Perspectives on Playing God (Creating): An exploration of crossbreeding, cloning, and medicine.

(19) You shall observe My laws.
You shall not let your cattle mate with a different kind; you shall not sow your field with two kinds of seed; you shall not put on cloth from a mixture of two kinds of material.

(37) Jacob then got fresh shoots of poplar, and of almond and plane, and peeled white stripes in them, laying bare the white of the shoots. (38) The rods that he had peeled he set up in front of the goats in the troughs, the water receptacles, that the goats came to drink from. Their mating occurred when they came to drink, (39) and since the goats mated by the rods, the goats brought forth streaked, speckled, and spotted young.

When the verse states: “And shall cause him to be thoroughly healed [verappo yerappe]” (Exodus 21:19), it is derived from here that permission is granted to a doctor to heal, and it is not considered to be an intervention counter to the will of God.

In accordance with this excellent principle, which we ought strictly to follow, our Sages teach us that we ought not to look at beasts or birds in the moment of their copulation. According to my opinion, this is the reason why the cross-breeding of cattle is prohibited (Lev. 19:19). It is a fact that animals of different species do not copulate together, unless by force. It is well known that the low class of breeders of mules are regularly engaged in this work. Our Law objected to it that any Israelite should degrade himself by doing these things, which require so much vulgarity and indecency, and doing that which religion forbids us even to mention, how much more to witness or to practise, except when necessary. Crossbreeding, however, is not necessary. I think that the prohibition to bring together two species in any kind of work, as included in the words, "Thou shalt not plow with an ox and an ass together" (Deut. 22:10), is only a preventive against the intercourse of two species. For if it were allowed to join such together in any work, we might sometimes also cause their intercourse. That this is the reason of the commandment is proved by the fact that it applies to other animals besides ox and ass; it is prohibited to plow not only with ox and ass together, but with any two kinds. But Scripture mentions as an instance that which is of regular occurrence.

בהמתך לא תרביע כלאים, “You must not mate your animal with another species.” Ibn Ezra writes that the Torah links the laws of not interbreeding species and the encouragement to become holy in order to make the point that after you have become a holy nation you must not commit violent acts against any person sharing your beliefs, and you must not even forcefully interfere with the animals’ natural way of behaviour which is, after all, the way they have been programmed to behave by the Creator. Animals are more loyal to the rules laid down for His creatures than man is.

Rashi writes that the prohibition against cross breeding must be seen as a Divine decree, G’d did not see fit to give us His reasons.

Nachmanides writes that the sages did not write anywhere that the underlying reasons for this legislation have been deliberately hidden, giving the evil urge and the gentiles a chance to ridicule and undermine our faith in the Creator.

Whereas such an argument is true with respect to the prohibition to mix wool and linen, [but not other fibers, Ed.] the reason for not mixing different seeds in a vineyard, or not crossbreeding species of animals are not at all a challenge to [test of, Ed.] our faith. On the one hand, all G’d’s laws, [especially those regulating our conduct vis a vis Him seeing that they emanate from a higher intelligence, are of a kind whose true intent we are unable to fathom, Ed.] are beyond our ability to fully comprehend, as opposed to the laws governing inter-personal relations which we are expected to try and understand. However, we are encouraged in many instances to examine some aspects of how the חוקים are beneficial to our successful existence on this earth. We must not make observance of these laws conditional on our understanding their usefulness.

There appears to be a perfectly rational reason for the legislation of forbidding crossbreeding, both of animals and plants. The Creator enabled each species to perpetuate itself by planting its seed in the appropriate counterpart. Crossbreeding, in the vast majority of cases, would foil the Creator’s plan, and such species would die out, as their seed would not produce any issue or issue that was capable of sustaining itself. G’d provided the seed to these creatures in order to enable His universe to endure as planned. Any activity that puts the Creator’s intent at risk, is therefore forbidden, is an act of insurrection if persisted in. This is the reason why already at the time of reporting creation, the Torah stresses again and again the words למינו and למיניהם, “according to its species,” or “according to their species.” He who interferes with this obviously finds fault with the Creator, implicitly criticizes Him. G’d does not need His creatures’ help in perfecting His universe, He is content if His creatures do not ruin it.

We know from experience that even if apparently well matched human beings mate with one another, especially those forbidden under the rules of incest, any children from such unions are liable to intensify genetic defects which no human being is totally without.

In other words, not only do totally different species not reproduce when crossbred, but, even members of the same species fail to reproduce satisfactorily if the rules of the Torah are not followed.

Who would know best what is good for us if not He Who had created us? When the Torah enlarges this prohibition by writing שדך לא תזרע כלאים, “you must not scatter more than one type of seed in your field,” it includes even relatively simple plants in its regulations. Our sages expressed their conviction that violating this commandment will be found detrimental to the farmer’s interest, even if he thought that he would benefit through such a stratagem.

Our sages (Bereshit Rabbah 10,7) have illustrated their approach to the whole subject when they told us that there is not a single species of plant which does not have its own mazzal, i.e protective guardian angel appointed in the heavens. Clearly, such a statement refers only to species created by G’d, not to new species created by man. Such species are without any heavenly protection.

Tyrannus Rufus the Wicked asked R. Aqiva: Which works are the more beautiful? Those of the Holy One or those of flesh and blood? He said to him: Those of flesh and blood are the more beautiful. Tyrannus Rufus said to him: Inasmuch as he finds pleasure in circumcision, why does no one emerge from his mother's belly circumcised? R. Aqiva said to him: And why does his umbilical cord come out on him? Does not his mother cut his umbilical cord? So why does he not come out circumcised? Because the Holy One only gave Israel the commandments in order to purify them. Therefore, David said (in II Sam. 22:31 = Ps. 18:31 [30]): {EVERY} WORD OF {GOD} [THE LORD] IS PURE….

Rava says: If the righteous wish to do so, they can create a world, as it is stated: “But your iniquities have separated between you and your God.” In other words, there is no distinction between God and a righteous person who has no sins, and just as God created the world, so can the righteous. Indeed, Rava created a man, a golem, using forces of sanctity. Rava sent his creation before Rabbi Zeira. Rabbi Zeira would speak to him but he would not reply. Rabbi Zeira said to him: You were created by one of the members of the group, one of the Sages. Return to your dust. The Gemara relates another fact substantiating the statement that the righteous could create a world if they so desired: Rav Ḥanina and Rav Oshaya would sit every Shabbat eve and engage in the study of Sefer Yetzira, and a third-born calf [igla tilta] would be created for them, and they would eat it in honor of Shabbat.