One has good reason to wonder how complex organisms like Apocrypta westwoodi (Fig Wasp) could arise from a gradual accumulation of random changes, especially since (a) random changes are generally disadvantageous and (b) many organisms have elaborate adaptions that are inextricably associated with parallel adaptions in other organisms.
We should first recognize that the complex systems that we observe in nature are typically more efficient than simple systems that we observe in nature as long as the native environment remains stable. Simple systems, however, are typically more adaptable to unstable environments. For example, opportunistic animals like brown rats (which are native to Asia) and house sparrows (which are native to the Middle East) are found worldwide near human settlements but only infrequently in areas relatively untouched by human settlement (except, of course, in their native environments). Highly specialized animals, on the other hand, typically face extinction when their habitats are disturbed. To take another example from nature, the diversity of plant species growing close to ancient settlements in Central American and South Asian jungles is noticeable lower than the diversity of plant species growing in the surrounding area even after the passage of hundreds of years. Even a small amount of change is generally disadvantageous for highly specialized species.
The same pattern is observable in spoken languages, the most elaborate of which are found among forest peoples of New Guinea, Central Africa, and Brazil. Modern English, by contrast, has a relatively simple and flexible grammatical structure but a vast vocabulary compared to Old English from which it derives. The difference between the two languages—and they are indeed different languages—is plainly illustrated by the opening lines of Beowulf: “Hwæt! Wé Gárdena in géardagum þéodcyninga þrym gefrúnon hú ðá æþelingas ellen fremedon!” How exactly did Modern English arise from such an unrecognizable ancestor? Modern English arose from Old English as the result of (a) millions of regional changes in pronunciation, only some of which became widespread, (b) the emergence of striking metaphors and turns of phrase whose gradual sublimation resulted in curious grammatical artifacts and occasionally inverted meanings, and (c) a simplified grammatical structure coupled with a complex vocabulary that naturally arose because the French nobles who ruled England had an outsized influence on how one should speak, and because English was not the native language of those who ruled England for hundreds of years after 1066.
We can infer (a) that extremely complex systems can develop aggressively from a relationship between a limited number of species if environmental conditions are relatively stable—the “arms race” scenario—but (b) that the playing field is reset by the emergence of generalist organisms if conditions suddenly change. We can also infer (c) that generalist organisms will begin to specialize over time and (d) that the cycle will begin all over again. Millions of intersecting cycles of varying timescale and complexity overlap and interact invisibly over the span of a human life, but things change noticeably over millennia. How exactly all this is happens has yet to be reliably worked out, but there’s an astonishing wealth of evidence that it does indeed occur.
