Evolution supposedly took place over the span of four billion years. No one observed the process. Today, the fossil record and the comparative anatomy, physiology, and biochemistry of various organisms allow scientists to infer about the past. If life evolved through the gradual development and multiplication of slight variations, then the fossil record should exhibit this kind of constellating progression. Dead organisms should be constellated in strata that are hardly differentiated.
"But for well over 150 years," says David Berlinski, "the dead have been remarkably diffident about confirming Darwin’s theory."
The disintegrated remains of primeval creatures do not appear how they should in the fossil record. Palaeontologists have classified fossils into different categories like theromorphs and therapsids. But there are significant gaps in the record; many key transitional forms are nowhere to be found.
Prior to the Cambrian era, which was roughly 600 million years ago, the fossil record exhibits a significantly small collection of biological forms.
A vast array of new biological forms suddenly emerges in the Cambrian era.
These new biological forms appear all at once in the fossil record.
Then, key courses of transitional progress are simply absent.
Consider the ancestral link between Eusthenopteron and Ichthyostega, which is the pivotal juncture of the fish and the amphibia. Most species come into the evolutionary arrangement entirely formed and go out unaltered.
"Where there should be evolution, there is stasis instead," says Berlinski. 
In building their theory of "punctuated equilibria," palaeontologists Stephen Jay Gould and Niles Eldredge had to resort to using the term 'stasis'.
Steven Stanley, a palaeontologist and evolutionary biologist at the University of Hawaii at Manoa, says the following: "The known fossil record fails to document a single example of phyletic evolution accomplishing a major morphologic transition and hence offers no evidence that the gradualistic model can be valid."