The Gemara says that exactly a kzayis of meis- since it will decompose shortly to be less than a kzayis, dont place a marker there.
This implies that once it decomposes into the ground to less than a kzays, it is no longer tamei. Does this apply to all graves once the body decomposes it's no longer tamei. If so older graves that we know contains no more remnants of a meis because its all decomposed, a kohen can go to?! I always thought that agrave is metamei forever, if so what does the gemara mean?!
Thank you
Dov Shapiro, Monsey NY USA
Even if the flesh has decomposed, the bones still remain. This Gemara refers to a case in which only a k'Zayis of the flesh of the Mes was found. However, if one finds the backbone or the skull etc. (and certainly if one finds an intact corpse), one must place a marker there, as we see a few lines later in the Gemara here, and thus we learn from this that we do not say that the bones will decompose.
Kol Tuv,
Dovid Bloom
Have a look at the Halachah of Melo Tarvad Rekev - see the comment of Rav Betzalel Rensberg on Tosfos DH she'Eno Metamei b'Ohel, and Rambam Tum'as Mes 2:11 (who implies that the bones do decay) an 3:3.
Y. Zirkind
Yeyasher Kokacha for the Ma'arei Mekomos, Yitzchak.
1. The Teshuvas Chasam Sofer (YD 337, cited by the Pischei Teshuvah YD 369:4) discusses the question one can assume that the bones in ancient graves have decayed. He cites the verse in Mishlei (14:30), "And the decay of bones is jealousy," which Chazal (see Shabbos 152b) explain to mean that if a person was jealous of others during his lifetime, his bones will decay after he dies, but if he did not suffer from jealousy, his bones will not decay. Based on this, the Chasam Sofer writes that one should assume that the bones of an ancient Kever have not decomposed (unless one has other reasons to be lenient), because the dead person has a "Chezkas Kashrus" that he was an upright person who was not jealous of others.
2. The law of Melo Tarvad Rekev is actually a source that the grave should still be Tamei, because the Mishnah in Ohalos (2:1) states that Melo Tarvad Rekev is Metamei in an Ohel. The Rambam (2:11) that you cited states that although the Mes decomposed and became "Rekev," it is still Tamei b'Ohel (he writes this in 3:3 as well). However, the aforementioned Chasam Sofer writes that since the Gemara in Nidah (27b) states that Melo Tarvad Rekev is Metamei only if the corpse was buried naked in a marble coffin, it follows that this Halachah is uncommon. In other words, even though Melo Tarvad Rekev would be a reason to be Machmir, in practice this Halachah is unusual, which is why the Chasam Sofer resorts to the other reasoning -- that one can assume that the Mes was not a jealous person and his bones did not decay.
3. Tosfos (DH she'Eino) appears to maintain that Tarvad Rekev is not Metamei in an Ohel, which is why Rav Betzalel Rensburg asks that Tosfos contradicts the explicit Mishnah in Ohalos (2:1, cited above) which says that it is Metamei. Perhaps we may answer Rav Betzalel Rensburg's question with the help of the Chasam Sofer cited before, that in practice it is unusual that Melo Tarvad is Metamei. (This answer requires further thought.)
Kol Tuv,
Dovid Bloom