"Ontogeny Recapitulates Phylogeny"

[MedPR]

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I remember learning this in several of my undergrad biology classes. EK even mentions that we should be familiar with it and know what it means.

However,

http://en.wikipedia.org/wiki/Recapitulation_theory

The theory of recapitulation, also called the biogenetic law or embryological parallelism—and often expressed as "ontogeny recapitulates phylogeny"—is a disproven biological hypothesis that in developing from embryo to adult, animals go through stages resembling or representing successive stages in the evolution of their remote ancestors. With different formulations, such ideas have been applied and extended to several fields and areas, including the origin of language, biology, cognition and mental activities,[1] anthropology[2], education theory[3] and developmental psychology.[4] While some examples of embryonic stages showing superficial features of ancestral organisms exist, the theory of recapitulation itself has been completely disproven within the field of biology.

So should we disregard it for MCAT?

 

[ljc]

Well seeing as I had zero idea what this phrase meant until now, I'll forego learning it and consider it disregarded!

But in all seriousness, they're not going to ask "Do developing embryos resemble evolutionary ancestors?," which is the only time such a distinction would matter. A) Yes, vs. B) No! That theory is false! I read it on Wikipedia!
A far more likely question would be "The theory that developing embryos in various stages resemble historical ancestors is known as:" or something similar. I'm going to keep it tucked away just in case, but it's really interesting that it's been disproven. Perhaps that was pretty recently, after all these exam materials were drafted?

 

[milski]

Was not one of the facts supporting evolution that the ebrios went from stages resembling its evolutionary predecessors? Am I mixing things up here? If the theory in question has been disproved how does it still support evolution?

 

[neurodoc]

"Ontogeny Recapitulates Phylogeny" (ORP) is basically the idea that an organism, in its embryonic development somehow reflects the biologic evolution of that organism. According to ORP thinking, human embryos, for example, go through a phase of development which includes having gill-slits. This is taken to represent a earlier evolutionary phase in which our ancestors had gills (like fishes).

ORP is a plausible and intellectually attractive idea. It may or may not be "true," but it is ceratinly "plausible." Despite the off-hand Wiki comment that it has been disproven, I',m not sure it has, and I would certainly like to see a definitive disproof of the idea.

 

[theseeker4]

Was not one of the facts supporting evolution that the ebrios went from stages resembling its evolutionary predecessors? Am I mixing things up here? If the theory in question has been disproved how does it still support evolution?

This is from the same Wikipedia article:

For example, Haeckel proposed that the pharyngeal slits of the pharyngeal arches in the neck of the human embryo resembled gill slits of fish, thus representing an adult "fishlike" developmental stage as well as signifying a fishlike ancestor. Embryonic pharyngeal slits, formed when the thin branchial plates separating pharyngeal pouches and ectodermal grooves perforate, open the pharynx to the outside. Pharyngeal pouches appear in all tetrapod animal embryos: in mammals, the first pharyngeal pouch develops into the lower jaw (Meckel's cartilage), the malleus and the stapes. At a later stage, all pharyngeal slits close, only the ear remaining open.[19] But these embryonic pharyngeal arches, pouches, and slits could not at any stage carry out the same function as the gills of an adult fish.
Haeckel produced several embryo drawings that often overemphasized similarities between embryos of related species. The misinformation was propagated through many biology textbooks, and popular knowledge, even today. Modern biology rejects the literal and universal form of Haeckel's theory.[8]
Haeckel's drawings were disputed by Wilhelm His, who had developed a rival theory of embryology.[20] His developed a "casual-mechanical theory" of human embryonic development.[21]
Darwin's view, that early embryonic stages are similar to the same embryonic stage of related species but not to the adult stages of these species, has been confirmed by modern evolutionary developmental biology.

Basically, the claims and evidence made by Haeckel were determined to be exaggerated and/or partially fabricated. Despite this, his work was and is used to promote evolution (even though it is in no way vital to the validity of evolution) and is even cited today in text books.

The important thing is, it was something promoted at the time but is no longer considered legitimate (even though some still refer to it as if it is valid and true). Creationists actually use the flaws in Haeckel's work as evidence to disprove evolution, even though casting doubt on his work doesn't negate evolution's validity.

I seriously doubt any of this will be needed for the MCAT.