Worlds in Shadow Submerged Lands in Science, Memory and Myth

Long before we developed writing, humans communicated information across generations by telling stories. Professor of Oceanic Geoscience Patrick Nunn contends that some of these record actual environmental changes that impacted our ancestors. Scientists interested in the rather obscure discipline of geomythology argue that, when studied carefully, such oral histories can be an additional source of data to help us reconstruct past climates and understand their impact. Supremely absorbing, Worlds in Shadow covers a wider range of topics than Nunn's previous books, making this of interest to a broader audience.

The starting point for Nunn's argument is the simple fact that during the coldest part of the last major ice age some 20,000 years ago, global sea level was 120 metres lower than it is today. This situation changed in a few millennia so that by 10,000 years ago sea level had risen to roughly today's level. As coastlines receded, our ancestors were forced to abandon huge tracts of land used for generations, as these turned into today's shallow seas. Is it such a stretch of the imagination to think that these events left an impression and became the subject of stories and, in time, myths and legends?

Nunn thinks not. Oral history can be read as myth, yes, but also as memory and even scientific observation. This book is a perfect counterpoint to Prothero's Weird Earth that I just reviewed. Though the flood geology idea of young-earth creationists is nonsense, we should not throw out the baby with the bathwater. I previously expressed my scepticism regarding the fidelity with which details can be retained in this intergenerational game of Chinese whispers given how unreliable human memory is. Though understandable, such criticism betrays "a prejudice against orality" (p. 57) and Nunn argues that "it is no longer good enough to tartly dismiss all such stories as inventions, as many scientists have done" (p. 64). The Edge of Memory mentioned how Australian Aboriginals cross-check their stories to retain fidelity and Nunn here points to the work of Lynne Kelly on memory preservation in other pre-literate cultures.

Nunn's previous two popular books focused on Pacific and Aboriginal oral histories, based on the decades he lived and worked in Fiji and Australia. Worlds in Shadow significantly expands on this topic in two aspects: the scope of stories considered and the kinds of natural events they record.

First, though Pacific and Australian narratives still feature, Nunn now discusses many stories from northwest Europe, North America, Asia, and elsewhere. Helpfully, he has organised three chapters on a sliding scale from more to less likely. There are many fascinating stories recounted here, but a small sampling will have to do. Archaeology backs up stories such as the lost city of Herakleion, remains of which were discovered in the Nile delta in 1999. Less reliable but still interesting stories, at the nexus of science and memory in Nunn's words, include the lost city of Cantre'r Gwaelod that would be somewhere (?) off the coast of Wales. Other myths are just that: myths. I was pleased to see Nunn bring a healthy dose of scepticism to this topic and lash out at pseudoscientists and the New Age movement: "[...] this is a field that has become overwhelmed by a tide of nonsense" (p. 71). Atlantis has clearly been documented as a figment of Plato's imagination. Instead, Nunn focuses on less well-known examples of the recurrent theme of mythical sunken continents, such as Lemuria, imagined to form a bridge between Africa and India.

Of course, most of our planet's history happened before humans evolved and can only be reconstructed through science. Nunn takes a brief detour into deep time, discussing geological topics that I find irresistible: the massive volcanic deposits left by large igneous provinces, ancient supercontinents such as Pangaea and Rodinia, and the idea of a supercontinent cycle.

The second aspect that gets more coverage in Worlds in Shadow is the kinds of natural events that can be encoded in oral history, with Nunn serving up one engrossing study after another. Steady sea-level rise from melting glaciers was punctuated by rapid increases when meltwater lakes burst their banks. Freshwater pulses from North American lakes some 8400 and 7600 years ago influenced global climate and led to near-instantaneous sea level rise in the Mediterranean, interrupting the spread of agriculture.

Land can be swallowed by the waves for many other reasons. Coastal towns can be destroyed when the land level changes during earthquakes, as happened to Port Royal in Jamaica in 1692. Destructive tsunamis can result from sudden flank collapses of volcanoes, or underwater landslides when sediment deposits downstream of river deltas reach a tipping point or are destabilised by earthquakes. There is much to be learned from the study of ocean floor deposits, as shown by the complex history of landslides around the Hawaiian islands. So-called jack-in-the-box volcanoes can lead to the periodic appearance and disappearance of land, while some volcanic islands self-destruct in a most spectacular fashion. You will have heard of the 1883 Krakatau eruption, but have you heard of the 1453 Kuwae eruption? No, nor had I.

What makes this book relevant is that it reminds us that we ignore oral history at our own peril. One eye-opener for me was that even though graphs of sea level always show today's level at zero, this is just convention; there is nothing "normal" or "natural" about this. Sea level has always fluctuated and with glaciers rapidly melting due to anthropogenic climate change, we will experience the same sort of land loss our ancestors did. From 1880 to 2012 there was an average 19 cm-rise, and Nunn thinks projections of an additional 120-cm rise by 2100 are likely. The last two chapters thus examine our past and current ways of dealing with this. Unsurprisingly, short-term engineering solutions dominate. Ever since we abandoned our nomadic lifestyle, "[...] people invested time and energy in constructing the trappings of civilisation in one place" (p. 281), making us reluctant to leave.

I previously complained that the maps in The Edge of Memory were poorly reproduced, some light grey areas near-invisible; this time around the maps are fortunately much improved. If you have not read either book, I actually recommend you start with Worlds in Shadow given its more general coverage. If you already read The Edge of Memory then you certainly want to read this book too. I found Worlds in Shadow to be an incredibly absorbing read, and it is another prime example of the kind of well-written popular science books on specialist topics that Bloomsbury Sigma excels in.