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Hullin 80a-b: Identifying the Koy

In the context of discussing animals that are produced from the mating of different species (see yesterday’s daf), the Gemara introduces a koy – an animal that has the features of both a wild animal and a domesticated one. At first, the Gemara assumes that the koy is the result of a union between a deer and a goat, but on today’s daf Rav Yehuda suggests that it is a beriah bifnei atzmah – it is a unique creation – about which could not conclude if it is a wild animal or a domestic animal. The Gemara points out that this is a disagreement that hearkens back to the time of the Tannaim, quoting a baraita where Rabbi Yosei echoes Rav Yehuda’s position that the koy is a unique species, while Rabban Shimon ben Gamliel testifies that it is a domesticated animal – the family Dushai would raise flocks of them.

Identifying the koy is a difficult task. Even though it is mentioned many times in the Mishna and Talmudic literature, that is not because it is a common animal, rather because its status between a wild and domesticated animal allows it to serve as a test case for many halakhot. The disagreement as to its identification began in the time of the Mishna, when some of the Sages argued that it is the offspring of a deer or similar animal with a goat. Others claim that it is a unique type of animal – an Ayal ha-bar ( a wild ram).

The Ayal ha-bar can be identified with the ovis musimon, which, according to many, is the forerunner of domesticated cattle. It is distinguished by its short hair and grey color, and it lives in mountainous regions, where it is a nimble climber – today mainly in uninhabited areas in Europe. It is likely that the clear similarities between a koy and a sheep, together with its being a wild animal, led to the Sages’ confusion about its classification.

Its name, “koy” and even the pronunciation of the name, are themselves the subject of disagreement.


This essay is based upon the insights and chidushim of Rabbi Steinsaltz, as published in the English version of the Koren Talmud Bavli with Commentary by Rabbi Adin Steinsaltz, and edited and adapted by Rabbi Shalom Berger.

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