Atavism

An atavism (from the Latin atavus, ancestor '), also dated check, is the recurrence of anatomical features in a subject who had trained at the more distant evolutionary ancestors, the immediate ancestors but went off. Frequently atavism are therefore perceived as a deformity. Count, as well as the rudiments of the classic Evolution documents. In a broader sense, the term is also applied in the ethology of original behaviors. The term is very common in the development of biological and cultural-historical research of the second half of the 19th century; later he is taken over in 1901 by Hugo de Vries.

Anatomical atavism

At the present stage of development, these anatomical features have no other function and are gone for generations. Examples in humans are: cervical fistulae in humans as a remnant of the applied during embryonic branchial arches, pronounced out -grown tail bone, horn tip, extra nipples along the milk lines ( polythelia and polymastia ), excess body hair ( lanugo ) and the Darwin - ear hump.

All living things can have pronounced anomalies an earlier stage of development, more or less.

In cattle, it happens that they three instead of two claws train in marine mammals such as whales and dolphins in the formation of limbs that resemble the legs of land animals.

Less well known are atavism in plants, but have been researched such as the 19th century. These include the Pelorienbildung in flowering plants, ash with only one - or three-membered sheets ( Einblattesche ) and cacti occurring with leaves.

Basically atavistic forms should also occur in bacteria, fungi and protists. However, they are difficult to identify clearly due to the strong variability of these organisms and partly not fully clarified lineage relationships and distinguish them from neoplasms.

Causes of atavism

The formation of atavism can have the following causes:

• Inhibition malformations: Saves species-specific differentiation temporarily accumulated by the embryo organogenesis stages with recapitulation of earlier features;
• Mutative atavism: recovery of the ancestral form by mutation of certain genes or changes in gene regulation with new activation of repressed (latent ) genes;
• Hybrid atavism: Education earlier joint features in the bastardization of closely related species with each other.

Verhaltensatavismus

A Verhaltensatavismus is occasionally observed eg in house sparrows. This usually build their nests in niches that are well adapted to their preferred environment. But it also happens that individual house sparrows build nests ball instead, as they are characteristic of original weaver birds.