Summary: The currency of evolution is fitness. Whatever traits and behaviors (and random luck) led to an organism leaving more copies of its genes than average in the next generation, meant it was contextually ‘fitter’ than its conspecifics 22 . However, this ‘fitness’ is not a conscious or even instinctive goal. Organisms don’t parade around trying to be biologically fitter than others, but instead just repeat the behaviors which worked for their ancestors, indirectly leading to reproduction. A male spider is sometimes consumed by the female after they have sex 23 . This obviously is a bummer for the male spider, but it can be explained by evolution if the nutrition provided for the offspring (carrying his genes) outweighs the sum of his lost future mating opportunities (because he’s dead). Thus, t he spider, when presented with a 'hot female spider' doesn’t calculate the odds of being eaten vs. how many nutrients are in his body but performs a behavior that was successfully passed down through his ancestor’s genes. Those genes are not looking out for the individual spider but lead him straight into a lethal embrace because they ‘feel good’. At the opposite end of the spectrum, elephant matriarchs are genetically long-lived because they protect not only their own children, but their grandchildren and great-grandchildren, who pass along those long- lived genes (euphemistically known as the “grandmother effect”) 24 . To the unthinking genes, the bodies are disposable. It’s about which gene sequences are more efficient at replicating. The fact they produce bodies which do complex things is, as far as evolutionary fitness is concerned, only relevant to that replication. TaaL: “Fitness” is something which is only determined retroactively. When a hundred baby sea turtles break through the sand where their eggs were laid and race for the ocean, their fitness relative to one another is an open question, indeterminate. Which one’s movements preferentially attract the attention of the different predators which happen to be on the scene? Which one’s coloration will t end to give it an edge over offshore predators? Which ones will be more attracted to eating colorful (fatal) plastic pollution rather than jellyfish? Which will tend to dive versus remaining immobile when a shark swims below them, and which species of shark will that be? Which is more resistant to cancer-causing chemicals it will encounter via its foraging decisions? The one baby turtle in a thousand which ultimately survives to reproduce will have been tested by millions of unique threats and opportunities and be fitter only in that context. Evolution mostly produces lottery winners, not excellence.
Moreover, what’s “fit” today will likely not be what’s “fit” tomorrow. Even herbivore bunny rabbits and baby ducklings have enormous vicious hunting
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