Archaea turn out to be closer kin to us than to bacteria, and that discovery — Carl Woese comparing ribosomal RNA — redrew all of life into three domains. The tree grows outward from LUCA in time order: bacteria and archaea appear earliest, around 3.5 billion years ago, while land plants and animals arrive only very recently. Every mass extinction lops off whole branches, after which adaptive radiation lets the survivors fan out into the vacated space.
Archaea turn out to be closer kin to us than to bacteria, and that discovery — Carl Woese comparing ribosomal RNA — redrew all of life into three domains. The tree grows outward from LUCA in time order: bacteria and archaea appear earliest, around 3.5 billion years ago, while land plants and animals arrive only very recently. Every mass extinction lops off whole branches, after which adaptive radiation lets the survivors fan out into the vacated space.
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