Category Archives: Torah & Science

Making Babies: Is it Possible to Influence Gender?

Note: for the purposes of this article, the terms “gender” and “sex” are used interchangeably.

This week’s double parasha, Tazria-Metzora, begins with the laws of when “a woman conceives and gives birth to a male…” (Leviticus 12:2) The actual Hebrew wording here is ishah ki tazria, literally “when a woman gives seed”. Based on this, our Sages taught that if a woman “gives seed” first, the child will likely be male, whereas if a man “gives seed” first, the child will likely be female (Niddah 31a). How exactly is this to be understood?

The classic explanation is that if the woman climaxes first during intercourse, the child from that union is more likely to be male—and vice versa. Of course, this statement is not a guarantee, for there have surely been countless situations where this was not the case. Some say, therefore, it is only a segulah for having boys. A further issue with the statement is that, scientifically-speaking, while for the man the climax does coincide with “giving seed”, for a woman the emission of the ovum (egg) is not related to climax. A woman “gives seed” on a cyclical basis, roughly once per month. Having said that, there may be a scientific basis to our Sages statement after all.

In the 1960s, Dr. Landrum B. Shettles, one of the pioneers of in vitro fertilization technology, proposed a method for sex selection during conception. Physiologically, it is the male seed that determines the gender of the baby: sperm carrying a Y chromosome produce a male, while sperm carrying an X chromosome produce a female. (Eggs, meanwhile, always have an X chromosome.) The Y chromosome is significantly smaller than the X chromosome which would, together with other factors, make the “male” sperm lighter and faster than the “female” sperm. At the same time, male sperm are more fragile and less likely to survive the acidic conditions of the uterus.

A karyotype showing all 23 pairs of human chromosomes. Note the size of the Y chromosome compared to the X chromosome.

Based on this, to conceive a male, it is best to wait a few days so that the egg has travelled further down the fallopian tubes, allowing the male sperm to reach it faster, and before dying out. To conceive a female, it is best not to wait at all, and try to conceive earlier, while the eggs are deeper in the fallopian tubes, where male sperm are unlikely to reach. Shettles recommended that, if a couple desires a boy, they should start trying at ovulation time while if the couple wants a girl, they should try two or three days before ovulation. Ovulation is usually around Day 14 of the cycle.

Factoring in halakhah, if we add the seven clean days following menstruation, it generally comes to around Day 12 of the cycle. All other factors aside, this may favour the conception of a girl. Waiting a couple of days, meanwhile, might favour the conception of a boy. It is important to note that cycles vary; for some women ovulation might be a day or two earlier, or later. This may explain why some families have all girls, or all boys, for it is likely that conception always takes place on mikveh night, ie. at the same point in the cycle every time. Having said that, the Shettles Method is thought to be only 75% effective, and some studies say it isn’t effective at all, for there appear to be no major physiological differences between Y- and X-carrying sperm.

Intriguingly, the Shettles Method also recommends, as our Sages did, that a woman should climax first if the couple seeks a male child. This is because a woman’s uterine environment is acidic, but the secretions are actually more alkaline (basic), which diminishes some of that acid and makes it more likely for the male sperm to survive the journey.

The most significant factors are probably not biological at all, but spiritual. At the end of the day, God will send whichever gender is meant to be born. Thus, our Sages state that whoever is expecting a child and prays for a particular gender, “it is a vain prayer” (Berakhot 60a). However, Rav Yosef raises an objection to this statement, since we see in the Torah how Leah, after six boys, prayed for her next child to be a girl, the result being Dinah. It appears that praying for the desired gender does work! The Talmud resolves the contradiction with a Baraita:

The first three days [after intercourse], one should pray that the seed not putrefy. From the third day until the fortieth, one should pray that it will be male. From the fortieth day until three months, one should pray that it will not be deformed. From the third month until the sixth, one should pray that it will not be stillborn. And from the sixth month until the ninth, one should pray that it will be delivered safely.

So, one is permitted to pray for the desired gender of the child until the fortieth day of pregnancy. This is an incredibly precise scientific statement from our Sages, as today we know that the sex organs begin to form in the fetus around Day 42. While the chromosomes may have already determined the gender right at conception, God could certainly make a switch before Day 40 (who would know?) but after that point, the sex organs have begun to form and there is no going back. The Sages were also accurate regarding the putrefaction of the male seed, for today we know that sperm survives in the uterus for around three days, and no more than five days.

For the strict materialist-rationalist, there is nothing that can be done to select gender—it is just a game of chance, depending on which sperm penetrates the egg first. For the most pious person, there is no need to do anything either, for God knows best and it all depends on Above. Truly, it makes no difference, for each child is precious, and a miracle in its own right. I believe this is the deeper message behind our Sages’ debate on what is the ideal number of children that a couple should strive to have (Yevamot 62a):

Rabbi Natan taught: Beit Shammai say two males and two females, and Beit Hillel say a male and a female… It was alternatively taught [in a different Baraita]: Rabbi Natan said that Beit Shammai say a male and a female, and Beit Hillel say either a male or a female. Rava said: what is the reason? …as it is written: “He did not create it to be void; He formed it to be inhabited…” (Isaiah 45:18)

We are first given the most stringent opinion, that of Beit Shammai as expected, that a couple should ideally have two boys and two girls. At the end, we are given the most lenient opinion of Beit Hillel, the school of thought that Judaism is practically based on, which is that even a single boy or girl is enough to fulfil the mitzvah of reproduction. The Scriptural proof is a verse in Isaiah where the prophet quotes God as stating how He created the world to be full of life. The Sages are making an equivalence between the entire world and the birth of even a single child, which is enough to fulfil the mitzvah of populating the entire world. Each child is a world of his or her own and, as Abarbanel (1437-1508) comments on that verse in Isaiah, brings the world one step closer to the Final Redemption.

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The Science of Chametz

As we continue celebrating Pesach this week, and avoiding all things chametz, it is important to take a moment and explore what exactly is chametz? While we spend a tremendous amount of time and effort learning about, and implementing, the various halakhot regarding eliminating chametz, we rarely think about what chametz actually is on the chemical level. If we did know, it would help to clarify what specifically is forbidden, and might save us a great deal of time and effort in our preparations. It would also help us better understand what actually happened in Egypt with our ancestor millennia ago (the answer may surprise you). So, what is chametz?

The critical Torah chapter for understanding it all is Exodus 12. It begins with God’s command to commemorate Nisan as rosh chodashim, the first of the months. Then, God commands that on the 10th of the month, each household had to prepare a sheep, to be slaughtered on the 14th. Its blood would then be pasted on the doorposts, and its meat entirely consumed, together with bitter herbs and matzot (12:8). Intriguingly, the Torah has not yet told us anything about chametz! The command to eat matzot preceded the well-known narrative about the dough not rising. Israel already consumed matzot the night before the Exodus!

Several verses later, God commands that henceforth Israel would always celebrate a holiday with seven days of matzah-eating, before which all the se’or (“leaven”) must be destroyed, and during which anyone who dares eat chametz will be spiritually “cut off” from the nation (12:15). We have still not been told what any of these things are, or why they cannot be consumed.

After describing the last plague, with Pharaoh finally relenting and letting the Israelites go, the Torah explains that “the people took their dough before it was leavened, their kneading bowls wrapped in their cloaks upon their shoulders.” (Exodus 12:34) The previous evening they had already eaten the pesach meat together with matzot. Now, in their haste to leave, the Israelites wrapped up their uncooked dough in their kneading bowls and carried them away on their shoulders. It is worth mentioning that Chizkuni (Rabbi Hezekiah ben Manoach, c. 1250-1310) comments here that this is why we have a custom to wrap the afikoman in a towel or cloth!

The Torah says the Israelites then journeyed out of the country, from the city of Ramses (in Egypt) to “Sukkot” (in the Wilderness). Presumably, they stopped to rest and set up their temporary sukkot there. Only at this point, free at last, did “they bake the dough which they had taken out of Egypt into cakes of matzot, for it had not leavened, since they had been driven out of Egypt and could not delay; nor had they prepared any provisions for themselves.” (12:40) This must be repeated: after coming out Egypt, and having already journeyed far away, they stopped to rest and eat and, only then, in the Wilderness, they baked matzot. The reason they couldn’t bake anything fancier is because the dough they had brought out had not risen. This sparks a huge question: How could it be that the dough had not risen? They have obviously been walking for a very long time by this point! Don’t we say that, halakhically-speaking, any flour-water mixture starts to become chametz after just 18 minutes? The Torah clearly tells us that the Israelites had taken prepared dough, already in their mixing bowls, and journeyed far out of Egypt’s borders before using that dough to make matzot. It should have become chametz a long time ago! How do we make sense of this puzzle?

Ancient Egyptian depiction of the breadmaking process, from the tomb of Ramses III in the Valley of the Kings

Fungus and Sourdough

Today, we are used to buying purified “active dry” yeast in the supermarket. We assume that when the Torah says se’or, “leaven”, it refers to the same type of yeast. Of course, in ancient times there was no such thing, and no way for people to isolate yeast at all; nor could they know that yeast was actually a microscopic living organism. Yeast, a type of fungus, occurs naturally all over the place. Such fungi are involved in symbiotic relationships pretty much everywhere we look, and are absolutely vital for the survival of all plants, if not all complex life forms. For instance, pretty much every plant on Earth is dependent on a family of fungi called mycorrhiza which lives in the soil, intertwined with the plant’s roots, and provides the plant with vital nutrients. Some mycorrhizae are endosymbiotic, meaning they actually grow into the plant’s cells! They become like one hybrid organism. (Wheat is an example of a plant that has inseparable mycorrhizae growing directly into it.) There are tens of thousands of species of mycorrhizae, and a single plant might have a dozen or more different types that it interacts with and depends on.

Other fungi grow on plant stems, leaves, and fruits. They are everywhere, and impossible to get rid of. We have all seen our fruits become covered in fungus when we leave them out too long—even fruits we have washed thoroughly. Why does this happen? Where does the fungus come from? It is already there embedded deep within the fruit’s skin, and even washing won’t help. Eventually, the fungus will grow out, like it or not! The same is true for wheat. Long before it is harvested, the wheat is already infested (enhanced?) with yeast. So, as soon as you add some warm water to flour, you are beginning the process of activating those yeasts. It takes about a week, and usually closer to two weeks, to get a rich amount of yeast turned on. The result is called starter dough, or sourdough. In ancient times, this was the only way to make fluffy bread. They didn’t have “active dry yeast” in a convenient package from the store. Either you wait a couple of weeks for your dough to rise or, since no one wants to wait that long, you keep a supply of starter dough, se’or, from which you can take a chunk and add it to a new batch of dough.

With that knowledge, everything becomes clear: the Israelites had new batches of dough, but no starter dough, for they hadn’t the time to “prepare any provisions…” (Exodus 12:40) So, when they grabbed their new dough and wrapped it up, and walked for many hours, the dough had not yet sufficiently risen, and they could only bake matzot! Based on this, I believe there is a better way to read the verse cited previously: “the people took their dough before it was leavened, their ‘kneading bowls’ [משארתם] wrapped in their cloaks upon their shoulders.” (Exodus 12:34) Most of the major commentators, including Rashi, read משארתם as misharotam, translating it as “kneading bowls”. However, it could also be read mi’se’orotam, “from their starter doughs”. In other words, the dough that the Israelites took out of Egypt was without added starter dough, which is why it did not rise despite the long journey.

Making Sense of Yeast

With the above in mind, it becomes clear that yeast itself is not the problem. Yeast is everywhere, and our ancestors did not have purified yeast like we have today. When our Sages spoke of the se’or sh’b’isah, the “leaven in the dough”, that metaphorically causes us to sin, they were referring to starter dough, not yeast. Yeast is inseparable and pretty much indestructible. In fact, recently scientists were able to extract yeast from ancient Egyptian pottery dating back over 4000 years—and then bring it back to life and bake with it! Yeast itself is not chametz, and cannot be, since we consume plenty of yeast on Pesach. In fact, we couldn’t have four cups of wine at our seders since wine is fermented with yeast, too.

Similar to breadmaking, winemakers today add yeast to speed up the fermentation process. In ancient times, however, the crushed grapes fermented on their own with the yeast that is already naturally growing all over them. Leave it longer and it will keep fermenting and turn into wine vinegar. This is mentioned in the Torah (Numbers 6:3), where it is called chometz yayin (חמץ יין). Interestingly, it is believed that hummus comes from the word chametz, too, as we read in Ruth 2:14, where Boaz tells Ruth: “Come over here and partake of the meal, and dip your pita in chometz.” Keep in mind that the letter tzadi was pronounced sa’adi back then (and still is in many Sephardic and Mizrachi communities, see ‘Shabbat or Shabbos: What’s the Correct Pronunciation?’ in Garments of Light, Volume II). So, Boaz would have told Ruth to dip her pita in chomes, ie. hummus!* This could have been either regular vinegar, or perhaps fermented beans of some sort, hence the hummus etymology.

Of course, wine and wine vinegar are kosher for Passover, so there is no issue with chometz yayin. Some might therefore argue that drinking chametz is not forbidden, since there is no prohibition on fermented grapes. After all, the Torah only speaks of achilah, “eating”, and not drinking (as in Exodus 12:15-16, 19, 13:3, and Deuteronomy 16:3). What does that mean for beer, vodka, and whiskey made from fermented grains, which are not kosher for Passover?

Drinking Chametz

How do we distinguish between drinking fermented grapes, which is allowed on Passover, and drinking fermented grains, which is forbidden? The simple answer, of course, is that fermented grains are directly related to fermented dough. Fruits are not an issue, and have nothing to do with the Exodus. Since the Torah prohibits eating fermented grains, namely dough, we can extend that prohibition to drinking fermented grains, too. The extension is certainly appropriate, for in olden times (and today) people make certain types of beer from old bread. As my mother recalls, her mother used to take old bread and dry it in the oven, then soak it in barrels of water and let it ferment to make kvass. This type of beer is made directly from old bread, undoubtedly chametz. There is no question that beer, in general, should be forbidden.

What about vodka and whiskey? These beverages are usually made from fermented grains, too. However, they are distilled, meaning that the ethanol (alcohol) is extracted from the fermented mixture. There is little left of the original grains, which is also why vodka and whiskey are gluten-free (while beer is not). In other words, the chametz would have been removed from the vodka or whiskey in the distillation process, leaving only ethanol, water, and perhaps tiny traces of flavour compounds. In the case of whiskey, it is when the liquid is later aged in casks that it develops its true flavour and colour.

Based on this information, vodka and whiskey probably shouldn’t be classified as genuine chametz. That does not mean they can be consumed on Pesach, since we are extremely stringent when it comes to this holiday, and don’t want to take even the slightest risk of contamination. After all, the Torah warns that one who consumes chametz will be karet, spiritually “excised”. Therefore, it is best not to consume something derived from fermented grains, even though the chances of it having real chametz is minimal.

So, what is chametz? As we’ve seen, it isn’t yeast itself, which we consume on Pesach. Starter dough is chametz, but has a special title in its own right, se’or. Can we pinpoint a specific chemical compound that is chametz? Well, chametz is what makes the dough rise. It isn’t the yeast itself that makes the dough rise, it is what the yeast generates: carbon dioxide (CO2). In bread, the carbon dioxide gas bubbles are released as a waste product by the yeast cells, and these gasses are trapped within the gluten proteins of the dough, forcing the dough to rise.

Alternatively, one can add baking powder, which has a combination of baking soda and some weak acid. As is well-known, when a base (like baking soda) meets an acid, they undergo a neutralization, “cancelling” each other out. When baking soda is neutralized, it releases CO2. Thus, adding baking powder to your cake can also make it rise, in lieu of (or in addition to) the yeast. Amazingly, the Tanakh already spoke of the neutralization reaction long ago:

In Proverbs 25:20, King Solomon teaches that trying to cheer up a sad person by singing them happy songs is like disrobing them on a cold day, or like pouring chometz al nater, “vinegar on natron”. Natron is a natural mixture containing baking soda (NaHCO3) that was mined even in ancient times. Of course, adding vinegar to natron is like adding vinegar to baking soda, causing them to neutralize each other, and making a vigorous reaction with lots of bubbles. Those bubbles are carbon dioxide.

Natural natron deposits in Chad

Can we say that CO2 is the real chametz? After all, it is the CO2 bubbles that make the bread rise. Upon further thought, carbon dioxide cannot be chametz since, once again, it is found all over the place, including within our bodies and in the air around us. Among many other things, it makes the bubbles in soft drinks, which we are permitted to drink on Pesach. Having said that, CO2 is definitely part of the chametz equation.

Perhaps we can come to the following conclusion: since what makes dough rise is the CO2 trapped within the gluten, the combination of both makes chametz. Therefore, something like wine, which is gluten-free, cannot be chametz, and neither can Coca-Cola, which has CO2 but not gluten. Beer has both gluten and CO2 so it would be chametz. Matzot generally have gluten, being made of grain flour, but no CO2, so they are not chametz. Defining chametz chemically as gluten+CO2 works well in every case I could think of.

(It is interesting to note that rice and corn also have proteins from the gluten family, so there may be something substantial to the prohibition of kitniyot besides tradition. Having said that, the types of gluten in rice and corn are not the same and can be consumed by people who are otherwise gluten-intolerant.)

A concluding thought: plants “breathe” in carbon dioxide and use it—with help from some other compounds absorbed through the roots—to make all kinds of macromolecules like sugars and proteins (gluten included). Humans, on the other hand, consume plants with their sugars and proteins and gluten, digest them and metabolize them into carbon dioxide that we then breathe out (and some other compounds excreted elsewhere). In short, what we do with carbon dioxide and gluten (chametz) is the exact reverse of what plants do with them. And so, it is quite beautiful that when we read the word chametz (חמץ) in reverse we get tzemach (צמח), a “plant”! Plants can teach us how to truly get rid of our spiritual chametz which, as our Sages teach, represents greed, ego, and “lawlessness”. Be like a plant: life-giving, oxygen-providing, food-distributing, sheltering, beautifying, purifying, peaceful and pleasant. This is how we reverse the corruption of chametz. And with this we can further understand why Mashiach—who will usher in a world with no spiritual “chametz” of any kind—is called by God to be ‘avdi tzemach, His “plant-like” servant (Zechariah 3:8).

Chag sameach!

*In multiple places in the Tanakh, the letter tzadi is replaced with samekh or sin, further indicating that tzadi was pronounced with an “S” sound. One such place is Psalm 71:4, where David asks God to save him from the “unjust and lawless”, the latter spelled חומץ, which Rashi says is the same as חמס, meaning “lawlessness” or “violence” throughout Scripture. This gives all the more meaning to removing חמץ from our homes!

Genetically-Modified Moses?

At the end of this week’s parasha, Ki Tisa, we read how Moses descended from Mt. Sinai with his face glowing brilliantly (Exodus 34:29-30). The people could not look at his face directly, so he had to wear a mask. The exact wording in the Torah is karan ‘or panav (קָרַ֖ן ע֣וֹר פָּנָ֑יו). The latter two words are clear: “the skin of his face”. But what does karan mean? The most direct translation would be “horn” which is actually why, comically, throughout history some artists depicted Moses with horns! Another way of translating it is as “radiant” (based on this, the Modern Hebrew term for a ray or radiation is k’rinah, קרינה). Rashi comments that both are accurate; karan does indeed come from the word for “horn” because light rays shoot forth like “horns”. If we take a look at Midrash (with a little help from science), we will find that the Torah is secretly encoding something much more profound. Continue reading