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Darwinism and popular culture: Fish story evolves in pop science media

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British physicist David Tyler looks at a recent find in cichlid fish which has been vastly overhyped as evidence for new species. He means hype like this Nature News story (1 October 2008), which proclaims “What you see is how you evolve: Differences in vision could give rise to new species.”

Here’s the abstract of the paper he discusses:

Speciation through sensory drive in cichlid fish

Ole Seehausen, Yohey Terai, Isabel S. Magalhaes, Karen L. Carleton, Hillary D. J. Mrosso, Ryutaro Miyagi, Inke van der Sluijs, Maria V. Schneider, Martine E. Maan, Hidenori Tachida, Hiroo Imai & Norihiro Okada

Nature 455, 620-626 (2 October 2008) | doi:10.1038/nature07285

Abstract: Theoretically, divergent selection on sensory systems can cause speciation through sensory drive. However, empirical evidence is rare and incomplete. Here we demonstrate sensory drive speciation within island populations of cichlid fish. We identify the ecological and molecular basis of divergent evolution in the cichlid visual system, demonstrate associated divergence in male colouration and female preferences, and show subsequent differentiation at neutral loci, indicating reproductive isolation. Evidence is replicated in several pairs of sympatric populations and species. Variation in the slope of the environmental gradients explains variation in the progress towards speciation: speciation occurs on all but the steepest gradients. This is the most complete demonstration so far of speciation through sensory drive without geographical isolation. Our results also provide a mechanistic explanation for the collapse of cichlid fish species diversity during the anthropogenic eutrophication of Lake Victoria.

Tyler comments:

“The strongest evidence yet” involves a correlation between the visual system, body colour and ecology. Instead of this being used to support a hypothesis of sexual selection based on body colouration, the authors claim to have demonstrated sexual selection in action. This has been picked up by the media as fact: “a fish species in the cichlid family has been observed by scientists in the act of splitting into two distinct species in Lake Victoria” (Source). The cover of Nature proclaims that this is “a textbook example of evolution in action”.

Let us suppose that the hypothesis is tested and confirmed, and the “sensory drive speciation” is validated. What are the implications for our understanding of evolution? It means that an ancestral fish population can split into two or more populations on the basis of colour. The daughter populations have differences in sensitivity to light frequencies and differences in body colouration. These may be accompanied by other ecological adaptations. There is no new genetic information – just fine-tuning of existing genetic systems. There is no evidence that these new species lack the potential to interbreed. Indeed, the differences are so slight that hybridisation to produce fertile offspring can be predicted with some confidence.

Talk about textbook examples- as the study authors themselves observe, for their particular proposed path by which new species may occur, “empirical evidence is rare and incomplete.”

Now, to their delight, they may have finally found an example (if the two schools of fish don’t just interbreed back into hybrids after a few decades).

The problem isn’t with the researchers, who sound suitably cautious. It’s the pop science media that jump on something like this and make far more of it than the current state of knowledge would justify. That wouldn’t matter if they were just speculating about some celeb’s tummy bump, but unfortunately, they help skew science textbook and science teaching. Tyler observes,

The punchline: ID scientists are not opposed to the teaching of evolution in schools, but want it taught properly – allowing critical appraisal and the recognition of spin. Let speciation in cichlid fish enter the textbooks, not as a proof of evolution, but as an example of how evidence is brought to bear on current hypotheses of the origin of species.

That would be higher quality teaching, but would lead to too many embarrassing questions. My guess is, both the pop sci mags and the textbooks will stick to “proof of evolution” for the present.

Also, just up at The Post-Darwinist:

Charges against Mark Steyn dropped but intellectual freedom battle continues

Darwinism and popular culture: Still not clear how mind emerges from mud

Morning coffee: Are you a redneck? A red diaper baby? And does it matter?

O'Leary - that's a good point. Van - thats the point I was making about the biological species concept (BSC). Although producing infertile/sterile offspring is one of way of determining if two species are reproductively isolated, it's not the only way. According to Coyne and Orr's book on speciation, species are considered to be reproductively isolated if there is very little gene flow in the wild. Like I said, this could even be due to behavioural differences or ecological differences - basically anything that causes the two groups to rarely transfer genes. So even if they were brought into the lab, crossed, and found to produce fertile hybrids, they still would not be considered conspecific because in the wild there is very little gene flow. For what it's worth, I think it would be much more accurate to say that we are seeing 'forerunners' of new species, or the 'process' of speciation, rather than the actual outcome of a speciation event. But hey, a title like that probably wouldn't get published ;) Green
Determining if these cichlids will interbreed or not is quite easy to test....so why haven't we seen these tests? And even so, "will" breed is different than "can" breed.....so whether or not one organism "will" breed with another is beside the point....the issue is whether or not two organisms "can" breed and produce viable, fertile offspring together...... I physically "can" breed with lots of different people, but the thing is I "choose" not to. Thus, it would be silly to assign a "species" label on an organism or group of organisms who simply "choose" (or not) to breed with other similar organisms. In short, one's sexual whims should not be a basis of categorization in a materialistic theory. van
Following along the same line as Green, is the variation in the DNA of these different Chiclids an order of magnitude greater than that found between all the various morphs of the domestic dog? On what basis are the different types determined to be "species"? Will they readily interbreed? SCheesman
Green wrote, "Incidentally, if all these PREmating barriers were applied to humans, I’m sure different races would be considered species; they speak different languages, are often temporally isolated etc etc." Ah yes! But don't forget that humans are a bit different because we actually see the big picture and we can know what is preventing us from achieving our goals. That is a very important outcome of consciousness, which currently lacks a useful science-based description - because it would not be a materialist description, and current science is the handmaiden of materialism. So, whereas an animal might simply fail to respond to calls it did not understand, a guy might say to himself, "Well, she seems like a nice girl. Maybe I should learn her language." O'Leary
Cheesman: "van: in fairness, all those quotes are at least 38 years old. A few other “engines” of variation have been proposed since then, though the origin of new genetic information is, I believe as much a mystery as ever. Got anything a lot more recent making the same point?" Well, here's evolution 101's explanation of the mechanisms of evolution....they include genetic drift, but that is not an adaptive mechanism.....as far as adaptive mechanims go, mutation + selection is the only thing they list: http://evolution.berkeley.edu/evolibrary/article/0_0_0/evo_14 then if you go to Talk Origins they say this: http://www.talkorigins.org/faqs/faq-intro-to-biology.html "The process of evolution can be summarized in three sentences: Genes mutate. [gene: a hereditary unit] Individuals are selected. Populations evolve." That's pretty darn strait-forward and up-to-date. van
"van: in fairness, all those quotes are at least 38 years old. A few other “engines” of variation have been proposed since then" The point is, some variation in the genetic (or at least epigenetic) information has to change, otherwise living beings stay the same as they are. If with the word "mutation" one means SNPs, then it is obvious that there are other causes of genetic variation: indels are a very trivial example. But if we use the word "mutation" in the sense of any genetic (or epigenetic) variation, then that is all. I am always surprises by the arguments about "engines of variation". There is no known engine of genetic variation that I know of, which is not some form of random genetic variation, or of intelligent adaptation according to pre-established patterns, like horizontal gene transfer, or antibody maturation (which is intelligent somatic genetic variation, but not transmissible). In other words, for a genetic variation to ensue, genetic information has to change. That can happen randomly, or according to some pre-existing procedure. All supposed darwinian engines are random. There is the interesting possibility of neo Lamarckian mechanisms, where phenotypic adaptations are translated into genotypic new information: that's an interesting idea, but I have never seen any detaile model of how that could happen. So, in practice, all the known "engines of variation", from SNPs to duplications, indels, inversions, genetic drift, sexual rearrangements, and so on, both in protein coding genes and non coding DNA, all add up to different kinds of random variations of the genetic information. I suppose that even epigenetic variations, of which I know nothing, would add up to that. A final note about the word "random" in the above context. That does not mean that they are all equally likely, or that tere are not laws of nature which can influence their occurrence. What I mean is that they are anyway random with reference to the informational output, because nothing in the laws which contribute to their happening has any informational relationship with the kind of information which can result and with its possible function. gpuccio
At 9 yeah but doest give you any macro change. Isolation without mutation cant do much at all. Frost122585
These types of ‘reproductive isolation’, and thus this type of ’speciation’ don’t necessarily require ANY genetic change at all!
With the new importance that epigenetic factors are being found to play, perhaps it's just different tools in the genetic toolbox being used the in the construction of fish as it grows in response to changing environmental factors. The inheritance of the epigenetic part of the code can account for the sustained speciation. SCheesman
van: in fairness, all those quotes are at least 38 years old. A few other "engines" of variation have been proposed since then, though the origin of new genetic information is, I believe as much a mystery as ever. Got anything a lot more recent making the same point? SCheesman
great quotes van. This is what troubled me as a teenager in biology class learning about evolutionary theory. I said "ok I get the natural selection part about survival of the fittest - and I get the micro mutations over millions of years".. "but I don't get why there should be positive ones in the first place!" And of course they all amount to a world full of living things that look and feel obviously designed. Frost122585
No genetic change, no evolution...period. "Mutation is the ultimate source of all genetic variation found in natural populations and the only new material available for natural selection to work on." {Ernst Mayr, POPULATIONS, SPECIES, & EVOLUTION, 1970, p.102} "The process of mutation is the only known source of the new materials of genetic variability, and hence of evolution." {T. Dobzhansky, AMERICAN SCIENTIST, v. 45, 1957, p.385} "Mutations are, indeed, the ultimate source of all new genetic materials . . . In the final analysis, all evolutionary change depends on mutations . . . all organic evolution is contingent on it." {George Gaylord Simpson & W.S. Beck, LIFE: AN INTRODUCTION TO BIOLOGY, Shorter ed., 1969, p.143} van
Incidentally, if all these PREmating barriers were applied to humans, I'm sure different races would be considered species; they speak different languages, are often temporally isolated etc etc. Green
"There is no evidence that these new species lack the potential to interbreed. Indeed, the differences are so slight that hybridisation to produce fertile offspring can be predicted with some confidence." The 'Biological Species Concept' defines species as reproductively isolated groups, which seems like a pretty good defintion. The only problem is, 'reproductively isolated' has been defined so broadly that pretty much anything can be said to be 'reproductively isolated'! For example, reproductive isolation includes PREmating barriers such as; 1. Behavioural isolation (e.g. a change in the courtship dance or mating call doesn't attract the other sex) 2. Ecological isolation (e.g. groups living in different habitats so they don't encounter one another. This even includes temporal isolation such as periodical cicadas). These types of 'reproductive isolation', and thus this type of 'speciation' don't necessarily require ANY genetic change at all! Green
Actually Chiclids are a very excellent example for "front-loading" of genetic information for a "parent species". African cichlid fish: a system in adaptive radiation research http://www.pubmedcentral.nih.g.....id=1635482 of special note: Interestingly, ecological opportunity (the availability of an unoccupied adaptive zone), though explaining rates of diversification in radiating lineages, is alone not sufficient to predict whether a radiation occurs. The available data suggest that the propensity to undergo adaptive radiation in lakes evolved sequentially along one branch in the phylogenetic tree of African cichlids, but is completely absent in other lineages. Instead of attributing the propensity for intralacustrine speciation to morphological or behavioural innovations, it is tempting to speculate that the propensity is explained by genomic properties that reflect a history of repeated episodes of lacustrine radiation: the propensity to radiate was significantly higher in lineages whose precursors emerged from more ancient adaptive radiations than in other lineages. --- Thus as you can see, the evolutionists are mystified that the radiations are not happening for the “sub-species” of cichlids but are always radiating from the “more ancient” parent lineage. This fact is totally contrary to what we would expect to find if the variation found in the sub-species were truly wrought by random mutations in the DNA generating novel information for variability! And this result is to be totally expected if the parent species were indeed created with a certain amount of flexibility for adaptation to differing environments already programmed in its genetic code! bornagain77
What a good "punchline" in that arn article: ID scientists are not opposed to the teaching of evolution in schools, but want it taught properly - allowing critical appraisal and the recognition of spin. And what important skills these latter two are. They can serve as the kindling to illuminate in new ways the stories being told in evolution, science in general and beyond science to the trash on TV, the oftentimes rubbish from the publishing world and the garbage trucked in from hollywood. steveO
Interesting you posted on this. I just read a post by Jonathan Wells over at evolutionnews.org about this. You should check it out if you haven't read it yet. He calls it "one long bluff." Reading what I've read lately I'm really starting to look at evolution as nothing more than a religion. It's promoted by supposed "scientific methods," but in reality by nothing more than just-so stories. I mean, didn't the whole deal with "eye spots" on butterflies to scare away predators sound reasonable? It certainly did to me. But as you know, once they actually put it to the test... it just failed. How much more of evolutionary thinking will be put to rest after more studies are done? For instance, some evolutionists suggest that animals that are "cute" are "cute" because it's a survival advantage. I say, "yeah right!" If I were to put a "cute" animal and an "ugly" one in front of a lion, were it hungry, it'd probably munch both of'em. I might not even have to test that idea, but if it could be done without actually killing animals, I'd do it. At least I'd be one step ahead of evolutionists. :P Seriously... can they stop with their stories? I'm really getting tired of it! Domoman

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