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How many ice ages has the Earth had and can humans live through one? —Mason C., age 8, Hobbs, New Mexico
First, what is a ice age† It’s when the Earth has cold temperatures for long periods — millions to tens of millions of years — that cause ice sheets and glaciers to cover large areas of its surface.
We know the earth has had at least five major ice ages† The first occurred about 2 billion years ago and lasted about 300 million years. The most recent started about 2.6 million years ago, and actually we’re technically still in it.
So why isn’t the Earth covered in ice now? It is because we are in a period known as an ‘interglacial’. In an ice age, temperatures fluctuate between colder and warmer levels. Ice sheets and glaciers melt during warmer phases, called interglacials, and expand during colder phases, called glacials.
Right now we are in the warm interglacial period of the most recent ice age, which started about 11,000 years ago.
What was it like during the ice age?
When most people talk about the “ice age”, they usually refer to the last ice age, which started about 115,000 years ago and ended about 11,000 years ago with the beginning of the current interglacial period.
At that time, the planet was much cooler than it is now. At its peak, when ice sheets covered most of North America, the average global temperature was about 46 degrees Fahrenheit (8 degrees Celsius). That’s 11 degrees F (6 degrees C) cooler than today’s global annual average.
That difference may not sound like much, but it led to most of North America and Eurasia being covered in ice sheets. The earth was also much drier, and the sea level was much lowersince most of the water on Earth was trapped in the ice caps. steppes, or dry grassy plains, were common. so were savannasor warmer grasslands and deserts.
A lot animals present during the ice age would be familiar to you, including brown bears, caribou and wolves. But there were also megafauna that became extinct at the end of the ice age, such as mammoths, mastodons, saber-toothed cats and giant ground sloths†
There are different ideas about why did these animals become extinct?† One is that humans hunted them to extinction when they came into contact with the megafauna.
Wait, there were humans during the ice age?!
Yes, people like us lived through the Ice Age. Since our kind, Homo sapiens† originated about 300,000 years ago in Africawe have spread all over the world.
During the Ice Age, some populations remained in Africa and did not experience the full effects of the cold. Others moved to other parts of the world, including the cold, glacial environments of Europe.
And they were not alone. At the beginning of the Ice Age, there were other species of hominids — a group that includes our immediate ancestors and our closest relatives — throughout Eurasia, such as the Neanderthals in Europe and the mysterious denisova people in Asia. Both groups appear to have died out before the end of the Ice Age.
There are many ideas about how our species survived the Ice Age when our humanoid cousins didn’t. Some think it has to do with how flexible we are and how we use our social and communication skills and tools† And it seems that humans did not descend during the ice age. Instead, they moved to new areas.
For a long time, it was thought that humans did not enter North America until after the ice sheets began to melt. But fossilized footprints found at White Sands National Park in New Mexico show that humans have been in North America at least 23,000 years ago — close to the height of the last ice age.
Hello, curious children! Do you have a question that you would like an expert to answer? Ask an adult to send your question to [email protected]† Tell us your name, age and the city where you live.
And since curiosity knows no age limit – adults, let us know what you’re wondering too. We won’t be able to answer every question, but we’ll do our best.
This article was republished from The conversation, a non-profit news site dedicated to sharing ideas from academic experts. It was written by: Denise Sue† Arizona State University†
Denise Su does not work for, consult, hold stock in or receive funding from any company or organization that would benefit from this article, and has not disclosed any relevant affiliations outside of their academic appointment.