Cambrian Explosion: role of oxygen (Introduction)

by dhw, Wednesday, January 06, 2016, 15:22 (3586 days ago) @ David Turell

DAVID: It has been proposed that an increase in oxygen triggered the Cambrian explosion. New date has appeared showing that oxygen was plentiful (4%) for some animals about 800 million years earlier:-http://www.sciencedaily.com/releases/2016/01/160104163200.htm-QUOTE: “The water column had an oxygen concentration at least 4 % of present atmospheric levels (PAL). That should be sufficient for animals to exist and evolve," says Canfield.”-QUOTE: "'Researchers know of simple animals, such as sponges and worms, that today are capable of managing with less than 4% PAL, even much less."-QUOTE: "'Sponges probably resemble some of the first animals on Earth. If they manage with less than 4 % today's oxygen levels, it is likely that the first animals could do with these concentrations or less," says Canfield.-QUOTE: “Maybe the oxygen rise had less to do with the animal revolution than we previously assumed," says Hammarlund."-David's comment: This leaves the Cambrian period with no explanation from an evolutionary standpoint as to why it appeared when it did. It remains the main stumbling block to Darwin's chance theory.-If the Cambrian produced NEW phyla, how can anyone possibly know that those hitherto non-existent organisms could have existed on 4% of the oxygen we have today? Look at the bold: should be, probably, it is likely, maybe...This is pure speculation, and I am surprised you take it seriously. The Cambrian remains an unsolved mystery, the oxygen factor remains a possible explanation, though we still need a mechanism to take advantage of whatever changes took place.