חולין קלד, ב
ת"ר (דברים יח, ג) הזרוע זה זרוע ימין אתה אומר זה זרוע ימין או אינו אלא זרוע שמאל ת"ל הזרוע
The rabbis taught in a baraita: The verse states with regard to the gifts of the priesthood: “That they shall give to the priest the foreleg…” (Deuteronomy 18:3)…is this the right foreleg, or is it only the left foreleg? The verse states: “The foreleg.” The definite article indicates that the verse is referring to the right foreleg.
מאי תלמודא? כדאמר רבא ’הירך’ - המיומנת שבירך. הכא נמי הזרוע - המיומן שבזרוע
But how is it understood from the definite article that the verse is referring to the right foreleg? It is derived like that which Rava said with regard to the verse: [“Therefore the children of Israel do not eat the sciatic nerve which is upon the hollow of the thigh”(Genesis 32:33). The definite article indicates that this is referring to the most important thigh. Here too, the definite article in the term “the foreleg” indicates that the verse is referring to the most important foreleg, i.e., the right foreleg.
But why did the rabbis derive that “the most important” thigh is the right one? Why not the left one?
Let’s take a trip into the worlds of comparative religion, chirality, astronomy, and neuroscience to find out.
The importance of the right side in Judaism
In the Talmud and in normative Jewish practice, the preference to favor the right over the left is everywhere. Here are just a few. (How many more can you think of?)
When walking up the ramp to the top of the Altar in the Temple, the Cohen must make a right turn at the top. Following that, every turn he makes must be a right turn. (זבחים נד,ב)
Actually, the entire service in the Temple in Jerusalem must be performed with the right hand. (ביאת המקדש 5:18 )
Rav Ashi rules that Tefillin must placed it on the left arm, because it is weaker than the right and the action of placing them should be performed with the stronger right hand (מנחות לז, א).
The Talmud teaches that a right-handed person who writes with her left hand on Shabbat has not violated the prohibition against writing. It doesn't count. Maimonides (הלכות שבת 11:14) agrees:
הַכּוֹתֵב בִּשְׂמֹאלוֹ אוֹ לְאַחַר יָדוֹ בְּרַגְלוֹ בְּפִיו וּבְמַרְפֵּקוֹ פָּטוּר
According to Rava, walking should start with the right leg, and not the left (יומא יא, ב)
The rite of חליצה must be performed with the right leg and a right shoe (יבמות קד, א).
The mezuzah can only be placed on the right side of the door (רמבם הל׳ מזוזה 6:12).
The best student of a rabbi should walk on the rabbi's right side, relegating the second best to the left (יומא לז, א).
After observing his teacher Rabbi Yehoshua, Rabbi Akiva taught that the left hand should be used after using the bathroom, out of respect to the right hand (ברכות סב,ב). When challenged as to why Rabbi Akiva was impertinent enough to report on which hand his teacher wiped himself he replied תורה היא וללמוד אני צריך - "this too is Torah, and I must study it".
It's not Just Judaism
The importance of all things right handed is found in other religions. For example, when Muslims perform any of the following, it is mustahabb [مستحبّ, - "recommended"] to start on the right or use the right hand.
putting on one's garment and pants and shoes
entering the mosque, using the siwaak [ a kind of toothpick]
putting on kohl [an ancient blue eye cosmetic]
clipping the nails
trimming the mustache
combing the hair plucking the armpit hair
shaving the head
saying salaam at the end of prayer
washing the limbs when purifying oneself
exiting the toilet, eating and drinking
touching the Black Stone [ٱلْحَجَرُ ٱلْأَسْوَد, al-Ḥajaru al-Aswad, a rock set into the eastern corner of the Kaaba, the ancient building located in the center of the Grand Mosque in Mecca, Saudi Arabia. Legend has it that the rock dates back to Adam and Eve.]
Conversely, the Bukhari Sharif , one of the six major hadith collections of Sunni Islam rules along the lines of Rabbi Akiva:
"... when you urinate, do not touch your penis with your right hand. And when you cleanse yourself after defecation, do not use your right hand."
In the New Testament, Jesus sits at the right hand of God. The Catholic theologian Thomas Aquinas who worked to synthesize Aristotelian philosophy with the principles of Christianity (and in that respect was a kind of Maimonides of the Church,) explained at some length how the notion of the right or left hand of God can have any meaning since God is incorporeal. (Spoiler alert: it is all metaphorical.)
Those at prayer make the sign of the cross with their right hand.
Offerings, such as flowers or garlands, are carried with both hands on the right side of the body.
"Pointing with the forefinger of the right hand or shaking the forefinger in emphasis while talking is never done. This is because the right hand possesses a powerful, aggressive pranic force, and an energy that moves the forces of the world."
Vāmācāra ( वामाचार, meaning "left-handed attainment" in Sanskrit) describes the "Left-Hand Path" or "Left-path" It is used to describe a particular mode of worship that is heterodox to standard Vedic teachings.
In Benares, the holiest of the seven sacred cities and sitting on the Ganges, "pilgrims circumambulate with their right hands towards the center, as Krishna is alleged to have done at the sacred mountain."
Well, you get the point. Judaism, along with all the major religions (and some you've never heard of) emphasize the dominance of the right hand in all things holy. Or mundane.
and It's not just religions
There are lots of things that have chirality - meaning they have a mirror image but cannot be mapped onto that mirror image by rotations and translations. They exist in left or right-handed versions. Let's start with in easy example. Um, your hands. Although your right hand mirrors your left, your right hand cannot (comfortably) fit into a handed-glove.
Here's another example. Bend your fingers and extend your thumb as in the figure. You've made two mirror images that cannot be mapped onto each other. (Go on. Give it a try. See what I mean?) That's chirality.
If we extend this to molecules, they are left or right-handed, meaning they are mirror images but they cannot be superimposed on each other. These are isomers. Like this:
And here is where things start to get really weird. Nearly everything in the universe - from chemicals and medications to fundamental particles and even galaxies themselves have a right-handed or left-handed preference. No, really.
Let's start with the essential building blocks of life: amino acids and sugars. Almost all amino acids (not you, glycine) used by life on earth (but not necessarily elsewhere in the universe) are left-handed. Right-handed amino acids exist of course. They're just not utilized by any life form on earth. Any. If you sit in a lab and cook up an amino acid from its ingredients, you will make an equal amount of the left and right handed variates. That's just good old chemistry at work. But life on earth can only use half the mixture: the L form. Some bacteria can actually convert right-handed amino acids into the left-handed version, but they can’t use the right-handed ones as is.
Like amino acids, sugars also come in two isomers, but those that are used by life forms on earth are the right-handed variety. All the enzymes that living things use to manipulate amino acids and sugars only work on left-handed amino acids and right-handed sugars. They simply can't use the opposites. Why did life turn out this way? Truth is, nobody knows.
Medications also exhibit chirality. For example, propranolol is commonly used to help control high blood pressure. Some of you reading this may be taking it. The left form (L-propranolol) is the one that helps. The right form (known as D-propranolol) is inactive. (The Latin for left and right is laevus and dexter, respectively.)
Quinine is an antimalarial drug. It has an isomer called quinidine, and quinidine has no anti-malarial action. But it's a great drug to reduce arrhythmias of the heart. One compound, with two isomers, each with their own remarkable and very different healing properties.
Now consider muons, a fundamental particle in our universe. It is kind of like an electron, but about 200 times heavier. Muons have an average life-expectancy of 2.2 microseconds (so don't expect any kind of long-term relationship) after which time they decay into an electron, a neutrino, and an antineutrino. The direction that the electron will come out depends on the direction in which the muon spins. Now you would expect there to be equal amounts of electrons that are ejected spinning one way or another. But there aren't. What happens is that 99.9% of muons decay in a right-handed fashion.
And while we are on the subject of decaying muons, let's talk about those neutrinos, which are a weird fundamental particle with the smallest mass of any known thing. They too, have a preference for the right or left. All neutrinos are left handed, while all anti-neutrinos (whatever that means) are right handed.
Ready for more? Statistically speaking our universe should contain an equal amount of left and right handed galaxies (as noted in how they spin). But this should not occur. In an analysis of over 2,600 nearby spiral galaxies and a later analysis of 15,000 more, Michael Longo demonstrated that that left-handed spirals are more common in the northern hemisphere, above the northern galactic pole. And although the signal is less strong, right-handed spirals appear more frequently in the south.
It's good to be a leftie
About 10-13% of humans are left-handed. (Captive chimpanzees are more left-handed than us, with an approximate 2:1 ratio of righties to lefties. In us it's more like 8:1) But aside from the problem of not finding scissors that work for you, being a leftie gives you some pretty good advantages.
At the undergraduate level they are more likely to take part in a whole range of events, from judo and fencing and soccer and volleyball. But when it comes to non-confrontational sports like cycle racing, running or swimming, the proportion of left handers fall back to that of the general population. Lefties make up about 10% of the population, but 23% of all Wimbledon tennis champions were lefties.
There is a lot more evidence that lefties have many advantages over (us) righties. In a complicated test of spatial skills which you can read about here, 47 lefties demonstrated faster and more accurate spatial skills than the 50 righties, along with strong executive control and mental flexibility. And in this study of 100 lefties and 100 righties, the left-handed demonstrated greater creativity than the right-handed on all 4 scales of the Torrance test which examines creative thinking.
And lefties appear to be smarter that righties. In a study of some 300 gifted children, left (-or mixed-handedness) occurred more frequently in those who were mathematically or verbally precocious (for our readers in the US, this meant an SAT-M score of more than 700 and an SAT-L score of more than 630). Of the last 15 US presidents, seven (about 47%) have been left-handed. That's almost 1 in 2! Oh, and compared with righties, college-educated left-handers in the US earn 10-15% more.
Despite these, and many other advantages, our cultures have stigmatized those who are left-handed. We all know that the word sinister (meaning something harmful or evil is going to happen) comes from the Latin sinister meaning left. But there are more examples of anti-left associations in other languages too. Adroit, meaning clever or skillful comes from the French word for right droite, meaning dextrous. In German, linkisch means awkward, and it comes from the German links, meaning left. And so it goes on.
Back to the Jewish Bible
Left-handed people are mentioned only three times in Tanach, and all come from the tribe of Benjamin:
There were the 700 men from the tribe of Benjamin who could use a sling with deadly accuracy (שופתים 20:16):
מִכֹּ֣ל ׀ הָעָ֣ם הַזֶּ֗ה שְׁבַ֤ע מֵאוֹת֙ אִ֣ישׁ בָּח֔וּר אִטֵּ֖ר יַד־יְמִינ֑וֹ כָּל־זֶ֗ה קֹלֵ֧עַ בָּאֶ֛בֶן אֶל־הַֽשַּׂעֲרָ֖ה וְלֹ֥א יַחֲטִֽא׃
There were the ambidextrous men who came to fight for King David at Ziklag, who were from the tribe of Benjamin (דברי הימים א, 12:2)
נֹ֣שְׁקֵי קֶ֗שֶׁת מַיְמִינִ֤ים וּמַשְׂמִאלִים֙ בָּֽאֲבָנִ֔ים וּבַחִצִּ֖ים בַּקָּ֑שֶׁת מֵאֲחֵ֥י שָׁא֖וּל מִבִּנְיָמִֽן׃
And perhaps most famously there was the left-handed Ehud ( אֶת־אֵה֤וּד בֶּן־גֵּרָא֙ בֶּן־הַיְמִינִ֔י אִ֥ישׁ אִטֵּ֖ר יַד־יְמִינ֑וֹ) who assassinated the Moabite king Eglon (שופתים 3:12-30). Because Ehud was left-handed he hid his dagger on his right side. In this way he got past the body search outside the throne room, where the guards looked for a weapon on the left. As for the rest, well, read on:
וַיִּשְׁלַ֤ח אֵהוּד֙ אֶת־יַ֣ד שְׂמֹאל֔וֹ וַיִּקַּח֙ אֶת־הַחֶ֔רֶב מֵעַ֖ל יֶ֣רֶךְ יְמִינ֑וֹ וַיִּתְקָעֶ֖הָ בְּבִטְנֽוֹ׃ וַיָּבֹ֨א גַֽם־הַנִּצָּ֜ב אַחַ֣ר הַלַּ֗הַב וַיִּסְגֹּ֤ר הַחֵ֙לֶב֙ בְּעַ֣ד הַלַּ֔הַב כִּ֣י לֹ֥א שָׁלַ֛ף הַחֶ֖רֶב מִבִּטְנ֑וֹ וַיֵּצֵ֖א הַֽפַּרְשְׁדֹֽנָה׃
Reaching with his left hand, Ehud drew the dagger from his right side and drove it into [Eglon’s] belly. The fat closed over the blade and the hilt went in after the blade—for he did not pull the dagger out of his belly—and the filth came out.
All of this is really strange because of course the name of this tribe - Benjamin - literally means "the son of the right" בן ימין.
Back to Chhulin
Today's daf yomi page of Talmud has a very short instruction. Give to the priests the most choice of meat cuts: those from the right leg of the animal. But this phrase reveals a profound truth about who we are as humans, and of the very stuff from which we are made. In culture after culture, in religions after religion, and in the very structure of our universe, there are left or right-handed preferences and predilections, many of which we simply cannot currently explain. Our religious and cultural preferences for the right likely stems from the simple fact that left-handedness is eight times less common. Unfortunately, a suspicion of the other, of those who are not like the majority, is a common trait that in one way or another we all share. But it needn't be so. The other, those in the minority, teach us and enrich our lives. Heck, they are often even smarter and quicker than the majority. We are all better off with them.
[An oldie but a goodie originally posted here.]