The ultimate reason that climate change is of such critical importance to us is that we are quite literally creatures of the climate. Our bodies, our communities, our cultures and our civilisations have all been moulded by the climate. Our entire existence as a species has evolved in response to the shifting climate. A changing climate facilitated our great migration out of Africa hundreds of thousands of years ago. The resilience gained from surviving repeated ice ages enabled us to colonise every corner of the planet. Sun and rain, light and dark, heat and cold, flowering, fruiting and decaying, these are the forces that shaped us. Without doubt or exaggeration, as a species and as communities, we are creatures of the climate. And that means as it changes again, we too shall change. In this chapter, I shall try to explain exactly what happened.
Modern humans, the species Homo Sapiens of which we are all members, emerged with all of our features, characteristics and abilities – but none of our knick-knacks nor knowledge – in the highland lake region of East Africa about 200,000 years ago. Their first venture out of Africa took place around 125,000 years ago, following the Nile to the Mediterranean and thence eastwards along the coastline as far as modern Syria. The journey was made possible by an ice age which cooled the region, lowered sea levels and opened the desert barrier across Sinai and Gaza. But it proved to be a dead end. A hot dry period followed, re-establishing desert conditions which barred their way further and closed off the the route back home. This group died out, isolated from other humans.
Tens of thousands of years passed. Through repeated cycles of climatic change, the varied geography of East Africa nurtured these early humans. The region roughly encompassing modern Uganda, the southern parts of Sudan and Ethiopia, Kenya and northern Tanzania, is a mosaic of climates, ecologies and species. Whatever the weather elsewhere, ice driven drought or flooded heatwave, this part of the world creates its own weather. Its location astride the equator ensures that whatever happens at the poles has minimal effect here. Its altitude of four to six thousand feet above sea level isolates it from incoming tides and tsunamis while ensuring there is amenable temperate weather somewhere all the time. When the world grows warm, you can retreat higher into the hills. When an ice age threatens, you can move into the lowlands. The Great Lakes provided unceasing fresh water throughout all these cycles. Animals for hunting and foodstuffs for foraging were plentiful. For a very long time there was little incentive to move elsewhere.
The probability is that these earliest ancestors of ours would have been similar to the surviving bushmen such as the San and !Kung tribes whose few remaining members are now confined to the harsh drylands of the Kalahari and Namib deserts in south west Africa. These people are amongst the world’s last hunter-gatherers. For nomadic people, living literally hand to mouth, when the weather changes, you have to move on. One day without water, one night exposed to freezing rain, one week without food, and your family group dies out. Foraging, scavenging, and moving on, these are the things that keep you alive.
At the peak of another ice age, a small group of people found themselves on the shore of the far north eastern edge of Africa, perhaps what we now call Djibouti or Eritrea. But at that time it wasn’t a shore and it wasn’t on the edge of a harsh desert as it is now. It was just another stretch of land made habitable by lower global temperatures and lower sea levels. The Red Sea was a big salty lake, cut off from the main Indian Ocean. Without even knowing what they had done, this group set up camp in what we now call Yemen. Corroborating DNA evidence with climatic data, we know this must have happened around 85,000 years ago. One of the ladies in the party, just one, is the ancestor of all modern non-Africans. Through the female lineage of mitochondrial DNA, everyone can trace their ancestry back to this one person. It’s kind of nice to call her Eve.
Eve and her band probably numbered no more than a dozen people. They lived by beachcombing, gleaning foodstuffs from the shore, and camping where they could find fresh water, at springs or near river mouths. We know they ate oysters because piles of ancient shells have been found in this very area. In this way, slowly meandering along the seashore, humans spread all around the coastline of south Asia, to Pakistan, India, Burma and Indonesia. It took ten thousand years.
During the next ice age, now around 65,000 years ago, sea levels fell again, and New Guinea and most of the larger islands of modern Indonesia comprised a continental land mass attached to south east Asia. Further onward movement would have required some island hopping and people took to the seas. It was a short hop to Australia. Indigenous Australians are amongst the oldest unmixed populations on earth. They’ve been there all that time. But sea levels rose again, cutting them off. Neither New Guinea nor Australia received any further influx, and didn’t mix with each other either. People retreated into their mountains and deserts and lived in isolation for tens of thousands of years, right into the modern era.
The next mild inter-glacial period enabled the peopling of Eastern Europe and Central Asia, so that by 50,000 years ago, humans were arriving in parts of Europe. Their routes passed through Turkey into the Balkans, and across the then dry bed of the Black Sea into Ukraine and thence towards Poland and Germany. The glaciers which blanketed Siberia, Russia and Scandinavia opened from around 45,000 years ago. People moved up the Indus Valley across the mountains into the Kazakh steppe and onwards into this vast unoccupied – and still sparsely populated – region. China was occupied from two separate directions: an eastward migration into the north along the Yellow River, and from the south following the fertile plains of the Yangtse.
By around 30,000 years ago, humans had settled Western Europe and we see evidence of their lifestyle and culture from cave paintings of the large mammals which they hunted. People spread too from central Asia north east to Siberia, the farthest point of Asia where it links to America. The bridge which took people across this last human frontier was not the result of lower sea levels but a frozen ocean which joined the Aleutian Islands in a sea of ice. The journey could only have been made by people already accustomed to living in Arctic conditions. The last time this would have been possible was around the height of the last major ice age, the so called Last Glacial Maximum (LGM) around 19,000 years ago. There may have been two or more separate migrations into the Americas. The first went south east across Canada towards the US east coast and thence into parts of central America. This was between 19,000 and 15,000 years ago. The second wave followed a route down the western seaboard of the USA and continued all the way down so that by 12,500 years ago all of central America and the coastal regions of South America had also been occupied.
That, in a nutshell, is the story of us, the people we think of as modern humans. As a species, we have survived multiple ice age cycles, at twenty thousand year intervals, since we set off on our great migration out of Africa. From these inauspicious origins, and against enormous odds, we peopled the entire planet. We learned to live, and finally to prosper, under vastly differing climatic and geographic circumstances through our ability to improvise, innovate, learn, adapt and move on.
Right up to the final phase, some 12,000 years ago, all humans all over the world – and there weren’t many of us – still lived pretty much the same subsistence makeshift lifestyle that we started out with, hand to mouth hunting and gathering, with few possessions and fewer comforts. Migration itself was an evolutionary response to changing weather patterns and the availability of foodstuffs. We adapted to different zones, and learned to digest different foods. We lived in harmony with nature but at the same time we were forced to battle its worst excesses. Perhaps it was discovering how to make fire that encouraged us to fight back. Fire enabled us fend off the cold, extend our diet, and create a social focus. But it also set us on our protracted mission to turn wood into smoke, carbon into CO2. You could argue that our own evolution made it inevitable that planetary damage would ensue.
But then something else changed. What made us settle down into the societies that are the recognisable forerunners of today’s patterns of living, the so-called dawn of civilisation? The answer again lies with the climate, and another ice age. The world had been warming after the LGM, but 12,800 years ago the temperature in the northern hemisphere plummeted by 15°C over a period of less than forty years. 1300 years later, there was an abrupt shift back to warmer conditions. This took less than five years. Yet another cold snap occurred around 8,200 years ago and another at 4,200. The record shows again that the climate changed rapidly, within a single human generation. The Sahara had blossomed into a vast savanna, but the cyclical shift brought back drought and desertification. People were forced to migrate towards the perennial waters of the Nile and Euphrates river systems. They congregated into the biggest communities that humankind had yet experienced. And when large numbers of people came together in one place, they were obliged to find ways to cooperate and to cultivate in order to survive under these novel conditions. It was this crowding along the banks of the Nile, the Euphrates, the Indus, the Yangtse and Yellow rivers that created the first towns. In these locations, and at this time, we find the first true cities and all that goes with them in terms of structure and culture: leadership, administration, accounting, market trading, and the emergence of technology. Climate change and environmental degradation had forced people not just to move but now to change their lifestyles.
At various times throughout human history, great deluges had swept the earth as ice sheets and glaciers melted and released their pent up waters. Entire communities were sometimes annihilated by sudden and torrential floods. 12,000 years ago, vast torrents flooded across North America, destroying everything in their path. 7,000 years ago, people living in pastoral settlements in what is now the Black Sea, awoke to find water flooding around them. The rising waters had breached the straits of the Dardanelles and swept across their homeland. So terrifying were these cataclysmic events, they seared an indelible mark into our collective psyche. The memory of that ferocious destruction is echoed in flood legends from many parts of the world. But in just one location, written records survive to tell us that at least one society counts its very existence in terms of before and after a great flood.
The retelling of a Sumerian folk tale, as recounted to a group of Jews exiled in Babylon, has been preserved as part of Christian scripture. It’s taught in European and American schools to this day as if it’s fact. Perhaps it is. We now know that parts of the previously dry Persian Gulf, where these first civilisations opened the written record of modern human history, were repeatedly flooded around 5,000 years ago. Settlers in the earliest Mesopotamian cities of Ur and Erech were driven from their ancestral homes. In ignorance, it was attributed to the displeasure of the ‘gods’. Noah and his Ark became primal avatars for survival against the worst excesses that nature – the ‘gods’ – can fling at us.
Our never ending battle with an apparently capricious nature led our species into a quest for explanations and influence which can be seen all over the world in stone circles, temples, churches, mosques, synagogues, astrolabes, horoscopes and UFO sightings. There is a powerful argument to suggest that the entire edifice of religion arose as a response to this collective recollection of divine displeasure. And that our attempts to appease this deification of natural forces has diverted our attention from the real causes. Lost civilisations from Peru and Mexico to Cambodia, Egypt and Iraq owe their demise not to an inability to comply with divine demand but rather to natural cycles of climate change. In our worst misguided excesses, vast numbers of our own children were slaughtered as sacrificial offerings to these gods who, it was supposed, controlled the weather. Faith in the supernatural led entire societies to the conviction that an afterlife was more important than this present one with all its uncertainties and tribulations. If damaging the planet was a necessary sacrifice then so be it. The malevolent influence of religion caused us to believe that we owed it to our gods to mould the world to our needs. “Be fruitful and multiply”, says the god of the Jews and Christians. “And replenish the earth and subdue it.” We followed these instructions to the letter. The earth has been thoroughly subdued. Seas are polluted, forests levelled, cities populated, lakes desiccated, ice caps melted. Large numbers of wild animals – “every living thing that moveth upon the earth” – slaughtered and exterminated. That god should be proud of our achievements. Except for one thing: the instruction was never given. It was imagined, in retrospective justification for what we were already doing.
We were deceived. It turns out that the health of our planet is the only thing that matters. Some of the older pagan gods and goddesses perhaps more accurately reflected our total dependence upon the forces of nature, the climate and the environment. In the northern hemisphere, our annual cycle of festivals continues to reflect this legacy of natural knowledge: mid winter’s darkest day celebrated as Yuletide in late December, the spring festival of Eostre in March, May Day, the Harvest Festival at the start of autumn in late September, and the fearful onset of winter on 31st October. Perhaps it would have been more realistic to have recognised the sun as the god of all energy. Come to think of it, maybe some of them did.
It was climate change that enabled the great migration out of Africa. It was climate change that enabled the ten thousand year trek around south Asia into Australia. It was climate change that opened up central Asia, Europe and China. It was climate change that made passable the Bering land bridge into the Americas. The distinctive skin pigmentation of our so-called races evolved from our different exposure to sunlight and from geographic isolation brought on by climatic shifts. It was climate-driven environmental degradation that impelled people to converge on rivers and settle in towns. It was climate change and environmental degradation that made possible the domestication of wild animals and wild crops. And it was the continuing cycle of drought and floods which caused empires to rise and fall.
Quite literally we are creatures of the climate. Because modern humans evolved in a time of ice, we are deeply programmed to abhor the cold and protect ourselves from it. We’re programmed to seek warmth. But unfortunately, we have developed no ability nor defence for living in a climate that is too hot. We can survive and thrive between 15-25 degrees, 10-30 at a stretch. It’s a narrow range. Without an amenable climate and shelter from its excesses, we suffer and die. The weather – wind and heat, rain and cold – affects our health, our moods, and our activities. Nowadays, those effects are perhaps most visible in our shopping trips and holidays. The so-called Seasonal Affective Disorder (SAD) – a winter depression –acknowledges our physical and mental need for sunlight. Police forces acknowledge an increase in violent crime during heat waves. We are truly creatures of the climate.
