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Did we just learn that eggs used to be a different size - and does this affect the kezayis?
Everyone’s getting excited about an archeological study by Professor Zohar Amar which shows, according to media reports, that “they were significantly smaller than previously thought” (and certainly much smaller than the elephant bird egg pictured above). This, we are told in the frum press, “may carry important halakhic implications, as various halakhic rulings are determined according to the size of an egg, for example, the directive to eat matzah ‘the size of an olive’ during the Passover seder. According to different halachic opinions, this is calculated as between a quarter to half an egg.”
Professor Amar, a friend and teacher of mine, is probably the world’s leading expert (of all time) on the flora, fauna, and realia of Tanach and Chazal. He is also a very cautious scholar who does not overstate his claims. Accordingly, I would like to explain why the press is presenting this story and its ramifications incorrectly.
First of all, as Professor Amar makes clear, while certain medieval and recent rabbinic authorities believed that eggs used to be bigger, it isn’t news in the academic community that eggs used to be smaller. Decades ago, Professor Yehudah Feliks examined eggs that were preserved whole in the volcanic destruction of Pompeii two thousand years ago, and stated that they were around 40cc. Professor Avraham Greenfield pointed out many years ago that the Talmud records that a vessel called the modius contains the volume of 217 eggs; we know the size of this vessel, and can accordingly calculate the size of eggs of that era as measuring 39.6cc. And in my own monograph on the evolution of the kezayis, I pointed out that domestic fowl have been selectively bred for larger eggs, which would mean that eggs used to be smaller. Furthermore, we know that the domestic chicken was domesticated from the red junglefowl several thousand years ago, and its eggs are very small, only 32cc. Assuming a gradual increase to the size of today’s eggs, this would indicate that two thousand years ago, eggs were around 40cc. Professor Amar’s archeological studies of eggs provides useful confirmation and further information regarding all this.
But what about the halachic implications? I find it fascinating that some people are seeing this as being relevant to the size of the kezayis, due to it commonly being presented in terms of its proportionate size to an egg. Because if your halachic epistemology takes into account archeological findings when determining the size of eggs, then it’s not an epistemology which should care about the size of eggs when determining the size of an olive!
As I made clear in my monograph on the kezayis, the only Rishonim who gave dimensions of olives in terms of eggs were the Ashkenazi Rishonim who didn’t have access to olives. They had to try to deduce their size from various statements in the Talmud regarding eggs. The Rishonim of Sefarad, on the other hand, who had olives, did not need to give their size in terms of eggs. Likewise, for us today, who have olives (along with various evidence that their size has not decreased over time), we do not need to concern ourselves with the size of eggs.
There is a potentially valid epistemology which would discount all this, and would say that the size of the kezayis, and does not take into account any historical context. But that same epistemology would discount the evidence that eggs used to be smaller. So, pick your epistemology, and stick with it!
Meanwhile, my monograph on the kezayis is no longer available online, but you can read it in my book Rationalism vs. Mysticism, which you can purchase at this link. Here is a list of other posts relating to this topic:
Matzah/Maror Chart for Rationalists - so that you, too, can have a chart! Patrons of the Biblical Museum of Natural History received a special version of this in the mail this week.
The Popularity of Olives - exploring why this paper is so popular and yet hated by some.
Why On Earth Would One Eat A Kezayis? - discussing the strange notion that one should aim to eat a kezayis of matzah on Seder night.
The Riddle of the Giant Kezayis Defense - wondering why many people would not accept that a kezayis is the size of an olive.
Zayit Ra'anan, by a Sefardic Torah scholar, which you can download at this link. I haven't had time to study it properly, but the numerous haskamot alone are fascinating in their diversity. Some of the rabbanim are greatly unnerved, some admit that the arguments seem compelling but are afraid to say that anyone other than "the Gedolim" can decide these things, and others forthrightly state that it is obviously true that a kezayit is the size of a contemporary olive.
Maniacal Dishonesty About Olives - exposing an error-ridden critique that appeared in the charedi polemical journal Dialogue.
It's Krazy Kezayis Time! - discussing the view that one should eat a huge amount of matzah in a very short time in order to fulfill all opinions.
The Kezayis Revolution - announcing the fabulous sefer by Rabbi Hadar Margolin, which presents the same arguments that I brought but in a more yeshivish manner. He also brings an astonishing array of evidence that many recent charedi gedolim likewise held that a kezayis is very small, including even the Chazon Ish! Best of all, the entire sefer can be freely downloaded.
Monsters & Matzos - a great riddle: what is the connection between the relatively rare findings of ancient whale bones on the coast of Israel, and the large size of matza that many people eat on Seder night?
Meanwhile, the Biblical Museum of Natural History is open for tours before and during Pesach. We expect most tours on Pesach to sell out, so book your tour now! Visit www.BiblicalNaturalHistory.org for more details.
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