There is an interesting blog on Simon Fodden’s Xanada, on a book called “Right Hand Left Hand: The Origins of Asymmetry in Brains, Bodies, Atoms and Cultures” by Chris McManus, a professor of psychology at University College London.
[ … ] McManus finally hooked me with the description of the problem of whether space is absolute or relative and how that relates to which side our hearts are on.
He continues, commenting on the fact that “right” and “left” are relative to some reference point, something obvious if you try to explain – or tell – what “right” and “left” means. You can’t. You’ll have to show.
All of this relates to hearts because it makes us wonder how embryos know their right from their left, in order properly to locate hearts (livers, lung lobes, etc. etc.). Well, one would have thought (I for one, certainly) it was genetically coded in the DNA. The interesting observation McManus makes is that DNA alone cannot do the job, because DNA is (merely) a set of telling symbols, not a showing device. Something in the maternal “environment” must, together with the DNA, cause hearts to come out right by a kind of “showing.”
Oh, and we thought we had opened Pandora’s box by “cracking the genetic code”? Nope.
[ … ] the fairly simple proof that the DNA of an embryo is not a full set of instructions as to how to build a human being, […] , consequently, though having “cracked the genetic code,” we must look still further afield in order to comprehend reproduction.
Nothing much to add here. I guess I will provide myself with a copy of this book.