Monday, January 5, 2015

Cambrian trilobites (Part 1: Where they lived)

This post will come in three parts. First I'll try to give an idea of what the environment was like when trilobites were around, then I'll explain what exactly these things were, and finally I'll tell you how you can go find one for yourself (and how to do so responsibly)!
The head of a trilobite, covered in mud 515 million years ago and hidden until it was pulled out of the rock this fall. What was the world like when these things dominated the waters?

Deep Time

The earth is a dynamic place. From the buzz of an insect's wings to the growth of an acorn into an oak, it seems that there is something interesting happening at every timescale humans are capable of monitoring, yet we know we're missing out on much more when we visit a museum and see the tarnish gathering, like age itself, on ancient weapons and jewelry. Things happening on this scale, centuries to millennia, are already beyond our direct observation, but we can still connect them with the chain of recorded history produced by our ancestors—They are not completely alien to us.

Walk into another wing of the museum however, and you're completely out of your depth. The thread of human history unwinds about 6,000 years ago into frayed, wispy fibers and there is no recorded thought that reaches back more than 40,000 years, to be quite generous. Imagine a race of human-like beings that experienced those 40 millennia as a single year of their impossibly long lives; only then can we even begin to see the real fluidity of our planet. At this scale, the equivalent of a century-old being could witness our full evolution from furry, arboreal apes to thinking, upright humans, while a few generations would be able to notice the motion of the continents. If these long-lived versions of ourselves followed a similar historical arc to scale with ours, the extinction of the dinosaurs would coincide roughly with the founding of their Catholic Church (Which would immediately split into warring factions over the issue of whether the dinosaurs went to Heaven). Within the realm of record, but clouded by age, even to these creatures the dinosaurs would be ancient history!

The oldest scrolls and tablets of their history would record the first mammal-like reptiles' appearance at the dawn of the Triassic period. Their development of agriculture would coincide with the appearance of the first tetrapods, 400 million year-old, newly-legged, near-fishes that would give rise to amphibians and, through them, all reptiles, mammals, and dinosaurs (including birds). Beyond that, this ancient culture would be essentially as devoid of historical reference as we are of life during the last Ice Age, so that even they would have to extract clues to the dawn of multi-cellular life from their equivalent of cave paintings and pottery fragments. The fossil record serves us nearly as well, and so at this point we are finally on near equal-footing. It is this period of time to which the trilobites belong: The ancient history of the ancients.