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: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.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.
- 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.
- 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.
- 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.
- 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.
- 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.
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.
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.