Saturday, 17 November 2018

The Anthropocene and The Ice People

Carlisle train station is probably not the place most people go to pick up classic works of apocalyptic science fiction. Waiting for my connection to Edinburgh, I rifled through a charity book stall to pass some time. The stall was unattended on the platform, with a tatty assortment of mass market fiction, biblical freebies, and the books only your mum reads. That’s where I found The Ice People, by René Barjavel.  

The paperback was so old and worn it felt like a grandmother’s cheek. The thin spine was a convergence of creases, and the pages tinted sepia yellow. It cost a heady 25 pence in 1972 – worth every penny. The cover boasted that this was ‘The novel that took Europe by storm’. I popped some pound coins in the padlocked donations box, and started to read.

Without giving away too much, the story begins with the discovery of a structure preserved beneath the ice of Antarctica. Inside, a man and woman are cryogenically frozen. They come from a human civilisation forgotten in the depths of time. They’ve slept for 900,000 years under the ice-cap, and when they wake up they tell us the story of their lost culture. 

Apocalypses, I can’t get enough of them. Nothing beats a good bit of apocalypse fiction, in book or film. Post/apocalyptic fiction conveys the anxieties and fears that thread through our society. It has a long history with its roots in religion. As a creative genre, it can be traced to works by Mary Shelley (The Last Man, 1826) and HG Wells (The Time Machine, 1895 and War of the Worlds, 1898). It then flourished in the 20th Century, undoubtedly stoked by the unprecedented destruction of the world wars, and maturing in the impending doom felt during the subsequent cold war. The recent increased popularity of this genre - particularly in film - reflects among other things, our increased concern about the long-term negative ecological impact of humankind on the planet. 

What struck me most about the story of The Ice People was the Atlantean myth of an exceptionally advanced civilisation lost to time through disaster. This idea was a hugely popular idea in the 1960s and 70s, fuelled by writers like Erich von Däniken (e.g. Chariots of the Gods), and saw a resurgence in the 1990s with the likes of Graham Hancock (e.g. Fingerprintsof the Gods). It persists today in multiple pseudoscientific 'documentaries' and 'alternative' histories. But reading my charity treasure, I wondered: could such a culture – advanced enough to produce cryogenics and build structures able to survive nearly a million years crushed beneath an ice cap - really leave so little impact on the earth that we couldn’t easily detect their traces 900,000 years later?

An artist's representation of the Antarctic aquatic system scientists believe is buried beneath the Antarctic ice sheet. By Zina Deretsky / NSF Source
According to recent research, the answer is a definitive, no. A series of reports by researchers from the British Geological Survey and the University of Leicester identifies the ways in which humankind has become the most significant landscape shaper on earth. We have carved out the Anthropocene from our landscapes; an informal geological age marked by our technological conquests. The need for resources to fuel our advanced consumerist world has resulted in us burrowing our way into the permanent geological record

The transformation of the Earth’s land surface by mineral extraction and construction is on a scale greater than natural erosive terrestrial geological processes. Humans are now the major global geomorphological driving force and an important component of Earth System processes in landscape evolution. (Source)

Key contributers to the stratigraphical signatures that could be used to define the base of the Anthropocene. From Waters et al., 2014.
Of course this isn’t a new realisation. Andrea Wulf argues in her stunning book The Invention of Nature, that it was Alexander von Humbolt who first recognised detrimental human impacts on the landscape in the 1800s, sowing the seeds of the environmental movement. The term Anthropocene was in use by the 1970s (creation of the word is often credited to the biologist Eugene F. Stoermer). However, although the term now used regularly to describe the age we live in – defined by humankind’s impact on the world around us and the rock record itself – it still hasn’t been formally adopted by the International Commission on Stratigraphy

A new term that has been adopted, as of July this year, is the Meghalayan. It is named for the location of the stratigraphic type section (the rocks used to define the lowest boundary of this age), which is taken from a stalagmite in Mawmluh cave in Meghalaya, India. The Meghalayan covers the last 4,200 years, and it begins with the collapse of some of the greatest ancient civilisations of the Old World, caused by a massive global drought. This drought is detected through a shift in isotope ratios, captured in the rocks as monsoon rains in Northern India decreased dramatically.

Chronostratigraphic chart next to the stalagmite from Mawmluh cave in Meghalaya that marks the beginning of the Meghalayan. Source: International Commission on Stratigraphy
Both the Anthropocene and Meghalayan are terms that recognise the impact of humans on the thin crust of the planet we inhabit. Both reinforce the fact that it is unlikely we could miss the rise and fall of a technologically advanced empire on earth, however romantic it may be to imagine.

Are you married? Do you wear a gold wedding ring? Take a look at that wedding band glinting on your left hand, and think about this: someone had to excavate up to twenty metric tons of rock to make that one ring. In ore mining alone, we currently generate 316 billion metric tons or sediment per year, which is twenty-four times more than is shifted by all the major rivers in the world combined. With surface deposits gone or built upon, we are now digging deeper into the earth to find the resources we need, build our infrastructure, store waste, and even test weapons.

Deep mining equipment (Source)
The lead author of one of the recent papers on the Anthropocene, Professor Colin Waters, said: “Our increasing interventions into the deeper parts of the planet will undoubtedly confound generations of geologists from the far future, as erosion and uplift will eventually expose our currently unseen activities.”

The Ice People, like so many works of classic fiction, could not have been written today because we now understand that our technology comes at a detectable cost. Its pages preserve a time before we really accepted this. In a way, this book tells a story about itself: culture frozen in time. Like the people found in the ice, this novel, which made such an impact on the world, has been all but forgotten. 

Unlike that fictional lost Antarctic civilisation, we continue to feel the impact of our own lost societies. They were societies who didn’t believe our activities could ever impact the vastness of nature, who thought resources were inexhaustible, and species would just keep on existing, even when we removed their homes and collected their heads for trophies. They have left an indelible impact on those who came after.

We understand these impacts now. Hopefully growing awareness of the repercussions of habitat destruction, pollution and climate change won’t be trumped by ignorance and invested economic and political interest. I’d like to hope we won’t be remembered as a civilisation lost to disaster, but instead, as the pioneers of a better future.

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A few recommended reads (please add yours in the comments):
What would happen if we all just, disappeared? For real answers to that question, check out The World Without Us
If you want a soul-crushing end of the world narrative, bum yourself out with The Road (which you can also enjoy as a relentless and depressing film)
To explore our geological impact on earth, take a look at The World After Us
 
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References

Amos, J. 2018 Welcome to the Meghalayan Age - a new phase in history [BBC New article]  

Cooper AH, Brown TJ, Price SJ, Ford JR and Waters CN. 2018. Humans are the most significant global geomorphological driving force of the 21st century. The Anthropocene Review, p.2053019618800234.

Terrington RL, Silva ÉC, Waters CN. Smith H and Thorpe S,.2018. Quantifying anthropogenic modification of the shallow geosphere in central London, UK. Geomorphology, 319:15-34.

Waters CN, Zalasiewicz JA, Williams M, Ellis MA and Snelling AM. 2014. A stratigraphical basis for the Anthropocene? Geological Society, London, Special Publications, 395:SP395-18. 

Waters CN, Zalasiewicz J, Summerhayes C, Barnosky AD, Poirier C, Gałuszka A, Cearreta A, Edgeworth M, Ellis EC, Ellis M and Jeandel C. 2016. The Anthropocene is functionally and stratigraphically distinct from the Holocene. Science, 351(6269), p.aad2622.  

Waters CNGraham CTapete D, Price SJ, Field L, Hughes AG and Zalasiewicz J. 2018. Recognising anthropogenic modification of the suburface in the geological record.

Saturday, 1 September 2018

All the Better to Hear You With: New Fossil Mammal Ears from Skye

One of the best things about autumn is the warm evenings. Darkness comes early enough for us to stay up and enjoy it, but winter hasn't started breathing down our necks yet. It's excellent bat weather. Head to a woody walkway or forest clearing after sunset, and you may be lucky enough to hear the high pitched peeps of pipistrelles as they listen their way to dinner on the wing. 

Pipistrellus pygmaeus (image)
Mammals have evolved such an outrageous range of hearing: everything from the sonar of nightly moth-hunters, to the deep belly-rumble of elephants. How have mammals evolved such amazing hearing abilities? Answering this question is one of the major goals of mammal palaeontology. It's not just about communication - how animals hear effects their ecology, such as hunting strategies. In the earliest mammals many of the bones which would later become part of the ear (the malleus and incus) are still attached to their jaws. Although the picture is getting clearer all the time, there are still lots of unanswered questions about the ears of the earliest mammals - their morphology as well as their hearing range.

The postdentary jaw bones of mammals reduced through time (left to right) and became incorporated into the ear. This probably happened more than once in different lineages (from Luo, 2011)
Adding to our knowledge of this subject, my colleagues and I just described the ear bones, called petrosals, of a mammal from the Jurassic of the UK. The animal is Borealestes. It is a docodont: a group of mammaliaforms that are outside the crown group of mammals, and have always really interested palaeontologists. They independently evolved complicated cutting and grinding teeth (convergent evolution) separately from crown mammals. Now that we have some of their complete skeletons, we know from their limb bones that they were also more ecologically diverse than anyone previously expected for mammals in the Jurassic, including specialist diggers, climbers and semi-aquatic species.

The fossil of docodont mammal, Docofossor brachydactylus (top left), a specialist digger similar to the modern golden mole (top right) (Images Luo et al 2015, and April Neander)
The first Borealestes fossils were found on the Isle of Skye, and I'm currently working on previously undescribed material from the island with my colleagues. Most of these fossils are in the collections at National Museums Scotland, where I'm based. It turns out that among the fossils are the previously unknown petrosal bones of this small, insectivorous docodont. These bones are only a couple of millimetres across, so we used micro-CT scans and synchrotron scans to digitally reconstruct and study them. The resolution was so good, we could even reconstruct the pathways for nerves and blood vessels in unprecedented detail.

Digital reconstructions of the left petrosal (front and back) of Borealestes, a docodont mammal from the Middle Jurassic of the Isle of Skye, Scotland. Bottom left: location of petrosal bones on bottom of skull.
As you can see from the image (above), the petrosals are located on the underside of the skull at the back. When we think of ears we think of the fleshy lobes that stick out of the head on most modern mammals (including us). Those lobes, also called pinnae or auricles, are only superficial surface structures - the real job of hearing takes place inside the ear, in the petrosal. The sounds which enter the ear canal are transmitted by the malleus, incus and stapes bones as vibrations into the inner ear, which includes the cochlea and semi-circular canals. What interests palaeontologists is the shape of all of these structures in the earliest mammals, because their shape tells us about their function and evolution.

In the picture above, the petrosal is semi-transparent, showing the pathways that snake through it carrying nerves (yellow) and blood vessels (blue). You can see how dense the network of blood vessels is in this bone - some of these pathways have not been seen or described before in such an ancient mammal. We created a digital endocast of the inner ears - basically like pouring plaster into a hollow to see the shape - and one such endocast is pictured below for the right petrosal. You are basically looking at the shape of a mammal ear from the Middle Jurassic of the UK. Pretty cool eh?

Endocast of the right petrosal of Borealestes, a docodont mammal from the Middle Jurassic of the Isle of Skye, Scotland.
So what does all this tell us? We compared this ear to the ones known for other early mammals (such as Haldanodon and Morganucodon), and found it was similar in many ways to them. It is most similar to one of its close relatives, the docodont Haldanodon, which is not unexpected for a close relative, but also suggests they had a similar ecological lifestyles. But there were a few key differences - the shape of the outer surface of the petrosal in particular - and two blood vessels that haven't been identified before. We've named them the anterior and posterior trans-cochlear sinuses, and they traverse the pars cochlearis around the cochlear nerve. These new features tell us the story of docodont hearing is more complicated than it seems at first glance.

We'll now need to explore what those morphological differences might mean in terms of their hearing capabilities and broader evolution. In the coming years you'll be seeing a lot more of these and many other Jurassic Skye mammals.

References

Luo Z-X. 2011. Developmental patterns in Mesozoic evolution of mammal ears. Annual Review of Ecology, Evolution, and Systematics, 42: 355-380.

Panciroli E, Schultz JA, and Luo Z-X. 2018 Morphology of the petrosal and stapes of Borealestes (Mammliaformes, Docodonta) from the Middle Jurassic of Skye, Scotland. Papers in Palaeontology.