One of the most famous debates that exists in genetics is the question of nature versus nurture. Are individual differences a result of a person’s innate makeup, or are differences due to one’s personal experiences?
Nevertheless, genetics is a lot more complicated than a simple separation between nature and nurture. To start, nature and nurture are so intertwined that there is often no clear line between the two. Additionally, Bob Weinhold, who has written about environmental health issues since 1996 as a member of the Society of Environmental Journalists, writes in the journal Epigenetics: The Science of Change from the Environmental Health Perspectives that a science referred to as epigenetics has recently been gaining notice and credibility. He continues that it has been linked to many phenomena, including, but not limited to, cancers, cognitive dysfunction, as well as respiratory, cardiovascular, reproductive, and autoimmune diseases [1].
Epigenetics involves changes in gene activity that get passed down to the next generation of offspring without the altering of genetic code. Such modifications are controlled by epigenetic tags located just outside the genome that turn on and off the expression of particular genes. These tags can be passed on to the next generation.
Not only has the fresh focus on epigenetics transformed the conventional discourse regarding nature and nurture, but the recent revival of epigenetic research legitimizes the thought seen throughout ancient Biblical text; external stimuli can determine physical characteristics of subsequent generations.
In ancient secular and Jewish societies, it was believed that characteristics obtained during one’s lifetime were passed on to his or her offspring. This is contrary to the common notion in modern science, which states that heredity is not affected by characteristics obtained from the environment itself [2]. In fact, there are quite a few cases throughout the Talmud that suggest that “what you see is what you beget” [3]. In Brachot (20a), the story is told that Rabbi Yochanan would sit outside bathing houses, women would gaze at his beauty after immersing, and as a result they would have beautiful children. The Talmud continues discussing this idea and states that after immersing in the bath house, a woman should be careful about what she looks at on her way home, so as not to affect her offspring when she conceives [2]. Similarly, in Avodah Zara (24b), the Talmud explains that in order to produce a red heifer, an Israelite placed a red cup in front of two cows as they mated, causing the heifer to be born red. Furthermore, in a story found in Bereshit Rabbah (73:10), a black man and a black woman gave birth to a white child. The black man went to Rabbi Yehuda HaNassi to question whether or not the child was his own. Rabbi Yehuda HaNassi asked the man if he had any white mirrors in his household, to which the man answered in the affirmative. Rabbi Yehuda HaNassi consequently attributed the pale color of the child’s skin to the white mirrors in the couple’s home. Likewise, Gittin (58a) describes Roman behavior during intercourse before and after the destruction of the Temple. Before the destruction of the Temple, the Roman noblemen wore rings with beautiful human figures during intercourse, and after the destruction of the Temple they forced attractive Jewish slaves to stand in the room while the Roman noblemen had intercourse.
Perhaps most prominent of the “what you see is what you beget” stories in ancient literature is the narrative of how Jacob received his wealth from his father-in-law, Laban. After Jacob married Leah and Rachel, he worked for Laban so that he could leave his father-in-law’s house with a livelihood. During this time, Jacob made a deal with Laban which stated that Jacob would be able to keep all the spotted sheep that were born to the flock of sheep that he was herding. To spoil this deal, Laban gave Jacob a herd of only white sheep to watch over. However, Jacob figured out a way to ensure the success of his deal. Jacob took rods from trees and peeled back their bark, revealing a streaked pattern, and placed them in the water-troughs of the sheep. As a result, “the flocks conceived at the sight of the rods, and the flocks brought forth streaked, speckled, and spotted [sheep]” (Genesis 30:39).
This partiality in texts towards the idea that heredity can be affected by a parent’s experiences was validated by Lamarckian inheritance, a theory published by Jean-Baptiste Lamarck, a plant biologist, in 1809 his book, Philosophie Zoologique. Lamarckism is described as an organism’s ability to pass characteristics that were acquired during its lifetime to its offspring, through a change in physiology due to experiences or behavior. For example, according to Lamarck, when a giraffe stretches its neck to reach leaves high up in a tree, its neck muscles are strengthened and its neck becomes slightly longer. Therefore, the offspring of this giraffe will have somewhat longer necks. However, according to the Darwinian theory of evolution, which combined with Mendelian genetics has become the accepted view of modern genetics today, a genetic mutation would engender a giraffe to have a slightly longer neck than the giraffe’s contemporaries. Because the giraffe with the longer neck has the ability to reach higher leaves on trees, an advantage for obtaining food, this trait would ensure the survival of the giraffe with the mutation, and thereby, the mutated gene will be passed
DERECH HATEVAH 53
by Rachel Siegel
