Abstract

While globalisation is often viewed as a contemporary transformation and symptom of the modern world, textual, archaeological, genetic, and other sources increasingly demonstrate significant interconnectivity – and linked biological exchange – in the ancient world. Already by the Bronze Age, major commercial networks existed in several parts of the Old World, leading to the human-mediated exchange of domesticated crops, animals, and other biological species. Trade links increased in the Iron Age, resulting in longer-distance commercial and biological exchanges. Species translocations in this period diversified subsistence but also resulted in the spread of deleterious species such as the black rat and the plague. Biological exchange further intensified in the Medieval period, with the emergence of expanded and intensified trade networks, particularly in the Indian Ocean. These brought a vast number of new breeds and species to societies across the Old World. Species moved for a whole variety of reasons, from the mundane to the symbolic, and were both intentionally and unintentionally transported by people. While introduced species are often vilified today, it is clear that the creation of increasingly cosmopolitan assemblages of organisms across the Old World not only at times transformed ecologies in negative ways, but also enriched diets, improved human health, made challenging landscapes habitable, and in many cases increased biodiversity.

Keywords: Biological exchange, invasive species, novel ecosystems, species translocation, Silk Road, trade, Indian Ocean

Globalisation tends to be seen as a contemporary phenomenon. Those of us alive today have the sense of living in a world that is undergoing profound change, as new technologies enable the collapse of age-old barriers to communication, travel, and economic integration. Linked to the globalisation of technology, ideas, culture, and commodities is a globalisation of the biological world, with intensive connectivity facilitating the spread of species beyond their native range. Like globalisation, the transfer of such ‘invasive’ species is seen as a recent phenomenon, a dangerous and costly corollary of a seemingly over-connected modern world. ‘Bioinvasions’ are described as ‘pathogens of globalization’ (Bright 1999), and scientists talk about the potential risk of invasive species as a feature of ‘bioterrorism’ and the need for ‘biosecurity’ (Meyerson and Reaser 2003).

But, in reality, the idea that either globalisation or invasive species are new is profoundly inaccurate. While the speed of communication and transport, and the degree of economic integration today may be greatly increased, we live in a world that has long been ‘globalising’.

Homo sapiens is essentially an African primate. The vast majority of our evolution occurred in Africa, and the migrations of both our own species and ancestral human populations out of Africa are, in the grand scheme of things, relatively late-in-the-day occurrences. Nonetheless, we have not only travelled and settled beyond Africa, we have also achieved a global distribution unparalleled in other mammals (Gamble 2013; Finlayson 2014). From the most arid deserts to the iciest reaches of the frozen poles can be found human societies of diverse types and forms. And processes of dispersal, colonisation, and migration continue. Indeed, we now travel faster, further, and more often than ever before. In 2006, a staggering 4.4 billion people passed through the world's main airports (ACI 2007, cited in Hulme 2009: 13).

We have travelled far, but we have not travelled alone. Linked to the spread of human populations has been the geographic expansion of an extraordinary range of other species. These species have moved with humans, either directly, by way of our bodies, our caravans, our ships, and our roads, or indirectly by way of new routes opened up by our activities, for example, as we transform environments and accordingly provide pathways for new types of species to migrate and colonise. Much of this movement has been inadvertent, leading to the unintentional co-migration of a wide array of parasites, microbes, disease vectors, and invasive and commensal species. But we have deliberately carried with us a whole host of species as well, in particular the domesticated crops and animals that have enabled our astounding demographic success.

This book is about the extraordinary movements of humans across the globe, and the equally remarkable role that we and our ancestors have played in shaping the geographic dispersal of other species. It draws together contributors from diverse disciplines, whose research explores a broad range of species, time periods, and regions. The chapters collected here do not provide a comprehensive account of human dispersals and human-mediated species movements – such an undertaking would span many volumes and probably many lifetimes. Instead, they offer a broad range of illustrative examples that underscore the complex palimpsest of species movements through time.