That is before there is any written evidence from the period in which you are interested.
那是一个你所感兴趣,而无任何书面记录的时代
We have written evidence from the people who went and they say why they did it.
这里有移民留下的文字材料,上面写得很清楚
Not at the same time, but the reason we have any written evidence at all is that there was some kind of conflagration that produced a fire that baked clay into pottery.
虽然不是在同一时间,不过我们能发现这些可读记录,全靠这些意外的火灾,将那些粘土烧制成了陶器
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