Credit: M.F. Bonnan via “I f***ing love science (on Facebook).
Yes, exactly! A significant percentage of the population (cough, creationists, cough) doesn’t understand that the evolutionary relationships between species is a lot like that between extended family members; just over a much longer time scale. Phylogeny is primarily a branching (family) tree-like pattern, not a single file, ladder-like, progression (cladogenesis vs. anagenesis).
Addendum: It has been pointed out to me that the cartoons depiction of a family “tree” superimposed on a cladogram is somewhat inapt and I absolutely agree that the cartoon is by no means a perfect analogy (comparing speciation, species giving rise to new species, with two parents coming together and bearing children). However, I think it gets the idea across much better than the linear iconography that has become so entrenched in peoples minds. Especially, I think, concerning the relationships between fairly closely related species like between chimps and humans. People incorrectly tend to think of humans as somehow being directly descended from chimps rather than our being “cousins” descended from a common “grandparent” (that was probably somewhat chimp-like in appearance).
Once you grok this fact you will understand what is fundamentally wrongheaded about questions like: “If humans evolved from [share a common ancestor with] apes why are there still apes?”
This sort of question is, except for the timescale involved, just like asking: “If you and your cousin share a common ancestor (grandmother), how can you both exist at the same time?”
Understanding this also answers the common creationist objection against many transitional fossil series based on species overlapping in time. For example:
“Early” horses have been preserved in strata from the same evolutionary age as several ‘”later” horses
Hyracotherium/Eohippus and Orohippus do for instance appear in the fossil record at the same time as Epihippus. Mesohippus and Miohippus appear together with Merychippus and Parahippus. Almost all other horses (with a possible exception of one or two)—Parahippus, Merychippus, Pliohippus, Equus and possibly also Miohippus—are represented at the same time during much of the period when they have been found as fossils.16 (But especially in the newer evolutionary schemes, different names have been given to very similar animals, giving the appearence of evolution as well as providing fame to their discoverers; see examples in Froehlich 20029 and MacFadden 20054). Fossils of Hyracotherium (sic) have also been found very high up in the strata (Pliocene), but these findings have been rejected as reworked (i.e. eroded and deposited at a later strata) in spite of the fact that the geological observations do not show any signs of disturbance.17 Thus, the fact that most of the horses lived almost at the same time undermines their proposed evolution. (Molén, 2009, emphasis mine)
Buzzzt, sorry but that is incorrect, thank you for playing, here is a home version of our game as a consolation prize.*
The coexistence of two genera of horses does nothing to undermine their evolutionary relationship any more than your grandparent or cousin coexisting with you undermines your familial relationship.
Evolution does not require that a parent species become extinct after a speciation event (after it gives “birth” to a new daughter species) nor does it require that once two lineages split apart that both will change at the same rate or in the same direction.
Fossil species A could be directly ancestral to species B, persisting relatively unchanged after the two lineages have split. Or species A could be a cousin to species B that only strongly resembles an as yet undiscovered common grandparent species. Such distinction are very difficult to make in fossil organisms.
[* Note: This is not even close to a comprehensive dissection of the problems with quoted article or even this paragraph.]
Molén, Mats (2009) “The evolution of the horse“, Journal of Creation 23(2):59–63 (downloaded on 9-14-2013)