1. By measuring how closely current populations are related, the authors trace the routes by which early humans migrated around the earth.
    通过测定当前人类种群间的亲缘关系，作者们弄清了地球上早期人类迁移的路线。

2. For fear the agents of other firms should be able to trace the kind of research they are likely to be undertaking.
    他们生怕别的公司的情报人员据此摸到他们可能要从事的某项科研项目。

3. We must trace the source of these noxious gases before they asphyxiate us.
    在我们被这些有毒气体窒息之前, 必须查出其来源。

4. There was no trace of fingerprints,
    巡官没有发现指纹，

5. This time, no trace of the boat — or the crew — was ever found.
    这一次，除了船员，连船也不见了踪影。

6. Here you can trace the history of China from its earliest beginnings to the modern era.
    在这里你可以追寻到中国人从远古到现代的全部历史。

7. He went to the police, to the cab companies, every place where a trace of hope led him.
    他找了警察局，找了出租马车公司，找遍了每一个有一线希望的地方。

8. A rescue plane was sent to search for the missing aircraft, and it, too, disappeared without trace.
    一架救援飞机被派出去搜寻失踪的飞机，但同样，它也消失得无影无踪。

9. Stone does not decay, and so the tools of long ago have remained when even the bones of the men who made them have disappeared without trace.
    石头是不会腐烂的。因此，尽管制造这些工具的人的骨头早已荡然无存，但远古时代的石头工具却保存了下来。