For by Him were all things created, that are in heaven, and that are in earth, visible and invisible,...For the invisible things of Him from the creation of the world are clearly seen, being understood by the things that are made, ...so that THEY ARE WITHOUT EXCUSE: Col 1:16 / Rom.1:20

Sunday, January 7, 2024

A “holey” fitness landscape

He that sitteth in the heavens shall laugh: the Lord shall have them in derision.
Psalm 2:4


"Sewall Wright concocted one of those metaphors in science that lingers long past its “best by” date. 
In 1932, he coined the term “the fitness landscape.” 
He envisioned a mythical land of peaks and valleys, with the peaks indicating higher fitness, and valleys populated by evolving organisms starting out on their journeys toward progressively higher fitness levels. 
Impelled by the struggle for existence, organisms would climb higher till reaching a peak. One difficulty with this picture appeared soon after the metaphor gained popularity: to get to a higher peak, an organism would have to climb down, lowering its fitness on the way to a neighboring peak. Some workarounds were concocted, but the evocative metaphor lent itself to 3-D graphs and formulas of positive selection, giving evolutionary biologists hopes of empirical rigor as they measured their research organism’s progress up the landscape.

Unwarranted assumptions are the bugaboo of clever models like this. One is the stability of the landscape. 
Q: Does the hypothetical landscape undulate over time, such that a peak at one epoch becomes a valley in another? 
After all, the dynamic environment is oblivious to the needs of organisms. 
Q: How quickly does a given habitat change? 
Q: How can evolutionists be sure that fitness for a savannah does not become a detriment if the population finds itself in a habitat undergoing desertification? 
For reasons like this, Mustonen and Lässig in 2009 dubbed it a fitness “seascape” instead of a landscape.

Another of Wright’s assumptions was that the fitness landscape follows Gaussian curves consisting of smooth lines without discontinuities. Even if some of those Gaussian curves rose steeply like a cliff, Darwin defenders like Richard Dawkins could get their organisms up to the summit of Mount Improbable by envisioning a gradual staircase from another direction, allowing natural selection to maintain Darwin’s narrative of the accumulation of small, incremental steps.

Q: But what if the Gaussian assumption is wrong? 
Q: What if, instead, the structure of the landscape is like a block of
Swiss cheese, flat and riddled with holes that a blind watchmaker cannot foresee? 
The probability of a “holey” fitness landscape 
becomes credible when considering dependent traits. These “quantitative traits” are made up of components that must cooperate to work. Without all of them emerging simultaneously, no organism can ascend to higher levels. 
With dependent traits in operation, such as in the case of powered flight, a mutation or defect in one can send the organism to immediate extinction — as if, as in the old board game, a trapdoor opened underneath it.

Sergey Gavrilets thought of this back in 1997 and raised it again in 2004. Now, worries about a “holey landscape” have been given new emphasis in a paper in PNAS — “Drift on holey landscapes as a dominant evolutionary process.

"Our understanding of selection has been strongly shaped by Sewall Wright’s conceptualization of an evolutionary landscape, with populations moving from areas of low fitness to areas of higher fitness. While the one- and two-trait landscapes Wright originally described have been criticized as unrealistic, including by Wright himself, the general metaphor has nonetheless guided much of evolutionary thought.....Holey landscapes are high-dimensional evolutionary landscapes that consist of trait combinations that are either of average fitness or that are inviable. This results in flat landscapes with holes at inviable or low fitness phenotypes."

Q: Can neo-Darwinism recover from the neglected view of holey landscapes
The authors do not offer any hope, other than to wish that better landscape models may be forthcoming. Even with that concession, they remain pessimistic.
"Our implementation of Wright’s metaphor represents only one of many possible evolutionary models. It is possible that unmodeled alternative landscapes may produce populations for which variation is distributed in a manner similar to holey landscapes and empirical estimates…. Importantly, and as mentioned previously, much of the exploration of evolution of quantitative traits has focused on simple landscapes like we have implemented here. Thus, it also is an open question what different models of selection “look” like when implemented for higher-dimensional phenotypes. For example, rugged landscapes of high dimensionality may give rise to holey landscapes as peaks average out and valleys are inviable…. Nonetheless, the close correspondence between empirical data and populations simulated as evolving on holey landscapes suggest that our understanding of quantitative trait evolution remains incomplete."

Q: Science is supposed to be about observable, quantitative data, isn’t it? 
---If observations do not fit Wright’s convenient metaphor, the metaphor must be revised or discarded. 
Intelligent design is consistent with flat optima and built-in mechanisms to detect and avoid holes (e.g., DNA error correction, immune systems, blood clotting). 
Once again, design with its emphasis on engineering specifications trumps Darwinism in the real world." 
EN&V/DavidCoppedge