数个世纪以来，天花对于人类来说是一种最可怕的致命性疾病，其历史可追朔到3500年前。

Over the centuries, smallpox has been one of mankind's most feared and deadly diseases with a history dating back at least 3500 years.

youdao

但对我们来说这很令人激动，因为它揭示了这个遗址最早的建筑层，可追朔到3000年前。

But it is really exciting to us, because it reveals the earliest construction layers of the site, dating to about 3, 000 years ago.

youdao

但对我们来说这很令人激动，因为它揭示了这个遗址最早的建筑层，可追朔到3000年前。

But it is really exciting to us, because it reveals the earliest construction layers of the site, dating to about 3,000 years ago.

youdao