The first animals evolved from an unknown single-celled ancestor in the Precambrian period. Recently, the identification and characterization of the genomic and cellular traits of the protists most closely related to animals have shed light on the origin of animals. Comparisons of animals with these unicellular relatives allow us to reconstruct the first evolutionary steps towards animal multicellularity. Here, we review the results of these investigations and discuss their implications for understanding the earliest stages of animal evolution, including the origin of metazoan genes and genome function.

中文翻译：

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后生动物的起源：单细胞的观点

在前寒武纪期间，第一批动物从未知的单细胞祖先进化而来。最近，与动物最密切相关的原生生物的基因组和细胞特征的鉴定和表征为动物的起源提供了启示。将动物与这些单细胞近缘动物进行比较，使我们能够重建出向动物多细胞性迈进的第一步。在这里，我们回顾了这些研究的结果，并讨论了它们对了解动物进化的最早阶段的意义，包括后生动物基因的起源和基因组功能。