Re: Apologetic Islamic take on Evolution … Or unkind dismissal?
In evolution the closest idea to what you are describing is ring species. Imagine in your chain if there existed a species z that could both mate and produce viable offspring with species x-- and species y++, however species x-- and y++ couldn’t mate with each other. Evolutionary scientists have claimed to discover such organisms and claim that these constitute different species (although their definition of species is not clear to me).
Also, its not a matter of millions of years for a new species to arise but probably many generations, and the length of one generation can differ from species to species. This is why scientists claim evolution has been observed in species that have short generation times such as the rise of a new species of Nereis acuminata from long beach california experiments.
Scientists today can’t agree on whether speciation is gradual or takes place quickly such as in the case of punctuated equilibrium.