化石动物

To avoid sampling bias, they restricted their analysis to one group of animals—the bivalve molluscs—that fossilise well.

为了防止取样的偏颇，他们将分析的对象限制一类化石记录保存完备——双壳类软体。

Perhaps 20 or more hominids (not all of them our ancestors) fill the gap between Lucy the australopithecine and modern humans.

阿法南猿（露西）与现代之，的化石也许超过20种（他们不全是我们的祖先）。