Renowned geneticist and anthropologist Spencer Wells has traced human evolution back to our earliest ancestors. He directs the Genographic Project, which is collecting and analyzing hundreds of thousands of DNA samples from people around the world in order to decipher how our ancestors populated the planet. Now, in his new book, he examines our cultural inheritance in order to find the turning point that led us to the path we are on today, one he believes we must veer from in order to survive.
Pandora’s Seed (Published by Random House; $26.00) takes us back to a seminal event roughly 10,000 years ago, when humans made a radical shift in their way of life: we became farmers rather than hunter-gatherers, propelling us into the modern world. But the dramatic shift in lifestyle had a downside that we’re only beginning to recognize.
By Spencer Wells
As I write this on a sunny spring day in Washington D.C., I’m thinking back just a few short months to the duet of blizzards (dubbed “Snowpocalypse”) that descended on us in early February.
This one-two punch left the city reeling–with around 40 inches of heavy snow on the ground, life came to a virtual standstill. Mail wasn’t delivered for several days (so much for “neither snow, nor rain, nor heat, nor gloom of night…”), the city and the federal government were laid low for over a week, and most people spent their time alternating between huddling inside and becoming intimately acquainted with their snow shovels.
Events such as these remind us–rather abruptly and forcefully–that we live in the natural world, with all of its occasional random fury, despite the widespread penetration of the rational, digital universe into our everyday lives. And because of their sudden, disruptive nature, they also tend to have significant social impacts.
Snowpocalypse occurred, appropriately, as I was completing final edits on my new book, Pandora’s Seed. As I described in its pages, another cold snap around 12,000 years ago had a much longer-lasting effect on humanity.
The Younger Dryas, as it was called, occurred suddenly during a period of warming at the end of the last ice age. Lasting for over a thousand years, it was set in motion–paradoxically–by the very warming that preceded it.
Warmer temperatures caused the Laurentide ice sheet that once covered much of North America, including present-day Chicago and New York, to retreat from its foray southward.
The pieces that remained around 12,700 years ago served to hold back Lake Agassiz, a massive body of fresh water located in what is today central Canada. Agassiz was composed of much of the rest of the former ice sheet–while today’s Great Lakes are large bodies of water, this was a monster larger than all of them put together, larger even than the state of California or the Caspian Sea.
When the ice dam holding the lake back melted, it released the water, which flowed into the Saint Lawrence river basin and out into the North Atlantic. The flood of fresh water formed a kind of “shield” on the surface of the ocean–it floated because its density is lower than that of salt water–which killed the Gulf Stream that brings warmer water from the tropical Gulf of Mexico into the North Atlantic.
This natural flow had warmed western Eurasia like a massive radiator since the end of the Ice Age, and still does. It’s the reason why palm trees grow in Cornwall, the southernmost point in Great Britain, despite the fact that its latitude is 50°, the same as Winnipeg in Canada, and nearly 30° north of the Tropic of Cancer.
When the influx of fresh water killed the Gulf Stream, the northern hemisphere was plunged back into Ice Age-like conditions–the Younger Dryas.
While all of this was going on in the North Atlantic, the inhabitants of places like the Middle East had been getting used to the warmer temperatures.
Between roughly 16,000 and 12,700 years ago things were warming up and becoming wetter, which led to the expansion of plant species that had formerly been limited in their distribution to mountain valleys, where there were reliable supplies of water.
The ready availability of these grasses–the ancestors of wheat, rye and barley–led some populations to focus much of their energies on gathering them. It was a plentiful and calorie-rich food source, so it made sense.
The so-called Natufian people, who flourished in the western part of the Fertile Crescent during this period, were largely grain gatherers. Gathering wild wheat yields more calories of food for each calorie of energy invested than did early forms of agriculture, which made it a fabulously valuable food source.
Moreover, it was a particular type of food resource that lent itself to long-term storage–a seed that could be stored dry for years. A couple of weeks of intensive grain-gathering in the fall can yield enough wheat to feed a family for a year, supplemented with nuts and game meat.
Life was good, and they made the most of it by…well…doing what people do: They had babies.
The hunter-gatherer way of life had limited the number of children people had as part of a complex feedback loop with the environment. If the population grew too large it was necessary to split and form two smaller groups, one of which would typically move on to new hunting grounds.
The calorie-rich environment of the Fertile Crescent’s wild grain fields increased the region’s carrying capacity (the number of people the land could support), and the human population responded.
Natufian settlements during this period expanded into villages of 150 people or more, complete with circular houses and stone storage pits. It was a radical shift in our way of life, and it only happened because the Natufians could rely on a steady supply of grain from the territory where they lived.
Then, suddenly, it all changed.
That burst dam thousands of miles away in North America, setting in motion the Younger Dryas, brought a return of the long winter. The population of the Middle East was cast back into the ice age, but this time they had a strike against them: they couldn’t move on to greener pastures.
They had invested too much in their villages, the collective memory of the good times probably still fresh in their minds (leave the village to return to the hardscrabble life of a nomad? Unthinkable!), and in all likelihood there were now too many people to return to life as nomadic hunter-gatherers. The Natufians were in a bind.
Although Dryas refers to a tundra plant species, it could more aptly refer to the drying effect during these periods of global cooling, for this was the main effect in the Middle East.
As the land dried out the wild grain retreated from the lowlands into the higher mountain valleys, its distribution determined by where it could get enough water. The Natufian gatherers had to travel farther and farther from their lowland settlements to find enough food to survive. This would have put tremendous pressure on the food supply, and probably resulted in an increased mortality rate in these people accustomed to a land of plenty.
It was humanity’s first real encounter with Thomas Malthus’s conjecture that population growth will eventually produce more people than can be supported by the available food supply.
Then, sometime between during the Younger Dryas, one of these stressed Natufians had a revolutionary idea. What if, instead of walking farther each day to gather grain, they simply planted it close to the village?
His or her first efforts must have been rewarded with admiration from the entire village, and the idea quickly spread. Virtually overnight humans had gone from being controlled by their food supply to controlling it.
This course of events can be seen in the bones of the people living in the region at the time, making use of something called the strontium/calcium ratio.
Strontium (Sr) is an element that accumulates in human bone, and its content is determined by the Sr level in the groundwater of the region where you live (as well as exposure to nuclear fallout, which has Sr-90 as one of its major constituents).
Plants absorb Sr as they grow, and then pass it on to the animals eating them. Animals excrete Sr, so not all of the Sr eaten is passed on to carnivores. Thus, the higher the proportion of plant food in your diet, the higher your Sr levels.
Natufian remains have a very high level of Sr during their intense gathering phase prior to the Younger Dryas, then the level drops significantly as the wild stands of grain shrank and they turned to hunting to survive.
The level then rises dramatically after the onset of domestication as the new culture took hold and plants made up a larger proportion of their diet.
The Fertile Crescent wasn’t alone–while this sequence of events was playing out in the Middle East, extraordinary things were happening in other places around the world.
The Neolithic Revolution seems to have been a global trend around this time, driven by a shift in the weather. This change in our relationship with nature had an extraordinarily far-reaching impact on the future of humanity–it was about far more than just food.
Although performing a seemingly trivial act, the first person to plant a seed set in motion ten millennia of extraordinary social and biological upheaval. Food became a fuel–a metaphorical biodiesel, if you will–for powering social change. It yielded our first encounter with something I call trans-generational power–the idea that, with the increase in our power over the world around us brought about through the development of agriculture and subsequent technologies, we gained the power to affect events many generations down the line.
Our minds, evolved over millions of years as hunter-gatherers whose only concerns about cause and effect extended perhaps a season into the future (will moving there make it harder to find game or gather plants in the dry season?), were not equipped to imagine a sequence of events that might occur long after we had died.
And given that as hunter-gatherers we were very much a part of the environment in which we lived, rather than in control of it, we didn’t really need to worry about how things might play out many years down the road. Our actions, like those of any other animal in the ecosystem, didn’t have a large enough effect to perturb the balance of nature.
The development of agriculture changed all of this. It also led to unforeseen changes in our selves and our society that would take many thousands of years to play out.
The end result of these events, with the ensuing shifts in population density, social structure and lifestyle, is the situation we find ourselves in today.
Increasing wealth and technological progress, certainly, but also a rising burden of chronic diseases and increasing rates of mental illness (according to the World Health Organization, this will be the second largest cause of death and disease in the world by 2020, after heart disease) as we become ever further distanced from the way of life we led for 95 percent of our species’ time on the planet.
Global warming, the result of the latest fossil-fueled phase of Neolithic Revolution, promises to remake not only the natural world, but our social systems as well, as we struggle to deal with the fallout from a change in the weather that’s forecast to be more momentous than any since the Younger Dryas.
Even religious fanaticism has its roots in the cultural shifts set in motion during the Neolithic, as more and more people in the modern world sense a loss of mythos and long for a return to old certainties, either imagined or real.
All were set in motion by the seeds planted around 10,000 years ago, and finding solutions to these deeply rooted crises looks set to be one of the great challenges of the 21st century.
Spencer Wells is an Explorer-in-Residence at the National Geographic Society and Frank H. T. Rhodes Visiting Professor at Cornell University. He leads the Genographic Project, which is collecting and analyzing hundreds of thousands of DNA samples from people around the world in order to decipher how our ancestors populated the planet. Wells received his Ph.D. from Harvard University and conducted postdoctoral work at Stanford and Oxford. He has written two other books, The Journey of Man and Deep Ancestry. (Photo credit: David Evans)