Herring or Black-Backed Gulls or…?
Image from http://birdingnewfoundland.blogspot.co.uk/2011/02/
At a recent talk by Professor Bill Clegg about science and faith (‘Age Old Enemies or Natural Allies’) I challenged him over his equation of creationism with fixity of species, which is something I have done previously in a talk he gave at Newcastle University a few years back. Now, he is far from alone in making this wrong equation. Creationists will often get particularly annoyed at this type of straw-man argument because even the most superficial perusal of creationist literature, whether popular level or peer-reviewed technical level, will reveal that this has NEVER been a position of modern Young Earth Creationism, right from the (putative) start in the 60’s (and indeed, from before then). I challenged Bill to cite any example of creationist literature that took this position, noting that I could easily find hundreds to thousands of articles proving otherwise. The trouble is that all too often opponents of creationism don’t ever actually read or engage with the argument, but rather feed off the most superficial of denunciations or their own side’s straw men (or, to be fair, occasionally the profession of creationist laypeople who haven’t fully grasped the basics – I remember being handed a pamphlet by one such which did indeed more or less describe creationism as involving fixity of species). In biology especially this is a repeated complaint of creationists. Bill Clegg cited the 1960’s book ‘The Genesis Flood’ and that was indeed a pivotal moment in the emergence of the modern ‘Young Earth Creationist’ movement, but creationism has moved on massively in pretty much every field since then. Now Bill’s talk was a popular level guide on a very broad topic, so his citing that book and nothing else didn’t bother me particularly. However, the trouble is that opponents of creationists only citing a couple of old and sometimes out of date creationist articles and ignoring huge swathes of more recent work happens in the technical literature too, and is completely inexcusable. Sure, to read every article there is isn’t possible, but it is dishonest not to make some attempt to engage with the best – or even more, simply the most basic and ubiquitous – arguments of your opponents.
So, you get a situation where, for instance, biologists in the field are amazed to find rapid speciation happening in a lizard or fish over a decade or two, and the ardent evolutionists will go ‘Hah, more proof creationism is wrong – in your face, creationists, show how you get out of this one’. Creationists find this very frustrating for one simple reason – their model not only allows for this, it also requires that rapid speciation happen, not always, but under certain conditions. Biologists are surprised at the speed with which these speciation events are observed to happen (although the uber-flexibility – non-falsifiability, dare I suggest? – of the evolutionary model allows them to adjust it to fit in speedy speciation), but creationists are emphatically not. But because of the strawman fallacy about creationism, such discoveries of observed rapid speciation are generally assumed to be logically the death-knell of creationism, except for the certainty that those darn fundamentalist religious nuts will just ignore ‘hard scientific fact’ yet again.
In the limited time I tried to explain again to Bill that creationists do not equate the ’kinds’ of Genesis 1 with species at all by saying that creationists seek to find out the limits of kinds in large part by which creatures can breed with other creatures, and he seemed to grasp, finally, that creationists usually place the ‘kind’ at higher taxonomic levels of classification, but he then said that whilst biology was not his field, he understood that whether creatures could breed was mainstream sciences’ definition of ‘species’, and I had to say yes, but had no chance to explain the issues that mean this seemingly sound counter-argument misses the mark. (For those readers unfamiliar with the issue, Genesis 1 repeatedly refers to plants and land, air and water creatures as being created to ‘reproduce after their kind’. Put simply, in creationist thought this means that living beings have certain limits beyond which they don’t change. Within those limits all kinds of significant variation and change can and do happen. A major issue for creationist biologists is seeking to establish scientifically where those boundaries of the original ‘kinds’ are.)
Perhaps one of the better ways to get into why it misses the mark is to examine the question of ‘ring species’, a concept that has been used to try and bash creationists over the head in the past (and indeed you can still find many articles online that still do this). To explain, a ‘ring species’ is one where a species, say of bird or butterfly, or whatever, reaches an effectively impassable large obstacle – say a large, high mountain plateau, an inland sea, or indeed, the polar ice-cap. As they spread out, parts of the population go to the left and right around this obstacle, and as each wing encounters different environmental pressures the populations change. If you take either wing, each neighbouring population around the obstacle can interbreed with each other, even though they are slightly different. However, when the two wings meet on the other side of the obstacle, they are just sufficiently different that they don’t interbreed, and therefore would normally be taken as a separate species, and yet there are two unbroken chains of interbreeding populations going back to the same original species. One of the few examples involved a Green Warbler around Tibet. Let’s have a bit of fun and say the original species was the Green Tibetan lesser-spotted Frog-throated Warbler and that at the other side of the Tibetan plateau we find the Blue-Green Tibetan lesser-spotted Frog-throated Warbler and the Yellow-Green Tibetan lesser-spotted Frog-throated Warbler who maintain separate populations and don’t interbreed. In mainstream biology there is some debate as to when something is a sub-population or sub-species and when it is a species, but given that the two types don’t appear to interbreed but maintain separate breeding populations in the same location then most would consider these to be two new species. Now, a main part of the reason ‘ring species’ were supposed to be a weapon against creationists is precisely because of the straw-man that creationists don’t believe in speciation, but in actual fact, creationists have never had a problem with such concepts and arguably would expect something like that.
However, as they say, the devil – or in this case, perhaps the divine – is in the details. There were only a handful of supposed ‘ring species’ to start with, but it turns out that every single one of them has been proved not, in fact, to be a ‘ring species’. Probably the classic example is a global-wide ring that ends and starts here in Great Britain. If, like me, you have been a bird-watcher at some point and have a book listing all native birds, you will find Herring Gulls and Lesser-Black Backed gulls as two separate species. If you head west from the UK, through Iceland, North America, Alaska, Siberia and Scandinavia you will find that even though each population of Herring Gulls can and do interbreed, they progressively get more and more like Lesser-Black Backed gulls as they go, until we get to the two UK species, who maintain their distinctions. At least, that was the idea. It turns out that whilst generally the two species do not interbreed, there are numerous reports of cases where they have interbred and produced offspring (and, in fact, as I understand it, there are also indications that at some points in the ‘ring’ that these gulls have also interbred with still other gull species, but we’ll leave that to one side for now and just focus on this pair of species). Now, creationists have no problem with these two types of gull being labelled as different species (their ability to interbreed definitely means to creationists, though, that they are of the same ‘kind’ in the biblical sense.)
So what is going on? Well, it looks like, at least in part, this is an example of ‘sexual selection’. For the most part Herring gulls prefer to mate with gulls with the same ‘Herring gull’ characteristics, and so can, by our modern scientific system, be classified as a separate ‘species’. They mostly don’t interbreed with the other end of the ‘ring’, but that doesn’t mean that they can’t. In fact, it is fairly common for scientists to say that two otherwise indistinguishable (to the non-expert eye, at least) populations are separate species, because they don’t interbreed whilst still being in the same geographical location and ecological environment. For creationists, when it comes to finding the limits of ‘kinds’, whether two types of creatures typically do or don’t interbreed isn’t of interest – what is of interest to them is whether they can or can’t interbreed. And even then, it’s not quite so straightforward, because creationists recognize that creatures descended from the same original members of a ‘kind’ can develop so far from each other that those at the far ends of a chain of species can’t interbreed. But if there is an unbroken chain of interbreeding, then they still belong to the same kind. So, for instance, lions and tigers are separate species within a ‘big-cat kind’, but they can and do interbreed and produce viable offspring. But if another cat of some sort has been shown to breed and produce offspring with one of the species within the ‘big-cat’ kind, then you have established that that type of cat is within the same ‘kind’. Simply put, if you have a nexus of various species that form part of the same ’kind’ because they can interbreed with at least some of the other species, and you find just one example of another species that has successfully interbred with one of those species, then you have established that that species is of the ‘same kind’, even though it may not be possible now for it to interbreed with all of those creatures.
This is not the whole of defining what is or isn’t a ‘kind’ in the creationist sense, but it is a major, major part of it. Also, creationists face the same limitations as evolutionists when dealing with extinct or effectively extinct creatures where we have only fossils to go on and so can’t even begin to consider interbreeding ability – all there is to go on, in effect, is the shape and form of the fossil remains. The basic difference would be that evolutionists would be interested in establishing as far as possible species, family and genus classifications, and whilst creationists would not have a problem per se with that, they would want to try and discern where the original ‘kind’ level might be, whether at family, or genus level, for instance, in any given set of fossil creature types. (I should also note that when it comes to bacteria and viruses, then there are special considerations at play. The basic concept of biblical ‘kinds’ still applies; however I think it fair to say that creationists generally argue that the great flexibility in the bacterial world, including mechanisms such as direct transfer of genetic elements, are part of a designed function where bacteria in particular are a mechanism to allow the biological world, creatures like us, elephants, birds and whatever, to interact with the inanimate world in ever-changing environments.)
The bottom line is, that despite both the evolutionist and creationist positions having the superficial similarity of using ‘whether something can breed’ as a major defining criteria for species and ‘kinds’, respectively, they are emphatically NOT talking about the same thing, and therefore evolutionists of all stripes should stop using straw-man arguments like the one that Professor Bill Clegg uses, and actually understand the basic differences in approach. Some do seek to do this to varying extents, but all too many do not, even after they have been told. I realize that, as came out from several scientists at the talk, one of the major problems in science is the incredible level of specialization, and so scientists are effectively non-scientist or lay-people when it comes to areas outside their own focus, and thus that, for instance, Bill is not a biologist, as I am not. However, what I have written should give anyone a clear guide to understanding just why the type of argument Bill used is a straw-man argument that is a ‘what evolutionists would like the creationist position to be so they can decisively demolish it’ rather than an actual reflection of creationist reality. Despite the similarities at a very superficial level, modern biological ‘species’ are emphatically NOT the same ‘species’ of concept as creationist biblical ‘kinds’ and creationists do NOT hold that Genesis 1 teaches anything like ‘fixity of species’ as most evolutionists apparently commonly believe.