Mastodons in Canada’s north were probably wiped out by the start of a new Ice Age, and not by human hunters, according to a new scientific study.
Early humans have commonly been blamed for hunting mastodons to extinction in North America. But scientists have discovered that the mastodons that once lived in what is now Alaska and the Yukon had already died out before the first humans arrived in the region.
Mastodons were distantly related to prehistoric mammoths and modern-day elephants. They lived in herds that ranged all over North America. Mastodons were about three metres tall, covered in shaggy wool, and they ate twigs, branches and other forest vegetation.
The scientists examined 36 mastodon fossils that had been found in the Arctic. The fossils were previously believed to be about 18,000 years old. But the scientists suspected that materials that had been used to preserve the fossils had interfered with the dating process.
They removed all contaminating substances, then used radiocarbon dating to determine how old the fossils were. The tests showed they were at least 50,000 years old – the oldest date that can be measured by radiocarbon dating.
The scientists now think that mastodons lived in the Artic during a brief “interglacial” period. An interglacial period is a time of warmer temperatures between two cold or “glacial” periods.
The last interglacial period lasted from 125,000 to 75,000 years ago. During that time, ice sheets that covered much of northern North America melted temporarily and forests were able to grow further north.
The scientists believe mastodons also moved further north during this time, following the trees and shrubs they fed on. When the temperatures turned colder again, the plants died and the mastodon’s food supply vanished.
The northern herds of mastodons likely died out from cold and starvation about 75,000 years ago. Scientists believe humans migrated into northern North America about 13,000 years ago, so the northern mastodons were gone before humans arrived.
Southern herds lived for another 65,000 years. Their numbers declined gradually due to a combination of colder temperatures and hunting. The last mastodons disappeared from North America about 10,500 years ago.
One of the scientists who worked on the study is Richard Harrington, a researcher at the Canadian Museum of Nature. He said paleontologists have always wondered why mastodons were living in the north when humans arrived. At that time, there was only ice and grassland, but no forest vegetation for mastodons to feed on.
Now that the correct age of the fossils has been determined, it all makes sense, he said.
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CURRICULUM CONNECTIONS
By Kathleen Tilly
Writing/Discussion Prompt
Draw a picture using any materials you choose of a Mastadon. Make sure to include details from the article, including what it looked like, what it ate and where it lived. Label the photo with these details.
Reading Prompt: Demonstrating Understanding
This article contains a lot of scientific facts and details about the lives of the Mastadons. Try to summarize this article only using 12 words. Make sure to read the article a few times before writing your summary.
Junior
Demonstrate understanding of a variety of texts by summarizing important ideas and citing supporting details (OME, Reading: 1.4).
Intermediate
Demonstrate understanding of increasingly complex texts by summarizing important ideas and citing a variety of details that support the main idea (OME, Reading: 1.4).
Language Feature: Prefix
A prefix is added in front of a root word and it changes the meaning of the word. For example, the word “interglacial” contains the prefix inter. Inter means ‘between’ so the word ‘interglacial’ means ‘between two glacial periods’.
Add prefixes to the following words and explain how the prefix changes the meaning of the words:
1. appear
2. legal
3. regular
4. stop
5. opened
