Friday Headlines, December 14, 2012
THE LATEST IN THE GEOSCIENCES
LAND CREATURES MIGHT NOT HAVE COME FROM THE SEA
Well, this is a little deceptive. What this headline conjures in the imagination is the traditional vision of the fish, dragging itself onto land, developing legs, and ultimately becoming human.
What’s being discussed here, however, is life before vertebrates. Life before bones. The oldest types of multi-cellular life, more than twice the age of that fish that crawled onto land. This new finding (probably pay-walled) is in reference to the Ediacara Fauna, which is thought to have been ancestral to modern organisms, vertebrate and invertebrate. It appears that the organisms of the Ediacara Fauna lived on land, not under water.
Ediacaran fossils are among the most bizarre looking fossils out there, causing paleontologists to scratch their heads for years. They seem to be soft-bodied animals that have been considered potentially related to primitive worms, or jellyfish, or maybe molluscs, all of which presumably would have lived in the ancient ocean.
In the new paper, Greg Retallack argues that the rocks that the fossils are found in are paleosols – which is a fancy term for a fossilized soil. Soils do not form under water. They are a land phenomenon. Retallack used many lines of evidence to support that he was looking at paleosols rather than a sea floor, including the rock texture (it looks more like wind-blown silt than ocean-floor clay), cracks from drying (definitely wouldn’t happen underwater), carbonate nodules (which are common in soils), and stable isotopic evidence.
This new interpretation affects how we think about the origins of multicellular life, because suddenly the earliest multi-cellular forms of life were already on land. It also affects how we interpret the lifestyles of the Ediacaran fossils. Suddenly, they’re not floating around any more and that changes the kinds of things an organism can do.
An important thing to think about here is that this does not mean that life originated on land. It also does not mean that multi-cellular live originated on land. What it means is that the earliest fossils of multi-cellular life that we have on Earth were land organisms. The earliest life-forms were all soft-bodies creatures. They don’t fossilize well, which is why we don’t have much of a record. Hard parts came about in Cambrian times (after the Ediacaran Fauna), and that’s when we suddenly have a great fossil record. There probably were soft-bodied organisms living in the oceans at the same time as the Ediacaran organisms – they just weren’t preserved.
BRILLIANT GEMINID METEOR SHOWER PEAKS TONIGHT (December 13)
The Geminids are a meteor shower that seems to radiate from within the Constellation Gemini. This meteor shower comes every year in early-to-mid December. We’re in luck this year, as it seems we’ll have a new moon, making the sky nice and dark and the meteors especially visible.
The Geminids are cool because they apparently arise from an asteroid (named Phaethon) rather than a comet like most other meteor showers. The orbit of Phaethon is much more like that of a comet than of a typical asteroid. Here’s a cool Java applet that shows its orbit. We know it’s not a comet because it lacks important features, like a tail, that comets have.
The Geminids will be just past their peak when this post goes live, but they should still be evident for a few more nights. Hopefully the skies will be clear so we can all go out and look for a while.
Penny Higgins - Storyteller • Artist • Scientist 