Nowadays, we can find salt in most kitchens. But in the past, salt was a rare and valuable mineral (矿物). Back in the sixth century, salt was even worth as much gold! During the Stone Age, people (eat) a lot of red meat. Because red meat is (natural) rich in salt, people didn't need to find salt elsewhere. However, as farming became popular and people ate more wheat and rice, they had less salt in their diets. So, people had to search for other ways (get) salt.
Around 6000 B. C., the Chinese began collecting salt from lakes to flavor(调味) their food. This is the (old) recorded history of salt production. But there were other (method) of collecting salt, too. People in Central Asia mined rock salt underground around 4500 B. C. Around 3000 B. C., the Egyptians began to collect salt from seawater. By 800 B. C., the Chinese were producing salt by boiling seawater. It took less time than waiting for the seawater to evaporate (蒸发). Because these methods took a long time, salt was very (value). In fact, it was even used as money. In China, people paid taxes (税) with salt. In Rome, soldiers (pay) part of their wages in salt. Salt is now very cheap to buy. But it remains important part of the human diet, and it is something we can't live .
