F Rosa Rubicondior: Creationism in Crisis - How A Complex Organ Evolved Naturally

Wednesday 10 April 2024

Creationism in Crisis - How A Complex Organ Evolved Naturally

Spotted dolphins, Stenella frontalis
Toothed whale echolocation organs evolved from jaw muscles | Hokkaido University

There is nothing a creationist fraud likes more than an organ or process that can be presented as 'irreducibly complex' because it will only work if all components are present and in the right place. They can sell this to their dupes as an example of something they claim couldn't have evolved gradually because it only works when all components are assembled, with no functional intermediate stages, so it must have been 'intelligently designed' - by the locally-popular god, obviously.

Creationist guru Michael J Behe, used the example of the E. coli flagellum for that purpose, confident that his target dupes would not be aware that almost all the components of the proton motor were present in the Type III secretory system and only needed a few minor changes to function as a hugely advantageous organ of motility. The process of exaptation of redundant structures is quite sufficient to explain how 'irreducibly complex' structures can evolve.

What are the current theories of how the Escherichia coli flagella evolved? The evolution of Escherichia coli flagella is a subject of ongoing research and debate among biologists. While there isn't a single universally accepted theory, there are several hypotheses and models proposed to explain the evolution of bacterial flagella, including:
  1. Co-option Hypothesis: This hypothesis suggests that the flagellum evolved from pre-existing structures that were repurposed for motility. Some researchers propose that the flagellum shares ancestry with the Type III secretion system (T3SS), a needle-like structure used by bacteria to inject toxins or other proteins into host cells. According to this hypothesis, mutations and selective pressures led to the transformation of T3SS components into flagellar components.
  2. Selective Advantage Hypothesis: This hypothesis proposes that the early ancestors of bacteria acquired flagella as a means of enhancing their ability to move towards favorable environments or away from harmful ones. The ability to move towards nutrient-rich areas or away from toxic substances would have provided a significant selective advantage, leading to the evolution and refinement of flagellar structures over time.
  3. Genomic Evidence: Comparative genomics studies have provided insights into the evolution of flagella by examining the genetic sequences of various bacterial species. By analyzing similarities and differences in flagellar genes across different organisms, researchers can infer evolutionary relationships and trace the origins of flagellar components.
  4. Modular Evolution: Some researchers propose that the flagellum evolved through a process of modular evolution, where individual components or substructures of the flagellum evolved independently before being integrated into a functional motility apparatus. This model suggests that the flagellum may have originated from the sequential addition and modification of simpler structures, such as proto-flagella or pili.
  5. Evolutionary Intermediates: Studying the flagella of diverse bacterial species can provide insights into the evolutionary intermediates that may have existed during the transition from non-motile to motile forms. By identifying and characterizing these intermediates, researchers can gain a better understanding of the stepwise process by which flagella evolved.
Overall, while there is still much to learn about the precise evolutionary history of E. coli flagella, ongoing research efforts continue to refine our understanding of how these remarkable structures originated and diversified over time.
Just such an example of exaptation of redundant structures has just been revealed by researchers working Hokkaido University, Japan, who have shown that the complex echolocation system used by the toothed whales such as dolphins and orcas evolved out of the muscles and jaw bones that had previously been used to chew food but were redundant due to evolutionary changes which meant the whales swallowed their food whole.

The team have published their findings in the journal Gene. It is explained in a Hokkaido University news release: Toothed whale echolocation organs evolved from jaw muscles

Genetic analysis finds evidence suggesting that acoustic fat bodies in the heads of toothed whales were once the muscles and bone marrow of the jaw.

Toothed whale echolocation organs evolved from jaw muscles

Genetic analysis finds evidence suggesting that acoustic fat bodies in the heads of toothed whales were once the muscles and bone marrow of the jaw.

Illustration of the body plan of a toothed whale, with a cross section of the head showing the melon (dark yellow) and the extramandibular fat bodies (light yellow) which are key organs for using sound such as echolocation.

Hayate Takeuchi, Takashi Fritz Matsuishi, Takashi Hayakawa. Gene. January 20, 2024
Dolphins and whales use sound to communicate, navigate and hunt. New research suggests that the collections of fatty tissue that enable toothed whales to do so may have evolved from their skull muscles and bone marrow.

Scientists at Hokkaido University determined DNA sequences of genes which were expressed in acoustic fat bodies—collections of fat around the head that toothed whales use for echolocation. They measured gene expression in the harbor porpoise (Phocoena phocoena) and Pacific white-sided dolphin (Lagenorhynchus obliquidens). Their findings were published in the journal Gene.

The evolution of acoustic fat bodies in the head—the melon in the whale forehead, extramandibular fat bodies (EMFB) alongside the jawbone, and intramandibular fat bodies (IMFB) within the jawbone—was essential for sound use such as echolocation. However, little is known about the genetic origins of those fatty tissues.

Toothed whales have undergone significant degenerations and adaptations to their aquatic lifestyle.

Hayate Takeuchi, first author
Division of Biosphere Science
Graduate School of Environmental Science
Hokkaido University, Sapporo, Hokkaido, Japan.
One adaptation was the partial loss of their sense of smell and taste, along with the gain of echolocation to enable them to navigate in the underwater environment.

The researchers found that genes which are normally associated with muscle function and development were active in the melon and EMFBs. There was also evidence of an evolutionary connection between the extramandibular fat and the masseter muscle, which in humans connects the lower jawbone to the cheekbones and is a key muscle involved in chewing.
The extramandibular fat bodies (EMFB) near the ear have a very high expression of the protein MYH16, a specialized protein typically found in the masseter muscle—indicating an evolutionary relationship between them.
Hayate Takeuchi, Takashi Fritz Matsuishi, Takashi Hayakawa. Gene. January 20, 2024

This study has revealed that the evolutionary tradeoff of masticatory muscles for the EMFB—between auditory and feeding ecology—was crucial in the aquatic adaptation of toothed whales. It was part of the evolutionary shift away from chewing to simply swallowing food, which meant the chewing muscles were no longer needed.

Assistant Professor Takashi Hayakawa, corresponding author
Section of Environmental Biology
Faculty of Environmental Earth Science
Hokkaido University, Sapporo, Hokkaido, Japan.
Analysis of gene expression in the intramandibular fat detected activity of genes related to immune functions, such as the activation of some elements of the immune response and regulation of T cell formation.
More technical detail is given in the team's paper in Gene:
  • Transcriptome analysis was conducted on the acoustic fat bodies of a harbor porpoise and a Pacific white-sided dolphin.
  • A close evolutionary relationship was identified between acoustic fat bodies and muscles.
  • The extramandibular fat body and melon may originate from intramuscular adipose tissue.
  • The extramandibular fat body exhibits a special homologous relationship with masticatory muscles based on the specific expression of MYH16.
  • A tradeoff evolution between acoustic fat bodies and facial muscles was highlighted in the context of aquatic adaptation in toothed whales.

Toothed whales have developed specialized echolocation abilities that are crucial for underwater activities. Acoustic fat bodies, including the melon, extramandibular fat body, and intramandibular fat body, are vital for echolocation. This study explores the transcriptome of acoustic fat bodies in toothed whales, revealing some insight into their evolutionary origins and ecological significance. Comparative transcriptome analysis of acoustic fat bodies and related tissues in a harbor porpoise and a Pacific white-sided dolphin reveals that acoustic fat bodies possess characteristics of both muscle and adipose tissue, occupying an intermediate position. The melon and extramandibular fat body exhibit specific muscle-related functions, implying an evolutionary connection between acoustic fat bodies and muscle tissue. Furthermore, we suggested that the melon and extramandibular fat body originate from intramuscular adipose tissue, a component of white adipose tissue. The extramandibular fat body has been identified as an evolutionary homolog of the masseter muscle, supported by the specific expression of MYH16, a pivotal protein in masticatory muscles. The intramandibular fat body, located within the mandibular foramen, shows possibilities of the presence of several immune-related functions, likely due to its proximity to bone marrow. Furthermore, this study sheds light on leucine modification in the catabolic pathway, which leads to the accumulation of isovaleric acid in acoustic fat bodies. Swallowing without chewing, a major toothed whale feeding ecology adaptation, makes the masticatory muscle redundant and leads to the formation of the extramandibular fat body. We propose that the intramuscular fat enlargement in facial muscles, which influences acoustic fat body development, is potentially related to the substantial reorganization of head morphology in toothed whales during aquatic adaptation.

Absolutely no sign there that the researchers might be about to abandon the TOE and adopt creationism with its' magic and unevidenced supernatural entity making chemistry and physics do things they couldn't do on their own.

And another example of how redundant structure can be exapted for a novel function by the slow, stepwise process of evolution by natural selection, to result in the superficial appearance of design and 'irreducible complexity'.

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