ABSTRACT
At the 1990 meetings for the British Association for the Advancement of Science, an experimental embryologist expounded an expert's view to a lay audience. 1 Martin Johnson was concerned to demonstrate the continuity of biological process. A person's birth begins with primitive gametes laid down when one's parents were embryos in the grandparental womb. Subsequent development depends not only on genetic coding but on extragenetic influences that operate on chromosomes from the start; these include stimulation from material enveloping the egg, 2 as well as nutritive and other effects derived from placenta and uterus.
