Gogonasus—a fish with human limbs?

by Daniel Anderson and Shaun Doyle

3 November 2006

So often, there are two stories to be heard when one hears of the latest ‘missing link’ finds: the popular media story and the proper story told in the science journals that rarely gets a mention. This has especially been the case this year with fish-to-frog evolution, with the discoveries of the Tiktaalik fossil and a new species of ‘walking’ shark recently paraded in the media as if they were irrefutable proof of fish-to-frog evolution. Now a new candidate has stepped up to take the spotlight: a magnificently preserved fish fossil called Gogonasus. Gogonasus has received the usual media parade reserved for ‘missing links’, boldly proclaiming that the fins are ‘like human arms’.¹ As usual, the original Nature article² is far more conservative about the claims. So what is the actual story behind this fossil?

Fantastic fossil formation

Gogonasus was exquisitely preserved in the Gogo formation, a limestone formation in the Kimberley region of northwest Western Australia. ‘It’s one of the few sites in the world where you can get whole complete fish in limestone’, John Long, one of the authors of the Nature paper, told LiveScience.³ It was so well preserved that scientists could even open and close the mouth of this fossil fish. ‘It’s like it died yesterday’, Long said.³ This formation ‘is widely acknowledged for its perfect three-dimensional preservation’ of fish fossils.²,⁴ But Gogonasus is placed in the late Devonian period, giving it a ‘date’ based on index fossils of around 380 million years.

Image from Williams, B. 1 Despite the descriptions in the media suggesting ‘fish with human arms’, this reconstruction accompanying one of the popular media stories shows that the reality is far more prosaic.

The standard uniformitarian interpretation of the Gogo formation is that the limestone deposits form part of an ancient coral reef.⁵ However, such certainty regarding interpretations of ancient environments is never justified.⁶ Rather than speaking of a coral reef ecosystem, which would have developed slowly, the limestone deposits interspersed with shale in the Gogo formation, together with the magnificent preservation of the anatomical structure of the fish buried, suggest a recent catastrophic burial during the Genesis Flood.^7,8 Therefore, Gogonasus looks ‘like it died yesterday’ because it died a lot closer to yesterday than 380 million years ago!

‘Earie’ holes and fins that’ll grab you

If Gogonasus is such a well-preserved fossil that is clearly a fish, why is there so much media attention? All the attention revolves around two structures, the spiracle opening and the pectoral fin.

The spiracle opening is a hole in the head of a fish that leads to the gill chamber. This opening in Gogonasus is ‘thought to be the forerunner for the middle ear in modern land animals.’ ³ This is based on Gogonasus possessing a stubbier-than-usual hyomandibula bone (a bone in the gill arch which suspends the jaw joint from the braincase⁹), making it look slightly more like the middle ear bone of the early tetrapod Acanthostega than most other fish fossils. The hyomandibula supposedly retracted from the spiracular opening from Eusthenopteron (the ‘model fish ancestor’ used at the beginning of the fish-to-frog evolutionary story), through Gogonasus and Tiktaalik, to the early tetrapods to basically begin turning a gill into an ear.^2,10,11

This is a new interpretation of the evidence, and is not supported by all evolutionists, e.g. Michael LaBarbera, a professor of organismal biology and anatomy at the University of Chicago. Not even convinced about the structure Brusseau and Ahlberg identified as a spiracle in Panderichthys (which has many similarities to Tiktaalik, supposedly two steps along the line from Gogonasus),¹¹ he states that Brusseau and Ahlberg’s idea is ‘based on the interpretation of a structure that would be completely novel and unprecedented in this lineage’.¹² One thing is clear, and that is the identification of the bone that supposedly underwent the change from gill to ear function (the hyomandibula, allegedly evolving into the stapes, a middle ear bone). In fish, including Gogonasus, it is always identified as a hyomandibula. In all tetropods, including the earliest, e.g. Acanthostega, it is always identified as a stapes.¹³

Concerning the pectoral fins of Gogonasus, the Nature article described them as ‘approaching the condition of Tiktaalik ’. ² Therefore, while superficially more ‘arm-like’ than most other lobe-finned fishes, Gogonasus ’ fin structure is not even as close to tetrapod limbs as Tiktaalik. Note that Ahlberg and Clack, who believe Tiktaalik is a true transitional form, wrote in their review of that fossil:

‘Although these small distal bones bear some resemblance to tetrapod digits in terms of their function and range of movement, they are still very much components of a fin. There remains a large morphological gap between them and digits as seen in, for example, Acanthostega: if the digits evolved from these distal bones, the process must have involved considerable developmental repatterning. The implication is that function changed in advance of morphology.’¹⁴

Therefore, if the fins of Gogonasus and the rest are a long way from turning into the arms of even their supposed closest land-dwelling ancestor, any claims that Gogonasus’ fins are in any new or spectacular way ‘similar to a human arm’¹⁵ are substantially misleading. Bat wings, whale fins and human hands all have the pentadactyl pattern, with five digits, a humerus, radius and ulna, but that doesn’t mean they had a common ancestry.¹⁶ Vast amounts of biological, genetic and soft tissue restructuring would be required to effect such a change. However, such restructuring has never been observed, tested or even successfully modelled in living organisms. A common designer is just as good an explanation for such a widespread pattern as ‘common descent’. In fact, common descent falls down when it comes to the obvious similarity between the bone pattern in forelimbs and hind limbs—clearly, no evolutionist teaches that this is the result of common descent from an ancestor which had only fore- or hind limbs. They would probably claim that the similarity was because natural selection chose the same pattern for good bioengineering reasons. This is precisely the argument one could apply as to why God utilized the same pattern repeatedly in different types of vertebrates—now including Gogonasus.

An object lesson in speculation

Molecular biologist Michael Denton once wrote, ‘To begin with, ninety-nine per cent of the biology of any organism resides in its soft anatomy, which is inaccessible in a fossil.’¹⁷ This is especially true of the parts of anatomy of all these recent fish-to-frog ‘missing links’ that are being used to establish evolution. In order to establish the evolution of what is most likely a respiratory structure into an ear, or a fin into a leg, much more needs to be known than the bone structures of these traits. A huge chasm exists.

The coelacanth is a perfect example of such imaginative speculation buckling under the weight of hard, scientific data. Thought to be extinct for 65 million years, the coelacanth was discovered alive and well off the coast of South Africa in 1938. Scientists were excited by this discovery because the coelacanth is a close relative of the Rhipidistia, considered by many scientists, at one time, to be the ancestors of amphibians. They thought that their bony pectoral fins enabled these fish to make the transition from walking in shallow water to walking on dry land and evolving into amphibians.

However, scientists have spent a considerable amount of time filming coelacanths underwater, and they do not walk at all. Instead their robust pectoral and pelvic fins are utilized for high powered, highly manoeuvrable swimming in the deep sea. In addition, a soft tissue analysis revealed that their physiology was 100% fish, and was in no way transitional between fish and amphibian.¹⁸

Extrapolating function from bones alone is a highly inexact science.

Where does Gogonasus fit?

Long et al. give a cladistic analysis of the traits of the fossils either side of the supposed aquatic/land-dwelling vertebrate barrier (figure 1). Cladistics is a method of classifying singular traits that are distributed though a collection of organisms.¹⁹ In this analysis, Long et al. place Gogonasus in a sister group alongside the two closest fish ‘relatives’ of tetrapods, Panderichthys and Tiktaalik, which is a large reshuffling of a number of the fossils in this group, compared to previous arrangements (figure 1). This shows that these evolutionary trees are based on a little bit of evidence and a whole lot of speculation. For all we know, another single fossil find will cause another complete revision of the entire arrangement!

So Long’s claim about this fish being our ancestor is ‘spin’ for public consumption, presumably to promote evolution to the gullible.

Homoplasy and evolution

Looking at the relationship between Gogonasus and the early tetrapods in the Nature article, Long et al. aver:

‘The conspicuously large spiracular opening is proportionally similar to those recently reconstructed for Panderichthys and Tiktaalik. … There are some surprising similarities to the recently described pectoral fin in the advanced elpistostegalian Tiktaalik. … such features could indicate homoplasy between Gogonasus and early tetrapods’. ²

The key word to note here is homoplasy.²³ It is very commonly used to describe the evolutionary relationships between different traits and different organisms. However, homoplasy provides no support for evolutionary explanations. Homoplastic structures are similar enough to require an explanation for the pattern observed, but are too different to be described as a ‘genetic throwback’²⁴ or don’t fit a pattern of common descent. So the idea of ‘parallel’ or ‘convergent’ evolution is used to maintain that evolution independently came up with the same solution more than once—in ‘parallel’. Indeed this is part of a mosaic pattern seen widely in living things and fossils, one that thwarts evolutionary explanations.²⁵ The tetrapod-like spiracle gap and fin structures in Gogonasus, combined with the many fish structures, provide an example of homoplasy. This homoplasy between Gogonasus and early tetrapods (this includes the comparison of Tiktaalik to the early tetrapods, and possibly other lobe-finned fish) is convergent,²³ which is not helpful for constructing an evolutionary lineage of tetrapods from a supposed evolutionary ‘ancestor’. As ReMine quipped, ‘convergence thwarts lineage’.²⁵

The conclusions of Daeschler et al. concerning Tiktaalik and the fish-to-frog picture, of which Gogonasus is now claimed to be a part, are instructive:

‘Major elements of the tetrapod body plan originated as a succession of intermediate morphologies that evolved mosaically and in parallel among sarcopterygians closely related to tetrapods, allowing them to exploit diverse habitats in the Devonian [emphases added].&rsquo ¹⁰

Despite the media hype, they are therefore not claiming that the fossils present a direct lineage from fish to tetrapods, but that different parts of tetrapod morphology evolved at different times, often independently in different lineages, in response to the demands of their habitats. However, mosaic and parallel evolution, convergence, homoplasy, etc. are part of the evolutionists’ contingency plan for when common descent fails.

Gogonasus, like many of the fossils closely related to it, appears to have a mix of traits that are similar to different animals. Though fundamentally a fish, Gogonasus provides an example of a chimera in a few features.²⁶ From a biblical viewpoint, this suggests that Gogonasus was fully functional, therefore designed for a specific habitat.

What are they claiming?

With all of the news hype, one would think they’ve actually found something akin to video evidence of fish turning into frogs. However, whatever Gogonasus is precisely, it is first and foremost a fish. In contrast to the statements made for public consumption, the Nature paper does not actually claim that Gogonasus is the ancestor of all land-dwelling vertebrates. Rather, the Nature article concludes somewhat more circumspectly: ‘A new phylogenetic analysis places Gogonasus crownward [i.e. closer to the tetrapods] of Eusthenopteron as the sister taxon to the Elpistostegalia.’ But then they boldly assert that their ‘new phylogeny replaces the tristichopterid Eusthenopteron as the typical fish model for the fish–tetrapod transition [emphasis added].’ Basically, they’ve found a new fish they can use in their textbooks as the starting point for telling the story of fish-to-frog evolution: ‘Once upon a (geological) time there was a fish called Gogonasus …’.

Gogonasus is yet another example of nothing much being blown up to look as if it is the final nail in the coffin for the Bible. When one actually takes the time to look beyond the media parade at the actual evidence, it is clear that the claims are far less spectacular and do not in the slightest threaten the straightforward history of Genesis. Even given the assumptions of the evolutionary model, they are at most mildly interesting—except, perhaps, for their potential use in the political struggle to make it look as if there is this barrage of evidence coming out to support evolution. As the Bible says: ‘Examine everything, hold to what is good’ (1 Thessalonians 5:21).

Image from Williams, B. 1 Figure 1. Old and new cladograms of fishes to early tetrapods. The upper left diagram shows the old position of Gogonasus, and the upper right one shows Long et al.’s new position for Gogonasus, which is much closer to the ‘early’ tetrapods. The lower image shows the inferred lineage showing the fin/foot structures of different fossils along the ‘lineage’. (From Long et al.1) Return to text.

Further reading

• Panderichthys—a fish with fingers?.
• Tiktaalik—sticking its head out of water?.

References

1. Williams, B., Fossil fish reveals the missing link, The Courier Mail, 20 October 2006, p. 15. See When fish grew legs for the online version. Return to text.
2. Long, J.A., Young, G.C. et al., An exceptional Devonian fish from Australia sheds light on tetrapod origins, Nature doi:10.1038/nature05243, advance online publication 18 October 2006. See here for the first paragraph Return to text.
3. Bryner, J., Discovery points to our fishy heritage, 18 October 2006 Return to text.
4. Ahlberg, P., Fossil fishes from Gogo, Nature 337:511–512, 1989. Return to text.
5. Wildsmith, D. The Gogo formation, 15 October 2002. Return to text.
6. Oard, M., Beware of paleoenvironmental deductions, Journal of Creation 13(2):13, 1999. Return to text.
7. Scheven, J. The Flood/post-Flood boundary in the fossil record; in: Walsh, R.E. and Brooks, C. L. (Eds.), Proceedings of the Second International Conference on Creationism, Vol. II, Creation Science Fellowship Inc., Pittsburgh, PA, pp. 247–266, 1990. Return to text.
8. Roth, A.A., Fossil reefs and time, Origins 22(2):86–104, 1995. Return to text.
9. Panchen, A.L., Ears and vertebrate evolution, Nature 342:342–343, 1989. Return to text.
10. Deaschler, E.B., Shubin, N.H. and Jenkins Jr, F.A., A Devonian tetrapod-like fish and the evolution of the tetrapod body plan, Nature 440:757–763, 2006. Return to text.
11. Brazeau, M.D. and Ahlberg, P.E., Tetrapod-like middle ear architecture in a Devonian fish, Nature 439:318–321, 2006. Return to text.
12. Brown, D., Evolution of ear is noted in fossil, Washington Post, p. A03, 19 January 2006. Return to text.
13. Waara, A., Did our ancestors breathe through their ears? Uppsala University, 19 January 2006. Return to text.
14. Ahlberg, P.A. and Clack, J.A., A firm step from water to land, Nature 440:747–749, 2006. Return to text.
15. Shtargot, S., Fossil fish nets new evolution theory, The Age, 20 October 2006. Return to text.
16. Sarfati, J., Refuting Evolution 2, ch. 6, Master Books, Green Forest, AR, 2002. Return to text.
17. Denton, M., Evolution: A Theory in Crisis, Adler & Adler, Chevy Chase, MD, p. 177, 1985. Return to text.
18. Denton, ref. 17, p. 179. Return to text.
19. ReMine, W., The Biotic Message: Evolution versus Message Theory, St Paul Science, St Paul, MN, p.267, 1993. Return to text.
20. Batten, D., A review of: The Biotic Message: Evolution versus Message Theory by Walter ReMine, Journal of Creation 11(3):292–298, 1997. Return to text.
21. Sarfati, J., Skeptics/Australian Museum ‘Feathered Dinosaur’ display: Knockdown argument against creation? Return to text.
22. See, for example, Long, J., Archer, M., Flannery, T. and Hand, S., Prehistoric Mammals of Australia and New Guinea: One Hundred Million Years of Evolution, Johns Hopkins University Press, Baltimore, MD, 2002. Return to text.
23. When evolutionists describe the relationship between organisms as homoplastic, it means they believe that their features supposedly evolved independently toward a similar design. It is also commonly called convergence. The contrasting term in evolutionary language is homology, which is where a characteristic is shared between two organisms through direct lineage. Return to text.
24. A genetic throwback (or atavism) is the unexpected appearance of a trait once present in a lineage after having disappeared from the lineage for a number of generations. Return to text.
25. ReMine, W., Evidence for message theory: a review of Life’s Solution: Inevitable Humans in a Lonely Universe by Simon Conway Morris, Journal of Creation 20(2):29–35, 2006. Return to text.
26. Garner, P., The fossil record of ‘early’ tetrapods: evidence of a major evolutionary transition? Journal of Creation, 17(2):111–117, 2003. Return to text.

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