I think this is BS. It strikes me as being very similar to the Elliott Wave and Kondratieff Waves in economics.
In the case of economic waves, the wave theorists basically mapped the ups and downs of the economy going back hundres of years and from that deduced laws of nature that said the economy will go up and down in regular interverals. The problem is that so much changes in every cycle that it becomes meaningless trying to find a pattern. Remember that thing about how the Democrats would win if the Redskins won their home game before the presidential election? The Redskins did it 12 times in a row so there must be something to it right? Well the Redskins won and John Kerry isn’t president. In 2008 they will find a new fun fact about something which has held true for 100 years (like, in years where the olympics are held in a non European country, the Republicans win if the Americans win both women’s basketball and men’s shot put).
Back to economic waves….trying to pick out a grand pattern over 400 years is a joke. The economy isn’t anything like it was 40 years ago, let alone 400. Everything is different: technology, demographics, culture, religions, transportation. Everything.
The same strikes me as true with this extinction study. Multicellular life really hit its stride about 500m years ago with the Cambrian explosion. If the scientists are right, that only makes for 10 major extinction events since the Cambrian. Of the major extinction events, we have a good idea about some (KT) and not so good idea about others (PT).
10 is way too small a number to pry any sort of trend out of. The best you can say is that it happened multiple times, not that it happens like clockwork. Each event could be different and the factors which caused past events might not exist anymore. Example: asteroid collissions are much more rare now than in the early days of the solar system, and we can detect them before hand now. Volcanism has probably died down considerably over the last 500ma. Increased diversity has made life more stable and less vulnerable to crashes by key groups.
Maybe the key to the cycle is looking at odd numbered eons with significant polar glaciation, without asteroid impacts in the previous 10ma, before the Redskins win a home field game.