Science in the Torah

Genetics and the Bible - Rabbi Zamir Cohen

Is it possible that the two most revolutionary laws in genetics discovered in recent generations – Mendel’s Laws of Inheritance and the Law of Heterosis – appear in the Torah, given more than 3300 years ago?

Genetics and the Bible - Rabbi Zamir Cohen

~Jacob Confronts Laban the Aramean~~

The Torah teaches that Jacob shepherded the flocks of Laban the Aramean for seven years, in exchange for the hand of Rachel, Laban’s daughter, in marriage. At the end of this seven year period Jacob was given Leah instead. In order to marry Rachel, Jacob was forced to work an additional seven years. With the birth of Joseph, Jacob’s eleventh son, Jabob said to Laban: “Send me out so that I might go to my own land” (Genesis 30:25).

But Laban was adamant that Jacob should stay and continue to serve him. He knew that as long as Jacob remained in his camp, God would continue to bless him. Laban offered a new salary to Jacob, to convince him to stay. As a result they agreed that Jacob would take ownership of all of the “speckled and spotted” animals in the flock.

After reaching an agreement, Laban suddenly changed the terms and interpreted the new arrangement to mean that only the newly born flock, speckled and spotted, would be given to Jacob. In order to prevent disagreements about which flock was born at which time, he immediately separated out all the speckled and spotted sheeps and goats, and assigned them to his sons, telling them to travel three days journey in the opposite direction of Jacob. This ensured a clear and complete division between the two groups. It further garunteed the likelihood that all animals subsequently born to Jacob’s flocks would be of a single color, and not speckled and spotted. (A careful reader of the text will note that Laban constantly changes the conditions of his agreement, in order to cheat Jacob of his rightful due. Laban’s trickery is confirmed by the words of the angel to Jacob (Genesis 21:12) as well as in Jacob's pained statements to his wives (ibid. 21:41) during this period. See the classical commentaries on the Torah for more explication of these issues).

Amidst Laban’s abuses, Jacob has a spiritual vision (ibid. 31:10):

"And it came to pass at the time that the flock was fertile and I [Jacob] raised my eyes and saw in a dream that the rams which leaped upon the flock were streaked, speckled, and spotted."

This is the opposite of reality, since Jacob’s animals were not spotted: Laban had already removed such animals out of Jacob’s portion of the flock.

"And an angel of God said to me in the dream: 'Jacob!' And I said: 'Here I am!' And it said, 'Lift up your eyes and see the rams upon your flocks streaked, speckled, and spotted. For I [the angel] have seen all that Laban has done to you.’"

From the point of this dream onwards Jacob begins to understand the depths of his father-in-law’s deception, and decides to send the least fertile animals to mate with Laban’s flock.

"He sent the feeble animals to Laban [those animals least likely to be fertile] and the strongest [and most likely to be fertile] stayed with Jacob’s flock."

And the result?

"And the man’s [Jacob’s] wealth grew and grew and he had scores of livestock and male and female servants and camels and donkeys."

We must understand two puzzling things in this narrative:

1. Why did Jacob see in his prophetic vision the more fertile animals as being spotted, when all he had in his flock were solid colored animals?

2. Why was Jacob careful to remove the less fertile livestock from his flocks and give them to Laban? What difference did it make between the less and more fertile animals in terms of his goal – that the newborns would be spotted?

Truthfully, we cannot understand the deep reasons behind the actions of our forefathers. Their spiritual level far exceeded anything of which we can conceive. But it is possible to understand that the Torah hints here to fascinating laws of nature recently discovered by science, as we will explain in the section that follows.

It is important to note that before his prophetic dream, Jacob devised a simple and natural plan for getting what he deserved:

"And Jacob took rods of green poplar from the almond and plane tree and peeled white streaks in them and made the white within the rods appear. Then he set the rods he had peeled in front of the flocks in the gutters of the watering troughs when the flocks came to drink – that they should conceive when they drank. And the flocks conceived before the rods and brought forth streaked, speckled, and spotted cattle" (Genesis 30:37-39).

This passage suggests that something seen at the time of conception can influence the physical nature of the developing offspring. For this reason the sheep that saw the streaked rods at the time of conception eventually gave birth to streaked offspring.

~Recently Discovered Laws of Genetics~~

According to the famous Israeli botanist, Professor Yehuda Flicks it is possible to find in Jacob’s prophetic dream and subsequent deeds a reflection of two fundamental laws of genetics discovered in recent generations: Mendel’s Laws of Inheritance and the Law of Heterosis. (This is not to claim that Prof. Flicks' findings represent the absolute truth of Scripture. The Ohr HaHayyim, in his introduction to the Torah, states that is proper for a God-fearing person to think deeply and formulate new approaches to understanding the Torah  – which are aspects of the “seventy facets” of the Torah – as long as these explanations do not contradict any of the core teachings or principles the Torah and Judaism .)

The famous genetic researcher Gregor Johann Mendel (1822-1884) – born in Morovia, Czechoslavakia – was able to isolate pure genetic strains of both yellow and green pea plants. After hybridizing them, the first generation produced only yellow peas. The second generation produced 75% yellow peas and 25% green peas. The “offspring” of the green peas were always green, but only 25% of the offspring yellow peas (bred only amongst themselves) remained yellow in all subsequent generations. Whereas the other 75% produced seeds that were yellow and green at a ratio of 1:3.

He concluded from here that despite the inbreeding of the yellow peas, the characteristic of the green peas remained latent within them. Only, the yellow characteristic was dominant, and the green recessive.

In our days, these hereditary factors are known as genes. In the specific case of Mendel’s peas, yellow was the dominant gene and green the recessive one. Despite the fact that at first glance a plant appears yellow, its genetic composition is actually yellow-green. Even when they are inbred, these strains will continue to produce 75% yellow and 25% green. Only 25% of yellow peas are pure yellow, without any green genes at all. On the genetic level, the rest of the peas are a mix of green-yellow.

If we removed the pure yellow strain and the green strain (which are also pure, for if they bore a yellow gene, it would immediately dominate the green element, resulting in yellow peas), and continued to inbreed the mixed yellow strains, the peas would continue to divide themselves according to the previous ratio. In even a few generations, the ratio would rise to 50% green and 50% yellow – namely, a direct reflection of the generation of the “parents.”

The Law of Heterosis was discovered only recently. According to this law, heterozygotes manifest stronger fertility traits than monozygotes. In other words, entities with mixed genetic strains are more likely to be more fertile than single genetic strains. For example, if we had before us a flock of animals with a solid color and one group within the flock included a mixed gene pool of both solid and spotted animals, this mixed group would be more fertile than the dominant solid color group.

There are hints to both of these genetic laws in the angel’s words to Jacob as well as in Jacob’s actions after he stopped using the technique of the streaked rods.

We now return to look carefully at the angel’s statement in Jacob’s prophetic dream:

"And it said, ‘Lift up your eyes and see the rams upon your flocks streaked, speckled, and spotted.’"

The angel implies that Jacob must “raise his vision” to see the truth, that even though the animals appear to be of a single color, their "internal" colors (i.e., genetic compositions) are streaked, speckled, and spotted. As a result, these are the colors of the offspring they will reproduce. According to Mendel’s Law of Inheritance, if we were to isolate the solid color animals with dominant spotted genes and compel them to mate with each other only, the spotted genes would begin to take over the solid color genes. The result? Spotted offspring.

How, though, did Jacob know which animals had recessive or dominant genes?

Here we must apply the Law of Heterosis, according to which we would know that the animals who mated most productively were the ones with the dominant spotted genes, despite their appearance as solid color.

Jacob divided the animals in his flock accordingly:

"He sent the late bearing animals [the least fertile, which, according to the Law of Heterosis, are genetically a single color strain] to Laban. [Jacob was careful to send these quickly to Laban, so that they would not impregnate his own flocks and produce single-colored stock.] Whereas the quickest to conceive [and the most fertile, which we know contain the spotted genetic strain] stayed with Jacob’s flock [in order to produce spotted flocks, as per his agreement with Laban]."

This is how Jacob recooped the wages of many years of labor, which had been stolen by his father-in-law, Laban the Aramean.

Known as Mendel’s Laws of Inheritance and the Law of Heterosis, only thousands of years later did the world of science discover what the Torah demonstrated through the deeds of Jacob. 


Adapted from The Revolution by Rabbi Zamir Cohen
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