When I was in college (20+ years ago), I had a bear of a biology professor who, while extremely tough, taught me alot. Anyway, I distinctly remember one lecture, in which he said," You may forget what this means, but I guarantee you will never forget this phrase." He proceeded to write “ontogeny recapitulates phylogeny” on the overhead.
He was right. I’ve forgotten what it means.( I also don’t know why it suddenly popped back into my head, but that’s another thread).
I got it as ontogeny begats phylogeny. IIRC, it was the idea that the developing fetus sort of runs through its evolutionary stages while coming to full term. I don’t know if it is an accepted idea or not.
And I think, with “begats” I wrote it down in reverse; it should be phylogeny begats ontogeny. Which I might have caught had I remembered what ontogeny or phylogeny meant.
Right. The only problem, or so my cytogeneteist friend tells me, is that it really isn’t true. It makes a nice catch phrase, but as a “rule” it does not seem to accurately reflect what really happens during embryonic development.
Damn. Next thing you know they’ll be telling you the Newtonian laws we learned in Physics I aren’t really true, either.
I’m certain that Cecil has addressed this question, but damned if I can find it in the archives. I’ll check the books tonight, but IIRC his conclusion is that it’s mostly bunk. I think that is over-generous, but I’ll expand on that when I find the column.
As the last couple of posters has indicated, the O-R-P theory has been discredited. The idea that mammalian embryos pass through the evolutionary stages is false. The idea was widely credited to Ernst Haeckel; unfortunately, it has been shown that his embryonic drawings were frauds–jimmied to fit with his preconceived notion. They can’t even really be considered honest mistakes on Haeckel’s part.
Two quick examples: human embryos do not have “tails” that are comparable to that of other species. Sometimes a flap of tail-like skin is present (even at birth), but it is not supported by skeletal, vascular, or nervous systems, as with other species.
Also, the claim that a human embryo has “gills” is false. Embryonic development includes “gill slits” which are better termed “pharyngeal pouches.” Unlike a fish gill (which is a vascularized structure used for gas exchange), a mammalian embryonic pouch is not. These pouches actually develop into specific anatomical features as the fetus develops.
Cecil Adams did shortly discuss the phrase on pages 476-477 of his book “More of the Straight Dope”. It wasn’t really a Straight Dope column. In that book they have short “quizzes” interspersed between the articles, and this is an answer to one of the quizzes. His verdict: