Back to David's theory of evolution: stasis,Darwin's problem (Evolution)

by David Turell @, Wednesday, August 19, 2020, 15:56 (341 days ago) @ dhw

Punctuated equilibrium was a theoretical answer that doesn't work:

After Chixculub:

"When things did settle back down, the pace of evolution would return to a virtual standstill. That’s the pattern we observe in the fossil record: disruption, change and then long periods of stasis. However, it took many years for scientists to accept this pattern. It contradicted the Darwinian paradigm, where evolution should occur through slow and gradual changes. Under the Darwinian view, the diversity of life can be explained by simply adding up many, many small inherited changes over a long period of time. Such gradualism was believed to be a necessary part of adaptation by natural selection – the process by which some variants of traits are lost each generation, because their bearers leave no offspring.

"But this persistent focus on natural selection as the sole mechanism of adaptive evolution has always been a sticking point. It can’t properly explain how anything new arises. After all, natural selection is a process that eliminates unfit variants – it doesn’t create, but changes the prevalence of what’s already there. Instead, novelty must come from the purely random process of genetic mutation. The problem is that when new mutations appear, they’re usually not a good thing. They are more likely to disrupt well-adapted systems than to improve them, especially if they have a big effect. The upshot is that the evolution of something new, such as eyes or feathers, requires a heck of a long waiting time. Not only is there a long wait for a beneficial mutation to come along, but then there’s the long process of accumulating enough of them to build up, step by step, a complex new structure. (my bolds)


"The pervasiveness of this pattern means that modern-day evolutionary biologists now have two enigmas to explain. First, what prevents species from changing for the majority of their existence? And second, when they do change, how does it happen so fast?

"The most frequently invoked mechanism to explain the first of these patterns is known as stabilising selection – a form of natural selection that keeps traits from changing by eliminating extreme variants. It’s the Goldilocks of selection, retaining variants that are ‘just right’. Not too fast and not too slow, not too large and not too small. But stabilising selection makes sense only if species inhabit an environment that isn’t changing. This puts it at odds with the ubiquity of large-scale environmental change throughout Earth’s history, in the form of climate cycles, sea level changes and alterations to the geomagnetic field. Besides, often we do see microevolutionary changes – the small-scale changes that occur within species – across much shorter timespans. This suggests that stabilising selection is not ever-present.

"Over the past several decades, evolutionary biologists have documented countless examples of rapid evolutionary changes in a wide variety of traits. These are heritable changes that occur over just a few years or decades, in everything from algae to moths to salmon. We also know that artificial selection in the lab produces even faster changes. In fact, one of the most consistent patterns is that rates of evolution over short periods of time are much higher than those over long periods of time.


"Evolutionary biologists have documented countless examples of rapid evolutionary change in the past few decades. Most of these are in species that are experiencing some sort of extreme environmental disturbance, such as invaders that have been released into a novel habitat or plants that rapidly adapt to the toxic soil of mine tailings. All of these examples show us that substantial evolutionary change can happen rapidly. They suggest that natural selection, rather than being a slow and gradual shaper of species, is most evident in brief bursts of change following major disruption. (my bold)


"...viewing evolution through a systems lens fundamentally changes how we view the story of life on Earth. It’s not a story of the constant struggle for existence. Rather, it’s a story that resides in the pauses – the uneventful interludes, where components of the systems maintain the status quo, and change necessarily comes with painful and extreme disruption.

Comment: Note my bolds. Environmental changes can drive rapid adaptation, but the species is still the same species. This Darwinist scientist cannot explain stasis in any terms that fit Darwin's original gradual theory. And she defines natural selection to be what it is, passive. The major portion of her essay is trying to excuse these dilemmas. She never does it, but if you wish to review her thinking go to it. Design is the only theory that fits.

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