They maybe hard to make sterol, which is important for medical uses and they tend to be weak.

它们可能很难制造甾醇，这对医疗用途很重要，而且它们往往很弱。

Most modern eukaryotes rely on fat-like compounds called sterols, such as cholesterol, to build cell membranes and carry out other cellular functions.

大多数现代真核物依靠类似脂肪的固醇类化合物（如胆固醇）来构建细胞膜并执行其他细胞功能。

This absence has led to speculation that before 800 million years ago, eukaryotes were not abundant enough to leave a detectable sterol trace.

这种乏导致了一种猜测，即8亿年前之前，真核物并不足以留下可检测到的类固醇痕迹。

That would suggest that modern sterols — not just their precursors — should also be present in rocks that are more than 800 million years old.

这表明现代固醇——不仅仅它们的前身——也应该存于超过8亿年历史的岩石中。

One possibility is that eukaryotes that make more-modern sterols gained a selective advantage between one billion and 800 million years ago, eventually displacing their protosterol-making counterparts.

可能的一种可能，10亿到8亿年前，制造现代固醇的真核物获得了选择优势，最终取代了它们制造原始固醇的同类。

Because sterols are found throughout the eukaryotic family tree, they are thought to have been present in the last common ancestor of all modern eukaryotes.

由于类固醇真核物系谱中随处可见，因此人们认为它们存于所有现代真核物的最后一个共同祖先中。

Benjamin Nettersheim, a geobiologist at the University of Bremen in Germany, Jochen Brocks, a palaeobiogeochemist at the Australian National University in Canberra, and their colleagues decided to focus on short-lived molecules that modern eukaryotes make while synthesizing sterols.

德国不莱梅大学的地球物学家本杰明·内特谢姆、澳大利亚国立大学堪培拉分校的古物地球化学家约翰·布洛克斯及其同事决定将重点放现代真核物合成类固醇时产的短寿命分子上。