The Tangled Tree

Quammen explains how molecular evidence revealed that life’s history includes genes moving between lineages as well as inheritance along branches.

Comparing genetic sequences lets scientists investigate relationships that appearances alone can hide.

Carl Woese’s work helped establish archaea as distinct from bacteria.

Horizontal gene transfer means genetic material can pass between organisms outside parent-to-offspring inheritance.

Major evolutionary changes can involve once-separate organisms becoming deeply integrated.

The branching tree remains useful, but cannot show every important transfer and merger.