Parashat Vayetzei

As a biology teacher at the high school, I rarely find instances to connect the weekly parashah to something I teach. This week, Parshat Vayetzei, however, is a delightful exception – one we even talk about in my ninth-grade honors biology class. 

As our patriarch Jacob’s story continues to unfold, we learn about how he runs to his uncle Lavan’s house and begins to work for him in exchange for the right to marry his daughter Rachel. In the narrative, we learn that after seven years of work, Jacob ends up being deceived and is tricked into marrying Leah. Jacob then works an additional seven years and is finally allowed to marry Rachel. Following this, Jacob is in fact ready to leave his uncle’s household, but Lavan convinces him to stay for several more years. Jacob and Lavan strike a deal, and agree that Jacob will continue to shepherd the “regular” sheep and goats in Lavan’s flock, and any “irregular” sheep and goats (spotted, speckled, or striped) that are born from this flock will be Jacob’s wages for the future. 

This is where some interesting biology comes into play. I hope you recall from Mendelian genetics (if not, you should join my class for that unit!), that each trait we have is the result of two copies of a gene. The “regular” trait, also known as the dominant trait, will always show up (phenotype) as long as one of the two genes is the dominant gene – meaning either a homozygous dominant (two dominant genes) or heterozygous dominant (one dominant gene, one recessive gene) individual. Likewise, in order for an “irregular” or recessive trait to be displayed, both copies of the gene must be recessive (homozygous recessive). 

This is where the genius of the situation comes into play. Lavan takes all of the irregular sheep and goats, aka spotted, speckled, and striped, and leaves Jacob with only the dominant, solid-colored sheep and goats. In doing so, Lavan eliminates many of the recessive genes that could be used to produce offspring that would belong to Jacob. Jacob, however, having spent 14 years around this livestock, is well aware of which ones have previously given birth to recessive children. In doing so, he is aware of which ones are the heterozygous dominant sheep and goats that could theoretically yield the recessive offspring. 

The Torah then relates (Genesis 30:37) that Jacob placed a variety of materials into the water of the livestock, which induced them to go into heat and mate. Many of the resulting babies were homozygous recessive, i.e., spotted, speckled, and striped, and thus Jacob was able to accrue a huge amount of wealth. 

When we learn this story as children, we often attribute what happened to the Godly and miraculous, and when we learn about this explanation in my class, my students often ask me if this detracts from the miracle. If there is a logical explanation to the situation, shouldn’t this remove some of the majesty that the Torah seems to be proclaiming? I explain to my students that it is still, in fact, miraculous, but perhaps not in the way we might have otherwise thought. The modern genetics movement is attributed to Gregor Mendel, often called the father of modern genetics. Mendel was a 19th-century monk who experimented with pea plants and meticulously recorded data and observations, the hallmark of the scientific method, which led him to learn about the genetics ratio we learn in biology classrooms today. Jacob, however, lived thousands of years before this. The fact that he could understand these deep and, at the time, hidden concepts points to the miracle that God allowed him to glean this knowledge. I truly love this story as it points to the concept from Pirkei Avot, Ethics of our Fathers (5:21) “בֶּן בַּג בַּג אוֹמֵר: הֲפָךְ בָּהּ וַהֲפָךְ בָּהּ, דְּכֹֽלָּא בָהּ” “Ben Bag Bag would say: Delve and delve into it, for all is in it.” The Torah is truly filled with all the knowledge in the world; we just need to delve into it to understand it all. 

Shabbat Shalom.