The Gemora discusses the case of kilayim for an ox, sheep and goats. I know that this is brought in multiple places in shas. I am not 100% certain but I think that breeding these species "naturally" i.e. without genetic engineering does not result in viable offspring (at least today. I do not know in the time of the gemora).
Thus I know we can say that the teva has changed but in the absence of that answer, how could such a case of kilayim occur? Is the gemora deeper than it would seem?
Rob Shorr Ph.D., D.I.C.
On very rare occasions sheep and goats have interbred to produce "geep." Neither can interbreed with cattle, though, and it is very unreasonable to say that this was ever possible. I think it's unlikely that the Gemara says it. Although the Gemara does speak about kilayim between goats and gazelles, which is likewise impossible (unless the Gemara is using tzvi to refer to the ibex... which is also unlikely).
As far as I understand, the Gemara does not talk about a case of an ox breeding with sheep and goats. However, if one would encounter such a discussion in the Gemara, it is very possible that the Chachamim were not stating that such a thing existed, but rather discussed what the Halachic ramifications would be if it did. Even if there are cases where such apparently impossible breeding would be discussed in the Gemara, it is very possible that under rare conditions that we are not aware of, such breeding could take place. In conclusion, there is one Golden Rule: the Gemara is always deeper than it seems.
All the best,