Creationist's nightmare - part 2

Borrowed from visitbalionline.com

 Mudskippers are an obvious and clear example of evolution in action, as they daily play out the prehistoric drama of life pushing beyond its oceanic nursery. It is no simple matter that animals that evolved for millions of years under water, made their way on to land. That’s one of the reasons that evolutionary biologists are drawn to mudskippers. When fish broke the water barrier they triggered an explosion of vertebrate diversity that flowered into amphibians, reptiles, birds and mammals, including us. So the big question when we’re looking at the mudskippers on the shores of Lantau, is: are we staring at one of our most important ancestors? 

    Unfortunately the answer is no. 

    So called “bony fishes” split into to two major branches more than 400 million years ago. The “ ray-finned bony fishes” and the “lobe-finned bony fishes” evolved completely separately. Living examples of the “ray-fins” include most of the commonly known fish such as carp, pufferfish and mudskippers. “Lobe-fins” alive today are more obscure, but they include lungfish, which have much more sophisticated air breathing adaptations than mudskippers, and coelacanths which were once thought to be extinct, until one turned up in a fisherman’s by-catch. It was the lobe-finned fishes that first crutch-walked and skipped out of the ocean, developed limbs, and walked off into the forest as tetrapods ñ or four-footed animals. They gave rise to all the other vertebrates including geckos, snakes, eagles, civet cats and monkeys.

    So “our” ancestors left the ocean independently of mudskippers. 

    But thanks to convergent evolution, we might well see in a mudskipper an animal remarkably similar to a human ancestor. And for that same reason, we can learn a lot about life from mudskippers. 

    Convergent evolution comes about when species that don’t share a “recent” ancestor independently evolve similar solutions to common environmental pressures. Their whole form could be similar to each other, or they might have similar body parts. Dolphins, for example have a similar shape to sharks, including fin or flipper swimming aids, and torpedo bodies to cut through the water. But sharks are fish whose ancestors never left the water, and dolphins are mammals whose ancestors walked on land on all fours. As predecessors of dolphins gradually adapted to life in the oceans, their legs dropped off, and they slowly evolved to resemble sharks.

http://bio-ditrl.sunsite.ualberta.ca/detail/?P_MNO=1800

    Elsewhere bats and birds independently evolved wings, as did moths. And bats developed sonar to catch moths long before humans developed radar on the same principles to guide fighter jets in warfare. And humans were playing a game of catch-up with moths when they created radar-evading stealth fighters. 

     Gadgets are worth mentioning because they show that our solutions to the restrictions of the environment are limited to certain choices by the universal laws of physics and chemistry. These same laws force convergence on animals that adapt to similar environments.

    The mudskipper’s constant companion on the mudflats is the fiddler crab, abundant in Hong Kong in the same places the skippers skip. They are popular attractions with their massively distorted single giant claw that they wave to show-off in the tidal zone. The fiddlers are invertebrates, no closer related to mudskippers than we are to shrimp. But the eyes of these two unrelated species sit in equivalent positions on their bodies, prominently atop the highest points.  On mudskippers they bulge above the crown of their heads, and on the crabs they wave high on stalks. The forces that pushed these eyes upwards are the same for both species, the need to see what’s happening above the water while their bodies are protectively hidden. The top position gives them the information they need before they venture out of the water. Watch the tide suck out of a mud flat and you’ll see beady eyes appear first, species indistinguishable until bodies emerge creeping and crawling, like a creationists’ nightmare.

AFCD

    But creationists are adept at wriggling out of a tight spot. “Of course these animals are similarly adapted to the environment, God made them that way so they can live there,” they’ll say, perhaps even suggesting that God may as well have saved time by using similar design solutions for the eyes of both species. There are no “transition” species in the eyes of creationists, because the so called transitionals just happen to be the animals that are perfectly crafted for the environment that God put them in, of course.

    The creationists live in a strange timeless world, where the present always has been and will continue to be, until the apocalypse. I much prefer seeing mutability in a fish that walks on land, a reminder of the fact that life changes, and we’re all just passing through. A mudskipper can inspire awe about the ancient origins of life, and optimism, for the constant search for better environments, and new modes of existence.

    Though, for some, they just inspire lunch.

    When I first learned about these excellent fish, I assumed that they wouldn’t taste good, otherwise I would have been offered one on a plate at some point in my life, surely. But I was wrong, there is a little-known niche for mudskipper-eaters across the tropics from West Africa to southeast Asia, and beyond the tropics to Japan, where the most northerly representatives of the family are eaten as a specialty on the island of Kyushu. Depending on local tastes the fish can be roasted, boiled, or eaten raw. In Yemen the fish are dried, pulverised, and dissolved in hot water and honey.

    Like a lot of traditional foods, Mudskippers are also prescribed for medicine. And as with much traditional medicine, there’s often some vaguely described link to sexual performance. From the honey flavoured beverage in Yemen, to Papua New Guinnea and China, people have ingested mudskippers in the belief that their sex lives would improve. Though I haven't seen a convincing theory of how walking fish can help out in the bedroom.

    I found one account from Malaysia about a man who swallows five live mudskippers a day, to prop up his apparently flagging libido. He said he had learned the secret from his father who had 16 children, which he took as evidence that there was something in it.

    But when you look at the huge range of animals, in whole or in parts, that have been passed off as tonics for boosting carnal desire and performance, it’s difficult to find a common link between them. Usually it is little more than suggestive shapes, and admittedly mudskippers do look like wet willies with fat heads sometimes. The idea that eating things that look like willies boosts the libido seems ridiculously simplistic, but I guess it is also testimony to the eternal human capacity for optimism.

    But swallowing mudskippers live could be a big mistake, especially if they’re taken from the wrong place. Although the fish are regarded as edible, with no particular toxins associated under normal conditions, they can absorb and accumulate pollutants from the environment. Because of this they are recognised by environmentalists as useful “biomonitors” for poisons that wash into the inter-tidal zone. Studies in Hong Kong in the Mai po marshes have shown worrying effects from two polluted streams, the Yuen Long creek and the Shenzhen river, that pour into brackish marshland of the Deep Bay estuary. Mudskippers have been found to be amongst the most contaminated species on the mudflats, recording high concentrations of heavy metals and insecticides.  This is disturbing, both for any human tempted to snack on the amphibious morsel, and for the thousands of hungry birds that fly in from distant breeding grounds, to shelter and fatten up in the renowned wetland sanctuary.

    Concern about a toxin build-up in mudskippers is not just a matter of being sentimental about some endearingly eccentric fish with chubby cheeks. As so-called “biomonitors” they indicate the state of health of the wider ecosystem, connecting aquatic life to the terrestrial. Finding a bunch of them along Hong Kong’s shoreline is a good sign for that particular locality, even if pollutants can be measured.  It shows that there is still enough life in the zone to keep the skippers alive, from various nutritious algae, to aquatic snails, little crustaceans, and small fishes. And as long as the skippers are fattening on that salty soup of flora and fauna, bigger predators remain attracted to the shoreline. These include other fish that catch the skippers in high tide, as well as terrestrial beasts such as snakes, lizards and of course beautiful shorebirds such as storks and pelicans. And as long as these keep coming, local mongoose and leopard cats have something to hang about for, as well as apex predators from afar such as raptors from Siberia and central Asia.