For example, the discovery by Luis Alvarez and Walter Alvarez of an iridium-rich layer at the Cretaceous–Tertiary boundary made asteroid impact and volcanism the most favored explanations for the Cretaceous–Paleogene extinction event.
The other main type of science is experimental science, which is often said to work by conducting experiments to disprove hypotheses about the workings and causes of natural phenomena – note that this approach cannot confirm a hypothesis is correct, since some later experiment may disprove it.
Paleontology lies on the border between biology and geology, but 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.
Micropaleontology deals with all microscopic fossil organisms, regardless of the group to which they belong.
Instead of focusing on individual organisms, paleoecology examines the interactions between different organisms, such as their places in food chains, and the two-way interaction between organisms and their environment.
Despite this, it is often adequate to illustrate the broader patterns of life's history.A relatively recent discipline, molecular phylogenetics, often helps by using comparisons of different modern organisms' DNA and RNA to re-construct evolutionary "family trees"; it has also been used to estimate the dates of important evolutionary developments, although this approach is controversial because of doubts about the reliability of the "molecular clock".Paleontology even contributes to astrobiology, the investigation of possible life on other planets, by developing models of how life may have arisen and by providing techniques for detecting evidence of life.Further, only the parts of organisms that were already mineralised are usually preserved, such as the shells of molluscs.Since most animal species are soft-bodied, they decay before they can become fossilised.Paleobotany focuses on the study of fossil plants, but traditionally includes the study of fossil algae and fungi.Palynology, the study of pollen and spores produced by land plants and protists, straddles the border between paleontology and botany, as it deals with both living and fossil organisms.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.) is the scientific study of life that existed prior to, and sometimes including, the start of the Holocene Epoch (roughly 11,700 years before present).It includes the study of fossils to determine organisms' evolution and interactions with each other and their environments (their paleoecology).