Are there limits to what evolution can produce?
October 25th 2009 08:53
Evolution has produced some exquisite examples of biological machinery, from bat echolocation to the human brain. But are there things that cannot ever evolve? And why?
To answer this question, we first need to understand a couple of things. The first is that natural selection is about preserving what works, not what is in principle the best "design" for something. We can envisage more efficient designs than those found in nature, but given that evolution is a population phenomenon that compares how well contemporaries do against one another, it will favour those designs that happen to work best, even if they are shoddy solutions (relative to a universal optima that we can imagine) to a problem. Secondly (and related to this first point), is that what gets selected has to be built upon what's already there. This means that selection will result in things that are ad hoc and convoluted. As Richard Dawkins has said about the laryngeal nerve (a nerve that exists in the pharynx or throat region of vertebrates), it is easy to imagine a more efficient, less resource-wasting design that has the nerve pass straight through the pharynx rather than under it and back up again, but the cost in embryological upheaval of such a change would likely be prohibitive because of the negative effects on other morphological arrangements as a side-consequence. The intermediates would never be selected for, and hence the less efficient, sub-optimal version is what gets preserved. Of course, it needn't have been so if organisms had been designed afresh by a deity or some other intelligent agent. What we actually see, though, are solutions to life's problems that clearly show the imprint left behind by history, because the solutions are often a patchwork of prior solutions that are "stuck" at local rather than universal (effectively imaginary) optima. Organisms carry, as Charles Darwin said of human beings (the most exalted of all organisms), the indelible stamp of their origins
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To answer this question, we first need to understand a couple of things. The first is that natural selection is about preserving what works, not what is in principle the best "design" for something. We can envisage more efficient designs than those found in nature, but given that evolution is a population phenomenon that compares how well contemporaries do against one another, it will favour those designs that happen to work best, even if they are shoddy solutions (relative to a universal optima that we can imagine) to a problem. Secondly (and related to this first point), is that what gets selected has to be built upon what's already there. This means that selection will result in things that are ad hoc and convoluted. As Richard Dawkins has said about the laryngeal nerve (a nerve that exists in the pharynx or throat region of vertebrates), it is easy to imagine a more efficient, less resource-wasting design that has the nerve pass straight through the pharynx rather than under it and back up again, but the cost in embryological upheaval of such a change would likely be prohibitive because of the negative effects on other morphological arrangements as a side-consequence. The intermediates would never be selected for, and hence the less efficient, sub-optimal version is what gets preserved. Of course, it needn't have been so if organisms had been designed afresh by a deity or some other intelligent agent. What we actually see, though, are solutions to life's problems that clearly show the imprint left behind by history, because the solutions are often a patchwork of prior solutions that are "stuck" at local rather than universal (effectively imaginary) optima. Organisms carry, as Charles Darwin said of human beings (the most exalted of all organisms), the indelible stamp of their origins
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