That their existence is part of the foundation of Christianity.
Anglican Curmudgeon usefully points out the reasons that an “evolutionary” interpretation of Christianity is impossible, citing atheist (and former Christian) Michael Ruse’s arguments in From Monad to Man:
Let me be open. I think that evolution is a fact and that Darwinism rules triumphant. Natural selection is not simply an important mechanism. It is the only significant cause of permanent organic change.
And that bias permeates his subsequent investigation into the conflicts, particularly when it comes to considering monogenism, the idea that current humans are the descendants of a single set of original parents.
Citing the work of evolutionary biologist and Dominican priest Francisco Ayala, Ruse writes (pp. 75-76):
Francisco Ayala (1967), a distinguished evolutionary geneticist (and at the time of this writing, a Dominican priest), points out that an essential component of Christian theology, confirmed by Pius XII in his encyclical Humani Generis (1950), is that humans are descended from a unique pair (monogenism). That part of the Adam and Eve story cannot be interpreted symbolically. Moreover, there are strong theological pressures to go along with this conservative reading, otherwise one has removed a major support of the doctrine of original sin . . .
As Ayala points out, the trouble is that [monogenism] goes completely against our thinking about the nature of the evolutionary process. Successful species like humans do not pass through single-pair bottlenecks . . . “There is no known mechanism by which the human species might have arisen by a single step in one or two individuals only, from whom the rest of mankind would have descended” (Ayala 1967, 15). More recently, “the genetic evidence indicates that human populations never consisted of fewer than several thousand individuals” (Ayala 1998, 36). . .
*Ayala, F. J. 1967. Man in evolution: a scientific statement and some theological and ethical implications. The Thomist 31(1): 1-20; and 1998. Human nature: one evolutionist’s view. In Brown, W.S., N. Murphy, and H.N. Malony, eds., Whatever Happened to the Soul? Scientific and Theological Portraits of Human Nature (31-48). Minneapolis: Fortress Press.
Many find it difficult to understand how Christianity Today could have blindsided itself so as to run an extended Valentine for the Christian Darwinists at BioLogos, past and present as a cover article.