There are few more enduring, recognizable ‘badges’ than the tonsure. If you want people to know the figure in the odd looking garment is a monk, make sure that you throw in a tonsure. And a tonsure is a small circle of baldness on the crown of the head, right? Not necessarily.
Not many people, I think, go into the subject more deeply, although Julia Barrow may be an exception. I only came across it because I was using Hrabanus Maurus’ De Institutione Clericorum as a text for practising Latin. We are told that this work was required as a response to the many questions being put to Hrabanus by his brethren as to how to carry out correctly all the duties of a monk. It is no coincidence that it is dated to 819, just after some synodal decisions on good practice. It must, therefore, be significant that the chapter on the tonsure, (Bk I, Ch. 3) at 59 lines, is longer than Chapter 1 (on orders of dress and the sacraments) and Chapter 2 (on the three categories of church members) put together. Does this imply it was a particularly thorny issue?
The answer, it seems, is probably.
Hrabanus attempts to trace its history through the Bible. In the Old Testament he cites the Nazarites (Num 6.18) who marked the taking of a vow by shaving off their hair and burning it and Ezekiel (Ez. 5.1) who had to take a sharp sword, cut off his hair and beard, weigh the hair, sort it and burn it. In the New Testament (Acts 18.8) Paul is mentioned as shaving his head ‘because he had made a vow’. But none of these references is actually to a tonsure – they all refer to removal of hair completely and two of them relate to a vow. But no circles, and no regular re-clipping.
Hrabanus pre-empts this objection and explains that the circle, combining the shape of the crown of the king and the head shaving of the priest, represents the conjunction of priesthood and kingship – mentioned in I Peter 2.9. He further explains that the New Testament usage of the tonsure is necessarily unlike that of the Old Testament because hair is a covering and the New Testament is all about uncovering, revealing things that were hidden to the prophets. For Peter, the first to wear the tonsure as we know it, Hrabanus says, there were three reasons for wearing the tonsure: to recall the crown of thorns, to distinguish New Testament priests from those of the Old Testament and to subject the disciples to the mockery of the Roman people, for whom shaved heads signified slaves. Hrabanus leaves it to the reader to decide if all this is true and moves on to less interesting but more secure topics.
There are other sources, not the least of which is Thehistoryofthehairsworld.com, on which I shall make no comment. Bede however (Hist. Ecc. Book V, chapter 21) opens up the idea of more than one style of tonsure. When the Celtic church agreed to follow the Roman church on the dating of Easter, at the Synod of Whitby, they were apparently also expected to amend their style of tonsure to the Roman style. Bede quotes a letter from Ceolfrith to King Nechtan of the Picts in which he does go into some detail about the dating of Easter but then goes on to talk about tonsure. Whilst allowing that a difference in style may be tolerated, he comes down heavily in favour of unity and specifically unity with the style worn by Peter, as opposed to that worn by Simon Magus (Acts 8.20-21). Ceolfrith, like Hrabanus 100 years later, links Peter’s tonsure (also known as ‘coronal’) to the crown of thorns and shows it therefore to be an honourable symbol. Simon Magus’ tonsure (known as the ‘insular’ tonsure) on the other hand, has the appearance of a circle only from the front and thus, though it may delude people in this life, in the next it will incur eternal punishment. Ceolfrith also talks about Adamnan of Iona, who in all other respects is a worthy man, but who refuses to conform to the Roman/coronal tonsure, even in the interests of church unity. Ceolfrith notes that on his return to Iona, Adamnan succeeded in persuading his brothers to adopt the new dating of Easter but not the tonsure. King Nechtan, presumably having read this letter, got the message and his clergy did adopt the coronal tonsure. So by this date, probably 716, the tonsure was well established in the British Isles but at least two distinctive traditions existed.
For Julia Barrow, the tonsure as such is a relatively late development.  She apparently finds no evidence of an unbroken chain from Peter to the early clerics, since the first record of tonsure is in Toledo in 527, noting that oblates were tonsured immediately on their admission, probably as a mark of status. In Gaul also, this ‘mark of clerics’ was not accepted until the early sixth century. The debate at Whitby was thus only about 150 years after the acceptance of the tonsure – presumably the coronal, since Iona was clearly under pressure to conform to the Roman tradition – on the mainland. Hrabanus does not seem to know about the two traditions, or if he does they are not significant for him.
As is often the case, a moment on Google changes everything. Christianity.stackexchange.com has a thread on tonsure which is quite credible. One contributor does say it’s all to do with controlling lice – which is more likely than some of the things you might find on Google – but another more seriously proposes a three part taxonomy:
- Roman – aka coronal, the ring of which Hrabanus speaks and thought to be first worn by Peter
- Celtic – aka insular, although apparently some monks were accustomed to taking the long hair at the back and arranging it ‘to form a semi-circle from one ear to the other.’
- Eastern – completely shaven
The Eastern style is attributed to St Paul, and tallies best with Hrabanus’ account, except that the implication here is that it was kept shaven, more like Buddhist monks rather than the apparently temporary shaving of the Nazarites. The contributor believes that the three styles were developed by various orders, which supports the pressure after Whitby to unite the two styles of British tonsure. As to the origin of the coronal tonsure, s/he refers us to ancient Egypt and ancient Greece, where the circle honoured not the crown of thorns but the pagan sun god. Apparently.
As Hrabanus concludes:
‘Sed de his quid suscipiat, lectoris iudicio derelinquimus’.
 The Clergy in the Medieval World, Cambridge 2015, pp. 29-30
 There is a belief that Paul was a Nazarite
 Op cit