Mosaic evolution is the concept that evolution

Evolution

Evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins.Life on Earth...

ary change takes place in some body parts or systems without simultaneous changes in other parts. Another definition is the "evolution of characters at various rates both within and between species".⁴⁰⁸ Its place in evolutionary theory comes under long-term trends or macroevolution

Macroevolution

Macroevolution is evolution on a scale of separated gene pools. Macroevolutionary studies focus on change that occurs at or above the level of species, in contrast with microevolution, which refers to smaller evolutionary changes within a species or population.The process of speciation may fall...

.

By its very nature, the evidence for this idea comes mainly from palaeontology. It is not claimed that this pattern is universal, but there are now a wide range of examples from many different taxa. Some examples:

• Hominid evolution: the early evolution of bipedalism in Australopithecine
  Australopithecine
  The term australopithecine refers generally to any species in the related genera Australopithecus or Paranthropus. These species occurred in the Plio-Pleistocene era, and were bipedal and dentally similar to humans, but with a brain size not much larger than modern apes, lacking the...
  
  s, and its modification of the pelvic girdle took place well before there was any significant change in the skull, or brain size.

• Archaeopteryx
  Archaeopteryx
  Archaeopteryx , sometimes referred to by its German name Urvogel , is a genus of theropod dinosaur that is closely related to birds. The name derives from the Ancient Greek meaning "ancient", and , meaning "feather" or "wing"...
  
  . Nearly 150 years ago Thomas Henry Huxley compared Archaeopteryx with a small theropod dinosaur
  Dinosaur
  Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...
  
  , Compsognathus
  Compsognathus
  Compsognathus was a small, bipedal, carnivorous theropod dinosaur. The animal was the size of a turkey and lived around 150 million years ago, the early Tithonian stage of the late Jurassic Period, in what is now Europe. Paleontologists have found two well-preserved fossils, one in Germany...
  
  . These two fossils came from the Solnhofen limestone
  Solnhofen limestone
  The Solnhofen Plattenkalk is a Jurassic Konservat-Lagerstätte that preserves a rare assemblage of fossilized organisms, including highly detailed imprints of soft bodied organisms such as sea jellies...
  
   in Bavaria
  Bavaria
  Bavaria, formally the Free State of Bavaria is a state of Germany, located in the southeast of Germany. With an area of , it is the largest state by area, forming almost 20% of the total land area of Germany...
  
  . He showed that the two were very similar, except for the front limb
  Limb (anatomy)
  A limb is a jointed, or prehensile , appendage of the human or other animal body....
  
  s and feather
  Feather
  Feathers are one of the epidermal growths that form the distinctive outer covering, or plumage, on birds and some non-avian theropod dinosaurs. They are considered the most complex integumentary structures found in vertebrates, and indeed a premier example of a complex evolutionary novelty. They...
  
  s of Archaeopteryx. Huxley's interest was in the basic affinity of birds and reptiles, which he united as the Sauropsida
  Sauropsida
  Sauropsida is a group of amniotes that includes all existing reptiles and birds and their fossil ancestors, including the dinosaurs, the immediate ancestors of birds...
  
  . The interest here is that the rest of the skeleton had not changed.

• Meadow voles during the last 500,000 years.
• The pterosaur
  Pterosaur
  Pterosaurs were flying reptiles of the clade or order Pterosauria. They existed from the late Triassic to the end of the Cretaceous Period . Pterosaurs are the earliest vertebrates known to have evolved powered flight...
  
   Darwinopterus
  Darwinopterus
  Darwinopterus is a genus of pterosaur, discovered in China and named after biologist Charles Darwin. Between 30 and 40 fossil specimens have been identified, all collected from the Tiaojishan Formation, which dates to the middle Jurassic period. The type species, D. modularis, was described in...
  
  . The type
  Type species
  In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...
  
   species, D. modularis was the first known pterosaur to display features of both long-tailed (rhamphorhynchoid
  Rhamphorhynchoidea
  The Rhamphorhynchoidea forms one of the two suborders of pterosaurs and represent an evolutionary grade of primitive members of this group of flying reptiles. This suborder is paraphyletic in relation to the Pterodactyloidea, which arose from within the Rhamphorhynchoidea, not from a more distant...
  
  ) and short-tailed (pterodactyloid
  Pterodactyloidea
  Pterodactyloidea forms one of the two suborders of pterosaurs , and contains the most derived members of this group of flying reptiles...
  
  ) pterosaurs.

• Evolution of the horse
  Evolution of the horse
  The evolution of the horse pertains to the phylogenetic ancestry of the modern horse from the small dog-sized, forest-dwelling Hyracotherium over geologic time scales...
  
  , in which the major changes took place at different times, not all simultaneously.

• Mammalian evolution, especially during the Mesozoic
  Mesozoic
  The Mesozoic era is an interval of geological time from about 250 million years ago to about 65 million years ago. It is often referred to as the age of reptiles because reptiles, namely dinosaurs, were the dominant terrestrial and marine vertebrates of the time...
  
   is undoubtedly one of the best examples.

Background

In the neodarwinist theory of evolution, as postulated by Stephen Jay Gould

Stephen Jay Gould

Stephen Jay Gould was an American paleontologist, evolutionary biologist, and historian of science. He was also one of the most influential and widely read writers of popular science of his generation....

, there is room for differing development, when a life form matures earlier or later, in shape and size. This is due to allomorphism. Organs develop at differing rhythms, as a creature grows and matures. Thus a "heterochronic

Heterochrony

In biology, heterochrony is defined as a developmental change in the timing of events, leading to changes in size and shape. There are two main components, namely the onset and offset of a particular process, and the rate at which the process operates...

 clock" has three variants: 1) time, as a straight line; 2) general size, as a curved line; 3) shape, as another curved line.

When a creature is advanced in size, it may develop at a smaller size; alternatively, it may maintain its original size or, if delayed, it may result in a larger sized creature. That is insufficient to understand heterochronic mechanism.
Size must be combined with shape, so a creature may retain paedomorphic features if advanced in shape or present recapitulatory appearance when retarded in shape. These names are not very indicative, as past theories of development were very confusing.

A creature in its ontogeny

Ontogeny

Ontogeny is the origin and the development of an organism – for example: from the fertilized egg to mature form. It covers in essence, the study of an organism's lifespan...

 may combine heterochronic features in six vectors, although Gould considers that there is some binding with growth and sexual maturation. A creature may, for example, present some neotenic features and retarded development, resulting in new features derived from an original creature only by regulatory genes. Most novel human features (compared to closely related apes) were of this nature, not implying major change in structural genes, as was classically considered.

See also

• Evolutionary biology
• Coevolution
• Co-adaptation
  Co-adaptation
  In biology, co-adaptation, or coadaptation refers to the mutual adaptation of:* Species: see mutualism, symbiosis* organs: see the evolution of the eye.* Genes or gene complexes: see Linkage disequilibrium, epistasis...
  
  
• Coextinction
  Coextinction
  Coextinction of a species is the loss of a species as a consequence of the extinction of another. The term was originally used in the context of the extinction of parasitic insects following the loss of their specific hosts...
  
  
• Parallel evolution
  Parallel evolution
  Parallel evolution is the development of a similar trait in related, but distinct, species descending from the same ancestor, but from different clades.-Parallel vs...
  
  
• Convergent evolution
  Convergent evolution
  Convergent evolution describes the acquisition of the same biological trait in unrelated lineages.The wing is a classic example of convergent evolution in action. Although their last common ancestor did not have wings, both birds and bats do, and are capable of powered flight. The wings are...