In evolutionary biology, punctuated equilibrium is a theory that proposes that once a species appears in the fossil record, the population will become stable, showing little evolutionary change for most of its geological history. This state of little or no morphological change is called stasis. When significant evolutionary change occurs, the theory proposes that it is generally restricted to rare and geologically rapid events of branching speciation called cladogenesis. Cladogenesis is the process by which a species splits into two distinct species, rather than one species gradually transforming into another.
Stephen Jay Gould was an American paleontologist, evolutionary biologist, and historian of science. He was one of the most influential and widely read authors of popular science of his generation. Gould spent most of his career teaching at Harvard University and working at the American Museum of Natural History in New York. In 1996, Gould was hired as the Vincent Astor Visiting Research Professor of Biology at New York University, after which he divided his time teaching between there and Harvard.
Speciation is the evolutionary process by which populations evolve to become distinct species. The biologist Orator F. Cook coined the term in 1906 for cladogenesis, the splitting of lineages, as opposed to anagenesis, phyletic evolution within lineages. Charles Darwin was the first to describe the role of natural selection in speciation in his 1859 book On the Origin of Species. He also identified sexual selection as a likely mechanism, but found it problematic.
Uniformitarianism, also known as the Doctrine of Uniformity or the Uniformitarian Principle, is the assumption that the same natural laws and processes that operate in our present-day scientific observations have always operated in the universe in the past and apply everywhere in the universe. It refers to invariance in the metaphysical principles underpinning science, such as the constancy of cause and effect throughout space-time, but has also been used to describe spatiotemporal invariance of physical laws. Though an unprovable postulate that cannot be verified using the scientific method, some consider that uniformitarianism should be a required first principle in scientific research. Other scientists disagree and consider that nature is not absolutely uniform, even though it does exhibit certain regularities.
Milford Howell Wolpoff is a paleoanthropologist and professor of anthropology at the University of Michigan and its museum of Anthropology. He is the leading proponent of the multiregional evolution hypothesis that explains the evolution of Homo sapiens as a consequence of evolutionary processes and gene flow across continents within a single species. Wolpoff authored the widely used textbook Paleoanthropology, and co-authored Race and Human Evolution: A Fatal Attraction, which reviews the scientific evidence and conflicting theories about the interpretation of human evolution, and biological anthropology's relationship to views about race.
Quantum evolution is a component of George Gaylord Simpson's multi-tempoed theory of evolution proposed to explain the rapid emergence of higher taxonomic groups in the fossil record. According to Simpson, evolutionary rates differ from group to group and even among closely related lineages. These different rates of evolutionary change were designated by Simpson as bradytelic, horotelic, and tachytelic.
In geology, catastrophism is the theory that the Earth has largely been shaped by sudden, short-lived, violent events, possibly worldwide in scope. This contrasts with uniformitarianism, according to which slow incremental changes, such as erosion, brought about all the Earth's geological features. The proponents of uniformitarianism held that the present was "the key to the past", and that all geological processes throughout the past resembled those that can be observed today. Since the 19th-century disputes between catastrophists and uniformitarians, a more inclusive and integrated view of geologic events has developed, in which the scientific consensus accepts that some catastrophic events occurred in the geologic past, but regards these as explicable as extreme examples of natural processes which can occur.
Cladogenesis is an evolutionary splitting of a parent species into two distinct species, forming a clade.
Pseudoextinction of a species occurs when all members of the species are extinct, but members of a daughter species remain alive. The term pseudoextinction refers to the evolution of a species into a new form, with the resultant disappearance of the ancestral form. Pseudoextinction results in the relationship between ancestor and descendant still existing even though the ancestor species no longer exists.
Phyletic gradualism is a model of evolution which theorizes that most speciation is slow, uniform and gradual. When evolution occurs in this mode, it is usually by the steady transformation of a whole species into a new one. In this view no clear line of demarcation exists between an ancestral species and a descendant species, unless splitting occurs. The theory is contrasted with punctuated equilibrium.
In biology, saltation is a sudden and large mutational change from one generation to the next, potentially causing single-step speciation. This was historically offered as an alternative to Darwinism. Some forms of mutationism were effectively saltationist, implying large discontinuous jumps.
Punctuated gradualism is a microevolutionary hypothesis that refers to a species that has "relative stasis over a considerable part of its total duration [and] underwent periodic, relatively rapid, morphologic change that did not lead to lineage branching". It is one of the three common models of evolution.
Principles of Geology: Being an Attempt to Explain the Former Changes of the Earth's Surface, by Reference to Causes Now in Operation is a book by the Scottish geologist Charles Lyell that was first published in 3 volumes from 1830–1833. Lyell used the theory of uniformitarianism to describe how the Earth's surface was changing over time. This theory was in direct contrast to the geological theory of catastrophism.
Dawkins vs. Gould: Survival of the Fittest is a book about the differing views of biologists Richard Dawkins and Stephen Jay Gould by philosopher of biology Kim Sterelny. When published in 2001 it became an international best-seller. A new edition was published in 2007 to include Gould's The Structure of Evolutionary Theory finished shortly before his death in 2002, and recent works by Dawkins. The synopsis below is from the 2007 publication.
Punctuated equilibrium in social theory is a conceptual framework for understanding the process of change in complex social systems. The approach studies the evolution of policy change, including the evolution of conflicts. The theory posits that most social systems exist in an extended period of stasis, which may be punctuated by sudden shifts leading to radical change. The theory was largely inspired by the evolutionary biology theory of punctuated equilibrium developed by paleontologists Niles Eldredge and Stephen Jay Gould.
The court jester hypothesis is used in reference to the idea that abiotic forces, rather than biotic competition between species, function as a major driving force behind the processes in evolution which produce speciation. In evolutionary theory, the court-jester hypothesis contrasts the Red Queen hypothesis.
The rate of evolution is quantified as the speed of genetic or morphological change in a lineage over a period of time. The speed at which a molecular entity evolves is of considerable interest in evolutionary biology since determining the evolutionary rate is the first step in characterizing its evolution. Calculating rates of evolutionary change is also useful when studying phenotypic changes in phylogenetic comparative biology. In either case, it can be beneficial to consider and compare both genomic data and paleontological data, especially in regards to estimating the timing of divergence events and establishing geological time scales.
Endogenosymbiosis is an evolutionary process, proposed by the evolutionary and environmental biologist Roberto Cazzolla Gatti, in which "gene carriers" and symbiotic prokaryotic cells could share parts or all of their genomes in an endogenous symbiotic relationship with their hosts.
Frozen Evolution is a 2008 book written by parasitologist Jaroslav Flegr, which aims to explain modern developments in evolutionary biology. It also contains information boxes which clarify important topics in science like peer review, scientific journals, citation metrics, philosophy of science, paradigm shifts, and Occam's razor. Flegr's previous research in toxoplasmosis is also mentioned.
The sloshing bucket model of evolution is a theory in evolutionary biology that describes how environmental disturbances varying in magnitude will affect the species present. The theory emphasizes the causal relationship between environmental factors that impinge and affect genealogical systems, providing an overarching view that determines the relationship between the variety of biological systems.
