# The Role of Sexual Selection in Human Intelligence Evolution
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Chapter 1: Understanding Human Uniqueness
The quest to understand how humanity has reached its current state is fascinating. What sets us apart so dramatically from other species? How did we become, relatively speaking, so extraordinarily intelligent?
Our evolution has equipped us with the ability to engage with complex subjects, even while multitasking in our daily lives.
Charles Darwin's theory of Natural Selection is so deeply embedded in our cultural consciousness—perhaps less so in the U.S. than in Germany—that it often feels unquestionable. However, as with many intricate scientific theories, the truth can be more nuanced than it first appears. Darwin introduced the idea of Sexual Selection, yet, as Geoffrey Miller notes in The Mating Mind, this concept was largely neglected in favor of the more straightforward Natural Selection.
Natural Selection, in essence, is about "survival of the fittest." If you are stronger, you are more likely to survive and reproduce, thus passing on your traits.
The strong endure while the weak perish. An organism's primary goal in evolution is to survive long enough to reproduce. Once reproduction occurs, the organism becomes less relevant and eventually dies.
The criteria for survival aren't always straightforward. Biologists like Richard Dawkins have shifted the focus from mere organism survival to gene survival in his influential book The Selfish Gene. This perspective sheds light on altruistic behaviors and other seemingly puzzling traits.
This viewpoint resonates with me as it highlights the fundamental building blocks of life, offering a more "pure" and mathematical lens.
Similarly, Erwin Schrödinger, in What is Life, described genes (and the yet-to-be-discovered DNA) as an aperiodic crystal that transmits structure and information through generations, forming the most basic unit of a self-replicating entity. While Schrödinger made some missteps, John von Neumann proposed an even more sophisticated theory, predicting the necessary structure of DNA before its function was fully understood.
Yet, while genes replicate, how are they chosen? It’s not immediately obvious how to evolve a complex organism like a dinosaur or monkey around genes that ensure their survival. Certain environments have favored specific traits over vast periods, leading to adaptations like the scales of fish or the keen eyesight of predators.
The environment shapes what traits enhance an organism’s fitness, and genes that confer advantageous characteristics for survival are selected. Those with superior eyesight or communication skills may have a survival advantage, leading to the enhancement of these traits under environmental pressure. If a species reaches an equilibrium with its environment, stagnation can be acceptable. This is evident in species like alligators, which have remained relatively unchanged for millions of years.
However, when environments shift, new survival challenges arise, prompting species to adapt, sometimes drastically. As African rainforests receded into savannahs, our primate ancestors were forced to adapt from a tree-based lifestyle to one on the ground, requiring significant changes in their social structures and survival strategies.
But did they truly need to evolve to our level of intelligence to survive? Perhaps various pressures contributed to this development. Consider a scenario where genes lead to traits that don’t necessarily enhance survival but are highly attractive to potential mates. Classic examples include the peacock's extravagant tail and the antlers of a stag.
These traits may seem useless and can even hinder survival. However, they persist because they signal to potential partners that the individual possesses the health and resources to support such traits.
This concept is especially relevant for humans, as it may help explain the evolution of our unique intellect. The rapid increase in brain size among our ancestors is a source of intrigue for scientists, raising questions about its adaptive value.
Despite the absence of immediate benefits from larger brains, the energy demands and complexities of nurturing offspring until maturity (which can take until age 25 for humans) present significant evolutionary costs.
One could argue that the need for larger brains arose when our ancestors faced new challenges in social hunting and cooperation. While there are valid reasons for increased brain size, it’s also possible that it wasn't strictly necessary for survival.
Reproductive success often hinges on minimizing genetic mutations, emphasizing the importance of sexual reproduction, which typically involves two partners sharing genetic material. A sophisticated mind could serve as an indicator of good genes, akin to a luxurious smartphone.
The more complex an organism, the more crucial it is to ensure that everything functions correctly. Thus, the mind may act as a fitness indicator, similar to a peacock's tail.
We admire those who excel in seemingly frivolous pursuits, such as sports, music, or art—activities that highlight specific cognitive and physical skills.
Moreover, sexual selection means the competition within a group shapes the standards individuals must meet. As William von Hippel notes in The Social Leap, one wouldn’t want to boost their IQ if everyone else’s IQ increased even more.
If intelligence becomes a desirable trait, the pressure to select for smarter individuals grows, leading to further evolution in intelligence across generations. Perhaps intelligence exists not just for practical survival but because it is inherently attractive.
In extreme cases, this can lead to a Runaway process, where a trait perceived as desirable spreads through a population. If the trait is not overly costly or confers unexpected benefits, it may endure.
This Runaway process is akin to chaos theory: shared ancestry may lead to vastly different outcomes due to small variations. The trajectory of human intelligence could hinge on random mutations that made intelligence appealing.
While Runaway processes alone cannot explain the evolution of human intellect, adaptive advantages certainly played a role. It’s reasonable to assert that sexual selection has influenced our development, suggesting that intelligence might indeed be the new allure.