Two scientists seriously argued Earth was deliberately seeded with life from space

In 1973, Francis Crick — who co-discovered DNA's double helix — and chemist Leslie Orgel published a paper arguing life on Earth could have begun when an advanced civilization deliberately sent microorganisms here aboard an unmanned spacecraft. They called it 'directed panspermia.' It remains an unproven, minority hypothesis, but it was published as serious science, not science fiction.

— Francis Crick & Leslie Orgel, Directed Panspermia — Icarus, 19(3), 1973