Classical and medieval authors debated long and hard about the material basis of
ID: 67317 • Letter: C
Question
Classical and medieval authors debated long and hard about the material basis of the facts of heredity. Many believed that the only possible solution was that the egg contains somewhere inside itself a tiny but complete chicken, which needed only to grow. In a prescient analysis, Aristote rejected this view, pointing out, for example, that certain inherited traits can skip a generation entirely. Contrary to Hippocrates, Aristote argued,
« The male contributes the plan of development and the female the substrate…. The sperm contributes nothing to the material body of the embryo, but only comunicates its program of development … just as no part of the carpenter enters into the wood in which he works. »
Aristote missed the fact that the mother also contributes to the « plan of development », but he made crucial progress by insisting on the separate role of an information carrier in heredity. The organism uses the carrier in two distinct ways :
It uses the software stored in the carrier to direct its own construction ; and
It duplicates the software, and the carrier on which it is stored, for transmission to the offspring.
Today we make this distinction by referring to the collection of physical characteristics of the organism (the output of the software) as the phenotype, and the program itself as the genotype.
It was Aristote’s misfortune that medieval commentators fastened on his confused ideas about physics, raising them to the level of dogma while ignoring his correct biology. Even Aristote, however, could not have guessed that the genetic information carrier would turn out to be a single molecule.
What is your comment ? Egg or chicken ? Can you discuss the vexing question from antiquity : the transmission of order from one organism to its descendants ? (Schrodinger did it).
Explanation / Answer
I feel that Aristotle is correct in defining the genetic information carrier, i.e male and female together plan for development. I refute the views that that the only possible solution was that the egg contains somewhere inside itself a tiny but complete chicken, which needed only to grow. So the answer is chicken.