An ancestor or forebear, especially a remote one in the distant past.
From Latin 'atavus,' meaning 'ancestor,' possibly derived from 'at-avus' (those before fathers). This ancient Latin term passed into scientific and formal English vocabulary.
Scientists use the term 'atavistic' to describe traits from ancient ancestors that still appear in modern organisms—like humans being born with tiny ear muscles we don't use. Your atavus might refer to an ancestor so ancient we don't know their name.
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