The belief in reincarnation has been part of Jewish thought for at least 750 years, so that changing our perspective of the issue is quite a challenge. We will here attempt to do so in three ways: first, we will show that reincarnation does not adequately solve the problems it is thought to address; second, that genetics provides a better solution to each of those; and, third, that a careful reading of the texts in which Ramban (Ramban, thirteenth century Spanish Biblical commentator and Talmudist) is thought to refer to reincarnation actually read better if we see him as groping towards what we now call genetics.

Never one to turn away from a challenge, I will actually go one step further (perhaps a step too far, if earlier readers reactions are any guage). After showing that levirate marriage, incest prohibitions, and theodicy make most sense based on an awareness of genetics, both objectively and as a reading of crucial medieval Jewish texts, we will argue that speculating about genetics in ways that current biological knowledge rejects offers explanations of several otherwise opaque areas of Jewish tradition.

Ramban is one of the most famous Jewish thinkers, and probably the most authoritative halachist (at least before the sixteenth century1), thought to have believed in gilgul neshamot, reincarnation. Although he does not use the term explicitly, his references to esoteric secrets in the context of levirate marriage (yibum), incest, and his claims about the meaning of the book of Job (which raises the issue of theodicy), have all been taken to point to gilgul. To see why this identification is in error, let us turn to the sources in which Ramban is thought to have hinted at the topic.

The first of those sources is where Ramban speaks of sod ha’ibbur, in Bereshit, when Yehudah encourages Onan to marry Tamar, to “establish seed” for his brother, Er, who had died without children. Onan, the text tells us, knew “that the seed would not be his,” so he refused to impregnate Tamar2.

To explain the issue, Ramban first rejects Rashi’s view that Onan was only expected to name his first child after his deceased bother. In Ramban’s view, The matter is a great secret from the secrets of the Torah about the birthing of people, and is visible to the eyes of all lookers to whom God has given eyes to see and ears to hear . And the early sages before the Torah knew that there was a great benefit in levirate marriage of the brother, and he was worthy of having priority in it, and after him any relative, for all of his close relatives from his family who would inherit from him can provide utility.

We will need to come back to this rich text further, but for now we should note that Ramban does not speak directly of reincarnation, but simply calls the matter a secret in the birthing of people. Similarly, in another text usually seen as his referring to reincarnation, Ramban calls God’s final answer to Job’s complaints an esoteric secret, sod ha’ibbur, a term we cannot translate without prejudicing our discussion.

In both of these cases, as well as when the Torah codifies levirate marriage as law, Rabbenu Bahya, a student of Ramban’s, speaks more explicitly of reincarnation. From there—or perhaps because Ramban spoke more straightforwardly than he wrote, and his students passed on this belief on as a direct tradition—all later writers have assumed that Ramban believed in reincarnation.

Ramban’s phraseology itself, even without reasoning about the issue, already should raise questions about that claim. In Bereshit, Ramban is speaking of a pre-Torah custom to have brothers or other relatives (as per the book of Ruth) marry the wife of a man who died childless, Ramban relates the practice to the nature of conceiving and giving birth. Unless he thought all babies were reincarnated, there is no obvious connection between reincarnation and reproduction.

More troubling is Ramban’s claim that this “secret” was obvious to all to whom “God gave eyes to see and ears to hear.” Whatever one may think about reincarnation, there is nothing in the theory that claims that the resulting implantation of a soul is obvious to the naked eye.

Moving to his phraseology, the term sod ha’ibbur Hazal otherwise used that term to refer to the algorithms for how to decide when the new moon had arrived, when one lunar month had ended and another had begun. The connection between the waxing and waning of the moon and reincarnation is obscure, to say the least.

Ramban’s other use of that same term, though, makes it even more difficult to read it as referring to reincarnation. In explaining the prohibitions of incest3, Ramban first rejects Rambam’s view that the Torah was trying to limit sexuality in general, since, as he notes, the laws of incest do not prevent a man from marrying many wives and engaging excessively in such activity anyway. He then remarks
אבל כפי הסברא יש בענין סוד
מסודות היצירה דבק בנפש והוא מכלל סוד העבור שכבר רמזנו לו:

But according to logic, there is in this matter a secret from the secrets of creation attached to the soul, and it is of the general category of the sod ha’ibbur to which we have already referred.

Ramban is claiming, in other words, that something about the sod ha’ibbur explains the laws of incest as well. The connection between incest prohibitions and reincarnation is even more difficult to understand, especially if we do not assume that every baby born is simply the reincarnation of a preexisting soul-why prohibit all of these relationships simply because some children are reincarnations of previous lives?

I would also add, and this will be important to remember later, that Ramban mentions sod ha’ibbur after exhausting issues of reward and punishment as an explanation for people’s suffering. To the extent that one can believe that the punishment is anticipatory reward or punishment, clearing the way for a more monochromic afterlife, the problem has been solved as far as Ramban is concerned. Reincarnation only adds another possible slate to explain the need for that reward or punishment, but Ramban’s language suggests he was offering another type of explanation, not a further nuance of one he had already provided.

Turning to genetics, we can see that it solves each of the issues at hand, more logically and meaningfully than reincarnation. In the case of levirate marriage, the modern understanding of genetics explains how it could mitigate only the tragedy of the man’s having died without children in a way that would be obvious to careful observers, and how all relatives could perform this act, although brothers were preferable.

Thinking genetically, levirate marriage does not seek to continue the deceased’s life, it looks to provide the continuity of lineage that he was denied. What he could have had, had he lived, was a child with the woman who was his wife. Their genes would have mixed and produced a child.

This insight explains Rashi’s reading of the verse in Bereshit that discusses marriage in the context of Eve’s creation. The verse says:”על כן יעזב איש את אביו ואת אמו ודבק באשתו, והיו לבשר אחד, therefore shall a man leave his mother and father and cleave to his wife, and they shall become [as] one flesh4.” Rashi says that the baby they create is one flesh from both.

At the simplest level, Rashi is explaining why the text refers to their becoming one flesh, but that is an embarrassingly literal reading of the text. Intuitively, Ramban’s explanation, that the couple creates a bond that links them to each other such that they become as one, seems preferable. Rashi’s explanation, though, fits well with the genetic issues we have raised here. The Torah was telling us that the reason people will leave their original nuclear family and create a new one is that that new family provides them the opportunity to leave their legacy for the world, children who combine their genetic contributions.

When a man dies without having accomplished that goal, the Torah (and ancient custom) mandated a way to come as close as possible to producing that child. Having one of his brothers- the closest people, genetically, to the deceased- marry the widow means that their child will be as close as possible to a genetic match of the child the original couple would have produced5.

This explains what the Torah meant by Onan realizing that the seed would not be his. The child he would have conceived with Tamar would have been Er’s child, genetically. However the manipulations of the genes works, Onan realized that he would have been helping Tamar conceive a child by Er, and refused. His evil was that he wanted any children from the marriage to Tamar to be his; he was unwilling to participate in the conception and rearing of Er’s child.

Moving to the perceptibility of the phenomenon, we know that genes will out; were Onan (or any levir) to have a child with his brother’s widow, and the child came out as an exact product of the deceased brother and the wife, there would be numerous ways in which that would reveal itself.

Genetics also explains the connection between the secret of the new moon and levirate marriage. Sod ha’ibbur refers to understanding the process of how and when one moon disappears and yet leaves behind enough material to start the next one- a related one, but not the exact same. Tradition envisioned each moon as a “new” one, so that as the moon disappeared, it was exiting the universe and leaving behind its successor. So, too, genetics is the secret of how human beings produce successor people, who continue their legacy when they leave the earth.

Genetics also explains incest. Too closed a gene pool is unhealthy and leads to various tragic mutations and diseases, as we see in our own times with “Ashkenazic” diseases that arose even without violating laws of incest. To avoid that, sod ha’ibbur recognized the need to go outside of the immediate family circle for marriage and mating prospects6.

Turning to theodicy, a much more challenging question, contrasting two views of genetics will help show that one of them offers a way to grapple with the issue7. The old model, what Francis Crick, one of the discoverers of the double helix structure of DNA, called the Central Dogma of molecular biology, believed that genes mapped out the biology of a person almost completely, that there is a “linear causal chain from DNA to RNA, to proteins (enzymes) and biological traits8”.

In that original view, genetics has no relationship to theodicy at all, except perhaps to question the whole concept of reward and punishment. In a world in which genes program people completely, determinism has been given a scientific basis, not just a philosophical one. That question aside, if reproduction just unites genes from two people, we have no entry to issues of theodicy.

Fritjof Capra assembles literature that points out that that view has become increasingly untenable9. In line with other arguments he has made in his book, Capra supports an alternate view, which sees DNA as part of a network, the whole of which governs the process of DNA replication, of genetic stability, of allowing mutations when they are productive, and- most importantly for our purposes- of the steps between genes and behavior.

Capra points out that in higher animals much of DNA is “junk DNA,” DNA whose role in producing proteins is not yet understood10. He raises that point to note that we still do not understand the role of DNA itself fully, let alone the other factors that guide the process of DNA’s impact on the body. In addition, he quotes Evelyn Fox Keller as noting that “genes do not simply act: they must be activated11.” In Capra’s summary, The program for activating genes does not reside in the genome, but in the cell’s epigenetic network… [the structures]involved in regulating gene expression…include structural proteins, hormones, networks of enzymes, and many other complexes.. What emerges is the growing realization that the biological processes involving genes…are all regulated by the cellular network in which the genome is embedded. This network is highly nonlinear, containing multiple feedbackloops… so that patterns of genetic activity continually change in response to changing circumstances12.

In this view, a complex web of factors governs gene expression and function- which proteins the gene produces, when, in response to what stimuli, and the exact impact of those proteins on the body’s workings. A group of factors, including “multiple feedback loops” – meaning that events in the body alter the genes’ workings for the future—affects how the genes express themselves and, even more so, how the person ends up behaving.

By adding some Jewish sources to this discussion, we can offer what Colin Tudge calls an “arm-waving” idea about a connection between genetics and theodicy. An arm-waving explanation is “one that seems plausible but for which here is no evidence worthy of the name13.” Arm-waving theories, I firmly believe, are the foundation of understanding the interaction between the spiritual and physical universes, and it is just such a theory that can show how the sod ha’ibbur could help explain the sufferings of the righteous.

It is possible that the actions a person takes during his lifetime affect his essence, including either his genetic makeup or at least the “epigenetic network” that affects his own gene expression, and that those changes have an impact on the genetic legacy the person imprints in his or her offspring14.

In suggesting this, I do not mean anything so unnuanced as that physical events of one person’s life will be passed directly to his children; I, too, know that August Weismann already distinguished between somatic cells and gametes in the nineteenth century. It is only the latter type of cells that are involved in reproduction and most bodily happenings do not affect those cells15. Recognizing the feedback loops in epigenetic networks, however, does allow for the possibility that actions taken by the larger organism will subtly influence the environment even of a reproductive cell, which in turn can effect at least gene expression and, I think, reproduction16.

1 See, for example, Yitzchak Blau, “Body and Soul: Tehiyyat ha-Metim and Gilgulim in Medieval and Modern Philosophy” TUMJ 10 (2001), 7-8

2 Gen 38; 8-9.

3 Vayikra 18; 6.

4 Gen 2:24, with Rashi.

fn5 Colin Tudge, The Engineer in the Garden (New York: Hill and Wang, 1993), 111-113, reviews the genetic closeness of the various kinds of relatives. Brothers share about 50 percent of their genes. I suspect that this view of levirate marriage would see God as helping work out the gene pool so that the child would receive from his biological father those genes that were present in the deceased brother whose name he is supposed to be continuing. If the deceased had a recessive trait, for example, and the brother has one dominant and one recessive gene, I think the Torah would be understood to be saying that the recessive gene will be passed on to the first child. The child will, in that sense, actually be the child the deceased would have produced.

6 Tudge, ibid, 3, points out that many animals and even plants have evolved ways of avoiding incest. The exact choices of which relationships are significant in which situations- inheritance, incest, and invalidation as witnesses are all categories in which halachah discusses relatives, but the list for each is slightly different—is too speculative even for this very theoretical discussion. It seems likely, though, that there are different types of genetic closeness which can raise concerns or provide comfort in different kinds of situations.

7 The discussion of genetics does not pretend to be complete, and is largely based on Fritjof Capra,The Hidden Connections, (New York: Doubleday, 2002), 163-175. Capra bases himself largely on Evelyn Fox Keller, The Century of the Gene, (Cambridge: Harvard U. Press, 2000), James Shapiro, “Genome System Architecture and Natural Genetic Engineering in Evolution,” in Lynn Helena Caporale (ed.), Molecular Strategies in Biological Evolution, Annals of the New York Academy of Scienceis, vol. 870, 1999, and Richard Strohman, “The Coming Kuhnian Revolution in Biology,” Nature Biotechnology, vol. 15, March 1997.

8 Capra, 169.

9 See also Guido Pincheira, “Human Genome: Facts, Enigmas, and Complexities,” in Jacquelyn Ann K. Kegley, ed. Genetic Knowledge: Human Values and Responsibility (Lexington, Ky.: ICUS, 1998), 9-21, especially 9-13 where he repeatedly stresses the dynamic interaction with environmental factors that affect the gene, a sentiment echoed by Kegley in her introduction to the volume, and by Richard Strohman, “The Nature of Polygenic Diseases: Toward a Holistic Theory of Biology,” 23-35 in the same volume.

10 Capra, 171. Tudge, 77, notes that junk DNA may affect gene expression, as might the topography of a gene within the cell.

11 Ibid., 172.

12 Ibid., 173.

13 Tudge, 87.

14 I recognize that I am making two claims here, first that actions affect genes or the epigenetic network, and second that those affects impact not only on the somatic cells, but on the gametes that shape the nature of one’s offspring.

15 See Tudge, 8. On page 25, however, he notes that mutations that happen within the sex cells themselves will indeed be passed on to offspring; my suggestion is that acts of spiritual significance affect the gametes as well as the somatic cells.

16 Physical actions may affect regular cells, some of which may pass to the somatic cells. We tend to think, for example, that the children of overeaters are more likely to overeat because of pre-existing genetic tendencies mixed with environmental factors. As a thought experiment, I am wondering whether children who receive an overeating gene from their parent will differ depending on how the parent handled that tendency in their own life prior to having the child. The children of an overeater who struggled to control that tendency might inherit a subtly different gene than the children of an overeater who yielded to that predilection.