Specific Species

Question #1: Wolf and Dog

Are wolves and dogs members of the same species?

Question #2: Bactrian and Dromedary

May I haul a wagon with two camels, a Bactrian and a dromedary?

Question #3: Tangelo

Is it permitted to crossbreed tangerine and grapefruit to create a tangelo?

Question #4: Crabapples

May I graft an apple branch onto a crabapple trunk?


At the beginning of parshas Noach, Rashi teaches us that, during the moral chaos that led to the Mabul, even members of the animal kingdom mated outside their species (min), something that no self-respecting and ethical animal would ever do.

At this point, we need to ask what is meant by min, which is usually translated as species. The dictionary definition of the word “species” is a pool of individuals that can breed together and do not breed with other individuals.

However, we will soon see that neither halacha nor science uses this definition. It is important that, when studying the Talmudic, aggadic and halachic topics germane to kil’ayim, we must understand properly the Torah’s meaning of the term “species.”


Many halachically knowledgeable people assume that the purpose of the laws of kil’ayim is to prohibit the hybridization or crossbreeding (two ways of saying the same thing) of unlike species, or, in simpler terms, not to attempt creating new biological species or to mix genetic material of different species. However, we will soon demonstrate that this assumption is specious, since it is inconsistent with halachic accuracy for two completely different reasons:

A. Most kil’ayim prohibitions have nothing to do with creating new species.

B. In numerous instances, the laws of kil’ayim permit mingling two varieties that are biologically different species, and there are situations in which the laws of kil’ayim prohibit mingling two varieties that are biologically considered members of the same species.

Types of kil’ayim

First, we will demonstrate that kil’ayim prohibitions rarely have anything to do with creating new species (point A). Mesechta Kil’ayim deals with six different mitzvos involving the intermingling of species:

1. Crossbreeding animal species. This prohibition is called harva’as beheimah, or sometimes simply harva’ah. In this instance, as in most of the cases of kil’ayim, there is no prohibition against using the product created by someone who violated the prohibition. Thus, it is permitted to use a mule, notwithstanding that mating a donkey with a mare to produce a mule violates a lo sa’aseh min haTorah.

2. Using two animal species to haul or work together. This mitzvah is usually called lo sacharosh, as in the words of the Torah: lo sacharosh beshor uvachamor yachdav,“Do not plow with an ox and a donkey together” (Devarim 22:10).

3. Grafting different tree species, harkavas ilan, which prohibits inserting a shoot or scion of one species into the wood stock, or lower trunk, of another species. Note that it is completely permitted to plant different species of trees next to each other (Yerushalmi, Peah 1:4).

4. Planting a non-woody edible plant, such as a vegetable or grain, in a vineyard. (A “non-woody” or “herbaceous” plant is a plant other than a tree or a shrub.) This prohibition is called kil’ei hakerem, and applies min haTorah only in Eretz Yisrael, although it does apply in chutz la’aretz as a rabbinic prohibition. This mitzvah is atypical in that it is the only prohibition of kil’ayim whose product is prohibited to use, min haTorah.

5. Planting two non-woody edible plants near one another. This mitzvah, called kil’ei hasadeh, kil’ayim of the field, applies only in Eretz Yisrael. In chutz la’aretz it is permitted to plant two herbaceous plants next to one another.

6. Wearing shatnez, clothing that includes both wool and linen. The prohibition is limited to wearing such clothing.

The two mitzvos of kil’ei hakerem and kil’ei hasadeh, apply min haTorah only in Eretz Yisrael, whereas the others apply min haTorah both in Eretz Yisrael and in chutz la’aretz.

I stated above that kil’ayim prohibitions usually have little or nothing to do with the creation of new species. Crossbreeding of plants involves pollinating the flower of one species with pollen from a different species. But none of the agricultural mitzvos listed above has anything to do with hybridization.

Let’s take a more careful look at the three agricultural prohibitions: 3, 4, and 5, above. In the cases of herbaceous, or non-woody, plants, kil’ayim is planting two crop species near one another (#5) or planting them inside a vineyard (#4). But planting the seeds of different species in close proximity does not change the DNA of the species or cause any hybridization, nor does it cause anything to grow of a variety different from either parent.

In the case of trees and shrubs, harkavas ilan (#3) means grafting one species onto another. When you graft a branch of one species onto the stock of another, the fruit that grows has the DNA of the scion branch and no DNA material of the species of the stock.

Also note that these three kil’ayim prohibitions are limited to species in which some part of the plant is edible.

Wool and linen

Wearing a garment that contains both wool and linen (#6) does not cause any hybridization. Wool grows on sheep, and linen is the product of a flax plant. Combining the two textiles in a garment does not affect their genetic material.

Lo sacharosh

Although some wish to explain that the prohibition of using two animal species to haul or otherwise be worked together is out of concern that someone will house them together or otherwise cause them to mate (Alshich, Devarim 23), there are many other ways to explain the “reason” for this prohibition (see, for example, Ibn Ezra, Devarim 22:10).

Harva’as Beheimah

The only one of the six kil’ayim prohibitions that involves hybridization is harva’as beheimah. But I presume that my readers agree that it is very strange to provide a reason for six different mitzvos that does not apply to five, or, possibly, not to four of them!

And, although we usually translate the word kil’ayim as “mixture,” some commentaries associate this word with the root כלא, as in the word “prison,” beis ke’le. Rav Hirsch explains the root word ke’le as holding something back, keeping someone incarcerated. The plural form kil’ayim is structurally similar to yadayim, raglayim or kesafayim,and means “a pair.” Thus, the word kil’ayim means pairing together items that should be kept apart (Hirsch Commentary to Vayikra 19:19), a definition that fits all six categories of kil’ayim, but has nothing to do with hybridization.

Dogs and wolves

My second point above (point B) is that there are numerous instances where the laws of kil’ayim permit mingling two kinds that are biologically considered different species, and there are also many instances in which the laws of kil’ayim prohibit mingling two kinds that are biologically considered the same species.

To explain, I will first pick examples in the animal world and then in the plant world. The Mishnah (Kil’ayim 1:6) states that wolves and dogs are kil’ayim together; it is forbidden to crossbreed them or to have them haul a load together. Yet, wolves and dogs breed together freely in the wild. Thus, we see that kil’ayim is not dependent on whether the varieties breed together.

From the Yerushalmi and the halachic authorities it appears that several factors are used to determine whether two varieties are considered different species, including how mankind views them, as the Torah teaches, “Hashem had created… all the animals of the field and the birds of the sky and He brought them to the man to see what he would call them… And the man gave names to all the domesticated animals and the birds of the sky and the animals of the field (Bereishis 2:19-20). This implies that man understood the purpose or uniqueness of each species and how it should be categorized, separately, from all other species.

Scientific dogs

The scientific system for classifying species, developed by Carl Linnaeus in the eighteenth century, names every species by two words: the first, its genus, which is capitalized, and the second, a lower case word for its species. Occasionally, a third word, also lower case, is added to indicate subspecies, which can also be called race, ethnic group, breed, variety or cultivar. (Humans are divided into races and ethnic groups, dogs into breeds, fruits and vegetables into varieties – or cultivars for boutique products.) Linnaeus categorized dogs as Canis familiaris and wolves as Canis lupus,meaning that he considered them two separate species. Today, most scientists categorize domesticated dogs as Canis lupus familiaris, which means that Canis lupus refers to a single species that includes both wolves and dogs, and familiaris is added for any domesticated dog breed.

An interesting comparison can be made with the dingo, a non-domesticated Australian dog. I checked Wikipedia regarding the dingo’s classification, and found the following: “The dingo, Canis familiaris, Canis familiaris dingo, Canis dingo, or Canis lupus dingo, is an ancient lineage of dog found in Australia. Its taxonomic classification is debated, as indicated by the variety of scientific names presently applied in different publications. It is variously considered a form of domestic dog not warranting recognition as a subspecies (Canis familiaris), a subspecies of either dog or wolf (Canis familiaris dingo or Canis lupus dingo), or a full species in its own right (Canis dingo).” I note that Wikipedia assumes that wolves and dogs are considered separate species.

The contemporary scientific world no longer defines a species by its ability to breed together and not to breed with a different species. As contemporary science has reinvented itself in the modern world, including its widespread misconceptions of spontaneous evolution of species and its unproved hypotheses regarding the origin of species, it can no longer use the definitions of breeds as its basis for defining species. This is because it accepts that species eventually mutate naturally into new species, which rejects or modifies the traditional definition of a species breeding within itself. As a result, science is forced to redefine “species” on the basis of similarity of DNA, but this piece of information has as yet not been communicated to the dictionary editors.


I have just demonstrated where, halachically, something can be considered two different species, notwithstanding that they breed together. I will now pick an example in which halacha considers two varieties to be the same species, notwithstanding that modern science categorizes them as separate species. The Gemara teaches that the one-humped Arabian camel, the dromedary, and the two-humped Bactrian camel (“Persian camel,” in Chazal’s lexicon) are, without question, one species. (By the way, “Bactria” was an area of ancient Persia; thus, Chazal’s method of distinguishing between the two varieties of camel is identical to modern nomenclature.) The Gemara states, rhetorically: “do you consider them different species, simply because one variety has a longer neck?” (Bava Kama 55a). Obviously, minor differences in physical characteristics are insufficient reason to treat two varieties as halachically different species.

Modern science counts three surviving species of camel, and, based on fossil remains, five extinct species. (How can one tell whether two extinct individuals could breed together or not?) The three existent species are Camelus dromedarius, the one-humped Arabian camel; Camelus bactrianus, the two-humped, domesticated variety; and Camelus ferus, the only remaining variety of wild camel, which lives today in desert areas of northwestern China and southwestern Mongolia. Formally, scientists will tell you that Camelus ferus is considered a separate species on the basis of genetic studies. Informally, they may admit that it is categorized as a separate species in order to facilitate research grants. Research money is more readily available to study “species” that are critically endangered than critically endangered “subspecies.”

Spelt wheat

Thus far, I have demonstrated that, in the animal world, halacha’s category “min,” and modern science’s nomenclature “species” do not necessarily coincide. Now, I will show that this is equally true in the plant world. Modern science does not consider wheat to be a species, but to be a genus, a group of related species, Triticum. Linnaeus categorized wheat into five different species, including spring wheat, winter wheat, Einkorn, and spelt as separate species. However, halacha recognizes spelt as one species and the other varieties as different forms of the species, wheat (Kil’ayim 1:1, see Rash and Rambam). Thus, it is permitted to plant different wheats together, or alongside one another, even in Eretz Yisrael, whereas one may not plant wheat and spelt together or alongside one another, without following the rules established for kil’ayim of two different species.


Science treats the various citrus fruits as species of the same genus. Thus, esrogim are Citrus medica; grapefruits, Citrus paradise; lemons, Citrus limonia;and tangerines are a varietyof Citrus nobilis called Citrus nobilis deliciosa. Yet, based on his extensive analysis of halachic sources, the Chazon Ish (Kil’ayim 3:7) considers lemons, esrogim, grapefruits and oranges to be the same species as regards the laws of kil’ayim, which would permit grafting a grapefruit tree onto a lemon stock. (However, in a different place, the Chazon Ish is hesitant about this decision and rules against relying on it [Hilchos Kil’ei Ilan 178:9]. His concern in the latter place is the difference in appearance of the various fruits. He also rules that chushchash, a variety of wild orange, and the oranges that we eat and juice are the same min for halachic purposes [Hilchos Kil’ei Ilan 178:11].) The Chazon Ish notes that his discussion is germane only to the prohibition regarding harkavas ilan, meaning that it is permitted to graft an esrog branch onto the stock of a different citrus for the objective of consuming the produce. However, an esrog grown this way will not be kosher to use as one of the four minim on Sukkos. (See Shu’t Rema #117; #126:2; Shu’t Maharam Alshich #110; Levush, Orach Chayim 649:4; Taz and Magen Avraham, Orach Chayim 649; Shu’t Bach #135 et al., all of whom agree that an esrog grafted onto a different species is not kosher for Sukkos use. The Shu’t Panim Me’iros, Volume II #173, and the Saba Kadisha,are among the small minority of authorities who permitted using an esrog grafted onto non-esrog stock for the four minim on Sukkos.) In other words, according to most authorities, an esrog grafted on lemon stock is not kosher for the mitzvah on Sukkos, notwithstanding that the grafter may not have violated any prohibition.


We can now discuss the third of our opening questions: “May I create a tangelo by crossbreeding a tangerine and a grapefruit?” Although the Chazon Ish did not discuss tangerines, it would seem that, according to his comments in Kil’ayim 3:7, this would be permitted, and that, according to his comments to Yoreh Deah, it would not.


At this point, we should examine the last of our opening questions: May I graft an apple branch onto a crabapple trunk?

The regular eating-apple is usually called Malus pumila. There are numerous varieties of crabapples, most of which are also included in the genus Malus and are called names such as Malus coronaria, Malus angustifolia and Malus ioensis. Many of these crabapples freely hybridize in the wild with apple cultivars. Thus, we see again that the dictionary definition of a species is no longer accepted by the scientific community.

What is the halacha of grafting apples onto crabapple stocks?

The Mishnah states that apples are kil’ayim with chazrad, some type of wild apple or other fruit bearing some resemblance to, or characteristics, of an apple. Some rishonim believe that chazrad is a variety of wild apple that produced a fruit that was used as feed, but was not considered suitable for human consumption, even after pickling or stewing. However, we do not really have any idea what species or variety chazrad is.

In early nineteenth-century eastern and central Europe, we suddenly find several major halachic authorities debating whether some variety of crabapple or wild apple could be used as the stock on which to graft edible apple trees. The crabapple fruits were usually not considered edible.

The Torah scholar who addressed this question to the author of Shu’t Mishkenos Yaakov considered grafting apples onto crabapple stocks a problem, quoting the Levushei Serad (Chiddushei Dinim #106, also quoted by Piskei Teshuvah, Yoreh Deah 295:2) that this graft is prohibited as harkavas ilan. The Mishkenos Yaakov (Shu’t Mishkenos Yaakov, Yoreh Deah #69) discusses some of the varieties of crabapple that were commonly used for grafting apples, and permits grafting an apple scion onto the stock of any of the crabapples available in his area. This conclusion is accepted by several other authorities (Beis Efrayim, quoted by the Mishkenos Yaakov; Shu’t Tzemach Tzedek, Yoreh Deah #221; Aruch Hashulchan, Yoreh Deah 295:15). Thus, again, the difference in scientific species identification has nothing to do with the halachicdefinition.


In all six types of kil’ayim mentioned above, the general criterion is to avoid the appearance of different species being intermingled. Concerning this, Rav Hirsch (Vayikra 19:19) writes, “The Great Lawgiver of the world separates the countless numbers of His creations in all their manifold diversity, and assigns to each one of them a separate purpose and a separate form for its purpose.”

In addition, the laws of kil’ayim help us bear in mind how various species obeyed Hashem’s instructions to remain separate during their creation. This reminds the contemplative Jew that if the plants heeded Hashem’s word during the Creation, how much more we are obligated to obey all His instructions.