Is the Human Brain a Product of Sexual Selection?
Geoffrey Miller's arguments regarding sexual selection as a key driver in the evolution of the human brain pose an intriguing question. While many animals have thrived with relatively small brains in their ancestral environments, humans have developed a disproportionately large and complex brain. This raises the possibility that sexual selection may have played a significant role in its evolution.
Understanding Sexual Selection in Nature
Sexual selection is a type of natural selection where traits are favored not because they improve survival, but because they enhance attracting a mate. This can lead to the rapid emergence of unique and seemingly 'freakish' traits.
Many animals display traits that can be seen as sexual selection in action. Cats, for instance, use their agility and stealth to catch prey, often showcasing their physical prowess. Dogs, known for their teamwork, use these cooperative behaviors to attract mates. Apes, skilled tool users, display intelligence which can be sexually selected.
The Expensive Brain and Sexual Selection
Brains, like muscles, require a significant amount of energy to sustain. Unlike muscles, which can rest and recover, brains must continuously consume energy. This raises the question of how sexual selection could justify the high cost of brain growth and maintenance in the absence of advanced tools or language.
Miller argues that the brain's development may have been "bank-rolled" by the power of sexual selection. Once developed, the brain could eventually adapt to fulfill practical advantages, leading to further evolution through natural selection. The ability to speak, complex problem-solving, and the sharing of communal knowledge could all have provided practical benefits, justifying the initial investment.
The Role of Art in Sexual Selection
Art has often been seen as a form of sexual selection, most famously in the case of the peacock's tail. However, the human appreciation of art and the instinctive sense of awe when watching a great performer can be seen as a more nuanced manifestation of this principle.
Just as a peacock's tail displays fitness and vigor, human art can serve as a form of "cognitive selection". The display of wit, dance, and visual composition can act as an audition for cognitive abilities. These performances may not serve a direct survival function, but they can attract mates, providing an evolutionary advantage.
The Limits of Cognitive Evolution in Other Species
Other species, such as cats, have evolved to efficiently meet the cognitive demands of their environment. However, the incremental increase in intelligence required to become a doctor, for example, would likely be useless and unselective. In contrast, art and the evolution of the human brain can be driven by a continuous drive towards "just-a-bit-more" cognitive complexity.
In this way, the human brain, once driven by sexual selection, slowly began to develop practical advantages. Before doctors became effective, they were often witch-doctors—highly charismatic, attractive individuals whose intelligence and creativity could be seen as a form of sexual fitness.
Conclusion
While the case for sexual selection as the initial driver of human brain evolution looks strong, it is likely that natural selection pressures became more prominent as the smarter individuals could effectively compete and reproduce. This process accelerated over time, leading to the complex and capable human brain we see today.
This theory, while not the only one, offers a compelling explanation for the rapid and seemingly inexplicable development of the human brain. Sexual selection, as Geoffrey Miller suggests, may have been the key to unlocking the potential of a cognitively demanding brain in early humans.