Researchers from the University of St Andrews, working with colleagues from the University of Aberdeen and the University of Oxford, have identified a pattern of gene evolution that appears to have been crucial to the origin and subsequent diversification of vertebrates from their common ancestry with invertebrates. They have just published their findings in BMC Biology.
This discovery will be a major disappointment for creationists who cling to the notion that there is no evidence for what they call “macroevolution” — a term so ill-defined that it can be stretched to mean whatever a creationist happens to need at the time. Sometimes it is invoked to mean the origin of a new species, at other times a new genus, an entire new order, or even the biologically absurd idea of one species giving birth to an individual belonging to a completely different order. More often, though, “macroevolution” is said to mean the origin of entirely new anatomical structures.
Even that definition collapses immediately under scrutiny. Asked what novel structure humans possess that chimpanzees lack, “macroevolution” abruptly becomes the evolution of anything creationists choose to label a “kind” — another conveniently nebulous term, defined precisely nowhere and flexibly everywhere.
Yet if the origin and diversification of vertebrates does not qualify as “macroevolution”, it is difficult to imagine what possibly could. The St Andrews–led team has shown that this transition was enabled by gene evolution — that is, mutation acted upon by natural selection — affecting the genetic control of cell signalling during embryonic development. These changes influence when and where new cell types arise as a developing embryo progresses from a single-celled zygote to a complex multicellular organism, complete with differentiated tissues and specialised organs.
As this gene regulatory system evolved, it allowed the vertebrate phylum to diversify into the many classes and orders that now dominate marine and terrestrial ecosystems. No doubt this will require yet another round of misrepresentation by creationists, along with further blurring of the already elastic definitions of “macroevolution” and “kinds”.
Background^ Gene Regulation and the Origin of Vertebrates. One of the most important drivers of evolutionary change is not the invention of entirely new genes, but changes in how existing genes are regulated — when they are switched on or off, in which cells, and at what stage of development.The work of the team, led by Nuria P. Torres-Aguila — then at the University of St Andrews and now at the Universitat de Barcelona — is summarised in a University of St Andrews press release.
In animals, these regulatory changes act through cell signalling pathways that guide embryonic development. As a fertilised egg divides, chemical signals between cells control processes such as cell differentiation, tissue formation, and the spatial organisation of organs. Small genetic changes affecting these signalling networks can therefore have large downstream effects on anatomy and body plan.
The study led by researchers at the University of St Andrews shows that a key regulatory gene involved in cell-to-cell communication evolved in early vertebrates in a way not seen in their invertebrate relatives. This altered how developmental signals were interpreted during embryogenesis, enabling the emergence of new cell types and greater organisational complexity.
Crucially, this is not a speculative mechanism or a hypothetical “just-so” story. The genetic changes are identifiable, their effects on development are measurable, and their evolutionary history can be traced through comparative genomics across vertebrates and invertebrates.
Far from being an obstacle to evolution, developmental gene regulation explains how relatively modest genetic changes can produce major evolutionary transitions — including the origin and diversification of the vertebrates themselves.
New discovery sheds light on evolutionary crossroads of vertebrates
New research from the University of St Andrews has discovered a crucial piece in the puzzle of how all animals with a spine – including all mammals, fish, reptiles and amphibians – evolved.
In a paper published today (2nd February) in BMC Biology, researchers found an intriguing pattern of gene evolution which appears to be significant for the evolutionary origin and diversification of vertebrates.
Xenopus Tadpole.Credit: Marika Salonna
All animals have major signalling pathways that their cells use to communicate with each other, which control things like how their embryos and organs develop. The signalling pathways are fundamental to animal development and are major targets in disease-causing mutations and for the development of pharmaceuticals.
Proteins at the base of these signalling pathways are crucial as they control the final output from them, like a traffic system, directing cells into specific responses and gene expression.
Researchers created new gene sequencing data in sea squirts, a lamprey and a type of frog. They found the genes that make these signalling output proteins have evolved in a distinctive way. The sea squirt is an invertebrate that helped to distinguish the change when moving from invertebrates to vertebrates. Lampreys are an early branch in the vertebrate group, which pinpoints that this change happened at the invertebrate-to-vertebrate transition.
Lamprey.Credit: Sebastian Shimeld
Researchers used long-molecule DNA sequencing, which allowed them to distinguish the different transcripts from each gene. Long-molecule sequencing had never been done on the genes expressed in these particular animals before. Therefore, researchers were able to characterise the real range of the transcripts and proteins produced from these genes in vertebrate development for the first time ever.
Unlike the invertebrate sea squirt, the lamprey and frog made higher numbers of different forms of proteins from the individual signalling output genes, compared to all sorts of other types of genes.
This significant change with the evolution of vertebrates is very striking. Given the importance of these pathways in how animals decide what types of cells, tissues and organs to make, it is highly likely these proteins have had a major role in making vertebrates (animals with backbones) different and more complex than invertebrates.
Ciona sea squirt.Credit: Shunsuke Sogabe
Publication:
Once again, the real difficulty for creationists is not that the evidence for evolution is lacking, but that it is overwhelming, detailed, and increasingly mechanistic. The claim that “macroevolution” is impossible has always been little more than an article of faith, sustained only by vague terminology and constant goalpost-shifting. When evolution produces small changes, creationists dismiss it as “only microevolution”. When those small changes accumulate over deep time into major transitions — such as the origin of vertebrates — they simply redefine the terms so that the evidence no longer counts.
But nature is not obliged to respect creationist word games. The diversification of vertebrates from invertebrate ancestors is precisely the sort of large-scale evolutionary transition that “macroevolution” was invented to deny. And far from being mysterious, the processes involved are now being mapped in extraordinary genetic and developmental detail. Changes in gene regulation, embryonic signalling pathways, and the timing and location of cell differentiation provide exactly the kind of stepwise, testable mechanisms that creationism lacks entirely.
What this research demonstrates is that evolutionary theory is not merely a description of change, but an explanation of how complex biological novelty arises through ordinary genetic processes. Mutation, selection, and gene regulatory evolution are not barriers to large-scale change — they are the means by which it happens. Creationists may continue to insist that such transitions are impossible, but the genomes of living organisms, the developmental pathways that build them, and the fossil record of their history all tell the same story: vertebrate complexity is not the product of sudden invention, but of deep evolutionary time.
And as always, the more science uncovers about the mechanisms of life’s diversification, the smaller the remaining space becomes for creationist mythology — until “macroevolution” is revealed for what it has always been: not a scientific objection, but a rhetorical refuge from the evidence.
Creationists may keep insisting that “macroevolution” cannot happen, but vertebrate genomes — and the entire history of vertebrate life — continue to demonstrate that it already has. As always, creationism can only stagger on by insisting the evidence doesn't exist and relying on the ignorant gullibility of their target audience, confident that they will never risk checking - and wouldn't understand it if they did.
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