Prehistoric: Dinosaurs, Megalodons and Other Fascinating Creatures of the Deep Past
HOLOCENE 10,000 YEARS AGO PRESENT DAY Humans evolved during an ice age For most of this time life was tough Temperatures were low The polar ice caps were more than just caps they were more like ice cloaks But around ten thousand years ago Earth entered a warming spell scientists call the Holocene and the ice sheets began to shrink This was good for humans Before long people were living all around the globe wandering across prairies through forests and along coastlines in small groups They hunted and fished for food or gathered roots nuts and fruits to eat while they traveled As the climate continued to warm some groups settled in small villages and began to farm the land They chose places where the soil was good for growing crops and with plenty of fresh water nearby in rivers or lakes Over time some of those villages grew into the first towns and cities Today most people live in urban areas Even with this warming we are actually still living in an ice age today It may not feel like it on a hot summer day but as long as there’s at least some ice and snow at the North and South Poles scientists say it’s an ice age 8
HOLOCENE YEARS PRESENT DAY AGO 10,000 Large mammals such as woolly mammoths mastodons and woolly rhinos still roamed the Earth at the beginning of the Holocene But within a couple of thousand years they were all extinct Along with the changing climate humans hunting with early weapons may have been partially responsible for their disappearance Earth today during ice age conditions Earth during the warm Cretaceous Period 70 million years ago ICE AGES The Ice Age during which we evolved began 2 6 million years ago Since then the Earth has alternated between times of warming and cooling But throughout this time the Earth’s poles have always been covered by ice sheets There have been four other ice ages before the current one Around 650 million years ago the Earth may have been so cold that it was totally frozen over Ice sheets stretched all the way to the Equator This period is called Snowball Earth Snowball Earth 650 million years ago
PLEISTOCENE 2 6 MILLION 10,000 YEARS AGO The time we call the Ice Age began 2 6 million years ago at the start of the Pleistocene Epoch During this time Earth’s climate cooled Ice caps formed at the North and South Poles and the planet began diving into a long deep cold spell At times thick fingers of ice reached nearly a third of the way down to the Equator
But the long history of the Ice Age has been punctuated by several warmer times too when glaciers and ice sheets retreated Scientists call the cold times glacial periods and the warmer ones interglacials During the warmer interglacial periods the environment provided plenty of water from melting glaciers Forests flourished and mammals at least some of them grew to extraordinary sizes Giant ground sloths stripped leaves from trees and huge armored glyptodonts skulked across forests and plains Saber toothed cats stalked their prey through the long grass When cold conditions returned in full force many types of large mammals went extinct The animals that survived the change were the ones best adapted for the cold weather like the huge woolly mammoths and musk oxen with their thick fur coats CLIMATE CHANGE Changing temperatures had drastic effects on life on Earth during the Pleistocene Epoch But why does the climate change over time Scientists have found clues in rock layers and fossils They also look closely at ice cores taken from deep within ancient glaciers and ice sheets which are formed from snow compressed over hundreds of thousands of years The recent cold and warm cycles of Earth’s climate are thought to have been caused in part by changes in Earth’s orbit around the Sun and in the way Earth wobbles like a top as it spins Today the climate is warming up once again But scientists have pointed to a different cause Humans are affecting the climate especially from burning fossil fuels such as coal and natural gas These fuels add greenhouse gases to the atmosphere As the amount of greenhouse gases goes up more and more heat from the Sun gets trapped and the Earth gets warmer Sun’s rays Earth’s atmosphere including greenhouse gases The 8-inch 30cm long canine teeth of the saber toothed cat Smilodon were used for stabbing and tearing into its prey Its enormous size meant Smilodon needed to be able to flex its jaw 90 degrees to take a full bite Some heat escapes from the Earth’s atmosphere into space Some heat is trapped in the atmosphere by greenhouse gases and warms the Earth 11
