A friend pointed this out. I find it fascinating. It comes from page 119ff of the book “Baptisms in the Early Church” by Stander and Louw (both are paedobaptists):

In the first four centuries of Christianity, the literature on baptism clearly shows how, in the majority of instances, it was persons of responsible age (generally adults and grown children) who were recipients of baptism. …The patristic literature of the first four centuries clearly shows how infant baptism developed. Probably the first instances known, occurred in the latter part of the third century, most likely in North Africa, but during the fourth century infant baptism became more and more accepted and though believer’s baptism of people of responsible age still continued in many areas, the development of the Church (after Church and State became reconciled) into a more unified body, controlled by the see of Rome, provided a theological base for infant baptism to be accepted…Finally, it needs to be remarked that the contention often found in modern literature, viz. that adult baptism in the early Church entailed a missionary situation, cannot be substantiated by the relevant patristic literature, since the transition from adult baptism to infant baptism occurred at a time when Christianity was already a widespread phenomenon in the ancient Church. Therefore, it is also unsound to scrutinize the New Testament writings for allusions to infant baptism, since the latter involved a historical development. Moreover, no distinction was ever made between persons coming from a heathen or Christian family. In fact, the reason for the transition to infant baptism was one of theological perspective and had nothing to do with a missionary situation.

Baptize those babies if you want, but don’t tell me that is has always been the practice of the Church. This bit of historic information stands much of Protestant paedobaptistic apologetics on its head.