Thursday, 11 June 2015

Spider Venom Toxic To Creationism

Tegenaria agrestis
Weaponization of a Hormone: Convergent Recruitment of Hyperglycemic Hormone into the Venom of Arthropod Predators: Structure

These examples of unintelligent design just keep piling up in the science literature. No wonder trying to get a creationist to read a proper, peer-reviewed science paper is like trying to get an acute arachnophobe to pick up a spider.

This paper, for example, if the Intelligent Design hoax was taken seriously by proper biologists who actually work in the field of biology and value their academic reputation, could only be seen as an example of this designer designing something to do the same job, even starting from the same point but doing it differently with one result not as good as the other.

I've pointed out before how reinventing the same thing to do the same job is evidence of inept, amnesiac, poorly planned design, not of intelligent design. Would you employ a designer who constantly forgets what he did yesterday and starts afresh? Me neither.

This paper, published in the journal Structure, shows that two distantly related arthropods, a spider and a centipede, which share a common ancestor, both evolved a component of their venom from the same precursor - a molecule similar to insulin and probably serving the same original function of regulating sugar levels as it does in other creatures.

  • ITP/CHH hormones were convergently recruited into the venom of spiders and centipedes
  • Venom ITP/CHH peptides were weaponized via key structural adaptations to form toxins
  • ITP/CHH-derived toxins are defined by a helical fold that is unique for venom proteins
  • We report the first three-dimensional structure of any centipede protein

Arthropod venoms consist primarily of peptide toxins that are injected into their prey with devastating consequences. Venom proteins are thought to be recruited from endogenous body proteins and mutated to yield neofunctionalized toxins with remarkable affinity for specific subtypes of ion channels and receptors. However, the evolutionary history of venom peptides remains poorly understood. Here we show that a neuropeptide hormone has been convergently recruited into the venom of spiders and centipedes and evolved into a highly stable toxin through divergent modification of the ancestral gene. High-resolution structures of representative hormone-derived toxins revealed they possess a unique structure and disulfide framework and that the key structural adaptation in weaponization of the ancestral hormone was loss of a C-terminal α helix, an adaptation that occurred independently in spiders and centipedes. Our results raise a new paradigm for toxin evolution and highlight the value of structural information in providing insight into protein evolution.

© 2015 Elsevier Ltd. Published by Elsevier Inc.

Scolopendra spinipriva
So starting from the same point, but proceeding by different routes, this supposed 'intelligent' designer has arrived at two similar but different solutions for the same problem, one of which is better than the other. I wonder how it decided which species had drawn the short straw.

But to be serious, this is a lovely example of evolutionary convergence. Regardless of the starting point, the evolutionary history of Tegenaria agrestis and the Scolopendra genus of centipedes has proceeded independently of one another, so there is no reason to suppose the evolution of this similar venom would be by the same route.

Quite simply, there is no intelligence involved and no way for information from one species to be passed across to another. This is, of course, where evolution differs entirely from as design process, especially a design process by a single, omniscient designer.

The observable evidence is entire consistent with evolution and entirely inconsistent with intelligent design. It's not even consistent with stupid design.

In fact, the evolution of venom in spiders, centipedes, snakes, etc, is an example of unplanned evolution with venom ending up with lots of different versions of the same toxin as the venom has to work on a whole range of prey species, each of which will react differently and each of which will be under selection pressure to evolve resistance to the venom. So the venomous predator will be involved in several evolutionary arms races simultaneously.

This presents the venomous predator with a problem: if it modifies the toxin to compensate for prey X becoming resistant, the toxin might not work on prey Y, so the best solution is to leave the toxin as it is but to also make a new slightly modified version. And, having lots of different toxins also makes it more difficult for any prey species to develop resistance.

Very many of the toxins in a complex venom will be similar because the simplest way to extend the range is gene duplication followed by modification of one gene to produce a slightly different toxin. So, a complex venom will show a clear evolutionary relationship between the different toxins, reflecting these arms races which have inevitably led to greater complexity both in the venom and in the genome. For more on this see my blog on the evolution of venom in snakes.

But why would an intelligent designer design an ecosystem where predator and prey indulge in arms races and where the prey needs lots of slightly different toxins because its prey react differently and develops resistance differently in different species? It should be quite within the capabilities of an omnipotent, intelligent designer to come up with a single, simple toxin which kills all prey and there should be no genetic record of lots of gene duplication in order to keep ahead of the competition.

A point creationists fail to grasp is that the hallmark of good, intelligent, design, is simplicity and getting it right first time. Complexity and the need to constantly revise the design is evidence not of intelligence, but of unplanned, undirected, evolution. This is how we know that species evolved and were not designed.

Venom, properly understood, should be toxic to the creation industry and the Intelligent Design hoax. Yes, you can quite understand why creationists won't read science journals.

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