“In progressive creationism there may be much horizontal radiation. The amount is to be determined by the geological record and biological experimentation. But there is no vertical radiation. Vertical radiation is only by fiat creation. A root-species may give rise to several species by horizontal radiation, through the process of the unraveling of gene potentialities or recombination. Horizontal radiation could account for much which now passes as evidence for the theory of evolution. The gaps in the geological record are gaps because vertical progress takes place only by creation.” (Ramm B.L., “The Christian View of Science and Scripture,”  Paternoster: Exeter, Devon UK, 1967, reprint, p.191)
Edward T. Babinski: Genetically speaking the distance between man and chimp is no greater than that between sibling species of fruit flies. So by what measure do progressive creationists distinguish between “horizontal evolution” and “vertical creation” in the case of human evolution? If all 300+ species of fruit fly found only on the Hawaiian islands are “horizontal evolution,” then why isnʼt the descent of chimp and human from a common ancestor also “vertical evolution?” The latest genetic data agree that human beings could be regarded as a third species of chimp, i.e., pan, bonobo and human.
Hereʼs a letter from a YEC who also critiques Rammʼs “horizontal/vertical” explanation. (I would like to know what Lubenow was speaking about below concerning Rammʼs “further movement” away from the historicity of Genesis.)
On Bernard Ramm and Spradley…
by Marvin L. Lubenow
Christian Heritage College
2100 Greenfield Drive
El Cajon, CA 92019
From: Perspectives on Science and Christian Faith 44 (September 1992): 218
The article by Joseph Spradley on Bernard Ramm and the ASA (March 1992) was fascinating.
There is an aspect of Rammʼs progressive creationism that as far as I know has never been addressed. While not denying theistic evolution as a viable option, Ramm claimed that progressive creationism was a strictly creationist system because it did not involve vertical radiation (evolution) but only horizontal radiation (The Christian View of Science and Scripture, 1954, p. 215 & 272). The vertical events he called creation events. While Ramm was quite stingy with details of his system, he seemed to suggest that creation took place at the Phyla and/or Family level (p. 215).
There is an inverse relationship between the number of creation events one has in his system and the amount of vertical evolution one must invoke to explain the variety and complexity of our present world. The fewer creation events one has, the more he must depend upon evolution to make up the difference. Hence, Rammʼs system is unworkable. There is no way that one can explain the complexity of our present world by having creation at the Family level (or higher) and depend only on horizontal radiation. Rammʼs progressive creationism is thus an evolutionary system, partially, even though he sincerely believed it was not.
The fact that Ramm has moved even further from an historical view of Genesis suggests that at gut level he realized that his progressive creationism emperor had no clothes. Spradley admits that “…t perhaps conceded too much to science.” However, the basic suppositions that allow such concessions are the gift that keeps on giving. Rammʼs newer view concedes even more of Genesis.