Friday, May 05, 2006

Blessed are the oysters

It is a common fallacy in biology that human kind is the pinnacle of evolution. Mostly this is because as humans, we are both smart and vain. We are smart enough to figure out where we come from (56% of redneck America notwithstanding), and vain enough to believe that this must make us special. But what does it mean to be evolutionarily advanced?

One approach is to look for the tried and true. The less a gene changes, the more superior it must be over any possible alternative that might arise throughout the depths of time. In fact, one could argue that the more something changes, the less evolutionary fitness it possesses. By this argument, the most advanced creatures on earth are not the most different, they are the most simple. So the most evolved creatures on Earth are the Archaea, those primitive, bacteria-like creatures that have been living in hot springs, unchanged, for as long as we have rocks for. These creatures are so advanced that any random mutation makes them less fit than their parent, so they remained genetically static through the entire evolution of multicellular life.

However, the existence of other, more recent forms does tend to suggest that the tried and true is not the only possibility. After all, one of the reasons Archaea are only found in extreme environments is that they get turned into lunch everywhere else. So what other quality could we use to determine the most advanced life form. Most new genes? Dunno how we stack up there, but I doubt we can hold a finger to the conifers, which have single chromosomes that are larger than many creatures’ entire genomes.

Of course, plants are notorious for doubling and quadrupling their genome at the drop of a (pine) needle. The red spruce genome has more repetition than a primary school arithmetic lesson. So perhaps instead of the most genes, it should be the highest number of different genes. But determining that could be rather difficult, considering that each year only a handful of species have their genomes sequenced, while hundreds of new species are discovered.

For this reason, looking at actual genes themselves is a fairly impractical task. After all, natural selection doesn’t work directly on genes anyway. It works on the chemicals and mechanisms for which they code.

This is where the whole idea of human intelligence as the epitome of evolution comes from. Intelligence is not a gene, it the expression of a (or more likely, many) genes.

This is a more interesting argument for the rest of us non-geneticists anyway, since we appreciate eyes and wings and brains more than interminable strings of the same four letters.

It also makes it easier for us to stroke our own egos. After all, we only need to show that the evolution of intelligence is the largest and most unique step ever taken in the history of evolution in order to crown ourselves as the cream-du-jour of this process.

Unfortunately, this may not be so easy. While vertebrate evolution has shown a tendency towards larger and more complicated brains, we are not, pardon the pun, the only fish in the sea. Back when our phyla was just a twinkle in a segmented worm’s eye, other creatures with brains far more developed than our forbearers were taking the Palaeozoic oceans by storm.

I am talking, of course, about the molluscs. The most intelligent creatures alive today outside the vertebrate kingdom are the free-swimming, many tentacled molluscs known as cephalopods. In fact, some of the octopi currently on display the world’s aquariums are actually smarter than the toddlers who come to gawk at them.

But cephalopods are not the most successful molluscs. They are third.

Starting in the late Cambrian, and continuing until the event that wiped out the dinosaurs, cephalopods were doing pretty well. For a time, way back when men were men, graptolites were graptolites, and continents were bare and devoid of multicellular life, they were the most complex and dangerous creatures on the planet. However, they were not the most numerous, or widespread. The molluscs that out-diversified them, gastropods and bivalves, lost their big brains, their free swimming ways, and their manipulative tentacles. Most of them became scavengers or filter feeders. This change to simplicity allowed them to colonize fresh water, and even land. In the process, some of them lost the mobility, the eyesight, even the prehensile manipulators that made their ancestors so complex. So from this point of view, the most evolved mollusc alive today is not the intelligent, free-swimming, predatory nautilus. It is the brainless, sessile, omnivorous oyster.

Is this our future? To evolve from mobile, free thinking predators to sessile filter feeders? It may seem unlikely, but consider that in the last 200 years, hunting and gathering societies have become all but extinct. And what have we invented to fill the time once occupied by devising plans to kill creatures faster and stronger than ourselves?

Oh, sure, some of us have composed symphonies, built cathedrals, and gone to the moon. But have you? I can count the number of men who have been to the moon on both of my six-fingered hands. And the last of these men left the dusty lunar surface before I was born.

No, to judge the true aspirations of mankind, we need to look a little closer. We need to look at ourselves. We need to look at a selection of inventions that all of us have used, and that some of us may be using right now.

I nominate three: The couch, the pizza delivery truck, and the television remote control. We are no longer intelligent, free-ranging, pretatory primates. Brainless, sessile, omnivorous primates are what we have become. It is my prediction that in 300 million years, hyper-intelligent beetles will be harvesting our progeny for pearls.

Of course, pizza on the couch is not the best possible position to be in, it is simply the one most easily obtained on a Friday night. With a little effort, we could evolve our way towards greater comfort. Instead of pizza, it could be nectar and ambrosia, those divine foods of the primordial gods. Instead of the delivery truck, we could have shapely handmaidens of an attractive, fertile phenotype. Instead of the couch, it could be the Jacuzzi. Or a hot spring. The Archaea have known this all along, which is why they have not left their bubbling spas for several billion years. Ladies and gentleworms, we have a winner.

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