Reverse evolution to gain back lost traits
Back evolution

Evolution do not strictly keep a history of how they were before. There is no way for a population to specifically produce mutations to reverse previously fixed mutations in order to evolve back in time. This has sometimes been called Dollo's law but very few people actually use this term today.

Note however that a population may have kept pseudogenes or specific developmental pathway or case of atavism that make the evolution of some traits similar to previously existing trait "easier". A very nice example of such mechanism is the case of Membracidae (treehoper).

Example of Membracidae

insects have evolved flight once. The first flying insect had 3 pairs of wings, one pair on each of the 3 segments of the thorax. Today, there exist no insects with 3 pairs of wings. In all lineages descendent of this flying ancestor many have no wings and many have 2 pairs of wings only. Here is a schema showing a typical insect with 2 pairs of wings.



As you can see there is no pair of wings on the first segment of the thorax (called prothorax) as it has been lost through evolution. Note that the diptera (true flies) have lost a second pair of wings (the one on the metathorax which has been replaced by halters).

Membracidae (treehoper) is a family of wingless insects. They use previously existing developmental pathways and previously existing genes (Prud'homme et al. 2011) for developing wings on the protothorax but instead of making wings, they make all kind of funny shape for defense purpose. Here are a few examples