| A | B |
|---|
| migrate | move to new places |
| ice ages | long periods of freezing weather |
| land bridge | a strip of land connecting two continents |
| Mesolithic Era | the Middle Stone Age |
| people learned to __________ to keep warm | sew animal skins into clothing |
| The first shelters were | in caves. |
| If there were no caves, they | built shelters called pit houses. |
| bone and stone tools were used in | the Mesolithic or Middle Stone Age |
