The meaning of hand gestures may vary widely from culture to culture. In the modern West, approval is popularly expressed by the “thumbs up” sign, and disapproval by the downward turn of the thumb. These hand gestures even seem to be universal, at least in the modern era. But perhaps it was not always so. The humanist Angelo Poliziano’s Miscellanies contains a passage in chapter 42 of his book that raises some doubts, at least to my mind. Philology may shed some light on the subject.
I think it is certain that in Roman times the downward turn of the thumb indicated disapproval. How many times have we seen, in film or in paintings, the spectators of a gladiatorial combat frenziedly thrusting out their arms to the victor in the arena, their thumbs gleefully inverted? As proof of this, Poliziano cites the following lines from Juvenal (III.36):
Et verso pollice vulgus
Cum libet, occident populariter…
This means, “and the crowd, with a turn of the thumb, kills whom they wish, to roars of approval.” The phrase verso pollice (“with a [downward] turn of the thumb”) makes it clear that the thumb is to be extended outward, and then turned down. We know the turning of the thumb went in a downward direction, because Poliziano provides us with another quotation, this time from the poet Prudentius’s Against Symmachus (II.1097):
Virgo modesta iubet converso pollice rumpi.
This means, “and the modest virgin, with her thumb turned down, commands that the chest of the prostrate be stabbed.” Now in this quote the poet uses converso pollice, which provides no room for ambiguity (as verso pollice arguably might) that the thumb was being inverted. So we can see from these two references that in Roman times, the downward rotation of the thumb expressed disapproval.
We may feel reasonably assured that the inverted thumb represented disapproval to the Romans. But what about expressing approval? Would the Romans have used our “thumbs up” sign? The answer appears to be no, if we rely solely on the evidence of language. It seems that approval was expressed by the clenching, or enclosing, of the thumb within the hand, and not by an upraised thumb projecting from the fist. This was what Poliziano thought, and I believe he is correct. He provides the following quotation from Pliny’s Natural History (XXVIII.25):
Pollices, cum faveamus, premere etiam proverbio iubemur.
This sentence means, “We are also informed by a proverb to clench our thumbs when we are in approval.” Here we have clear evidence of the hand gesture that indicates approval. But here is the problem. The meaning of this line hinges on the meaning of the verb premere. Unfortunately, it is one of those Latin verbs that has a number of meanings. Not only this, but Pliny writes in a rapid, condensed style, the kind of prose that a man writing his own encyclopedia might write. Perhaps his compactness invites misunderstanding–or perhaps not. The Oxford Latin Dictionary lists no less than twenty-eight meanings for premere, and some of these entries have additional sub-meanings. One of these meanings admittedly is to lower, or to keep down. But the general thrust of premere is to press, enclose, or squeeze. This is the shade of meaning that is most often given to premere. W.H.S. Jones’s 1963 translation of Pliny mistakenly (I believe) translates this line as “There is even a proverb that bids us turn down our thumbs to show approval.” To his credit, Jones mentions in a footnote that an earlier translator (Wolters) has rendered premere as “enclose.”
I think the reading of premere preferred by Poliziano and Wolters is the correct one. We already know, from the quotations given above, that the inverted thumb is used as a gesture for disapproval. It would make no sense for the inverted thumb to be used for both disapproval and approval. So approval must be shown by a different gesture: the “clenching” or “enclosing” of the thumb. But what does this mean, exactly? How does one go about “clenching” the thumb? I I think it can only mean the enclosing of the thumb in a clenched fist. If this conclusion is true, then the “thumbs up” sign would have been unfamiliar to the Romans. They would have shown disapproval (thumbs down) in a way that is familiar to us, but approval (thumbs clenched) in a way that is different from our own.
Read more in the comprehensive essay collection, Digest: