Ralf Josef Sommer (born 23 September 1963) is a German biologist specializing in evolutionary developmental biology.
Sommer studied biology at the RWTH Aachen University, at the University of Tübingen and at the Ludwig Maximilian University of Munich where he obtained his Diplom degree in 1989 and earned his Ph.D. in the lab of Diethard Tautz on a study of the evolution of segmentation genes in insects in 1992. His work was one of the first molecular studies in the field of evolutionary developmental biology (evo-devo in short), a discipline that started its revival in the late 1980s and early 1990s. From 1993-1995 he was a Research Fellow at the California Institute of Technology in Pasadena. Since 1999, he has been Director of the department Evolutionary Biology at the Max Planck Institute for Developmental Biology in Tübingen, Germany and was appointed Adjunct Professor (Honorarprofessor) at the University of Tübingen in 2002. He is awardee of the FALCON Prize of the German Society for Cell Biology and was head co-organizer of the 19th International C. elegans Conference, UCLA, USA in 2013. In 2015 he was elected as an EMBO member.
Ralf Sommer works in the field of evolutionary developmental biology on nematodes. He has developed and established the nematode Pristionchus pacificus as a model system for integrative studies in evolutionary biology.  Described in 1996 as a new species by Sommer and co-workers, P. pacificus has grown as an important model system, in which laboratory studies that aim for a mechanistic understanding of evolution can be combined with fieldwork.   The latter allows ecological and population genetic studies to complement the gene-centered and development-centered perspectives of evo-devo.  
The original work of Sommer´s research focused on the evolution of developmental processes showing that homologous structures can be generated by distinct molecular mechanisms, a phenomenon now known as developmental systems drift.    More recent work incorporates many additional areas of evolutionary biology.      The nematode P. pacificus is associated with scarab beetles, an observation that provides an ecological framework and represents one of the cornerstones of his current research.  Similarly, a population genetic framework for P. pacificus research has been established with the identification and exploration of La Réunion Island in the Indian Ocean, where this nematode shows an extraordinary genetic diversity.  P. pacificus work on La Réunion Island is supported by a field station at the local Insectarium in Le Port. The integrative research program on P. pacificus represents a major paradigm shift for studying phenotypic evolution, by simultaneously investigating in one organism, the same patterns and processes from independent evolutionary perspectives.
Consequently, the most recent studies investigate the evolution of novelty, focusing on developmental (phenotypic) plasticity as a facilitator of biological diversity. Specifically, the combination of laboratory studies with fieldwork allows new insight into the molecular mechanisms of developmental plasticity.  
Evolutionary developmental biology is a field of biological research that compares the developmental processes of different organisms to infer how developmental processes evolved.
Panarthropoda is a proposed animal clade containing the extant phyla Arthropoda, Tardigrada and Onychophora. Panarthropods also include extinct marine legged worms known as lobopodians ("Lobopodia"), a paraphyletic group where the last common ancestor and basal members (stem-group) of each extant panarthropod phylum are thought to have risen. However the term "Lobopodia" is sometimes expanded to include tardigrades and onychophorans as well.
Evolutionary biology is the subfield of biology that studies the evolutionary processes that produced the diversity of life on Earth. It is also defined as the study of the history of life forms on Earth. Evolution is based on the theory that all species are related and they gradually change over time. In a population, the genetic variations affect the physical characteristics i.e. phenotypes of an organism. These changes in the phenotypes will be an advantage to some organisms, which will then be passed onto their offspring. Some examples of evolution in species over many generations are the Peppered Moth and Flightless birds. In the 1930s, the discipline of evolutionary biology emerged through what Julian Huxley called the modern synthesis of understanding, from previously unrelated fields of biological research, such as genetics and ecology, systematics, and paleontology. The importance of studying Evolutionary biology is mainly to understand the principles behind the origin and extinction of species.
In evolutionary developmental biology, heterochrony is any genetically controlled difference in the timing, rate, or duration of a developmental process in an organism compared to its ancestors or other organisms. This leads to changes in the size, shape, characteristics and even presence of certain organs and features. It is contrasted with heterotopy, a change in spatial positioning of some process in the embryo, which can also create morphological innovation. Heterochrony can be divided into intraspecific heterochrony, variation within a species, and interspecific heterochrony, phylogenetic variation, i.e. variation of a descendant species with respect to an ancestral species.
Dauer describes an alternative developmental stage of nematode worms, particularly rhabditids including Caenorhabditis elegans, whereby the larva goes into a type of stasis and can survive harsh conditions. Since the entrance of the dauer stage is dependent on environmental cues, it represents a classic and well studied example of polyphenism. The dauer state is given other names in the various types of nematodes such as ‘diapause’ or ‘hypobiosis’, but since the C. elegans nematode has become the most studied nematode, the term ‘dauer stage’ or 'dauer larvae' is becoming universally recognised when referring to this state in other free-living nematodes. The dauer stage is also considered to be equivalent to the infective stage of parasitic nematode larvae.
Evolutionary developmental biology (evo-devo) is the study of developmental programs and patterns from an evolutionary perspective. It seeks to understand the various influences shaping the form and nature of life on the planet. Evo-devo arose as a separate branch of science rather recently. An early sign of this occurred in 1999.
Androdioecy is a reproductive system characterized by the coexistence of males and hermaphrodites. Androdioecy is rare in comparison with the other major reproductive systems: dioecy, gynodioecy and hermaphroditism. In animals, androdioecy has been considered a stepping stone in the transition from dioecy to hermaphroditism, and vice versa.
Gerd B. Müller is an Austrian biologist who is emeritus professor at the University of Vienna where he was the head of the Department of Theoretical Biology in the Center for Organismal Systems Biology. His research interests focus on vertebrate limb development, evolutionary novelties, evo-devo theory, and the Extended Evolutionary Synthesis. He is also concerned with the development of 3D based imaging tools in developmental biology.
Endless Forms Most Beautiful: The New Science of Evo Devo and the Making of the Animal Kingdom is a 2005 book by the molecular biologist Sean B. Carroll. It presents a summary of the emerging field of evolutionary developmental biology and the role of toolkit genes. It has won numerous awards for science communication.
Diethard Tautz is a German biologist and geneticist, who is primarily concerned with the molecular basis of the evolution of mammals. Since 2006 he is director at the Max Planck Institute for Evolutionary Biology in Plön.
Diplogastridae, formerly Diplogasteridae, are a family of nematodes (roundworms) known from a wide range of habitats, often in commensal or parasitic associations with insects.
Pristionchus is a genus of nematodes (roundworms) in the family Diplogastridae that currently includes more than 50 described species. They are known mainly as non-parasitic associates of insects, especially beetles, while others have been reported from soil, organic matter, or rotting wood. The genus includes P. pacificus, a satellite model organism to the well-studied nematode Caenorhabditis elegans.
Pristionchus pacificus is a species of free-living nematodes (roundworms) in the family Diplogastridae. The species has been established as a satellite model organism to Caenorhabditis elegans, with which it shared a common ancestor 200–300 million years ago. The genome of P. pacificus has been fully sequenced, which in combination with other tools for genetic analysis make this species a tractable model in the laboratory, especially for studies of developmental biology.
Pristionchus maxplancki is a species of diplogastrid nematodes (roundworms).
The extended evolutionary synthesis consists of a set of theoretical concepts argued to be more comprehensive than the earlier modern synthesis of evolutionary biology that took place between 1918 and 1942. The extended evolutionary synthesis was called for in the 1950s by C. H. Waddington, argued for on the basis of punctuated equilibrium by Stephen Jay Gould and Niles Eldredge in the 1980s, and was reconceptualized in 2007 by Massimo Pigliucci and Gerd B. Müller. Notably, Dr. Müller concluded from this research that Natural Selection has no way of explaining speciation, saying: “selection has no innovative capacity...the generative and the ordering aspects of morphological evolution are thus absent from evolutionary theory.”
The evo-devo gene toolkit is the small subset of genes in an organism's genome whose products control the organism's embryonic development. Toolkit genes are central to the synthesis of molecular genetics, palaeontology, evolution and developmental biology in the science of evolutionary developmental biology (evo-devo). Many of them are ancient and highly conserved among animal phyla.
Human evolutionary developmental biology or informally human evo-devo is the human-specific subset of evolutionary developmental biology. Evolutionary developmental biology is the study of the evolution of developmental processes across different organisms. It is utilized within multiple disciplines, primarily evolutionary biology and anthropology. Groundwork for the theory that "evolutionary modifications in primate development might have led to … modern humans" was laid by Geoffroy Saint-Hilaire, Ernst Haeckel, Louis Bolk, and Adolph Schultz. Evolutionary developmental biology is primarily concerned with the ways in which evolution affects development, and seeks to unravel the causes of evolutionary innovations.
In biology, reciprocal causation arises when developing organisms are both products of evolution as well as causes of evolution. Formally, reciprocal causation exists when process A is a cause of process B and, subsequently, process B is a cause of process A, with this feedback potentially repeated. Some researchers, particularly advocates of the extended evolutionary synthesis, promote the view that causation in biological systems is inherently reciprocal.
Ecological evolutionary developmental biology (eco-evo-devo) is a field of biology combining ecology, developmental biology and evolutionary biology to examine their relationship. The concept is closely tied to multiple biological mechanisms. The effects of eco-evo-devo can be a result of developmental plasticity, the result of symbiotic relationships or epigenetically inherited. Developmental plasticity that is controlled by environmental temperature may put certain species at risk as a result of climate change.