Jun 08 2021
Evolutionary Compromises
Evolution if one of the most fascinating scientific phenomena because it is so complex and operates over such varying and long timescales. It’s a real challenge to wrap one’s head around. There is therefore a tendency to settle on overly simplistic evolutionary narratives. This is not a criticism, we all do this in an attempt to grapple with evolutionary thinking. The challenge is to recognize this fact, and be open to a deeper, more complex and nuanced understanding of evolutionary processes. It’s a great example of what should be a general intellectual posture – recognize the limits of our current understanding (wherever that may be on the spectrum) and not only be open to, but seek out new information and concepts to keep incrementally pushing our understanding forward.
In that spirit, here is a study on the evolution of broad-horned flour-beetles that illustrates some of evolution’s complexity. The male broad-horned has exaggeratedly large mandibles, which is uses to compete with other males for mating access to females. This is an example of sexual selection, when a feature specifically increases mating success but is not necessarily broadly adaptable. The go-to example of this is the peacock’s tail feathers – a garish display meant to attract females, but an evolutionary burden in many other aspects. This sets up an evolutionary tug-of-war, where a feature may be advantageous in one respect but disadvantageous in another. Evolutionary processes are fairly efficient at balancing such conflicting forces.
As an aside, the balances tend to be only metastable. They can alter with changes in the environment or behavior. Even different individuals within a species can adopt different survival strategies that result in a different balance of traits. If a population within a species does this it may even eventually lead to a speciation event. For example, it has been documented that within some primate species dominant males will have access to females due to their alpha status, while others gain access by currying favor with the alpha, and still others gain access by gaining favor with the females and sneaking behind the alpha’s back. Still others may act as a “wing man” to a close kin, promoting their genes into the next generation by proxy. The lesson here is – no one strategy captures the wide diversity of behavior even within a single species.