It seems plausible that people had some ideas about how progeny resembled parents in prehistoric times, but those ideas were oversimplified and often quite wrong. Aristotle thought that fathers were solely responsible for the children's ancestry, for example.
At one point, the royal families of Europe, and the Hapsburgs in particular, thought that blood determined heredity, and in order to maintain the purity of their royal blood, only married other royals of their own family. Because all of us harbor some deleterious recessive genes, this kind of strict endogamy is a good recipe for concentrating them, and over the generations the Hapsburgs lost their health, their fertility, and their minds, in the process promoting the decline and ultimate collapse of the Spanish empire. The damage done by the sangria pura doctrine didn't stop there. It was also invoked by the inquisition to persecute Jews and Muslims, including those who converted.
Fast forward to the dawn of the twentieth century. Mendel had been rediscovered, and the idea of the gene had emerged. A man named Henry Goddard was trying to find better ways to treat what were then called the feeble minded, and became director of Vineland, a New Jersey home for them. He learned about Mendel's results and, travelling to Europe, learned of Binet's test for children's mental age. Despite his skepticism, and that of others, he brought the test back and administered it to his pupils. He found a close correlation between the mental ages and teacher's assessments, and was later able to test students in public schools, where he found most mental ages closely matched to chronological ages with a few students well behind and a few more well ahead.
He then tried to trace the genealogy of one of his students, and found a pattern of feeblemindedness, criminality and insanity. He wrote up his results in a book called The Kallikak Family (a pseudonym). His results created a sensation, and he was enlisted to test potential immigrants to the US (finding Italians, Jews, and Russians very deficient intellectually) and potential soldiers for World War I (finding a large fraction of the populace in the same boat).
The combination of rampant feeblemindedness and heredity created a sensation and a panic. Newspaper editors and politicians foresaw an impending apocalypse of stupidity*. Drastic solutions were needed to weed out the unfit, and sterilization laws were proposed and frequently adopted. Meanwhile, Thomas Hunt Morgan was studying fruit flies and getting a more balanced view of heredity. In particular, he noticed that most traits were governed by many genes and that environment played a crucial role in gene expression.
These results would eventually bring the whole edifice crumbling down. More careful researchers looked at Goddard's genealogy and found gross errors that refuted the story. The family was not all feebleminded, criminal, or insane, and was in many ways normal. But The Kallikak Family was not done. It found its way into the hands of an angry, imprisoned German named Adolf Hitler, and became a crucial blueprint for his plans for extermination of the unfit.
These two tales, one of how misguided interpretation of heredity manage produce a hereditarily feeble monarchy, and another one managed produce a reckless and ultimately catastrophic panic, probably have lessons for us even today, despite the fact that we now know what genes are and something about how they work.
*Lest we feel superior - Donald J Trump