The absence of unambiguous animal body fossils in rocks older than the late Ediacaran has rendered fossil lipids the most promising tracers of early organismic complexity. Yet much debate surrounds the various potential biological sources of putative metazoan steroids found in Precambrian rocks. Here we show that 26-methylated steranes—hydrocarbon structures currently attributed to the earliest animals—can form via geological alteration of common algal sterols, which carries important implications for palaeo-ecological interpretations and inhibits the use of such unconventional ‘sponge’ steranes for reconstructing early animal evolution.

中文翻译：

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前寒武纪类固醇的地质变化模仿早期动物特征

在比埃迪卡拉纪晚期更古老的岩石中缺乏明确的动物体化石，这使得化石脂质成为早期有机体复杂性最有希望的示踪剂。然而，许多争论围绕着在前寒武纪岩石中发现的假定后生动物类固醇的各种潜在生物来源展开。在这里，我们表明 26-甲基化甾烷——目前归因于最早动物的碳氢化合物结构——可以通过常见藻类甾醇的地质改变形成，这对古生态学解释具有重要意义，并抑制使用这种非常规的“海绵”甾烷进行重建早期动物进化。