Research team finds new explanation for Cambrian explosion

Nov 29, 2011 by Bob Yirka report
Fossil of Marrella splendens (Marrellomorpha). Image: Wikipedia.

(PhysOrg.com) -- For hundreds of years, researchers from many branches of science have sought to explain the veritable explosion in diversity in animal organisms that started approximately 541 million years ago here on planet Earth. Known as the Cambrian period, it was the time, according to fossil evidence, when life evolved from simple one celled organisms, to creatures that had multiple cells with varied functions. Now, new evidence by a team of biologists, paleobiologists and ecologists suggests that the sudden explosion of new life forms may not have been so sudden after all. In their paper published in Science, the teams says that it appears likely that most of the new life forms that show up in fossil finds, were well on their way to development before the Cambrian period and that many of them, by their behaviors, may have helped pave the way for others.

To better understand what was happening before and during the Cambrian period, the team took a two-pronged approach: one side studied, compiled and updated the , while the other focused on the of various organisms to uncover their gene history to create a more precise family tree. By combining the evidence from both sides, the team was able to put together a picture of what they believe went on.

From their work it appears that the basic for the organisms that seemingly sprang into existence during the Cambrian period were in place long before the show. In fact, there appeared to be evidence of a slow march of development for 200 million years before the sudden diversity became evident, which indicates that many such organisms were slowly evolving and only showed when conditions became ripe.

The team suggests that for many of those 200 million years, Earth went through some very cold periods where the entire planet was likely frozen, stagnating development. Then, there came a time of warming, partly brought about, they theorize, by the development of organisms that were capable of changing the environment by pulling carbon from seawater and releasing more oxygen when they died and also by those that burrowed into the seafloor aerating it, providing a new type of environment for new types of organisms.

As more organisms developed, environmental conditions changed as a result, allowing for more diversity and so on and so forth through the , resulting in the explosion of all those new kinds of life forms that scientists have been puzzling over for years.

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More information: The Cambrian Conundrum: Early Divergence and Later Ecological Success in the Early History of Animals, Science 25 November 2011:
Vol. 334 no. 6059 pp. 1091-1097
DOI: 10.1126/science.1206375

ABSTRACT
Diverse bilaterian clades emerged apparently within a few million years during the early Cambrian, and various environmental, developmental, and ecological causes have been proposed to explain this abrupt appearance. A compilation of the patterns of fossil and molecular diversification, comparative developmental data, and information on ecological feeding strategies indicate that the major animal clades diverged many tens of millions of years before their first appearance in the fossil record, demonstrating a macroevolutionary lag between the establishment of their developmental toolkits during the Cryogenian [(850 to 635 million years ago (Ma)], and the later ecological success of metazoans during the Ediacaran (635 to 541 Ma) and Cambrian (541 to 488 Ma) periods. We argue that this diversification involved new forms of developmental regulation, as well as innovations in networks of ecological interaction within the context of permissive environmental circumstances.

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User comments : 11

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Jeddy_Mctedder
1 / 5 (5) Nov 29, 2011
i love evolutionary and early period biology, but 1 billion years of entropy almost guarantees that whatever empirical evidence clues we can discover can only be a mere fractionth of the evidence that would be needed to make any firm conclusions. the story of letting things go applies particularly to thinking well ever know the story of the past. that said --- primitive molecular soup research has real world applications to engineering self organizing molecular systems.
so that shows a good crossover reason for hypothesizing the primo-ooze being worthwhile
rawa1
1 / 5 (5) Nov 29, 2011
IMO the Cambrian Conundrum is related to the Snow Ball period. It's a sort of phase transform of organic life: if you cool the environment, many new species will condense and emerge from genome as the result. IMO just the formation of sexual reproduction belongs into this era: it accelerates the speed of mutations as a response to fast changing conditions of life.

http://en.wikiped...ll_Earth

This process is actually reversible, because all living conditions have their optimal mutation rate. The lost of sexual dimorphism, parthenogenesis and some civilization diseases like the endiometriosis are the sign of wealthy living conditions and of the return to asexual forms of reproduction. After all, many organisms (protozoa) are going to sex just during the cold winter period.
mattbroderick
not rated yet Nov 29, 2011
What?
Moose Dr_
2 / 5 (4) Nov 29, 2011
I am glad to see that someone is trying to find a way for many million years to be involved in the Cambrian event. Currently this is one of the strongest cases the ID community has.

I am puzzled, however, because it is my understanding that there is a good selection of fossils of soft-bodied creatures in the late Precambrian and early Cambrian periods.
Cynical1
1 / 5 (4) Nov 29, 2011
Wow... I wanna study the Precambrian period at Areslv's school...
Nerdyguy
1.7 / 5 (6) Nov 30, 2011
What? It's not so easy to dig up a few rocks and draw conclusions about something that happened almost 600 million years ago? Who knew?

Seriously, whatever the subject, be it global warming, superluminal neutrinos, or fighting AIDS, it's fascinating how little we actually know about some things we believe to be "settled".
rubberman
1.8 / 5 (5) Nov 30, 2011
I am happy that Rawa's mutant orgy eventually spawned me....
jimbo92107
not rated yet Nov 30, 2011
This further converges on the notion that life is a kind of force that optimizes the biosphere area of a planet's crust. It is difficult to see why this would not happen wherever conditions allow the requisite chemical reactions.
rubberman
1 / 5 (4) Nov 30, 2011
Agreed Jimbo! Tracking the pattern of evolution from single celled organisms to the lifeforms we have today is a fascinating journey. What ever life forms exist do so because of their ability to adapt to the environment AND adapt their environment to suit them. Sudden changes resulting in mass extinctions seemingly pave the way for the next dominant organism to step up and resume the cycle, always building on what the predecsors left behind. The fact that this is initiated at a genetic level through mutation (mixed with a bit of trial and error) has always amazed me. I wish I had the time to study it indepth.
rwinners
1.3 / 5 (4) Dec 05, 2011
So? It might have been a gestation rather than an explosion. Scientific theory moves on.
I think that scientists cannot get past their "human" condition. I think it is entirely possible that organisms of some sort can exist in chemical conditions quite different from ours.
Time might tell.
Nerdyguy
1 / 5 (3) Dec 05, 2011
So? It might have been a gestation rather than an explosion. Scientific theory moves on.
I think that scientists cannot get past their "human" condition. I think it is entirely possible that organisms of some sort can exist in chemical conditions quite different from ours.
Time might tell.


No need to wait. Ocean-floor hydrothermal vents spawn odd life. There have been some other case. One recently in Mexico. If I recall correctly, it was bacteria living in a hostile chemical environment inside a deep cavern. Something along those lines. Anyway, the point is that we're already seeing some evidence along these lines.

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