Darwin Meets Jacob

Rabb Moshe Ben-Chaim

Reader: The Gemara says that Rabbi Yochanan would hang out by a mikveh so the women would see his handsome features, and somehow through their hopeful conception that night, the women would transmit his facial features to their fetuses. I don’t buy into this rationale. It has no real place in science. How do we explain this rationally?

Rabbi: Studies show the following:

Effects of Environment on Phenotype (an organism’s altered appearance resulting from genotype interaction with environment): Genes play an important part in influencing phenotype, but genes are not the only influence. Environmental conditions, such as temperature and availability of nutrients can affect phenotypes. For example, temperature affects coat color in Siamese cats. Height in humans is a complex phenotype influenced by many genes, but it is also influenced by nutrition. A person who eats a diet poor in nutrients will not grow as tall as they would have had they eaten a more nutritious diet.

Another source states this:

Transgenerational plasticity (TGP) is a change in offspring phenotype that is cued by an environmental signal in the parental generation (and possibly the previous ancestors) without involving genetic change in offspring. It can occur through environmental influence on maternal (or more generally, parental) effects, whereby the phenotype of an offspring depends on the phenotype of its parents, regardless of their genotype.   (Read more from at this page: )

This validates genetic adaptation: evolution. Jacob peeled branches creating striped patterns and placed them in the watering troughs of his flock. He engaged cunning to protect his interests, as Lavan deceived him. Daas Zikanim coments:

If you were to ask how a righteous person such as Jacob could play such a trick, the answer this that according to the agreement between him and Lavan, Jacob had told his father-in-law to remove all the sheep of his that had speckled and spotted skin patterns, etc., meaning the young animals, so that he could not be accused later on as these having been stolen by him. This did not include mature animals with those skin patters. Lavan [altered the agreement and] removed all such animals—regardless of their age—making it almost impossible for animals that had never shown such skin patterns to bear young ones that did. Jacob was therefore perfectly fair in looking after his own interests, seeing Lavan had made it almost impossible for him to own flocks of his own without resorting to ingenuity; as a matter of fact he did so, with the help of advice from an angel in a dream, as we read in 31,10. In addition, the sage Rabbi Chaim added that careful reading of the text will show that Lavan changed unilaterally the terms of their contract, which had referred only to animals with the skin pattern known as nikudim, whereas he now had added those with skin patterns known as akudim. This is why Jacob on his part saw free to do what he did, fulfilling what is written “With the pure You act in purity, And with the perverse You are wily” (Samuel II 22:27).

Jacob followed the Torah principle if acting with others as they act. He placed the peeled sticks in the watering troughs so the flock would see these patterns and transmit the patterns to their offspring’s phenotype. Thereby, Jacob produced flock that he would own according to his terms with Lavan. 

It’s notable that no sage questioned the efficacy of this method of genetic alteration. Perhaps, Jacob—having studied with Noah’s son Shem for 14 years—learned about the various animal species on the Ark, including their unique natures. We know that certain species like the chameleon and octopus can mimic their surroundings, proving that vision affects bodily characteristics. Shem was with all the animals for a year on the Ark and he could have transferred that knowledge to Jacob. (Questioning Daas Zikanim, Torah does not openly say the angels taught Jacob about adaptation, camouflage or evolution.) 

Rabbi Yochanan apparently possessed this information. Obviously he valued mothers having beautiful children, as he felt this would generate in the mother a greater affection for the child, which is the role of the mother. The child in turn would be raised with a healthier psyche due to the stronger emotional bond with its mother.

Both Jacob and Rabbi Yochanan expressed the view that immediately prior to conception, visual stimuli can affect a phenotype.

We now see how genetic alteration through environment taught in Torah complies with science. God created the natural world and Torah. They must comply with each other.