thumb|[[Heck cattle were bred in the 1920s to resemble the aurochs.]]

Breeding back is a form of artificial selection by the deliberate selective breeding of primarily domestic animals, in an attempt to achieve an animal breed with a phenotype that resembles a wild type ancestor, usually one that has gone extinct. Breeding back is not to be confused with dedomestication.

Though bred-back breeds may be very similar to the extinct wild type in phenotype, ecological niche, and to some extent genetics, the gene pool of that wild type was different prior to its extinction. Even the superficial authenticity of a bred-back animal depends on the particular stock used to breed the new lineage. As a result of this, some breeds, like Heck cattle, are at best a vague look-alike of the extinct wild type aurochs, according to the literature.

Background

thumb|left|[[VOA report about the Quagga Project]]

The aim of breeding back programs is to restore the wild traits which may have been unintentionally preserved in the lineages of domesticated animals. Commonly, not only the new animal's phenotype, but also its ecological capacity, are considered in back-breeding projects, as hardy, "bred back" animals may be used in certain conservation projects. In nature, usually only individuals well suited to their natural circumstances will survive and reproduce, whereas humans select animals with additional attractive, docile or productive characteristics, protecting them from the dangers once found in their ancestral environment (predation, drought, disease, extremes of weather, lack of mating opportunities, etc.).

In such cases, selection criteria in nature differ from those found in domesticated conditions. Because of this, domesticated animals often differ significantly in phenotype, behaviour and genetics from their wild forerunners. It is the hope of breeding-back programs to re-express, within a new breeding lineage, the wild, ancient traits that may have "lain buried" in the DNA of domestic animals.

In many cases, the extinct wild type ancestors of a given species are known only through skeletons and, in some cases, historical descriptions, making their phenotype poorly understood. Given that situation, there is currently no certainty of achieving success with a back-breeding attempt, and any results must be reviewed with great caution. In order to test genetic closeness, DNA (both mitochondrial and nuclear) of the breeding animals must be compared against that of the extinct animal.

Successful breeding back might be possible: humans have selected animals only for superficial traits, and as a rule did not intentionally change less-observable traits, such as metabolic biochemistry.

During the Second World War, the Heck brothers crossed Koniks with Przewalski's horses and ponies, such as the Icelandic horse and the Gotland pony; the result is now called the Heck Horse. During recent decades, Heck horses have been continually crossed with Koniks, making the two phenotypes at present nearly indistinguishable, excepting that the Heck horse tends to have a lighter build.

Pigs

Boar–pig hybrids, which are hybrids of wild boars and domestic pigs and exist as an invasive species throughout Eurasia, the Americas, Australia, and in other places where European settlers imported wild boars to use as game animals, are also used for selective breeding to re-create the type of pigs represented in prehistoric artworks dating from the Iron Age and earlier in ancient Europe.

A project to create them, under the name of the Iron Age pig, started in the early 1980s by crossing a male wild boar with a Tamworth sow to produce an animal resembling what Iron Age pigs are believed to have looked like. Iron Age pigs are generally only raised in Europe for the specialty meat market, and in keeping with their heritage are generally more aggressive and harder to handle than purebred domesticated pigs.

The two most noticeable characteristics of the quagga, fewer stripes and a darker pelage, are frequently observed to varying degrees in wild plains zebra populations. Animals with these two traits have been sought out for the Quagga Project breeding programme.

The project has been criticized for its focus on the morphological characteristics of the quagga, as the extinct animal may have possessed unrecorded behavioral or non-visible traits that would be impossible to reliably breed back from plains zebras.

Galápagos giant tortoise

thumb|Volcán Wolf tortoises hybridised with the Floreana Island tortoises, allowing for breeding back to restore the extinct subspecies.

In 2012, several hybrids of the Volcán Wolf and extinct Floreana giant tortoise subspecies were discovered on Isabela Island in the Galápagos Archipelago, a territory of Ecuador. It is believed that sailors left these tortoises on the island during their travels in the early 19th century. In 2017, back breeding efforts began to help the hybrids regain genetic purity of the Floreana subspecies.

By 2023, 400 Floreana offspring have been hatched from these hybrids on Santa Cruz Island, with plans to release these back bred animals into the wilds of Floreana Island to regain their niche following the successful extirpation of invasive species.

See also

  • De-extinction
  • Otto Antonius
  • Lazarus taxon
  • Preservation breeding

References

Further reading

  • Koene, P., & Gremmen, B. (2001). Genetics of dedomestication in large herbivores. In 35th ISAE Conference, Davis, California, 2001 (pp. 68–68).
  • The Dire Wolf Project
  • The Quagga Project
  • TaurOs Project