Evidence for Evolution — Palaeontology

Palaeontology is the scientific study of fossils — the preserved physical remains, impressions or mineralised traces of organisms that lived at some point in the geological past — and it provides some of the most direct, physical evidence available that evolution has genuinely taken place over the immense span of geological time. A fossil can take many different forms: the mineralised, petrified bones or shells of an ancient organism; an impression left in fine sediment by a leaf, footprint or skin texture, later hardened into rock; or, more rarely, an organism preserved almost intact in amber, ice or tar. Fossils are typically found embedded within layers, or strata, of sedimentary rock, formed as successive layers of sand, silt and mud were deposited, one on top of another, over enormous spans of geological time — often many millions of years for a single sequence of visible rock strata.

Because sedimentary rock strata are deposited in a fixed, predictable order, with each new layer settling on top of the layers that were already there, the deepest strata in an undisturbed rock sequence are necessarily the OLDEST, while progressively shallower strata are progressively YOUNGER — a principle geologists call superposition. When palaeontologists examine the fossils found within such a layered rock sequence, a consistent and striking pattern emerges again and again, at fossil sites studied all across the world: the deepest, oldest rock strata generally contain fossils of the simplest, most primitive-looking life forms, such as early single-celled organisms and, later, simple multicellular invertebrates; progressively younger, shallower strata contain fossils of organisms that are progressively more structurally complex, and progressively more similar in their anatomy to species living on Earth today; and the very oldest rock strata are essentially devoid of any fossils resembling modern species at all. This orderly sequence, moving from simple to complex, and from very unlike modern life to increasingly like modern life, as one moves from older to younger rock strata, is exactly the pattern that a gradual process of evolutionary change occurring over the same span of geological time would be expected to produce — and it is a pattern that has been observed and confirmed at an enormous number of independent fossil sites, rather than depending on any single, cherry-picked example. …