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.

大多数现代真核生依靠类似脂肪的固醇类化合（如胆固醇）来构膜执行其他功能。

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，即在8亿年前之前，真核生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——仅仅是它们的前身——也应该存在于超过8亿年历史的岩石中。

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.

由于类固醇在真核生系谱中随处可见，因此人们认为它们存在于所有现代真核生的最后一个共同祖先中。

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.

可能的一种可能性是，在10亿到8亿年前，制造现代固醇的真核生获得了选择性优势，最终取代了它们制造原始固醇的同类。

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.

德国莱梅大学的地球生学家本杰明·内特谢姆、澳大利亚国立大学堪培拉分校的古生地球化学家约翰·布洛克斯及其同事决定将重点放在现代真核生合成类固醇时产生的短寿命分子上。