section_path: History
section_name: History
paragraph_text: History
  
  Although paleontology became established around 1800, earlier thinkers had noticed aspects of the fossil record. The ancient Greek philosopher Xenophanes (570–480 BCE) concluded from fossil sea shells that some areas of land were once under water. During the Middle Ages the Persian naturalist Ibn Sina, known as Avicenna in Europe, discussed fossils and proposed a theory of petrifying fluids on which Albert of Saxony elaborated in the 14th century. The Chinese naturalist Shen Kuo (1031–1095) proposed a theory of climate change based on the presence of petrified bamboo in regions that in his time were too dry for bamboo.
  
  In early modern Europe, the systematic study of fossils emerged as an integral part of the changes in natural philosophy that occurred during the Age of Reason. In the Italian Renaissance, Leonardo da Vinci made various significant contributions to the field as well as depicted numerous fossils. Leonardo's contributions are central to the history of paleontology because he established a line of continuity between the two main branches of paleontology – ichnology and body fossil paleontology. He identified the following:
  
  At the end of the 18th century Georges Cuvier 's work established comparative anatomy as a scientific discipline and, by proving that some fossil animals resembled no living ones, demonstrated that animals could become extinct, leading to the emergence of paleontology. The expanding knowledge of the fossil record also played an increasing role in the development of geology, particularly stratigraphy. Cuvier proved that the different levels of deposits represented different time periods in the early 19th century. The surface-level deposits in the Americas contained later mammals like the megatheriid ground sloth Megatherium and the mammutid proboscidean Mammut (later known informally as a "mastodon"), which were some of the earliest-named fossil mammal genera with official taxonomic authorities. They today are known to date to the Neogene - Quaternary. In deeper-level deposits in western Europe are early-aged mammals such as the palaeothere perissodactyl Palaeotherium and the anoplotheriid artiodactyl Anoplotherium, both of which were described earliest after the former two genera, which today are known to date to the Paleogene period. Cuvier figured out that even older than the two levels of deposits with extinct large mammals is one that contained an extinct "crocodile-like" marine reptile, which eventually came to be known as the mosasaurid Mosasaurus of the Cretaceous period.
  
  The first half of the 19th century saw geological and paleontological activity become increasingly well organised with the growth of geologic societies and museums and an increasing number of professional geologists and fossil specialists. Interest increased for reasons that were not purely scientific, as geology and paleontology helped industrialists to find and exploit natural resources such as coal. This contributed to a rapid increase in knowledge about the history of life on Earth and to progress in the definition of the geologic time scale, largely based on fossil evidence. Although she was rarely recognised by the scientific community, Mary Anning was a significant contributor to the field of palaeontology during this period; she uncovered multiple novel Mesozoic reptile fossils and deducted that what were then known as bezoar stones are in fact fossilised faeces. In 1822 Henri Marie Ducrotay de Blainville, editor of Journal de Physique, coined the word "palaeontology" to refer to the study of ancient living organisms through fossils. As knowledge of life's history continued to improve, it became increasingly obvious that there had been some kind of successive order to the development of life. This encouraged early evolutionary theories on the transmutation of species. After Charles Darwin published Origin of Species in 1859, much of the focus of paleontology shifted to understanding evolutionary paths, including human evolution, and evolutionary theory.
  
  The last half of the 19th century saw a tremendous expansion in paleontological activity, especially in North America. The trend continued in the 20th century with additional regions of the Earth being opened to systematic fossil collection. Fossils found in China near the end of the 20th century have been particularly important as they have provided new information about the earliest evolution of animals, early fish, dinosaurs and the evolution of birds. The last few decades of the 20th century saw a renewed interest in mass extinctions and their role in the evolution of life on Earth. There was also a renewed interest in the Cambrian explosion that apparently saw the development of the body plans of most animal phyla. The discovery of fossils of the Ediacaran biota and developments in paleobiology extended knowledge about the history of life back far before the Cambrian.
  
  Increasing awareness of Gregor Mendel 's pioneering work in genetics led first to the development of population genetics and then in the mid-20th century to the modern evolutionary synthesis, which explains evolution as the outcome of events such as mutations and horizontal gene transfer, which provide genetic variation, with genetic drift and natural selection driving changes in this variation over time. Within the next few years the role and operation of DNA in genetic inheritance were discovered, leading to what is now known as the "Central Dogma" of molecular biology. In the 1960s molecular phylogenetics, the investigation of evolutionary "family trees" by techniques derived from biochemistry, began to make an impact, particularly when it was proposed that the human lineage had diverged from apes much more recently than was generally thought at the time. Although this early study compared proteins from apes and humans, most molecular phylogenetics research is now based on comparisons of RNA and DNA.