New species in 3 generations

Rapid hybrid evolution over three generations of birds and within forty years of observing humans. Rapid hybrid speciation has been witnessed between Darwin’s finches in the Galápagos archipelago, on the small island Daphne Major.

"It's an extreme case of something we're coming to realise more generally over the years. Evolution in general can happen very quickly," said Prof Roger Butlin, a speciation expert who wasn't involved in the study ... "We tend not to argue about what defines a species anymore, because that doesn't get you anywhere,"
Galapagos finches caught in act of becoming new species | BBC

Not the ultra slow evolutionary Doctrine of Uniformity but quick animal evolutions? Some changes in 3 generations not 100's.

evolution

This example shows that reproductive isolation, which typically develops over hundreds of generations, can be established in only three.
Abstract - Rapid hybrid speciation in Darwin’s finches

How young could the present generation of planets life forms be since the last catastrophic event?

evolution

A population of finches on the Galapagos has been discovered in the process of becoming a new species. This is the first example of speciation that scientists have been able to observe directly in the field.

... In 1981, the researchers noticed the arrival of a male of a non-native species, the large cactus finch ... this male proceeded to mate with a female of one of the local species, a medium ground finch, producing fertile young. Almost 40 years later, the progeny of that original mating are still being observed, and number around 30 individuals.
Galapagos finches caught in act of becoming new species | BBC

What is a new species?

What makes a species? This new finch population is sufficiently different in form and habits to the native birds, as to be marked out as a new species, and individuals from the different populations don't interbreed.

Prof Butlin told the BBC that people working on speciation credit the Grant professors with altering our understanding of rapid evolutionary change in the field. In the past, it was thought that two different species must be unable to produce fertile offspring in order to be defined as such.

But in more recent years, it has been established that many birds and other animals that we consider to be unique species are in fact able to interbreed with others to produce fertile young.
Galapagos finches caught in act of becoming new species | BBC