Evolution is a tinkerer that cobbles together new functions from old ones, and the genome is a kind of parts bin of recyclable elements. When new features evolve, the parts in the bin are co-opted to operate in new roles. As a result, the same parts appear in anatomically and evolutionarily distinct structures because it is faster and easier to reuse an old gene network that almost does what is needed, than it is to spend another few million years evolving a distinct gene for the function.
This makes these master genes precisely analogous to the stock of goods found in a hobbyist’s electronics store. Standard subunits—oscillators, op-amps, field effect transistors, switches, rheostats, and so forth—will get incorporated into many different kinds of projects; whether she is building a radio or a synthesizer or a burglar alarm, the hobbyist will find it easier to just grab an oscillator integrated circuit off the shelf than to design her own. We could sample devices built by different hobbyists with different purposes, and when we rummaged about in their insides, we would find the same subunits incorporated into novel, larger assemblies.
An important concept - homology- explained elegantly using ...an analogy ...he.. he... Read the rest here....Tip: 3QuarksDaily