Decisive Evidence of Design in Turtles
[EDITORS’ NOTE: Abby Mitchell holds a B.S. in Environmental Science from Freed-Hardeman University as well as an M.S. in Biology from the University of West Florida. As a previous intern for Apologetics Press, we asked her to write an article discussing some of the evidences of design she observed in her graduate studies on turtles.]
The plethora of diversity in nature is astonishing, and it is also eye-opening how each special characteristic demonstrates God’s creativity and power. We get a glimpse of God’s unique designs when we undertake the study of turtles, categorized under class Reptilia (where snakes, crocodiles, and lizards are found) in the order Testudines. Within that order, there are three basic divisions: sea turtles, tortoises, and freshwater turtles.
Sea turtles are found exclusively in the ocean and can be characterized by their large, front, paddle-like limbs and enormous size—ranging from 3 to 9.5 feet, depending on the species. (There are only seven different species alive today.) Despite their low numbers, no reptile receives quite as much attention and affection as do sea turtles. Perhaps a part of their popularity stems from their beautiful shell patterns, gentle nature, or even the inspirational journey the babies take from hatchlings to full-sized adults.
Tortoises can’t claim quite the fanbase as sea turtles, possibly in part due to their rugged, tank-like appearance. They aregenerally unable to swim but instead live fully on land with stumpy, elephant-like feet and a high dome-shaped shell to help protect them from predators.
Freshwater turtles, on the other hand, are the smallest group on average—reaching the size of a large dinner plate at most. They spend the majority of their lives in or close to freshwater, whether that be in seasonal ponds and creeks or lakes and rivers.
There is an incredible abundance of diverse traits to explore among turtles, even in such a seemingly small order of God’s creatures. By looking at how their traits and abilities are crafted specifically for how they breathe in water, for surviving in their specific environment, and especially in ways that remain mysterious to scientists even today, it is easy to see that turtles could only be fashioned by the hand of God.
Breathing Mechanisms: Proof of Design
Both sea turtles and freshwater turtles are air-breathers yet live in and around water their whole lives. As a result, they exhibit diverse adaptations1 to help them thrive in this environment. Just like marine mammals, sea turtles breathe air using lungs and yet spend almost their entire lives in the water. In order to survive in an aquatic environment, sea turtles have lungs that are “subdivided to a degree much greater than any other reptile, and the enhanced surface area results in a lung oxygen diffusivity that approaches that of the mammal.”2 While evolutionists consider this to be an example of “convergent evolution,” we can appreciate the evidence of God’s consistency in design. This lung feature is a trait sea turtles share with marine mammals; however, at least one aspect of their oxygen control sets them apart from marine mammals. Unlike marine mammals, the amount of time they spend in a dive is not restricted by the brain’s oxygen supply. Rather, “the brain is able to function in the complete absence of oxygen allowing the turtle to endure long periods of total anoxia [lack of oxygen—AM].”3 This trait provides sea turtles with more control over their breathing without the potential of losing consciousness. By allowing air to exit their lungs as needed, sea turtles can control their descent in water.
Freshwater turtles, on the other hand, have a different adaptation for staying underwater for long periods of time: the ability to “breathe” under water without any need of their lungs. Research has found that there are three main ways turtles absorb oxygen from water: their skin, their mouths, and their intestinal opening at the end of the digestive tract called the cloaca. The cloaca accounts for almost 50% of the oxygen that turtles absorb from water.4 This opening is lined with skin formations that increase its surface area and are filled with blood vessels to absorb as much oxygen as possible. By contracting the muscles of the cloaca in a rhythmic way, oxygen-filled water continually flows over the skin, enabling oxygen to be absorbed. Although the ability may seem odd to us, this specialized design allows freshwater turtles to remain fully submerged in water for a very extended period of time. Such a unique, pre-planned design could only come from an all-knowing Designer.
Specialized Adaptations: Proof of Design
Turtles are found on every continent except Antarctica, as well as every ocean on the planet, meaning they have a wide range of adaptations to accommodate the varying climates they inhabit. Sea turtles, being confined to the deep oceans for their entire lives except for laying eggs, must be able to sense their surroundings even while underwater. Most air-breathing animals that live in the water such as blue whales or sea lions, have what is called a nasal plug that seals off the nose to keep water out when diving. Sea turtles, on the other hand, have no visible nasal plug, but rather water freely enters the nasal cavity in order to allow sea turtles to sense—we could say “smell”—chemicals around them. Their nasal cavity “significantly differs from those of other animals, including terrestrial and semi-aquatic turtles.”5 While most reptiles have separate chemical sensing organs from their nasal cavities, sea turtles have sensory organs inside the nasal cavity. Due to the shape and structure of the nasal cavity, water cannot flow all the way through it but still enters far enough for “smelling.” This special design allows them to sense the world around them while keeping seawater from entering their lungs in a way that is specialized and unique to sea turtles.
Tortoises also have specialized functions tailored to their environment. They are mainly found in desert and arid environments, which means plants—their primary source of food—are sporadic and often extremely fibrous. While this would spell disaster for most digestive systems, tortoises are able to gain a large concentration of nutrients from the food they digest due to their specially designed “hindgut”—the latter half of the digestive tract—that holds food for digestion over extended periods of time, up to 49 days.6 Their guts are also occupied by specialized bacteria capable of breaking down highly fibrous food.7 This feature is one of the reasons tortoises are so long-lived, as their metabolism is extremely slow but consistent throughout their lives.8
Freshwater turtles—like sea turtles—spend most of their lives in water, mainly leaving water to lay eggs, yet also exhibit adaptations fit specifically for their freshwater habitats. While sea turtles limit their habitats to more tropical climates, freshwater turtles inhabit a much wider climate range. During winter months, adult freshwater turtles of northern species brumate—the reptile form of hibernation—by burrowing into the soil at the bottom of ponds, leaving their shallowly buried nests to fend for themselves in the freezing temperatures. How do the hatchlings survive? Many of the northern species are specially equipped for overwintering in the freezing topsoil and are what is considered “freeze tolerant,” allowing some hatchlings to survive temperatures down to -4˚C for an extended period.9 Other species can survive winter as hatchlings by “supercooling.” This term refers to cooling below the freezing point of water without the water forming ice crystals. In this way, these northern freshwater turtle species possess a special design to prevent ice crystals from forming, helping them avoid frostbite and survive freezing temperatures unharmed.10 In both cases, these baby turtles exhibit an incredible ability to survive in extreme conditions. If evolution were true, how could the first northern freshwater turtles have survived if they were not already equipped with these necessary survival abilities? God is amazing in His foreknowledge, and characteristics such as these show His care for His creation.
Mysterious Complexity: Proof of Design
Despite advances that have been made in science and studies that have been done on turtles, there are still many mysteries surrounding them by which evolutionists are stumped. One of these traits is the “Rathke’s gland,” which can be found in all freshwater and sea turtles but is absent in tortoises. Rathke’s glands excrete a brown, very foul-smelling liquid. Though scientists are unsure of their function, they are hypothesized to be used for both repelling predators and communicating with other turtles.11 The intriguing fact about this particular gland is that there is “general similarity in the anatomy of the glands among extant species and fossils,” meaning this specialized communication gland has remained seemingly unchanged for supposed hundreds of millions of years as required by evolutionary thinking.12 In contrast, it makes more sense to conclude that these animals appeared on Earth much more recently than evolution requires, created by an all-knowing Designer Who left hints of His handiwork all around us.
Another trait still shrouded in mystery is the navigation ability of sea turtles. “The total distances certain green turtles (Chelonia mydas) and loggerheads (Caretta caretta) traverse over the span of their lifetimes exceed tens of thousands of kilometers.”13 These journeys include returning to the beaches where they hatched to lay eggs and small feeding grounds. How is it possible that they can travel such distances without a map? Researchers have found that sea turtles seem to utilize two main methods of navigation. Sea turtles can detect chemical cues in the water, and it is hypothesized that they are able to utilize distinct variations in those chemical cues to help orient themselves to their location. Second, sea turtles have what could be called a “magnetic compass sense” that allows them to utilize variations in Earth’s geomagnetic field to navigate across the faceless ocean. Even with all the years of research and tagging of sea turtles to monitor their movements, at the end of the day, “how adults navigate across vast expanses of seemingly featureless ocean, however, remains an enduring mystery.”14
Conclusion
The beautiful sea turtles of the ocean inspire awe in many, with nasal cavities unique even among the reptiles, lungs and brains designed for deep dives, and the ability to navigate across the expanse of the ocean without maps. Tortoises were designed like tanks inside and out, with a thick, domed shell and strong legs to carry them on land, and the inner gut designed to digest whatever food the tortoise comes across. Meanwhile, freshwater turtles exhibit some incredible specialized abilities mirroring that of their seawater relatives, able to withstand freezing temperatures and extract oxygen from water around them. Both sea and freshwater turtles are also able to communicate in ways that confound scientists with their highly advanced communication glands—clearly designed by a Being more intelligent than modern scientists.
God has truly designed an incredible creation filled with mysteries we may never find the answers to, and often the more we explore and learn, the more complex the picture becomes. Isn’t it hard to fathom how, according to evolutionists, “[f]rom the Triassic the turtles have come down to present times practically unchanged,”15 yet we still understand so little about them? Is it reasonable to suggest that such complex, intentional features could emerge by pure accident over millions of years? Truly, only an omniscient Designer could have created such complex and specialized designs.
“But now ask the beasts, and they will teach you; and the birds of the air, and they will tell you; or speak to the earth, and it will teach you; and the fish of the sea will explain to you. Who among all these does not know that the hand of the LORD has done this, in whose hand is the life of every living thing, and the breath of all mankind?” (Job 12:7-10).
Endnotes
1 By using the term “adaptations,” we are not endorsing the Darwinian evolutionary idea that, through adaptation, one form of life can evolve into a completely different kind of life. Rather, we are referring to the heritable genetic variability with which creatures have been designed that allows a narrow limit of offspring varieties, some more suited to various habitats than others (i.e., microevolutionary change, not Darwinian macroevolutionary change across phylogenic boundaries).
2 M.E. Lutcavage, P.L. Lutz, and H. Baier (1987), “Gas Exchange in the Loggerhead Sea Turtle,” Journal of Experimental Biology, 131:365-372.
3 P.L. Lutz, J.C. LaManna, M.R. Adams, and M. Rosenthal (1980), “Cerebral Resistance To Anoxia in the Marine Turtle,” Respiration Physiology, 41:241-251; P.L. Lutz, M. Rosenthal, and T. Sick (1985), “Living without Oxygen: Turtle Brain as a Model of Anaerobic Metabolism,” Molecular Physiology, 8:411-425.
4 S. FitzGibbon & C. Franklin (2010), “The Importance of the Cloacal Bursae as the Primary Site of Aquatic Respiration in the Freshwater Turtle, Elseya albagula,” Australian Zoologist, 35[2]:276-282.
5 D. Kondoh, C. Kitayama, & Y.K. Kawai. (2021), “The Nasal Cavity in Sea Turtles: Adaptation to Olfaction and Seawater Flow,” Cell and Tissue Research, 383:347-352, https://doi.org/10.1007/s00441-020-03353-z.
6 E. Sadeghayobi, et al (2011), “Digesta retention time in the Galápagos tortoise (Chelonoidis nigra),” Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, 160[4]:493-497.
7 P.S. Barboza (1995), “Digesta Passage and Functional Anatomy of the Digestive Tract in the Desert Tortoise (Xerobates agassizii),” Journal of Comparative Physiology B, 165:193-202, https://doi.org/10.1007/BF00260810.
8 T.K. Brown, K.A. Nagy, and D.J. Morafka (2005), “Costs of Growth in Tortoises,” Journal of Herpetology, https://doi.org/10.1670/0022-, 39[1]:19-23.
9 J.P. Baker, et al. (2003), “Adaptations to Terrestrial Overwintering of Hatchling Northern Map Turtles, Graphtemys geographica,” Journal of Comparative Physiology B, 173:643-651, DOI 10.1007/s00360-003-0373-5.
10 Ibid.
11 A.M. Bezerra, et al. (2020), “Anatomical, Histological, and Histochemical Analyses of the Scent Glands of the Scorpion Mud Turtle (Kinosternon scorpioides scorpioides),” The Anatomical Record, 303[5]: 1489-1500.
12 Ibid.
13 K. Lohman, J. Hester, & C. Lohman (1999), “Long-Distance Navigation in Sea Turtles,” Ethology Ecology & Evolution, 11:1-23.
14 Ibid.
15 A.S. Romer (1933), Vertebrate paleontology (Chicago, IL: The University of Chicago Press), p. 133.
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