Climate Change: The Human Companion

In the modern world, climate change has frequently been presented as a human creation that threatens to change society both globally and locally. Flooding witnessed during late 2012 across Britain, and 2013’s second winter, alongside extreme global climatic events, have acted as ever-present reminders that our climate and environment remain unpredictable and potentially damaging. However, what few appreciate is that climate change was one of the main driving forces behind the evolution of Homo sapiens and has continued to influence some of the most emphatic human innovations during our time on Earth. This has important implications for our planning and responses to the ever-evolving climatic context.

For the last few decades, anthropological and genetic consensus held that humans evolved 200,000 years ago at a time when the nature of the Earth’s orbit and orientation was resulting in increasingly rapid climatic change and the onset of glacial cycles. Despite this uncanny timing, accounts tended to argue that about 60,000 years ago, a single human population left Africa during a period of  unfavourable climatic conditions that would have channelled demic movement into abundant coastal environments. Populations were thought to have tracked the coast around the Indian Ocean rim and into Southeast Asia, or follow riverine environments and grassland up into Europe. In this scenario, Homo sapiens expanded rapidly, reaching Britain and Australia at around the same time (approximately 45,000 years ago) at the expense of a number of contemporary hominin species, including the Neanderthals. As a result, Homo sapiens are considered as having some inherent competitive advantage, facilitating rapid and wholesale mobility across the globe.

Recent work by Professor Michael Petraglia and Dr Nicole Boivin of the University of Oxford as part of a research team investigating the climatic and environmental context of human expansion beyond Africa is starting to form quite a different narrative. Evidence for early human populations in the Levant at the cave sites of Skhul and Qafzeh dated to c. 100,000 years ago are seen as pioneering success stories rather than humans left fatally stranded by the spectre of dramatic climate change prior to a later successful exodus. Similarly, expansion of further populations into Arabia under variable climatic conditions between 100,000 and 80,000 years ago are thought to have focused on ancient rivers and springs that are beginning to be mapped by environmental specialists. This work bolsters previous research at the University of Oxford that implied human populations might have reached India as early as 80,000 years ago, surviving beyond a massive volcanic eruption from the Toba vent in Southeast Asia that spread fallout for 2500km c. 75,000 years ago and would have impacted on the flora and fauna of South Asia.

This latter model also agrees with developing genetic evidence that, using the application of different mutation rates, suggests that humans left Africa as early as 100,000 years ago. Furthermore, genetic analysis of Neanderthal specimens and hominins known as the ‘Denisovans’, alongside modern human populations, imply a greater degree of genetic admixture and complexity than a simple ‘replacement’ scenario. For example, modern human populations in Eurasia share c. 4% of their genome with Neanderthals, while those in Africa share none, strongly implying interbreeding across the geographical range where Homo sapiens and Neanderthals overlapped. Similarly, recent refinements in radiocarbon dating techniques at the University of Oxford have allowed more accurate chronologies of Homo sapiens expansion and Neanderthal demise across Europe, implying a short period of overlap during a period of relative climatic instability. This new data seems to suggest that humans were not intrinsically more prepared for success. Rather, they were better placed to face increasingly rapid climatic change, and the resulting contingent environments, that began to affect the Earth from 200,000 years ago.

This flexibility of response was not limited to the initial evolution of our species on a global scale. The development of agriculture and urbanisation, two achievements focused upon by many archaeologists, can also be attributed to climatic fluctuations and difficult environments. Agriculture – the domestication of plants and animals genetically and – first developed in the Near East around 10,000 years ago during a period of cold glacial conditions, which gave way to rapid warming of up to 5°C cut short by rapid cooling. Whereas many assume that agriculture is a sign of plentitude, its origins may in fact lie in instability and a desire of hunter-gatherer populations to minimise uncertainty in their food supply. The developed agricultural package of the Near East then spread across Europe, from Bulgaria to France between 5800 and 5500 BC. It then proliferated into Britain and Scandinavia 1,500 years later. During this expansion, populations had to take into account the divergent environments and climates of Europe. As with the example of first human expansion out of Africa, agricultural populations succeeded not because of some inherent competitive advantage, but because of their ability to buffer and adapt to climatic uncertainty.

The rise of the first cities in the Near East and Egypt around 4000-3000 BC also formed in the face of difficult environmental circumstances. In both areas, vast swathes of desert and aridity surrounded the alluvial plains of rivers, on which populations agglomerated into new organisational forms. The Nile, as well as the Euphrates and Tigris, still dictate the population structures of humans in those regions today. Similarly, early cities in the Indus Valley of Pakistan formed during a period when rivers provided focal points in the midst of desert. As solutions to climatic instability and focused resources, urbanism itself is often inherently unstable. The collapse of many cities in the Near East as well as the Indus frequently followed periods of enhanced aridity and the drying up of river-beds. Similarly, shifts in power in the Near East, such as the rise and fall of the Assyrian Empire, can often be related to geographical distributions of intense drought. This should act as a warning to populations in similar regions today. In particular, the decrease of Himalayan glaciers threatens to leave dense urban populations in northern India and southern Pakistan without a source of clean drinking water.

Although by no means is it possible to reduce the entirety of human achievement to the vagaries of climate change, it is clear that climate has played a considerable part in the evolution and expression of Homo sapiens during our time on this planet. One feature that distinguishes us from other hominin populations lies in our ability to overcome rapid climatic change. This has major implications for our understanding and approach to “climate change” today. Very few would suggest that increasing industrialism and urbanism are not contributing to the release of pollution into the environment and atmosphere, with inevitable consequences for our climatic systems. However, in terms of our response, this is irrelevant. As climate change and environmental adaptation scholar Michael Rowland has made clear, climate change has and always will impact upon human populations. As I have shown, it has played a crucial role in our evolution and some of our most emphatic legacies. What has always mattered throughout the history of human interactions with climate change is our response.

Green power and energy, as well as reductions in pollution are certainly necessary moves to decrease the rate of global warming and any other complex effects that this might have on the interlocking climatic systems of the Earth. However, it should also be realised that with our influence or not, glacial cycles are occurring. Climate change should be planned for on a local, regional, national and international level, whether in the form of hose-pipe bans,  investment in new power sources, or legislation to limit emissions. As the past should demonstrate, it is not a case of “whether” climate change is occurring, but “when.” Furthermore, as the past suggests, it will be those who innovate and who adapt that will determine the impact of climate change on our unstable planet.