What is an ice age? How did the latest period of glaciation form our species? How has the abundance of this latest period of interglaciation changed our behavior? Watch this lesson to find out.
What is an 'Ice Age'?
The term ice age refers to a period of time in which the surface of the earth is covered with sheets of ice called glaciers. This does not mean that earth is one big snowball for an entire ice age. While this happens on occasion, most ice ages are made up of a series of warm and cold spells.
In cold periods of glaciation, glaciers extend from poles toward the equator. And in warm periods of interglaciation, the glaciers retreat back to the poles.
During interglaciation, glaciers retreat back to the poles
So while the term ice age might bring to mind images of wooly mammoths and saber-toothed tigers, it is important to remember that we are currently in an ice age, and have been for about 2.8 million years. We just happen to be in a period of interglaciation.
Ice ages create new challenges for life by significantly altering the environment in which life forms compete. Ice ages lower the world's temperature, making it hard for cold-blooded animals to survive. Ice ages also tend to make the world a drier place by locking up the moisture in ice. This makes it difficult for plants to survive on land. This, in turn, makes it very difficult for land-dwelling animals to find food.
Yet these challenges also present new opportunities. Mammals owe their current primacy to ice ages wiping out much of their competition. And while most primates suffered from the reduction of lush rainforests into arid grasslands, one sub-branch of this family would abandon the protection of trees to wander the earth in search of food. These were the first hominids, ancestors of modern humans.
Early Humans and the Herds
I will spare you the details of our development as a species. What is important for this lecture is that at some point we stopped simply foraging and scavenging, and began hunting. Because at the time, the most reliable sources of food were migratory herds.
To keep up with these herds, our ancestors had to be as mobile as the animals they were hunting, so we developed longer legs and upright form of walking. To outsmart and track those herds, we developed bigger brains. To take down large game we combined those bigger brains with finer hands and teamwork, and started making tools. In short, the challenges presented by the ice age forged man into the hyper-intelligent, highly adaptable, upright walking, tool generating creature we know today.
And so now we come to the latest period of interglaciation, a great thaw that began around 10,000 BCE. Human beings had been following the migrations of herd animals for thousands of years. The scarcity of plant life required herds to move constantly. The herds moved to find new vegetation to eat; the humans moved to follow the herds.
With the thaw, plant life thrived again. Herds no longer needed to move such long distances to find fodder. Yet countless generations had made these migrations instinctive to herd animals. Human beings, on the other hand, had no such instincts to constrain them. They quickly realized that the animals they hunted would survive just as well without walking for thousands of miles every year. Now if only they could find a way to convince the animals to abandon their instincts.
The Domestication of Animals
This marks the beginning of domestication of animals. Human beings did whatever they could to break animals of their migratory habits. This proved easier with some animals than with others. Likely the first herd animal to be domesticated was the sheep. Sheep are smaller than humans, and do not move very quickly. When a herd of sheep began to migrate, all it took were a few humans to restrain them and drive them back to more convenient pastures. Humans might have been helped in this process by the domesticated animal, the dog.
The dog makes an excellent shepherd. He's fast, he's intelligent, he's deadly, and he's absolutely terrifying to your average herd animal, who thinks he's a wolf. These factors combined to make the dog an appealing ally even during our early days as hunters, which was probably when we first formed our alliance with the canine species.
We probably first formed our alliance with dogs during our early hunting days
With the dog for an ally, and ample vegetation for grazing, humans came to domesticate many of the large species on the planet: the sheep, the goat, the pig, the cow, the horse, the donkey, the water buffalo, the wide variety of camels, the yak, the reindeer and even the elephant.
Still, many species evaded domestication, being too ornery, too fierce, too independent, or too prone to panic to be controlled. Others required a very specific diet that humans could not replicate. And still others simply refused to breed in captivity.
Nevertheless, humans were able to break enough species of their migratory habits to allow us to settle in one place. Instead of humans following herds through their endless migrations, the herds would now follow the humans leading them from pasture to pasture. This system is called pastoralism. Yet despite these advances, the shepherd must still move about, albeit in a much smaller circuit than migratory hunters.
The Effects of the Domestication of Animals
Though domestication had made these animals dependent on man, man was still dependent on those domesticated animals. The warming earth would soon provide another option: the domestication of plants through settled agriculture. Yet it is important to remember that without the domestication of animals, human beings would likely never have been able to stay put long enough to raise a crop of wheat without starving to death.
So we've seen how humanity developed in response to the extraordinary challenges presented by the ice age. Equipped to survive the utmost scarcity, our species entered this warm period of abundance. The same adaptations that had allowed us to survive the depths of glaciation would enable us to dominate this interglacial period: The brains we'd developed to find food would later come up with ways to make food. The hands we'd developed to make and use knives and spears would go on to construct the millions of tools we use today. Finally, the teamwork we'd needed to pull down a mastodon would allow us to build cities, states, and empires.