The earliest fossils of animal-like organisms occur in Ediacaran rocks that are approximately 571 million years old. Yet 24-isopropylcholestanes and other C₃₀ fossil sterol molecules have been suggested to reflect an important ecological role of demosponges as the first abundant animals by the end of the Cryogenian period (>635 million years ago). Here, we demonstrate that C₃₀ 24-isopropylcholestane is not diagnostic for sponges and probably formed in Neoproterozoic sediments through the geological methylation of C₂₉ sterols of chlorophyte algae, the dominant eukaryotes at that time. These findings reconcile biomarker evidence with the geological record and revert the oldest evidence for animals back into the latest Ediacaran.

最早的类动物生物化石出现在距今约 5.71 亿年的埃迪卡拉纪岩石中。然而，有人提出 24-异丙基胆甾烷和其他 C ₃₀化石甾醇分子反映了海绵动物作为低温纪末期（>6.35 亿年前）第一批丰富动物的重要生态作用。在这里，我们证明 C ₃₀ 24-异丙基胆甾烷不能诊断海绵，并且可能通过叶绿藻类（当时主要的真核生物）的 C _{29甾醇的地质甲基化在新元古代沉积物中形成。}这些发现将生物标志物证据与地质记录相协调，并将最古老的动物证据追溯到最新的埃迪卡拉纪。