Two interesting sections from John Calvin's commentary on 1Corinthians:
Regarding the covering of the head:
Let us, however, bear in mind, that in this matter the error is merely in so far as decorum is violated, and the distinction of rank which God has established, is broken in upon. For we must not be so scrupulous as to look upon it as a criminal thing for a teacher to have a cap on his head, when addressing the people from the pulpit. Paul means nothing more than this — that it should appear that the man has authority, and that the woman is under subjection, and this is secured when the man uncovers his head in the view of the Church, though he should afterwards put on his cap again from fear of catching cold. In fine, the one rule to be observed here is το πρέπον — decorum If that is secured, Paul requires nothing farther.
Regarding verses 14–15:
“Doth not even nature itself…” He again sets forth nature as the mistress of decorum, and what was at that time in common use by universal consent and custom — even among the Greeks — he speaks of as being natural, for it was not always reckoned a disgrace for men to have long hair. Historical records bear, that in all countries in ancient times, that is, in the first ages, men wore long hair. Hence also the poets, in speaking of the ancients, are accustomed to apply to them the common epithet of unshorn. It was not until a late period that barbers began to be employed at Rome — about the time of Africanus the elder. And at the time when Paul wrote these things, the practice of having the hair shorn had not yet come into use in the provinces of Gaul or in Germany. Nay more, it would have been reckoned an unseemly thing for men, no less than for women, to be shorn or shaven; but as in Greece it was reckoned all unbecoming thing for a man to allow his hair to grow long, so that those who did so were remarked as effeminate, he reckons as nature a custom that had come to be confirmed.