Any living or extinct ecosystem can be understood as one frame in a continuous film running backward: the familiar present dissolves into progressively stranger but equally functional worlds. Reconstructing each layer on its own terms, rather than as a primitive draft of the present, reveals that no epoch is the destination toward which earlier ones were building.
Extinction events do not merely remove species; they clear ecological roles that surviving and newly evolving lineages then refill, often with unrelated organisms converging on similar forms. The recovery can take millions of years, and what returns is structurally familiar but phylogenetically different.
Around 5.5 million years ago the Mediterranean was cut off from the Atlantic and largely evaporated, leaving vast salt flats kilometres below the surrounding land and a thick buried layer of salt. When the Atlantic breached the Gibraltar gap, water refilled the basin in a flood lasting perhaps only a couple of years, one of the most sudden large-scale landscape transformations in Earth's record.
A fossil preserves a biased, incomplete slice of a once-living system: hard parts over soft, certain environments over others, rare moments of exceptional preservation over the ordinary. Understanding a vanished world means inferring color, behavior, climate and community from scattered clues, treating absence of evidence as a known gap rather than evidence of absence.