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Our uncertainty about the meaning of this view in the Yerushalmi
undermines the proof we brought earlier from the halachah that even
a partial sheep is considered a sheep. That may hold true only of two
animals – one wild and the other domesticated – that mate, in which
case both are certainly partial parents. In our case though, where the
other fornicator may have contributed nothing substantial beyond
some slight addition, he may not even be considered a partial father.

We can resolve this doubt from a question asked in the sefer, Ker-
em Nata (on Sotah 42b) on the Aruch who says that Goliath was also
the offspring of a dog. He points to the difficulty in understanding
this in light of the gemara in Sanhedrin (58a) which says that two
humans unite to produce offspring but neither domesticated nor
wild animals can produce offspring from a human, nor can a human
produce offspring from an animal. He answers by suggesting that the
fetus’s [i.e. Goliath’s] body may have been formed after fertilization
by a man, whereas from the dog [with which his mother also had
intercourse] he may have absorbed some additional characteristic.
The Kerem Neta writes that according to this it is possible that not all
one hundred Philistines were actually his fathers; he may have been
formed from only one of them, while absorbing some characteristic
from the others.

According to this assumption tissue-typing cannot rule out that a
woman did not become pregnant from two men. One may have sired
the fetus while the other just added some quality or property, which
is not detected by tissue-typing.



As discussed above, there is a view in the Yerushalmi that a woman
can become pregnant from two men at once. I have also heard howev-
er that contemporary physicians opine that according to their current
knowledge, this is impossible. I presented this question to Dr. Yigal
Gat, who heads a Fertility Department – his response follows:

It is known that a living cell contains two sets of chromo-
somes [containing the genetic material]. One set of twenty

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