A Redefined KeZayis, Because They Had A Smaller Strain of Olives

(Note: Not halacha lemaaseh, as should be clear even from my choice of language.)

I am all for realia. Still, I am not sure I am entirely convinced. It is perhaps a gemara, about the existence of olives of different sizes.

First, the research:

Prof. Mordechai Kislev, who headed the team with Dr. Orit Simhoni, Yonit Tabak and Ofer Tzarfati-Zuta, maintains that Syrian and Nabali strains, whose weight per olive is only around five grams (about a sixth of the weight of a machine-made matza), are the model for the halachic standard. The researchers said these types of olives, smaller than today's olives, were the most common during ancient times.

...

Kislev and his colleagues said Syrian olives, which each weigh 2.5-3.5 gr., and Nabali, which each weigh 4-6 gr., were common in this area during Talmudic times. About 2,000 well-preserved olive pits of these two varieties were identified in archeological digs at the Masada fortress near the Dead Sea - destroyed in 73 CE. In addition, the Bar-Ilan researcher said, there are dozens of three-millennia-old olive trees of these strains around the country that still produce fruit.

and so on. Read it all.

Berachot 38b-39a:

אמר ר' חייא בר אבא אני ראיתי את ר' יוחנן שאכל זית מליח ובריך עליו תחלה וסוף

...

אמר ליה רבי ירמיה לרבי זירא רבי יוחנן היכי מברך על זית מליח כיון דשקילא לגרעיניה

בצר ליה שיעורא אמר ליה מי סברת כזית גדול בעינן כזית בינוני בעינן (והא איכא) וההוא דאייתו לקמיה דרבי יוחנן זית גדול הוה דאע"ג דשקלוה לגרעינותיה פש ליה שיעורא דתנן זית שאמרו לא קטן ולא גדול אלא בינוני וזהו אגורי ואמר רבי אבהו לא אגורי שמו אלא אברוטי שמו ואמרי לה סמרוסי שמו ולמה נקרא שמו אגורי ששמנו אגור בתוכו

So what is this distinction between beinoni and gadol? I have always read it as referring to species of olives, and still incline towards that reading. Do they account for this? If not, perhaps one could read the gemara as referring to different sized olives within the same species. After all, these researchers to give spans. But it would have to be that within the same species, the size of a large olive is greater than a small olive by the size of its pit. I don't know if this is so for the range of sizes of the olives they identify here. If between species, perhaps the Nabali olives could be reckoned the large ones while Syrian olives would be the middle ones. Or perhaps they had in mind certain uncommon olives which were still larger. We should make some kind of determination of what is "small," "medium," and "large." It does make sense, though, that the beinoni upon which the kezayit measure is based would be a common one.

I also would not assume that this is necessarily a kula. While it is a kula for eating matzah, as they cast it, it is a chumra in terms of certain prohibited minimum eating, and other things. Even within the laws of Pesach, the violation of bal yeraeh and bal yimatzei is on chametz the size of a kezayis.

There are other gemaras and Yerushalmis which relate the size of a kezayit to other sizes, such that this is perhaps calculable. For example, a reviit is supposed to be able to be nikrash (congeal/shrink) to the size of kezayit, but there are different measures as to the reviit, quite possible influenced by girsology (though Tosafot IIRC explains it otherwise). I don't think I'll have a chance to discuss it this year, as I've already sat on that post for several years running.