Tiger snake jaws evolve, claim scientists who studied tiger snakes on Carnac Island – a tiny rocky island off the coast of western Australia. The snakes are the descendants of a collection of snakes believed to have been taken to the island in 1930 by a travelling showman who was in trouble with the authorities for having a dangerous carnival show.
The island was previously free of snakes, and was also lacking the small animals, such as frogs, that tiger snakes normally ate. However, the snakes survived by eating baby seabirds, which are larger than the snakes’ usual prey, and now Carnac Island snakes have larger jaws than mainland snakes.
Scientists from University of Adelaide and Flinders University studied the jaws of island and mainland snakes to see how the snakes could have evolved larger jaws in less than 100 years. They raised baby snakes from Carnac Island and snakes from Herdsman Lake on the mainland and fed them two different diets – small mice and large mice. Baby Carnac Island snakes had larger jaws than mainland snakes when they were born, and if they were fed on a diet of large prey their jaws grew larger than snakes of fed a diet of small prey. Mainland snakes fed on large prey did not develop larger jaws than snakes fed on small prey. The research team claim the Carnac Island snakes have undergone rapid evolution and “phenotypic plasticity”.
Alessandro Palci of University of Adelaide commented: “Not all evolutionary change takes millions of years, as it is often assumed by people when they think of Darwinian evolution.” He went on to explain: “After a year of feeding them large mice, basically they grew five per cent longer than the other ones that were fed on small mice. It’s super fast and it’s why this study is so interesting, and for vertebrates it’s one of the few examples of really fast evolution.”
Editorial Comment: The jaws of the Carnac Island snakes may be different in their growth pattern compared with the sample of mainland snakes, but the snakes have not evolved. They are still the same species of snake, and a 5% increase in jaw size is not the same as developing a new feature it did not have before, which is what has to happen before a biological process can be really called evolution.
In an environment where the main food source is larger than on the mainland it is no surprise that after 90 years the Carnac Island snakes have larger jaws, simply because large jawed snakes survived and reproduced while small jawed snakes died out. This is natural selection at work, but it is not evolution.
What is “phenotypic plasticity’? It is the ability to respond to the changes in the environment by modifying an already existing body structure, e.g. developing larger muscles and thicker bones following increased exercise. This is a useful feature as it enables living creature to cope when changing demands are put on the body, but not waste resources on building bigger structures until they are needed.
The increased growth of the jaws in Carnac Island fed with large mice is a genuine example of this, but it is not an evolutionary process. It is a design feature. It can only happen if the genes that control the jaw growth are already primed to respond to the stimulus of trying to eat large prey, i.e. it is the result of forward planning and has to be built in. Snakes that already had this ability survived to reproduce on Carnac Island, those that did lost out in the struggle for life. It seems that the sample of mainland snakes used in this study had lost this ability, but it hasn’t prevented them from surviving as there was plenty of small prey for them to eat where they live.
Creation Research News 3 March 2023
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