Scientists have been able to track the entire life of a mammoth (猛犸象) that lived more than 17,000 years ago. The team figured out where in Alaska it likely was at any given point of its 28-year life.
To do so, the researchers closely studied a 1.8-meter-long mammoth tusk (象牙) dating back around 17,100 years. Mammoth tusks grow by adding layers of tissue almost daily, forming rings like a tree that can reveal detailed information.
The main thing the researchers analyzed was strontium isotopes (锶同位素), which can act almost like an ancient GPS. Different areas have different isotopic features, which start in minerals deep underground and make their way to the top of the land, into plants and water. Finally, they can be seen on the animals that consume those plants and water.
Previous studies had produced an isotopic map of Alaska by analyzing isotopes in the teeth of hundreds of small animals, which don’t travel far in their lifetimes and so represent a local area. The researchers can then compare isotopic signals from each part of the mammoth’s tusk to this map, to get an idea of where the mammoth most likely wandered throughout its life.
The scientists started from where its remains were found. Working backwards, the scientists then looked at the isotopic feature of where the mammoth was about a week before death, then searched the map for the best match in a nearby area. A model then worked backwards stepwise to determine the most likely routes the mammoth might have taken.
According to the research, the mammoth seems to have spent his early years in the Yukon River Basin and Alaska, constantly trekking between several territories in a predictable pattern. The team says that this behavior seems to be like modern elephants, moving regularly from place to place.
【小题1】What is the key to reading the mammoth’s tusk?| A．The length of the tusk. | B．The age of the mammoth. |
| C．The area the mammoth lived in. | D．The tissue found in the tusk’s layers. |
| A．Plants and water are main carriers of isotopes. |
| B．The isotopes in the tusk came from the underground. |
| C．It was difficult to analyze the isotopic features of an area. |
| D．The researchers were surprised to find isotopes in the tusk. |
| A．By explaining the significance of tusks. | B．By recording the animal species of Alaska. |
| C．By offering researchers a map to compare with. | D．By proving the possibility of analyzing isotopes. |
| A．Looking for food. | B．Escaping from dangers. |
| C．Making a long journey. | D．Sending warning signals. |
