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Saturday 16 October 2021

I.D as heuristic?

 

Studies on Stickleback Fish Further Validate Engineering Models for Adaptation

Brian Miller

In my previous article, I described how studies of cichlid variation confirm the predictions of the engineering models for adaption (herehere). This article will describe how the models are further validated by research on stickleback fish diversity. Like cichlids, stickleback populations demonstrate constrained variation, natural genetic engineering (NGE), and phenotypic plasticity. 

Constrained Variation 

All studies of stickleback diversity demonstrate that variation is tightly constrained, and the sticklebacks’ underlying design plan or blueprint always remains intact. Hohenlohe et al. in a 2010 study documented how the same variation in traits and genetics appears repeatedly in separate populations:

Genomic regions exhibiting signatures of both balancing and divergent selection were remarkably consistent across multiple, independently derived populations, indicating that replicate parallel phenotypic evolution in stickleback may be occurring through extensive, parallel genetic evolution at a genome-wide scale.

Miller et al. in a 2019 study came to the same conclusion after analyzing the genetic differences between populations that inhabited lakes in the presence and absence of prickly sculpin, a fish that is a stickleback predator. Sticklebacks that interacted with prickly sculpin rapidly acquired similar alterations to hundreds of the same genes. 

Parallel differentiation of genomes between stickleback from the different lake types involved ~1.8% of the genome, overlapping 587 genes with a wide diversity of biological functions. Widespread adaptation is implicated because genetic drift is unlikely to cause repeated, parallel evolution in multiple evolving populations in association with a specific environmental feature. These extensive changes underscore the rapid and profound effects of a seemingly simple biotic interaction on stickleback evolution.

Natural Genetic Engineering

The two studies demonstrate that sticklebacks adapt genetically to environmental changes predictably and rapidly. These observations suggest that NGE might be driving targeted genetic alterations. 

Other research has identified NGE more explicitly. Ishikawa et al. in a 2019 study discovered that multiple stickleback species duplicated the Fads2 enzyme allowing the species to better synthesize the essential fatty acid DHA. This enhanced ability allowed them to colonize DHA-deficient freshwater environments. The authors suggest that the duplications were facilitated by NGE, possibly the relocation of transposable elements. 

Future research will almost certainly uncover additional examples of variation resulting not from random mutations but from targeted genetic rewriting.

Phenotypic Plasticity

Other investigators identified examples of phenotypic plasticity. McCairns and Bernatchez in a 2010 study discovered that sticklebacks inhabiting freshwater and saltwater zones of a large estuary measure the salinity of the water. They use this information to optimally regulate the expression of genes controlling the transport of salt ions, so the fish can quickly adapt to salinity changes. 

Baker et al. in a 2015 study demonstrated that stickleback females track internal physiological information (e.g., lipid supply and liver glycogen level) and environmental cues such as availability of food and population density. Different cues initiate adjustments to such reproductive parameters as time of breeding, egg size, and clutch or brood size. The alterations improve the likelihood for the population’s continued survival. The researchers also discovered that individual fish coordinate the fine-tuning of multiple traits to ensure optimal reproductive success:

…traits are linked both genetically and functionally, and thus expressed plasticity in one trait would seem to require simultaneous plastic expression in at least one other trait, and perhaps more.

As a final example, Tibblin et al. in a 2020 study raised sticklebacks in an aquarium with different color backgrounds. The investigators also mimicked the presence of predators by chasing fish with a dip-net and introducing chemical cues mimicking the presence of Pike, which is a natural predator. Both color and predatorial stimuli triggered changes in the dorsal coloration that assisted the fish in avoiding detection. 

The Toppling of Evolutionary Icons

Cichlid and stickleback fish are two of the most iconic examples of adaption that biologists present as evidence for the plausibility of evolutionary processes driving large-scale transformations. Yet research over the past few decades supports the opposite conclusion. Evolutionary and adaptive processes are constrained in cichlids and sticklebacks, as in all complex organisms, to only minor alterations to existing traits or to the loss or duplication of an existing structure. Most adaptation results from engineered processes that leave little to chance. The belief in the limitless creative capacity of evolutionary processes now rests on little more than blind faith in the philosophy of scientific materialism.  

A theory in crisis?

 

Is Darwinism a Theory in Crisis?

Evolution News DiscoveryCSC

A new ID the Future episode spotlights The Comprehensive Guide to Science and Faith, and specifically, an essay in the new anthology by biologist Jonathan Wells, “Is Darwinism a Theory in Crisis?” As Wells and host Casey Luskin note, the essay title alludes to philosopher of science Thomas Kuhn’s influential 1962 book The Structure of Scientific Revolutions. Kuhn argued there that if one studies the history of scientific revolutions, one finds that when the scientific evidence has begun to turn against a dominant scientific paradigm — when its days are numbered — its adherents do not simply concede defeat. Instead they use all their institutional power to suppress dissent and punish proponents of any competing paradigm.

This is the period of crisis, which can last for years and even decades. Wells contends that modern evolutionary theory is a current instance of a dominant paradigm in crisis. He briefly makes the case in this episode, and at greater length in his essay, which appears in the newly released anthology from Harvest House, edited by William Dembski, Casey Luskin, and Joseph Holden. Download the podcast or listen to it here.