12.Researchers have not been able to find traces of the compounds in rocks older than that, despite the existence of fossils of a red and a green alga — both eukaryotes — dating back about one billion years.
尽管存在着约10亿
的红色和绿色藻类的化石(都是真核生物),研究人员却无法在比
更古老的岩石中发现这些化合物的痕迹。