Sunday, 18 September 2016

Caving for Creationists

A waterscorpion (Nepa sp.) attacks its crustacean prey.
Photo credit: Patrick Landmann/SPL
BBC - Earth - The bizarre beasts living in Romania's poison cave

News that a cave near the Black Sea in Romania which has been isolated from the outside world for 5.5 million years has multiple examples of unique and strange creatures living it it, comes as no surprise at all to evolutionary biologists.

In fact, provided that there is a source of energy so living things can continue to live, this is exactly what we would expect of an evolutionary process.

Evolution of course not only takes place in species but in entire ecosystems and given that there is no plan, there is no reason why isolated creatures should evolve in parallel with those outside the isolated system and every reason why they would evolve in entirely different directions. In fact, if there is a plan, it is completely indiscernible in this instance even more so than usual.

A centipede (Criptos anomalans) with extra-long antennae.
Photo credit: Patrick Landmann/SPL
The Movile Cave in Constanța near the Bulgarian border was only discovered in 1986 and the extreme difficulty in reaching the inner caves has meant that very few people have actually visited the caves. To date, only about 100 people have been there. Not only is the cave isolated physically from the outside world but it is even sealed by a layer of clay above it which prevents water from the surface percolating down into it.

Analysis of the water in the cave shows it to be free from the radioactive caesium and strontium that should be there following the Chernobyl nuclear reactor accident which contaminated the ground-water in the surrounding area. The cave appears to be getting its water from a 25,000 year-old supply from the surrounding spongy sandstone and so this will not be bringing food into the cave. The only ultimate source of energy is the limestone rock itself which is gradually being eroded by the sulphuric acid in the air, so gradually enlarging the cave. The ecosystem is literally eating its own habitat, a process which left to its own devises would inevitably lead to extinction of the life forms in it. If not for an accidental discovery in 1986 we may never have known about these species!

Two woodlice (Armadillium sp.), which lack skin pigment.
Photo credit: Patrick Landmann/SPL
The journey to the inner caves not only involves a long descent by rope but a hazardous underwater journey through a maze of narrow tunnels in complete darkness save only for the light from a helmet lamp. Then when you get there, the atmosphere is toxic, being low in oxygen and high in carbon dioxides and hydrogen sulphide as the waste products of the bacterial chemosynthesis that the system relies on for its energy source, there being no sunlight whatsoever. Specialist bacteria are literally digesting the rocks and forming the mats of bacterial foam on the surface of the acidic water which is the basis of the multicellular organisms' food chain. Predators such as spiders, centipedes, pseudoscorpions and water scorpions are apex predators and a carnivorous leech lives on earthworms. Spiders still spin webs even though there are no flying insects and only springtails which jump into the air to avoid other predators.

A spider (Lascona christiani)
Photo credit: Patrick Landmann/SPL
Despite its toxic atmosphere (toxic to 'normal' life that is) Movile cave has some 48 different species, 33 of which are believed to be unique. The number and abundance of these different organisms appears to be directly related to the toxicity of the atmosphere for reasons which are not clearly understood. Many of them have no eyes unlike their terrestrial relatives and many are translucent having lost pigments - which have no purpose in complete darkness. Appendages such as antennae and legs tend to be very long because of the need to feel around in the darkness.

It is not clear how the ancestors of these creatures got into the cave. Interestingly, one of the spiders seems to be a close relative of one found in the Canary Islands and the evidence suggests a snail may only have been isolated there for about 2 million years. The view is that the isolation of the cave was a result of Africa moving north and coming up against Spain, so closing the Mediterranean off from the Atlantic and causing it to dry out along with the Black Sea to which it is connected via the Bosphorus. Species might have taken refuge in the caves which then became sealed. Another possibility is that they may not all have arrived together but fell in at various times.

But however they got there, the existence of an entirely self-reliant ecosystem and the subsequent evolution of so many unique species illustrates the power of natural selection is shaping not only the ecosystem itself but the species that live in it, and it is all, naturally, understandable as the product of an evolutionary process.

Given that these creatures were completely unknown to humans before 1986 and appear to have no benefits to us whatsoever, it would be interesting to hear how creationists manage to fit this cave system and its unique species into their Bible narrative of all life being intelligently designed for the benefit of humans. Its would also be interesting to hear how this fits in with the creationist claim that somehow the conditions on Earth are allegedly perfect for human life and that somehow 'life' requires very precise conditions. This cave, of course, just like the life around the Pacific volcanic vents gives the lie to that clam.

Any takers?

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