Yevamot 97a ~ Rava on Delayed Puberty in Boys

THIS POST IS PART TWO OF TWO, ABOUT TODAY’S PAGE OF TALMUD.

On this page of Talmud we read of Rava's observation that delayed puberty may be related to body mass:

יבמות צז, א

כי אתו לקמיה דרבא אי כחוש אמר להו זילו אבריוהו ואי בריא אמר להו זילו אכחשוהו דהני סימנין זמנין דנתרי מחמת כחישותא וזמנין דנתרי מחמת בריותא

Whenever people came to Rava [with a case of a man who had not developed pubic hair]  he would tell them, if [the man was] thin, ‘Let him gain weight’; and if they were overweight he would say ‘Go lose weight’; for these signs [of sexual maturity] are sometimes delayed as a result of emaciation and sometimes  as a result of obesity.   (Yevamot 97a)

There has been some discussion of what appears to be the increasingly earlier onset of puberty in girls. In fact, menarche, (the age of a girl's first menstrual period) has been steadily decreasing by a consistent three years per century of record keeping. In an article in The New York Times published only a couple of weeks ago, the headline read “Puberty Starts Earlier Than It Used To. No One Knows Why.” It noted that “some girls are starting to develop breasts as early as age 6 or 7.”

However, Rava was addressing not the early onset of puberty in girls, but its delayed appearance in boys.  He noted that this delay was sometimes related to extremes of nutritional status, and so in these cases, was amenable to intervention.

“Rava may have been the first first to report an association of obesity and delayed puberty in boys.”

Rava was on to something. He may in fact have been the first to report an association between obesity and delayed puberty in boys.  This association has been confirmed by several studies which found that obesity has different effects on puberty in boys and girls. In girls, obesity is associated with earlier puberty, while in boys it has the opposite effect, and delays sexual maturation. But it was not until 2010 this association was confirmed by a longitudinal population-based study. This reported that a "higher BMI z score trajectory" (i.e. obesity)  during early to middle childhood may be associated with later onset of puberty among boys. 

Rava also claimed that puberty may be delayed in boys who are underweight, and this has also been confirmed. As far as I can tell, none of the researchers has credited Rava (who died around 350 CE.) for being the first to notice these associations. But Rava was first, and firsts count for something in science.

Rabbi Hiyya’s claim

The same passage is repeated in Bava Basra (155b) but in the name of Rabbi Hiyya.  Hiyya probably lived in the second half of the second century, and so predated Rava by a few decades.  The claim of primacy regarding the association with nutritional status and delayed puberty may therefore have to be extended back to R. Hiyya.  But so far I have found nothing in the works of Hippocrates, Aristotle and Galen that address this issue, so this association does not appear to have been a widely held belief in antiquity that was simply being echoed in the Talmud. As all good scientific papers end, further research is needed...

Yevamot 97a~ Plagiarism, citation, and the lips of the dead

יבמות צז, א

דְּאָמַר רַבִּי יוֹחָנָן מִשּׁוּם רַבִּי שִׁמְעוֹן בֶּן יוֹחַי: כל תַּלְמִיד חָכָם שֶׁאוֹמְרִים דְּבַר שְׁמוּעָה מִפִּיו בָּעוֹלָם הַזֶּה, שִׂפְתוֹתָיו דּוֹבְבוֹת בַּקֶּבֶר

Rabbi Yochanan said in the name of Rabbi Shimon bar Yochai: The lips of a [deceased] scholar move in the grave when his teachings are said in his name

Plagiarism is Widespread

Plagiarism, it seems, has never been so popular.  Remember How Opal Mehta Got Kissed, Got Wild and Got a Life, the 2006 debut novel from Harvard undergraduate Kaavya Viswanathan? The author had plagiarized several passages from others (including Salman Rushdie) and the publisher Little Brown recalled and destroyed all its unsold copies.  It's not just authors; politicians plagiarize too.  In 2013 the German minister for education resigned amid allegations she had plagiarized her PhD. thesis, and last year Senator Jon Walsh of  Montana had his Master's Degree revoked by the US Army War College which determined that it had been plagiarized. (Walsh dropped out of the Senate race as a result of the scandal.)  

Plagiarism. It's not just for authors and politicians. Retraction Watch has reported at least 268 academic papers that were plagiarized.  Plagiarism has become so pervasive in academia (and the need to report it has become so important) that a recent paper paper in Ethics & Behavior outlines advice for academics considering becoming plagiarism whisleblowers. 

This  seems to be a very good era in which to remind ourselves - and our students - that the full and proper attribution of the work of others is a core Jewish value. 

Sadly, Jewish literature has a many examples of plagarism, improper attribution, and other infractions of publication etiquette.  We are going to look at four of these. They are all different, and their ethical breaches are not to be equated, but they are reminders of the responsibility of those who publish to check, double check, and attribute.   

1.  Partial or inaccurate citation

Inaccurate citation is a relatively lightweight problem, but it's a problem nevertheless. The  English language Schottenstein Talmud, published by ArtScroll, chose a censored text of the Talmud as the basis for its translation project. (Full disclosure: I enjoy the Schottenstein Talmud, and study from it each day, God, bless it).  As I've pointed out elsewhere, this was a sad choice, and a missed opportunity to return the text to its more pristine (and more challenging) state. 

One example of ArtScroll's decision is found very early on in Berachot (3a).  There, the original uncensored text records a statement said in the name of Rav: אוי לי שהחרבתי את ביתי ושרפתי את היכלי והגליתים לבין אומות העולם

Woe is me [God], for I destroyed my home [the Temple], burned my Sanctuary,  and sent [the Jewish People] into exile among the nations of the world. 

However, the editors of the English ArtScroll Talmud chose to use a censored text in which an additional phrase was slipped in by the censor:  אוי לבנים שבעונותיהם החרבתי את ביתי ושרפתי את היכלי והגליתים לבין אומות העולם

Woe to my children who sinned, [and hence made me, God] destroy my home [the Temple], burn my Sanctuary,  and send them into exile among the nations of the world. 

Here is a version of the uncensored text- the one that ArtScroll could have used.  As you can see, the censor's additional text is not there:

Babylonischer Talmud - BSB Cod.hebr. 95, 1342

Then, to compound the error, the ArtScroll Talmud addes a footnote explaining the metaphorical meaning of this erroneous text!

Schottenstein Talmud, Mesorah Publications, Berachot 3a

To be clear: ArtScroll did not plagiarize anything, but they could have done a better job of quoting the text accurately. After all, isn't that what Rabbi Yochanan taught us to do? Had they done so, the lips of the great sage Rav, whose teachings were improperly amended by the censor, would again "move in his grave".

 Now on to more egregious  issues - hard core palgarism.

 2.  Plagiarism in part

Sometimes another author says it just right, and uses language in so perfect a way that others will want to claim it as their own.  One example of this is found in the 500 year long debate over whether Jews could believe in the Copernican model of the solar system in which the sun was stationary.  In the late nineteenth century Reuven Landau (c. 1800-1883) took a hard core conservative position against this model. He found it to be existentailly threatening, and argued that because humanity was the center of the spiritual universe, it must live in the very center of the physical one. But rather than outline his claims in his own words, he stole from the very  widely read Sefer Haberit, an encyclopedic work that had been published some one hundred years earler.  Here is an excerpt from Landau's text, in which he raises what he believes to be scientific objections to the Copernican model.  The bold text shows where the text is identical to Sefer Haberit, first published in 1798. 

If it is as Copernicus has written, and the earth circles the sun at great speed from west to east, it would be the case that a stone which falls to the ground from the top of a high tower on its western side should not land exactly at the foot of the tower but rather should come to rest slightly to the west of the tower. For while the stone is in free-fall, the earth together with the tower have moved in orbit to the east, by three and two-thirds parsa’ot. Yet we see with our own eyes that this does not occur. Rather the stone falls and comes to rest precisely at the foot of the tower.

Quite simply put, Landau stole from Sefer Haberit. A simple attribution was all that was needed. And it was not there. (You can read more about this plagarism here, and more about Sefer Haberit in my book, and in this recently published work from David Ruderman)

Well, you say, that's not quite right. but it's not too bad either. Well, here comes full, unadulterated plagiarism.

 3. Plagiarism in full: Stealing an entire chapter, word for (almost) word

In 1788 in Berlin, Barukh Linda (not to be confused with the plagiarist Reuven Landau) published a small encyclopedia for children called Reshit Limmudim. In it, Linda carefully explained the heliocentric model of Copernicus and how the planets moved around the sun. This book became, in the words of the  historian Shmuel Feiner the “most famous, up-to-date book on the Hebrew bookshelf at the end of the eighteenth century,” And then, a year after it was published a Rabbi Shimon Oppenhiemer, living in Prague, stole from it.

Oppenheimer (1753-1851) objected to the claim that the earth revolved around the sun, and in 1789 in Prague he published Amud Hashachar in which he detailed his opposition. But rather than use his own words, he stole, word for word, the descriptions of the solar system from the pro-Copernican Reshit Limmudim, carefully leaving out the bits that supported Copernicus.  In a move that pushes hutzpah to a new level, Oppenheimer even published a moving poem as if it had been written to him. However, the poem was a dedication to the real author Linda - from Naphtali Herz Wessely.  Oy.

Had enough of Rabbi Oppenheimer? There’s more.  When it came to plagarism, this Rabbi Oppenheimer was a repeat offender, (enough perhaps to earn a special mention in a Jewish Retraction Watch).  Because in 1831 he published Nezer Hakodesh, a book on religious ethics (I'll say that again in case you missed it - it's a book on religious ethics)...which he plagarized from the 1556 work Ma'alot Hamidot !  Here's a random example so you can see  the scale of the plagiarism.

מעלת המדות, 1556

נזר הקודש 1831

There is a fascinating end to the story.  The famous Rabbi Yechezkel Landau (that’s the third Landua/Linda in this little post –sorry), head of the Bet Din in Prague, banned Oppenheimer from printing further copies of Amud Hashachar, but not because it was plagarized.  Rather, Chief Rabbi Landau objected to the book’s frontispiece, in which Oppenheimer described himself as “The great Gaon, sharp and famous, the outstanding investigator Shimon”.  Read it for yourself:

First edition of עמוד השחר, Prague 1789. From the Jewish National and University Library, Jerusalem

In his rebuke, the head of the Bet Din made no mention of the fact that sections of the book were plagiarized, even though this information was widely known. Oppenheimer proceeded undeterred, and published a second edition of his plagiarized and anti-Copernican work – although he was “honest” enough to remove the stolen poem praising his book - a poem that had originally been written by Naphtali Herz Wessely in praise of Lindau’s Reshit Limmudim.

4.  Incomplete quotation of a passage

Our last example of plagiarism and citation misuse is again from the ArtScroll publishers, though this time it’s a little more serious than their using a censored manuscript. This time Arscroll is itself the censor.

In their new edition of the Mikra’ot Gedolot, (or, as they call it, Mikra'os Gedolos) the editors have censored an entire passage from the commentary of the great eleventh century French scholar Shmuel ben Meir, known as the Rashbam , without any indication that they have tampered with the text. In a famous passage, Rashbam claimed that – contrary to normative Jewish thought, the twenty-four hours of the Jewish day should begin at sunrise, and not after sunset, as is our practice.  This antinomian position seems to have been too much to share with its readers, so ArtScroll just expunged it.

Here is the Rashbam as it appears in the new ArtScroll edition:

חומש מקראות גדולות בראשית. ארטסקרול–מסורה 2014. The red arrow indicates censorship of the Rashbam.

And here is the original text of the Rashbam with the censored text in bold.

ד) וירא אלהים את האור - נסתכל במראהו כי יפה הוא. וכן ותרא אותו כי טוב הוא, נסתכלה במשה שנולד לששה חדשים כמו שמואל לתקופת הימים וראתהו כי טוב ויפה הוא שנגמרו סימניו וצפרניו ושערו, ותצפנהו שלשה ירחים, כלו' עד סוף ט' חדשים שהרי ראתהו וידעה  שהוא טוב ויפה בסימנים, שאינו נפל

ויבדל אלהים בין האור ובין החשך - שי"ב שעות היה היום ואח"כ הלילה י"ב. האור תחלה ואח"כ החשך. שהרי תחלת בריאת העולם היה במאמר יהי אור. וכל חשך שמקודם לכך דכת' וחשך על פני תהום לא זהו לילה

ה) ויקרא אלהים לאור יום - תמה על עצמך לפי הפשט למה הוצרך הקדוש ברוך הוא לקרוא לאור בשעת יצירתו יום? אלא כך כתב משה רבינו, כ"מ שאנו רואים בדברי המקום יום ולילה כגון יום ולילה לא ישבותו, הוא האור והחשך שנברא ביום ראשון, קורא אותו הקדוש ברוך הוא בכ"מ יום ולילה. וכן כל ויקרא אלהים הכתובים בפרשה זו. וכן ויקרא משה להושע בן נון יהושע, האמור למעלה למטה אפרים הושע בן נון, הוא אותו שקרא משה יהושע בן נון שמינהו קודם לכן משרתו בביתו, שכן דרך המלכים הממנים אנשים על ביתם לחדש להם שם כמו שנאמר ויקרא פרעה שם יוסף צפנת פענח, ויקרא לדניאל בלטשצר וגו'

ולחשך קרא לילה - לעולם אור תחלה ואח"כ חשך

ויהי ערב ויהי בקר - אין כתיב כאן ויהי לילה ויהי יום אלא ויהי ערב, שהעריב יום ראשון ושיקע האור, ויהי בוקר, בוקרו של לילה, שעלה עמוד השחר. הרי הושלם יום א' מן הו' ימים שאמר הק' בי' הדברות, ואח"כ התחיל יום שיני, ויאמר אלהים יהי רקיע. ולא בא הכתוב לומר שהערב והבקר יום אחד הם, כי לא הצרכנו לפרש אלא היאך היו ששה ימים, שהבקיר יום ונגמרה הלילה, הרי נגמר יום אחד והתחיל יום שיני

This censorship of the Rashbam is not unique to ArtScroll. It exists in other standard printings of Mikra'ot Gedolot, like this one from Machon Hama'or, (Jerusalem 1990), although not in the Torat  Chaim from Mossad Harav Kook.

Marc Shapiro,  who brought this to the attention of Jewish world, has called for ArtScroll to give a full refund to any one who purchased these censored copies. And he is absolutely correct. A recent academic editorial noted that improper quotation is a type of plagiarism; like complete plagiarism, this selective quotation strips ownership away from the original author, and leaves in its wake a text never intended.  

THE need for recognition

In his recently published autobiography, the British comedian John Cleese (of Monty Python and Fawlty Towers fame) recalls how he reacted the very first time that he was recognized after a stage performance.  As he walked home, a family who had been in the audience pointed at him and waived. It was by all accounts a small gesture, but Cleese recalled its effects in detail even fifty years later:

I can still remember the sudden feeling of warmth around my heart that swelled and swelled and lifted my spirits. It is as though I had been accepted into a new family, and acknowledged as having brought them something special that they really appreciated. It was only a moment but it was wonderful, and they didn't even know my name...in today's celebrity culture it must be hard to imagine that a tiny moment of recognition like that could feel so uncomplicated and positive...

The need for recognition is not a vice or a character flaw, but a profound human need. To ignore it is not just an oversight but an act of neglect.  The rabbis of the Mishnah and the Talmud understood the corollary: that to attribute is to nourish.  To acknowledge the creative act of another person is a kind of blessing, like those required before eating, or on seeing a beautiful vista.  Blessings and citations acknowledge the creative impulse in others, and so make the world a little bit better. They are redemptive. As this Mishnah taught:

“ כל האומר דבר בשם אומרו מביא גאלה לעולם, שנאמר (אסתר ב), ותאמר אסתר למלך בשם מרדכי

Whoever cites something in the name of the person who originally said it, brings redemption to the world. As the prooftext states - “And Esther told the King in the name of Mordechai...””

— Pirkei Avot (Ethics of the Fathers) 6:6

Yevamot Interlude~ Henry VIII, Yibum, and the Sotheby's Auction

About forty years ago, while a medical student in London, I had the good fortune of visiting the Valmadonna Trust Library, then the finest private library of Hebrew books in the world. (How I got there is another story for another time).  And while there, I held the Talmud that once belonged to Westminster Abbey. It also may been owned by Henry VIII, who had brought it from Venice in order to help him end his marriage to Catherine of Aragon, the first of his many wives. The story of Henry VIII's purchase of the Bomberg Talmud - the first complete printed Talmud -  actually hinges on Yevamot, and whether the rules of levirate marriage, or yibum, applied to him. 

Henry VIII performed Yibbum

Catherine of Aragon was actually a widow, having first been married to Henry's older brother Arthur.  About six months after Catherine married Arthur he died childless, and in 1509 his younger brother Prince Henry married his widow. (Is this beginning to sound familiar?) One more thing to know: Catherine claimed that her marriage to Arthur had never been consummated; this is important later in the story. (And here is an interesting historic footnote: it was Catherine's parents, Ferdinand and Isabella who had expelled the Jews from Spain.)

Fast forward to 1525. Henry is now King Henry VIII, and has had one daughter with Catherine. He wanted a son, and now wished to marry Ann Boleyn, but what was he to do with Catherine, his existing wife?  Divorce, remember, was tricky for this Catholic King.  And here is where the Talmud comes in.  

Henry argued that his marriage to Catherine should be dissolved since it was biblically forbidden for a man to marry his sister-in-law.  (Henry claimed years earlier that he could marry her because the marriage to his brother had not been consummated. See, I told you that was important information...)

“Turpitudinem uxoris fratris tui non revelavit
עֶרְוַ֥ת אֵֽשֶׁת־אָחִ֖יךָ לֹ֣א תְגַלֵּ֑ה עֶרְוַ֥ת אָחִ֖יךָ הִֽוא ”

— Lev 18:16 in the Vulgate

But as we all know from the last several weeks of study, the Bible commands a man to marry his widowed sister-in-law if his brother died without children. Since Arthur died childless, it could be argued that Henry was now fulfilling the biblical requirement of levirate marriage - known as yibum.

“quando habitaverint fratres simul et unus ex eis absque liberis mortuus fuerit uxor defuncti non nubet alteri sed accipiet eam frater eius et suscitabit semen fratris sui
כִּֽי־יֵשְׁב֨וּ אַחִ֜ים יַחְדָּ֗ו וּמֵ֨ת אַחַ֤ד מֵהֶם֙ וּבֵ֣ן אֵֽין־ל֔וֹ לֹֽא־תִהְיֶ֧ה אֵֽשֶׁת־הַמֵּ֛ת הַח֖וּצָה לְאִ֣ישׁ זָ֑ר יְבָמָהּ֙ יָבֹ֣א עָלֶ֔יהָ וּלְקָחָ֥הּ ל֛וֹ לְאִשָּׁ֖ה וְיִבְּמָֽהּ ”

— Deut. 25:5, in the Vulgate

How was this conundrum to be resolved? Let's have the late great Jack Lunzer, the custodian of the library, tell the story. (You can also see the video here. Sorry about the ads. They are beyond our control.) 

Adapted from Dailymotion.com

As Lunzer tells us, the Talmud was obtained from Venice to help King Henry VIII find a way to divorce his wife (and former sister-in-law) Catherine, and so be free to marry Ann Boleyn. In fact, it's a little bit more complicated than that.  Behind the scenes were Christian scholars who struggled to reconcile the injunction against a man marrying his sister-in-law, with the command to do so under specific circumstances. In fact the legality of Henry's marriage had been in doubt for many years, which is why Henry had obtained the Pope's special permission to marry. 

John Stokesley, who later became Bishop of London, argued that the Pope had no authority to override the word of God that forbade a man from marrying his brother's wife. As a result the dispensation the Pope had given was meaningless, and Henry's marriage was null and void. In this way, Henry was free to marry.  But what did Stokesley do with the passages in Deuteronomy that require yibum?  He differentiated between them.  The laws in Leviticus, he claimed, were both the word of God and founded on natural reason. In this way they were moral laws; hence they applied to both Jew and Christian.  In contrast, the laws found in Deuteronomy, were judicial laws, which were ordained by God to govern (and punish) the Jews - and the Jews alone. They were never intended to apply to any other people, and so Henry's Christian levirate marriage to Catherine was of no legal standing. There was therefore no impediment for Henry to marry Ann.  As you can imagine, this rather pleased the king.

The origins of the Valmadonna Talmud

It is unlikely that the Valmadonna Library Bomberg Talmud was indeed the very same one that Henry had imported from Venice. According to Sotheby's and at least one academic,  it actually came from the library of an Oxford professor of Hebrew, who bequeathed it to the Abbey. In any event, the Bomberg Talmud lay undisturbed at Westminster Abbey for the next four hundred years.  How Lunzer obtained it for his library is possibly the greatest story in the annals of Jewish book collecting.  In the 1950s there was an exhibition in London to commemorate the readmission of the Jews to England under Cromwell. Lunzer noted that one of the books on display, from the collection of Westminster Abbey, was improperly labelled, and was in fact a volume of a Bomberg Talmud.  Lunzer called the Abbey the next day, told them of his discovery, and suggested that he send some workers to clean the rest of the undisturbed volumes.  They discovered a complete Bomberg Talmud in pristine condition, and Lunzer wanted it. But despite years of negotiations with the Abbey, Lunzer's attempts to buy the Talmud were rebuffed.  

“Mr. Lunzer, we at the Abbey consider our Babylonian Talmud to be part of the Abbey itself. ”

— Howard Nixon, Librarian of Westmisnter Abbey (as remembered by Jack Lunzer)

Then in April 1980, Lunzer's luck changed. He read in a brief newspaper article that the original 1065 Charter of Westminster Abbey had been purchased by an American at auction, but because of its cultural significance the British Government were refusing to grant an export license. Lunzer called the Abbey, was invited for tea, and a gentleman's agreement was struck. He purchased the Charter from the American, presented it to the Abbey, and at a ceremony in the Jerusalem Chamber of  Westminster Abbey the nine volumes of Bomberg's Babylonian Talmud were presented to the Valmadonna Trust. It's a glorious story, and it's so much better when Lunzer himself tells it, as he does here: (You can also see the video here, and end it at 14.35. We continue to apologize for those ads.)

Adapted from Dailymotion.com

In December 2015, the Westminster Abbey Talmud was sold at Sotheby's in New York $9.3 million. The buyer was anonymous, and so, in a flash, the magical Talmud I had once held in my hands moved to a new private collection. I hope the owner enjoys his (or her) new treasure.   

Yevamot 75a~ Voltaire, Rabbi Yishmael, and the Man with One Testicle

VoltaIre’s Count

In 1587, Pope Sixtus V decreed that all marriages in which the man did not have two testicles in the scrotum should be dissolved.  Voltaire (1694-1778) felt the need to share some further observations on the testes and the Pope's edict, which he did in his Philosophical Dictionary:

This word [testes] is scientific, and a little obscure, signifying small witnesses. Sixtus V... declared, by his letter of the 25th of June, 1587, to his nuncio in Spain, that he must unmarry all those who were not possessed of testicles. It seems by this order...that there were many husbands in Spain deprived of these two organs...We have beheld in France three brothers of the highest rank, one of whom possessed three, the other only one, while the third possessed no appearance of any, and yet was the most vigorous of the three.

...[The] Parliament of Paris, on the 8th of January, 1665, issued a decree, asserting the necessity of two visible testicles, without which marriage was not to be contracted.

Which brings us to tomorrow’s daf, Yevamot 75a. To catch up quickly: The Mishnah (on 70a) listed the circumstances under which a Cohen is not allowed to eat terumah. Among those banned from this edible delight is a Cohen with an injury to his testicles - and this same injury, the Mishnah continues, when found among other Jewish men, may prevent that man from marrying. 

In discussing the details of what kind of testicular injury results in a ban on marriage, we read the following:

יבמות עה, א

אמר רבי ישמעאל בנו של ר' יוחנן בן ברוקה שמעתי מפי חכמים בכרם ביבנה כל שאין לו אלא ביצה אחת אינו אלא סריס חמה וכשר סריס חמה

Rabbi Yishmael the son of Rabbi Yochanan ben Berokah said: I heard from the sages in the vineyard at Yavneh that whoever has only one testicle [at birth] is called "sterile from the sun" [i.e. naturally sterile] and is allowed to marry...

So according to this report of Rabbi Yishmael, the sages in Yavneh allowed a man born with one testicle to marry.  The Talmud is describing a condition known as cryptorchidism in which one or sometimes both of the testes remains undescended and hide somewhere within the abdomen.

Cryptorchidism 

To understand all this, there's some embryology involved. Here is what you need to know:

The testes develop in the abdominal cavity and migrate southwards into the scrotum. Usually they land there by birth, or soon after, if they behave themselves.  Which they don't always do. Sometimes one of the pair (and very rarely both) fail to migrate. Sometimes they descend and then, apparently disappointed by their new cool accommodations, bolt back north to the warmth of the abdomen.

Which brings us to the question, just how common is cryptorchidism?

The best answer will be an educated guess because the data is not great. One of the few studies of the epidemiology of this condition comes from the medical examination of English schoolboys published in 1941. It reported that the incidence of cryptorchidism in 3,300 boys under 15 was almost 10%, but that this number dropped to less than 1% in boys older than 15.

And then in this paper comes this memorable line:

“Sir Robert Hutchison tells me that he knew a man in whom descent occurred while he was an undergraduate at Oxford (an event duly celebrated by a party).”

— Smith RE. The undescended testicle. The Lancet 1941;14: 747-751

A more recent  study from 2007 put the incidence of undescended testes at 1-4.6% at birth (depending on the infant birthweight), while at age 11 the incidence is anywhere from 1.6-2.2%. The incidence is higher in low birth-weight and premature boys.

What is clear is that there is an association between fertility and cryptorchidism, even when the testicle that went AWOL is retrieved and secured in the scrotum.

“The incidence of azoospermia in men with unilateral cryptorchidism is 13% regardless of the fate of the testis”

— Canadian Urological Association Journal, 2011

Which brings us back to the prohibition against a man with injured testes (or penis- as in Deut. 23:2:   לא יבא פצוע דכא וכרות שפכה בקהל) marrying. It is related to his presumed inability to father a child.   Voltaire seems to have been unsure of the role of the testes (whether one, two, or in one lucky case "three,") but Rabbi Yishmael's  סריס חמה, a man with only one visible testicle, while certainly less fertile than a normal man, is capable of fathering a child.  Hence his marriage, while not encouraged, is recognized, and this is codified as normative Jewish law.

 שולחן ערוך אבן העזר הלכות קידושין סימן מד, ד

   סריס שקדש, בין סריס חמה בין סריס אדם, וכן אילונית שנתקדשה, הוי  קדושין

If a man with one testicle married, whether this condition is from birth or later acquired, he is legally married.

Today, an undescended testicle is surgically brought into the scrotum at an early age, so that the cryptorchidism described by Rabbi Yishmael has been virtually eliminated, as have been some very interesting parties at the University of Oxford.