Intelligent Design’s problem with the Cambrian explosion

Last night I made a grave error. I made the mistake of attempting to peruse the Intelligent Design movement’s main website, Evolution News and Views, to see what they have said about recent developments on the Cambrian explosion. I personally don’t think that researchers should give them much thought, but as I am currently just a blogger I will occasionally address them. It is my intention to get my hands on Stephen Meyer’s book Darwin’s Doubt and review it though that may be a long time coming, especially considering that they have made a follow-up to address critics. Until I have read their books, I don’t plan on getting into the details of their arguments. Right now, however, I am more concerned with their approach to the supposed debate.

Firstly, they sound desperate to appear original and as though scientists researching the Cambrian explosion are slowly coming round to their way of thinking. They often state things in a way which suggests that Meyer got there first, for example, Graham Budd was apparently recently “confirming Meyer’s denial” about Precambrian organisms, when the reality is that the interpretations Meyer favours were first offered by evolution-accepting palaeontologists. Cambrian and Ediacaran experts are constantly described as admitting to something which the ID crowd believes; their loaded language is meant to give the impression that they are way ahead of the experts.

The ID presentation of the Cambrian explosion appears to be that is that it was relatively short (10 million years appears to be a figure they will accept), that bilaterian phyla appeared very suddenly in the Cambrian, that there were no precursors found amongst Ediacaran organisms, and that there is no satisfactory evolutionary explanation for it. You will find all of these views, even the last one, preceding Meyer’s publications and from experts in relative fields. The problem for them here is that they are not trying to solve any problems – they already think that they have the answer, yet it really offers no explanation.

Secondly, they consistently complain that they are being ignored. Nobody name-drops Meyer, nobody cites his book, nobody addresses his main thesis. They even do this when discussing papers which focus on specific phenomena, as though every single paper relating to the Cambrian explosion must address their pet theory (I use that term loosely). They are like the guy in a bar who seems to want everyone to fight him (perhaps better left ignored). Scientists are quite happily dissecting every aspect of the Cambrian diversification, looking at the genetic changes involved, the divergence times, the environmental changes, taphonomic changes, identifying fossils and working out how they fit in, looking at the timings of the events and so on. The debate is ongoing, there are many, many voices clamouring to be heard, trying desperately to tie together an overwhelmingly large, yet incomplete, dataset which befuddles even the most astute mind. Teasing out cause and effect in deep time is difficult and frustrating, people come at it from different angles, new evidence and new ideas can cause major shifts in thought. Meyer and his crew are desperate to be the most heard voice, they want their issue addressed and until someone addresses it they will assume that they are being ignored (which is tantamount to admitting defeat, by the looks of it).

Their third issue is that their main focus isn’t actually at the heart of the Cambrian explosion, despite their best wishes. The diversification can be perceived in many ways, with current thought often favouring its interpretation as an ecological explosion. It has often been perceived as an explosion in disparate body plans, which is not exactly the wrong way to look at it, but can be seen as the result of the ecological driving forces. The ID proponents take this a step further; it isn’t simply about body plans – it’s about the new information behind those body plans. With their rapid appearance narrative of the Cambrian explosion, this perspective on the diversification seems like a major issue, a sudden, unprecedented influx of biological information. Understandably, when addressing some of the ecological forces at play we don’t necessarily need to address the genetic changes, but they can’t always accept that. The genetic changes are important, but it does seem to be the case that the genetic toolkit necessary was already largely in place well before the Cambrian explosion (sponges, for example, appear to have some functioning genes which are used in more complex organisms in the development of the nervous system). So some Precambrian organisms may have had the capacity for evolving some of the body plans we see in the Cambrian, but nothing to cause them to do so – having a football pitch, a ball and 22 people does not ensure that a football match will take place.

This pushes the issue back, which ID theorists would like to present as a retreat, as hiding from the problem. The reality is that when you are concentrating on the Cambrian explosion you look at the stage which has been set and then analyse the changes. The environment is part of the stage, the organisms which preceded the radiation are part of it too, and the genetic toolkit is part as well. This is not to say that no new genes were necessary for the Cambrian explosion, but that it is not a major issue. The evolution of regulatory networks and of new genes is a separate question, which I get the impression that they know as it allows them to paint this picture of retreating evolutionary biologists. They can keep pushing back and back because ultimately they know that the origin of information goes back to the origin of life and that is where they truly set up camp, not the Cambrian explosion.

In summation, one tactic of the ID proponents is to try to sound original, when the reality is that the majority of their views on the Cambrian explosion are taken from actual researchers who accept evolution. They also complain repeatedly that they are being ignored, often because their personal favoured views are not being addressed. Finally, their issue is not really with the Cambrian explosion, but with the origins of information at life’s beginnings. The Cambrian explosion isn’t what they think it is, but as long as they continue to present it their way they will always feel ignored and as though experts are conceding to them. They will just persist in offering only criticisms and complaints.

What’s in a title? – Eokinorhynchus the spiky, armoured worm

If this were a popular blog and not in its nascent stages I would run this as a competition. Titles for science news articles are tough to write and are not often the choice of the author of the article. They need to be attractive, yet risk being misleading click-bait, and they need to be informative which risks being dull. Here is a recent example that has me stumped and wondering what others might come up with.

The news in question is the discovery and description of Eokinorhynchus rarus, along with other unnamed kinorhynchs, providing the first evidence for phylum Kinorhyncha in the fossil record. It is from the Cambrian period and may prove crucial in understanding the evolution of related groups, not least its own. The scientific paper naturally went for the informative title: Armored kinorhynch-like scalidophoran animals from the early Cambrian.

Image credit: Dinghua Yang

Here are a few examples of science news sites and the headlines they went with. First, I Fucking Love Science:

Naturally I did click it when I saw it, but that’s because I am already interested in anything which lived “half a billion years ago”. Calling it a spiky, armoured worm is not helpful at all, especially given the attention span of many of their readers – they often think two different pieces of news are about the same thing, even when the articles clearly state otherwise (I dare you to read the comments). They have published a few articles about spiky, armoured worms from the Cambrian, from many different phyla, so whilst it might be attempting to sound interesting it will inevitably create confusion. livescience went with the following:

They have obviously gone for attention grabbing with no hint at the importance of the beast. Possibly my favourite comes from ZME Science:

Yep, you read that correctly. The great news about Eokinorhynchus is that it is “ridiculously” armoured (as armoured as it gets!). The article itself isn’t much better. The South China Morning Post went for the most optimistic and patriotic option:

It’s the most sensational of the lot and, though it does mention it in the headline, its focus is not the armour of old E. rarus. And finally, forgive me for this, but the Daily Mail seemed to really want to put emphasis on how old it is.

Half a BILLION indeed. I can mock the headlines offered by other sites, but I honestly don’t know what would be better. Emphasising its potential importance might not be appealing to the casual reader without risking exaggeration (or capital letters). Trying to sound exciting has focussed on the armour of E. rarus, which doesn’t have wide appeal (and may make some think they know it already). What’s the secret to a good headline for palaeo-news?

Ediacaran ecosystem engineers – the Savannah hypothesis and our Skynet-type origins

Image from Wikipedia.

Out on the savannah, it is easy to find certain resources as they tend to be concentrated in limited areas. Trees, termite mounds, changes in terrain, all contribute to this concentration of resources. It is this sort of environment which has been hypothesised as resulting in our own bipedality which enabled human ancestors to move efficiently between resource hotspots. In a recent review, Budd and Jensen have proposed a ‘savannah’ hypothesis as an explanation for the evolution of bilaterian animals and consequently the Cambrian explosion.

Bilaterian animals are widely thought to have driven the Cambrian explosion, particularly as they function as ecosystem engineers altering the environment around them. The burrowing activities of bilateral organisms altered ocean chemistry and the nature of the sediment, opening up more resources to be exploited and resulting in a cascade of diversification. But why did bilaterians evolve in the first place? Ecological causes for the Cambrian explosion tend to presuppose features they should be explaining, such as the ability to burrow or the presence of predation (both likely contributed enormously to the diversification, but were also caused by it). Environmental causes tend to suggest limiting factors such as a lack of oxygen, which may actually be mistaking cause for effect.

The savannah hypothesis suggests that the Ediacaran biota also functioned as ecosystem engineers, causing carbon hotspots in the sediment and water around the organisms which were exploited by bilaterian animals which went on to diversify, eventually displacing their Ediacaran providers. Dissolved organic carbon in Ediacaran seas would not likely have clumped together, instead being spread out through the water column – not an economical resource for active organisms. Burrowing is highly energetic and would require dissolved carbon to be concentrated; without the Ediacaran organisms it would have been too diluted and sequestered away by the abundant microbial mats. Just like trees on the savannah, the Ediacaran biota concentrated dissolved organic carbon, providing sufficient resources for active burrowing and the need for motility.

In their thorough review, Budd and Jensen challenge the view that Ediacaran organisms went extinct by the start of the Cambrian period having been outcompeted and devoured by bilateral organisms. Instead, they survey putative evidence that shows that bilaterians first appeared towards the end of the Ediacaran period and that Ediacaran-type organisms persisted well into the Cambrian (and perhaps longer). At first, bilaterians would have been dependent on the Ediacaran ecosystem engineering, but went on to evolve their own sessile forms, such as crown-group sponges, and predatory habits which made them a threat to the Ediacaran biota – comparable perhaps to humans in the Terminator franchise creating Skynet and setting up their own demise.

They also reviewed the phylogeny of basal animals and take the view that sponges form a single clade which is the sister group to all other animals. They coined the term “Apoikozoa” which encompasses all animals and their sister group the choanoflagellates. And they made a case for Ediacaran organisms being early animals, albeit hugely problematic, whilst being highly critical of some of the optimistic interpretations. It is a paper which has provided a lot to mull over.

References 

Budd, GE. and Jensen, S. 2015. The origin of the animals and a ‘Savannah’ hypothesis for early bilaterian evolution. Biological Reviews. doi: 10.1111/brv.12239

Darroch, SAF., Sperling, EA., Boag, TH., Racicot, RA., Mason, SJ., Morgan, AS., Tweedt, S., Myrow, P., Johnston, DT., Erwin, DH. and Laflamme, M. 2015. Biotic replacement and mass extinction of the Ediacara biota. Proc. R. Soc. B 2015 282 20151003; DOI: 10.1098/rspb.2015.1003

Own your own Ediacarans

If they were alive today they would probably have made terrible pets, but you may well have had some of them in a home aquarium. Like sponges in modern aquariums, the likes of Charnia and Charniodiscus might have featured in the odd fish tank, absorbing nutrients and sitting around looking pretty. Most Ediacarans depended on the slimy microbial mats in some way or another, whether they grazed on it or lived within, beneath or on it. And over all the Ediacarans were not a very mobile bunch. As fossils, however, they are hugely important in helping us to understand the evolutionary history of animals (and in helping us to admit to how little we know). Some of them are recognisable to any fossil-nerd worth their salt. Last year I invested in casts of some familiar Ediacaran beasties from a company called GeoEd, which makes replicas of thousands of important specimens:

I opted for some of the most recognisable taxa, as you can see I bought Charniodiscus, Charnia, Spriggina, Dickinsonia and Parvancorina. I have not been disappointed and would thoroughly recommend buying some from there if you, like me, are interested in the Ediacaran. The prices are very good, but do note that they don’t include shipping costs – those come after you complete your purchase.

The only issue I have with them is that the information can be outdated. For starters, the Ediacaran period fossils are listed as Vendian, a term which you will find in a lot of older texts about the period. I recently bought a cast of Charnia as a gift for my friend Dean Lomax and noticed that the little informative label on the back listed it as a Pennatulacean (a sea pen) despite that this interpretation was rejected scientifically by Antcliffe and Brasier (2006) who noted that sea pens grew by adding polyps to the bottom of the frond, whilst Charnia grew by adding segments to the tip. (I also hadn’t noticed that the descriptions on the website mentioned whether they were in positive or negative relief – the pictures are misleading – so pay careful attention if this matters to you.) Here’s the one I bought for Dean, the image pinched from his Facebook, and as you can see it is a very well made cast:

Many key Ediacaran specimens can not be collected, particularly those from Charnwood Forest in Leicestershire, so this is your only way to get your hands on them. Casts are extremely useful for studying such unique specimens and on top of that can make excellent ornaments for the enthusiast.

If anyone knows of any other good sites offering Ediacaran casts please let me know in the comments, I’d love to get my hands on some more and can do a comparison and a bit of advertising.