Secondary indicators

I really was fascinated by libraries and museums when I was a kid. I even made a tiny museum of my own, complete with an illustrated card catalog for each of the exhibits, including acquisition-date and provenance. Most were of particular interest only to an eight year old, (like the posable gumby I traded-for, in the school-yard). But I did have one genuine trophy. You see, I'd spent several hours on a beach near Collingwood playing with chunks of slate, trying to make myself a nice native-style arrowhead. I'm lucky I didn't get any chips in my eye (and probably lucky too, that I never did get the knack of putting a fine edge on flint), but one particularly hefty chunk did split along a precise plane (as slate is wont to do) and revealed not just the fossil impression of a trilobite, but the fossilized skeleton itself! Long lost now (sadly), but still enough of a gee-whiz influence on my early brain that the idea of digging for clues to the past - palaeontology and archaeology both - continues to fascinate me to this day.

Solnhofen limestone (top picture)

Naturally, limestone is one of the finest materials for the preservation of signs of prehistoric life - but even then, how you're using it makes a big difference. In the case of Solnhofen limestone, an especially fine-grained and consistent variety, the rock has been quarried for centuries now, for use in lithography - which means breaking it down into super-thin slices - which has revealed an extraordinary number of creatures from the past. No less than six exhibits at the ROM come from Solnhofen finds - and many other museums around the world also have reason to appreciate their imperfect arrowheads.

Palaeozoic flower arranging

Here's something even older than a trilobite - a so-called "Sea Lilly" though it appeared quite some time (300 million years) before flowers on land (themselves 200 million), and is not actually a lily at all, but a carrion-feeding sea-floor animal with a fixed stalk. More specialized versions of these critters exist to this day, but the 5000 extinct species known, some of which were twenty meters long, are used all the time as 'index fossils' to help date other, more ambiguous samples found in close proximity. While I'm on it, a note about flowers - another favourite topic of mine. They've finally sequenced the genome of a plant that Darwin himself suspected might be the link between the super-ancient ferns (gymnosperms) and the later flowering plant (angiosperm) family, which includes a rather high proportion of everything we warm-blooded critters like to eat. The plant in question - Amborella - seems to be the very oldest common angiosperm ancestor which exhibits genomic-doubling - the chief difference between those two huge classes. The flowering plants ultimately evolved almost 1200 genes which are unique in the living world, and allowed them a huge variety of new mechanisms and ultimately, adaptation-solutions. The really wild thing about Amborella's complete sequence though, is in the mitochondrial DNA, which is six times larger than that of any other known plant! How could such a key piece of early coding get so bloated? Inside it's mtDNA, they found the complete mtDNA sequence of three types of green algae, one moss, and individual genes from other species - none of which are 'active'. Perhaps a clue to the genomic doubling itself? The first hybrid team? (not all of whose members turned out to be helpful?) ;o)

Kind of screwy

This is a cast of a type of formation which was found all over the place for centuries and thought geologic, before their true origin was finally deduced. The form is remarkably even, and to our helically-inclined minds, both modern and technological. Not so. I like a brain-teaser, so I spent a few minutes thinking about it myself, before reading the card, but I couldn't think of any geologic process from vulcanism to erosion that would produce such an even and well-crafted seeming result. Indeed - it turns out that well-crafted is the right idea exactly. These incredibly deep and regular structures were the burrows of tiny prehistoric beavers! Way deeper than many modern burrows, very nice predator-protection - and a smooth even spiral staircase for a lazy way to make your way up and down that long distance - why burn all your calories, just coming and going? They really do mean it. There is nothing new under the sun - corkscrews (and spiral staircases) included!

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