Darwin’s ‘Imps of darkness’: the marine iguanas of the Galápagos
Gazing out the window of my airplane, I was filled with wonder at the beauty and immensity of the aquamarine waters of the Galápagos archipelago, its many rugged islands laced with white sandy beaches and black basalt. Adding to my excitement about arriving at this biological paradise was the desire to get to know a unique creature found nowhere else on the planet. Charles Darwin found them to be so hideous he called them ‘imps of darkness’.1 However, when I finally got to meet the marine iguanas (Amblyrhynchus cristatus) they were neither hideous nor imps, but complicated and wonderful organisms.
A very special lizard
The marine iguana is the only ocean-dwelling lizard in the world. Endemic to the Galápagos, the seven subspecies are dark-coloured and emblazoned with various reds, grays and greens, depending on what island they are from.2 The faces of iguanas are often light in colour due to the encrustation of salt they ‘sneeze’ out of their system. Salt glands connected to the nostrils allow them to expel excess sea salt, an ingenious design that saves wear and tear on the kidneys.2 Males are more brightly coloured and larger than females, generally ranging from 75 cm (30 inches) to 1.3 m (4.3 ft) long, depending on their home island.
Marvelling at their lack of fear, I sat amongst them. Their long, clawed toes were quite unusual. Their feet seemed cumbersome, until I watched them scale and descend vertical walls and realized what amazing tools they were. Those powerful feet and claws are well suited to climbing on and clinging to rocks, especially when they get bombarded by powerful surf. They are good swimmers but do not use their legs for this; instead, they undulate their bodies from side to side.
Exploring the mangrove swamps and rocky tidal zones, I found many iguanas ‘sunbathing’. The waters here are often cold, and iguanas spend a lot of time controlling their temperatures because they are poikilothermic (cold-blooded), meaning their body temperatures depend on the surrounding temperature.
The environment and special behaviors are crucial to maintaining their internal temperatures at an optimal operating range for processes like foraging, egg development and digestion. For example, they will orient themselves so that solar energy is absorbed through the skin. This behavior allows them to use their bodies as a heat shunt, transferring absorbed heat to the blood stream for transport to the rest of the body. Excess heat is released through the skin of the belly.3
They are largely herbivorous, a pretty rare behaviour for reptiles but common in the iguanids.4 They forage on the red and green algae that grow on the rocks in and near the water. While feeding, iguanas have been known to submerge for up to an hour, though 5 to 10 minutes is more common, and they can dive to depths of 10 m (33 ft).5
They have also been observed eating the feces (coprophagy) of crabs and sea lions.2 At first this might seem a puzzling behavior, but if one understands the problem with efficiently digesting plant-like materials, the reasons may not be so mysterious. Most herbivorous animals have a community of micro-organisms, mostly bacteria, in their intestinal tract that have the equipment to properly digest various plant chemicals and render them nutritious for the host. Many of these plant eaters would not survive without this community of micro-organisms.
In return, the host provides a home with free food for the micro-organisms. Eating the feces of crabs and sea lions may be the way an iguana obtains them. Recent research has provided some of the first direct evidence that iguanas use these micro-creatures in their digestive tract.4
Female iguanas lay about four leathery eggs in sandy areas and protect the nest while the eggs are incubating. Once the hatchlings break free, they are on their own and are often preyed upon by snakes, lava gulls and herons. Of particular concern are feral dogs and cats that take large numbers of young; to the point that there are several populations with no juveniles. Despite current success in eradicating the dogs and cats, there is still sufficient concern about the future of the marine iguanas for them to have been listed as a vulnerable species.2
In the case of the marine iguana, the fossil evidence for its origin is scanty. They are currently classified in the family Iguanidae. Most evolutionary scientists agree that there are eight groups within Iguanidae. One probable subfamily is the Iguaninae, containing eight genera including Amblyrhynchus.6 The Galápagos Islands are home to 10 species of iguanids. They include seven species of lava lizards (genus Tropidurus), two species of land iguana (genus Conolophus) and one species of marine iguana.7
At least one creationist scientist has statistically analyzed the eight groups and agrees that all iguanids stem from an original pair that survived on board the Ark.7 The land and marine iguanas are different in many ways. For instance, they eat very different foods. Despite their differences, they have similar enough genetics to produce hybrids (photo below top right). This suggests that the two species diversified from that original pair, and thus all belong to the same original created kind. Interestingly, the Galápagos land iguanas Conolophus subcristatus also appear to possess salt glands.8
The precise mechanisms by which the iguanas diversified and became part of the Galápagos fauna are not fully understood. Many evolutionists would claim that there was a single colonization by a land ancestor that arrived on floating vegetation mats, and that evolution took place over millions of years. Evolutionists believe that random mutations (changes in DNA coding sequences), are acted on by natural selection. There is much evidence that even if billions of years were available, no brand new complex features are likely to form in this way.9 But even using evolutionary assumptions, it would still require vast eons of time, which do not seem to be available, given the current assumed age of the islands.7,10
Contrary to the empty worldview of philosophical naturalism, creationists realize that God is the Mastermind behind the breathtakingly complicated genetic code. According to the Bible, there was a huge genetic bottleneck about 4,500 years ago, when Noah brought two of every kind of the world’s land vertebrates on board the Ark (Genesis 6–8). From this small group came the great diversity of vertebrates seen today. This means the diversification and speciation (formation of new species) from Noah’s parental stock had to have been explosive. Such large-scale processes are not observed today. However, several instances of small-scale speciation have been observed, and their rapidity has surprised the evolutionary establishment—though not those who trust in God’s outline of history.11
This suggests that God pre-designed information systems into His creatures that would allow them to adapt to rapidly changing and unpredictable environments, such as those prevailing after the Flood. This explanation is known as mediated design, and is a testable hypothesis.12 The complicated genomes of living things can be examined to determine the actual mechanism(s) for how traits might be expressed and or ‘reshuffled’ rapidly in order to allow such speedy adaptation.13 The potential for all of this would already be there, in the complex genome of the original kinds.
Iguana ancestors, with all this built-in potential for subsequent variation, may have colonized these islands multiple times on post-Flood debris rafts, ripped off the land by storms and floods or pushed out to sea at major river mouths.14
Each time species diversify, of course, it limits the potential for future variation, as they become more specialized and lose some of that originally created information.
Whatever the means by which iguanas arrived at the Galápagos, the Bible gives us a reliable outline of Earth history and allows us to develop reasonable models for the observations we make that are consistent with both history and experience.
As I reflect on the design and mysteries of the marine iguana, I am in awe of their Creator. If Jesus put this much thought and love into a creature from whom many, like Darwin, would recoil, how much more love and thought did He put into us who are made in His image and likeness?
References and notes
- Charles Darwin’s diary of the voyage of H.M.S. “Beagle”, edited from the manuscript by Nora Barlow, <www.galapagos.to/TEXTS/DIARY.HTM>, 20 January 2008. Return to text.
- Marine iguanas (Amblyrhynchus cristatus), Charles Darwin research station fact sheet, Charles Darwin Foundation for the Galápagos Islands (AISBL), Galápagos, Ecuador. Return to text.
- Pough, F.H., et al., Herpetology, 3rd edition, Pearson Prentice Hall, New Jersey, USA, pp. 258–259, 2004. Return to text.
- Mackie, R.I., et al., Biochemical and microbiological evidence for fermentive digestion in free-living land iguanas (Conolophus pallidus) and marine iguanas (Amblyrhynchus cristatus) on the Galápagos Archipelago, Physiological and Biochemical Zoology 77(1):127–138, 2004. Return to text.
- Marine iguanas, Cornell University, <www.geo.cornell.edu/geology/GalapagosWWW/MarineIguanas.html >, 1 February 2008. Return to text.
- Ref. 3, p. 125. Return to text.
- Wood, T.C., A creationist review and preliminary analysis of the history, geology, climate and biology of the Galápagos Islands, Center for origins research issues in creation, Wipf & Stock Publishers, Oregon, USA, 1:92–94, 2005. Return to text.
- Peaker. M. and Linzell, J.L., Salt glands in birds and reptiles, Monographs of the Physiological Society, no. 32. Cambridge University Press: Cambridge, London, 1975, as cited on <www.aquaticape.org/saltglands.html>, 4 August 2008. Return to text.
- Batten, D., Genetic algorithms—do they show that evolution works? <creation.com/ga>, 14 November 2001 (updated June 2008). Return to text.
- Gauge the Galapagos with a younger age—new estimates of islands’ ages, Science News 127(150):227, 13 April 1985. Return to text.
- Catchpoole, D. and Wieland, C., Speedy species surprise, Creation 23(2):13–15; <creation.com/speedy>. Return to text.
- Wood, T.C., Mediated design, Impact 363, September 2003, <www.icr.org/article/ 118/>, September 2003. Return to text.
- For example, we know today that there are such phenomena as ‘jumping genes’, parts of the DNA that are able to rearrange their own location, leading to rapid changes. Return to text.
- Batten, D., (editor), et al., The Creation Answers Book, Creation Book Publishers, Queensland, Australia, 2006, ‘How did the animals get to Australia?’ Return to text.