tattersall, of the American Museum of Natural History in New York City, is a paleontologist who sometimes oversees the construction of models for the museum.  Of personal interest to Here Be Monsters producer Jeff Emtman are reconstructions of very lifelike early humans, one with an arm draped over the other.  Ian calls these the “Laetoli Figures”—named for the place in modern-day Tanzania where some remarkable footprints of two hominids were found preserved in volcanic ash.  

As far as early humans go, Australopithecus Afarensis are well understood.  There are 300+ individuals in the fossil record, including the famous ~40% complete fossil of “Lucy”.

Given the evidence, there’s a lot scientists can be pretty certain in declaring: they lived in the trees, but they could walk upright.  They had small brains and big jaws, but their canine teeth looked a lot like a modern human’s.  

There are other questions that are answerable through inference, through studies of modern animals and other fossils.  These techniques can yield a strong degree of certainty.

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But if the artist were to stop constructing at the edge of certainty, the models would never be completed. There are certain things that are essentially unknowable about these early hominids, like: “What did their skin look like?” “What color was their hair?” “Did they have the dark sclera of an ape, or the whites-of-the-eye of a modern human?”

These uncertainties are ultimately up to the artist to answer.  “When you’re making a museum exhibit,” Ian (not an artist) points out, “you’re trying to create an illusion.  And to work at all, the illusion has to be complete.  And so you have to have all the details in there.”

But these details are a form of artistry used as evidence by biblical creationists to lambast hominid reconstructions.  They see it as part of an effort to deceive the public, to lead them to believe that these ancient hominids were more human-like than they actually were.  Of particular interest to them is that question of the light sclera vs. dark sclera.  One author writes:

Notice that a fossilized eyeball was not found.  So how would anyone know that the sclera was white, which would cause it to look more human. [sic] The reconstruction is pure speculation about how Lucy’s eye looked.

A replica of the specimen of Australopithecus Afarensis colloquially named “Lucy”.

A replica of the specimen of Australopithecus Afarensis colloquially named “Lucy”.

Natural history museums are faced with a decision: create full-flesh reconstructions that by necessity contain elements of artistic license, or, present the public with mere bones.  Most seem to opt for the former, and understandably so.  The museum serves the public, and, like HBM producer Jeff Emtman, they want to see something relatable and remarkable, a piece of scientifically-oriented art.  

And this question the artist must face, the question of the dark sclera (more ape-like eyes) and the light sclera (more human-like eyes) reveals something interesting about the artist and the process used to create the art.  The choices an artist makes can speak to their worldview, their biases, and their knowledge per their location in the world and the current moment in time.  

Ian recognizes this, saying,

You could not do a reliable reconstruction of an ancient human being or a dinosaur, or an extinct mammal without the science; and you certainly couldn’t do it without the art.  And this is where the two really intersect in a meaningful way.

And the AMNH itself houses exhibits related to the ways in which modern assumptions about the past have affected the way the past is present, such as:  Griffins in the Gobi Desert (protoceratops), Cyclops of the Mediterranean (dwarf elephants), and the infamous unicorn horns of Western Europe (narwhal).

Ian says that, in the quarter century since the construction of the Laetoli Figures, dominant scientific perception has changed to suggest that Australopithecus afarensis might have actually had dark sclera. As he puts it, “science is a work in progress.”

Jeff Emtman produced this episode.  
Voicemails from HBM listeners including Daniel Greene, Rachel Schapiro and Tony Baker.   

Music: The Black Spot | | | The Other Stars


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