Paleontology

Paleontology (/ˌpeɪliɒnˈtɒlədʒi, ˌpæli-, -ən-/ PAY-lee-on-TOL-ə-jee, PAL-ee-, -⁠ən-), also spelled palaeontology^[a] or palæontology, is the scientific study of life that existed prior to the start of the Holocene epoch (roughly 11,700 years before present). It includes the study of fossils to classify organisms and study their interactions with each other and their environments (their paleoecology). Paleontological observations have been documented as far back as the 5th century BC. The science became established in the 18th century as a result of Georges Cuvier's work on comparative anatomy, and developed rapidly in the 19th century. The term has been used since 1822^[1]^[b] formed from Greek παλαιός ('palaios', "old, ancient"), ὄν ('on', (gen. 'ontos'), "being, creature"), and λόγος ('logos', "speech, thought, study").^[3]

"Palaeontology" redirects here. For the Science journal, see Palaeontology (journal).

Paleontology lies on the border between biology and geology, but it differs from archaeology in that it excludes the study of anatomically modern humans. It now uses techniques drawn from a wide range of sciences, including biochemistry, mathematics, and engineering. Use of all these techniques has enabled paleontologists to discover much of the evolutionary history of life, almost back to when Earth became capable of supporting life, nearly 4 billion years ago.^[4] As knowledge has increased, paleontology has developed specialised sub-divisions, some of which focus on different types of fossil organisms while others study ecology and environmental history, such as ancient climates.

Body fossils and trace fossils are the principal types of evidence about ancient life, and geochemical evidence has helped to decipher the evolution of life before there were organisms large enough to leave body fossils. Estimating the dates of these remains is essential but difficult: sometimes adjacent rock layers allow radiometric dating, which provides absolute dates that are accurate to within 0.5%, but more often paleontologists have to rely on relative dating by solving the "jigsaw puzzles" of biostratigraphy (arrangement of rock layers from youngest to oldest). Classifying ancient organisms is also difficult, as many do not fit well into the Linnaean taxonomy classifying living organisms, and paleontologists more often use cladistics to draw up evolutionary "family trees". The final quarter of the 20th century saw the development of molecular phylogenetics, which investigates how closely organisms are related by measuring the similarity of the DNA in their genomes. Molecular phylogenetics has also been used to estimate the dates when species diverged, but there is controversy about the reliability of the molecular clock on which such estimates depend.

The oceans may have become more hospitable to life over the last 500 million years and less vulnerable to mass extinctions: became more widespread and penetrated to greater depths; the development of life on land reduced the run-off of nutrients and hence the risk of eutrophication and anoxic events; marine ecosystems became more diversified so that food chains were less likely to be disrupted.^[104]^[105]

dissolved oxygen

Reasonably complete are very rare: most extinct organisms are represented only by partial fossils, and complete fossils are rarest in the oldest rocks. So paleontologists have mistakenly assigned parts of the same organism to different genera, which were often defined solely to accommodate these finds – the story of Anomalocaris is an example of this.^[106] The risk of this mistake is higher for older fossils because these are often unlike parts of any living organism. Many "superfluous" genera are represented by fragments that are not found again, and these "superfluous" genera are interpreted as becoming extinct very quickly.^[103]

fossils

The Last Days of the Dinosaurs: An Asteroid Extinction, and the Beginning of our World written by Riley Black

[129]

The Rise and Reign of the Mammals: A New History, from the Shadow of the Dinosaurs to Us written by Steve Brusatte

[130]

^[131] written by Thomas Halliday

Otherlands: A Journey Through Earth's Extinct Worlds

Books catered to the general public on paleontology include:

Smithsonian's Paleobiology website

University of California Museum of Paleontology

The Paleontological Society

The Palaeontological Association

The Society of Vertebrate Paleontology

The Paleontology Portal

– a collection of more than 100 digitised landmark and early books on Earth sciences at the Linda Hall Library