Guide to Darwins Theory of Common Descent

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It was clear that Charles Darwin, unlike most other people, was greatly unsettled by the sight of a peacock displaying a splendid and colorful tail.   Darwin was troubled by the peacock tail as he saw no obvious advantage to its selection.  In The Descent of Man, Darwin took on many such puzzles of natural selection.

Today it is widely recognized, however, that the evolution of a peacock’s tail does serve a purpose. It is the same purpose as a modern man promoting his advantages and wealth, extravagance with a red Alpha Romeo Spider, or in the case of Donald Trump, a serious classy toupee atop a self-aggrandizing braggadocio. The peacock’s tail is simply an advertisement: “Look at me: I am so healthy and strong, I can afford this extravagance and offer it to your offspring.” And for pea hens, anyway, this advertising works.  Eventually, Darwin himself went on to work this out.  Modern women, hopefully, will note extravagance of this sort is a sign of male insecurity, if not a tendency for the self-promoting male to be more exploitative than virtuous.

Today, in Biology and other sciences,  Darwin's theory of common descent is taken as fact.  Without the discovery that evolution through selection occurs over eons of time, science could not conduct the research allowed by acknowledgement of shared descent with other living organisms. Darwin's greatest insight is that this comes about through selection, both natural and artificial, and our common ancestry is quite complex at times, diverse and  very ancient.

The Descent of Man, published in 1871, details many insights about common descent through natural sexual selection.  It finds many overlapping attributes that most other animals share with the human animal.  Darwin felt that there were certainly more shared traits hinting at human kinship with animals than there were differences. He wrote that humankind shared a “multitude of points” with their non-human cousins.  He pointed out, for example, that embryonic stages of mammals and similarities of organ design and function are obviously related.  Also noted was the variation on a theme for all the great apes, monkeys and even dogs.

Still, the Descent of Man has raised issues about what later became known as Social Darwinism (not his term) and eugenics. These two concepts, influenced by Darwin’s cousin Francis Galton and Herbert Spencer, a contemporary, would lead to many nightmare scenarios of exploitative injustice of supposed “survival of the fittest.” This phrase, by the way, was coined by Spencer, not Darwin.

Simply put, many people felt that “natural” inferiority or superiority gave tacit justification for exploitation, although Darwin himself warned about the importance of using caution in making any such assumption.

However, as a product of the time he lived in, Darwin was racist about “civilized man’s” supposed superiority over what were then called savages. That said, he was also an avowed abolitionist.  Darwin saw nothing but tragedy in the curious institution of slavery. On the peoples he observed on his voyages, his early writings make clear that he believed them to be a more unfortunate and brutish version of the one race of men.  He did not believe, as some, that they were of another race. Darwin wrote about this monogenetic theory he favored over a more racist, and devaluing, theory of poly-genetics, which postulated that there is more than one race of humankind.

By contrast, today modern science looks to the wisdom of aboriginal peoples to discover better ways for society to return to a healthier relationship with the resources of the planet.  In Darwin’s day no one foresaw the crisis of climate change and starvation and disaster unleashed by unchecked industrialization.  Nor did they imagine civilization had much to learn from non-European peoples of the Earth.

From the time of The Descent of Man, civilization has witnessed both the greatest barbarity, such as genocide and class warfare, and also the highest of what Darwin called “the noblest part of our nature."   In this, Darwin referred to the human tendency to show compassion to those born “weaker” or with traits unfortunately at the time called “inferior.” One example might be the natural vulnerability to smallpox in whole populations of natives.

Another was the supposed “superiority”: of men over women.  In the twenty-first century, differences of sex and gender are no longer grounds for discrimination against whole classes or populations of people, although clearly society still struggles with such issues.

Altogether, the rich insights provided by The Descent of Man overwhelm the flaws of its time and culture.  That humanity could at last begin to accept total kinship to the whole creation was a great step forward by the cleverest of the apes. 

More about this author: Christyl Rivers

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