CREATION - Snowball Earth - page 97

exactly as they once lay—Newfoundland is the only place in the world where you can walk around on
the Ediacaran seafloor.
This rare preservation method has another benefit. Each layer of ash provides the Ediacarans it
killed with a handy age marker. Volcanic ash is a great way to date rocks, because it contains traces
of radioactive elements; uranium, for instance, which decays into lead at a precise, well-defined rate.
When a volcano explodes and its ash forms, this uranium clock starts ticking. With each tick, the rock
loses uranium and gains lead, and the ratio of these two elements gradually changes over time. In an
ash layer, geologists can measure the ratio of uranium to lead today, and can tell how much time has
passed since the ash formed.
Here at Mistaken Point, the ash that smothered these jellied fronds and spindles gives an age of
565 million years. 9 The creatures here are much older than the ones in Australia or the White Sea.
They lived just 25 million years or so after the Snowball.
They're not even the oldest fossils in Newfoundland. The next day we find ourselves on another
part of the coast, this time close to a beach where each receding wave sucks the pebbles backwards
with a sound like a crackling flame. The rock layers here are giant black slabs, tilted sideways like col-
lapsed dominoes. We head for one that has some kind of large discs etched into it. “Pizza to go, any-
one?” says Guy Narbonne, the Canadian researcher who is leading the trip. He's right. These fossils
look exactly like pepperoni pizzas. Or at least they are the perfect size and shape; but the pepperoni
pieces are mud-coloured and the region around them is apple green, like slightly mouldy dough. A
careful hike over the slippery rocks takes us to a red surface, which bears the faintest trace of what
looks like a long-stemmed cocktail glass. Near it are two thin fronds, several feet long. At least these
don't remind anyone of food; they look more like the prints from a bicycle tyre. 10
Where the rock layer disappears into the ground, we can see, edge-on, the ash layer that preserved
these faint fossils. I'd half expected it to be dark and crumbly, but instead it's as solid as concrete, and
the same pale green colour as the pizza “dough”. This ash has been dated. The result bears the status
of a “rumourchron”—geologist slang for a date that has been measured but is not officially out in the
world. It comes from the lab of Sam Bowring at MIT, one of the most reliable geochronologists in the
world. Sam has told the date to many people. He's presented it at conferences. 11 But he hasn't quite
published it yet. It's 575 million years. If his date holds, these fossils are almost as old as the final days
of the Snowball.
S TEP BY step, the date for the invention of complexity is approaching the end of the Snowball. For
many people this is beginning to look like more than a coincidence. But one serious problem still
remains. A few researchers have turned up what they think could be signs of complexity before the
Snowball. If multicellular life really did emerge before there were even glimmers of global ice, that
could scotch the whole biological part of the Snowball theory.
Some of the evidence is still highly controversial. An outcrop in northern Canada bears perhaps
a thousand discs, somewhere between the size of a dime and a quarter, impressed into the bottom of
sandstone rocks. The rocks date from around 100 million years before the end of the Snowballs, and
their discoverer, Guy Narbonne, insists that they are complex creatures. 12 But they left no trails, and
have virtually no structure. Other biologists say they could well have been simple blobs of jelly or
colonies of bacteria.
And etched on billion-year-old rocks from India are pencil-thin branching tubes, which their dis-
coverer—a most respected researcher named Dolf Seilacher—believes were made by some kind of