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Cambrian Time Machine

Cambrian Diorama image of ocean scene

Image courtesy of Ken Doud, Videoscapes    

    For the sake of this essay, let's say you are the ultimate explorer, one who has somehow gained access to a fully functional time machine. Thus equipped, you are able to travel back to any point in the past… from the birth of Planet Earth some 4.54 billion years ago, to your romantic dinner date last Wednesday. 
    With the entire history of the world quite literally at your fingertips, perhaps your interests would lead you back to the Old West to experience the sight of buffalo by-the-millions covering the Great Plains. Or maybe you'd sojourn to the time of the Roman Empire to watch Julius Caesar at the pinnacle of his powers. Perhaps your curiosity would propel you back to the savannas of Eastern Africa two million years ago to witness the lifestyle of our earliest hominid ancestors.
    But now let's say you are really adventurous, and that as you sit at the controls of your time machine, just prior to hitting the “go” button you plug in a date 510 million years in the past. Such a decision would require a lofty degree of gumption and preparation along with perhaps more than a modicum of foolhardy intent, for the world you would encounter upon arrival would be far different than the one you had just left behind. Indeed, the environs of Middle Cambrian Earth would resemble nothing more than those of an alien planet, which in all honesty, is exactly what this primal world would be. 
   If your time machine emerged upon the recently formed continent of Laurentia, you would immediately note a virtually barren landscape. Amid active volcanic fields and frequent earthquakes caused by ever-shifting continental masses, you would see no animal life, and the few primitive plants would resemble mere microbial mats as they dotted beaches along certain tidal estuaries. While the average daytime temperature might hover near a perfect 70 degrees, the surrounding acrid-smelling atmosphere would present a number of survival problems for any modern human - Carbon Dioxide levels nearly 16 times higher than 21st Century levels, and an Oxygen content only 60 percent of what we today enjoy. 
   If you had been resourceful enough to bring along a diving apparatus -- one which would allow for exploration of the primeval seas - you'd be prepared to encounter quite a different scenario. There, life would appear abundant, varied and nothing less than astonishing. Indescribably bizarre invertebrate creatures of all sizes and shapes would fill virtually every aquatic niche. Amid patches of filtered sunlight, legions of small, soft-bodied arthropods would float by on tidal currents, while a multitude of trilobite species such as Kochina vestita and Marjumia typa, would either jet past in water-propelled bursts, or scamper across the sea floor on rows of spindly appendages. Perhaps if you're fortunate, you might even glimpse a large, predatory Anomalolaris as it menacingly glided past.
    Needless to say, this would be a world beyond even our most vivid imagination, but one that trilobite enthusiasts might find ever-so-slightly disappointing. The fact is that until fairly recently it was standard scientific thought that trilobites dominated these early seas. But a number of recent discoveries made in appropriately aged strata around the globe have shown that while trilobites were indeed numerous in the ancient Cambrian oceans, other life forms -- including the astounding array of soft-bodied arthropods --actually dominated the fauna.
    Somewhat surprisingly, in light of this apparent abundance, life in the oceans 510 million years ago was already in sharp decline, especially when compared to the undersea world that had blossomed soon after the advent of the Cambrian Explosion some 30 million years earlier. A marked drop in speciation had already begun to impact the trilobites, so as hydrogen sulfide levels - caused by undersea eruptions - began to rise, and as marine oxygen levels continued to dissipate, survival for all these early oceanic creatures became ever more tenuous. 
     Thus it would seem that any time-traveling excursion back to the Middle Cambrian would be a trip defined by both an abundance of amazing opportunities and more than a few unexpected dangers. Yet even in light of such apparent adversity, are there any among us -- whether or not we're the ultimate explorer -- who would pass on the chance to take part in such a monumental sojourn and witness complex life in one of its earliest, and most important stages?