Chinese palaeontologists hope to explain the rise of the animals

Squeaky the Squirrel

http://www.economist.com/news/science-and-technology/21573951-chinese-palaeontologists-hope-explain-rise-animals-kingdom-come

AMONG the mysteries of evolution, one of the most profound is what exactly happened at the beginning of the Cambrian period. Before that period, which started 541m years ago and ran on for 56m years, life was a modest thing.

Bacteria had been around for about 3 billion years, but for most of this time they had had the Earth to themselves. Seaweeds, jellyfish-like creatures, sponges and the odd worm do start to put in an appearance a few million years before the Cambrian begins. But red in tooth and claw the Precambrian was not—for neither teeth nor claws existed.

Then, in the 20m-year blink of a geological eye, animals arrived in force. Most of the main groups of the animal kingdom—arthropods, brachiopods, coelenterates, echinoderms, molluscs and even chordates, the branch from which vertebrates went on to develop

To try to link the evolution of these species with changes in the environment, Chu Xuelei of the Institute of Geology and Geophysics in Beijing and his colleagues have been looking at carbon isotopes in the Doushantuo rocks. They have found that the proportion of ¹²C—a light isotope of carbon that is more easily incorporated by living organisms into organic matter than its heavy cousin, ¹³C—increased on at least three occasions during the Ediacaran period.

They suggest these increases mark moments when the amount of oxygen in seawater went up, because more oxygen would mean more oxidisation of buried organic matter. That would liberate its ¹²C, for incorporation into rocks.


Each of Dr Chu’s oxidation events corresponds with an increase in the size, complexity and diversity of life, both plant and animal. What triggered what, however, is unclear.

Capt'n Midnight

http://www.bbc.co.uk/programmes/b00vw49d

Sir David Attenborough goes back in time to the roots of the tree of life, in search of the very first animals

interesting , they did 3D x-rays of fossil eggs too