Earliest animals lived in a lake environment, research shows

Jul 27, 2009
Researchers study exposures of the Doushanto Formation along a creek in the Yangtze Gorges area, South China. Credit: M. Kennedy, UC Riverside

Evidence for life on Earth stretches back billions of years, with simple single-celled organisms like bacteria dominating the record. When multi-celled animal life appeared on the planet after 3 billion years of single cell organisms, animals diversified rapidly.

Conventional wisdom has it that animal evolution began in the ocean, with animal life adapting much later in Earth history to terrestrial environments.

Now a UC Riverside-led team of researchers studying ancient rock samples in South China has found that the first animal fossils in the paleontological record are preserved in ancient lake deposits, not marine sediments as commonly assumed.

"We know that life in the oceans is very different from life in lakes, and, at least in the modern world, the oceans are far more stable and consistent environments compared to lakes which tend to be short-lived features relative to, say, rates of evolution," said Martin Kennedy, a professor of geology in the Department of Earth Sciences who participated in the research. "Thus it is surprising that the first evidence of animals we find is associated with lakes, a far more variable environment than the ocean."

The study, published in the July 27-31 online edition of the , raises questions such as what aspects of the Earth's environment changed to enable animal evolution.

In their research, the authors focused on South China's Doushantuo Formation, one of the oldest fossil beds that houses highly preserved fossils dated to about 600 million years ago. These beds have no adult fossils. Instead, many of the fossils appear as bundles of cells interpreted to be animal embryos.

"Our first unusual finding in this region was the abundance of a clay mineral called smectite," said lead author Tom Bristow, who worked in Kennedy's lab. "In rocks of this age, smectite is normally transformed into other types of clay. The smectite in these South China rocks, however, underwent no such transformation and have a special chemistry that, for the smectite to form, requires specific conditions in the water - conditions commonly found in salty, alkaline lakes."

The researchers' work involved collecting hundreds of rock samples from several localities in South China, carrying out mineralogical analysis using X-ray diffraction, and collecting and analyzing other types of geochemical data.

"All our analyses show that the rocks' minerals and geochemistry are not compatible with deposition in seawater," Bristow said. "Moreover, we found smectite in only some locations in South China, and not uniformly as one would expect for marine deposits. This was an important indicator that the rocks hosting the fossils were not marine in origin. Taken together, several lines of evidence indicated to us that these early animals lived in a lake environment."

Bristow noted that the new research gives scientists a glimpse into where some of the early animals lived and what the environmental conditions were like for them - important information for addressing the broader questions of how and why animals appeared when they did.

"It is most unexpected that these first fossils do not come from marine sediments," Kennedy said. "It is possible, too, that similarly aged or older organisms also existed in marine environments and we have not found them. But at the very least our work shows that the range of early animal habitats was far more expansive than presently assumed and raises the exciting possibility that animal evolution first occurred in lakes and is tied to some environmental aspect unique to lake environments. Furthermore, because lakes are of limited size and not connected to each other, there may have been significant parallel evolution of organisms. Now we must wait and see if similar fossils are found in marine sediments."

Source: University of California - Riverside (news : web)

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QubitTamer
1 / 5 (1) Jul 28, 2009
Oh the CERTAINTY...life must have originated in the oceans... NO the LAKES!!! I remember getting a D in cultural anthropology class because I DARED to propose a hypothesis for "rogue traveler or boundary interaction" spread of cultural ideas / tools / technologies. My professor insisted that there was no way for core cultural traits to be exchanged between peoples except for warfare and mass migration and intermixing. I argued that human beings capacity to make on the spot value judgements about a superior idea to make a tool or a prettier / more unique style of art would be able to just as effectively spread through "word of mouth" as "Tip of spear" People are People and Fads are Fads... Turns out I was right and the prof was wrong.
http://www.indepe...638.html

Whenever I read an article like this i am constantly amazed at how CERTAIN people are about theories for which there is NO clear cut empirical evidence...



Interesting article nonetheless...
RayCherry
not rated yet Jul 28, 2009
The new open China is providing possibilities for research that were unavailable until recently. Is there as much effort being made to review and translate the knowledge of the ancient, industrial age and contemporary Chinese as there is application of Western knowledge to China?

Extraction of new data sets is very useful, to everyone. Isolated local cooking pots for multi-cellular life forms makes somewhat more sense than exclusively ocean-based development, when we consider the diversity of life that followed.

Were the Chinese academia aware of these fossilised lake beds before U.C. Riverside arrived?
Ethelred
4 / 5 (1) Jul 28, 2009
Oh the CERTAINTY...life must have originated in the oceans... NO the LAKES!!


The article makes no such claim. Neither claim is in the article. Why are you making things up? For once Physorg had a decently written article without extravagant claims that admitted to the possibility that there might be other answers.

I remember getting a D in cultural anthropology class because I DARED to propose a hypothesis for "rogue traveler or boundary interaction" spread of cultural ideas / tools / technologies.


And that relates to this article in what way?

My professor insisted that there was no way for core cultural traits to be exchanged between peoples except for warfare and mass migration and intermixing.


Since you misread this rather short article I can't be sure that you are reading your professor correctly either. However if you have it correct than he is an idiot. Trade has been around for a very long time and only a complete imbecile would think that trade doesn't spread technology. It still does today.

Whenever I read an article like this i am constantly amazed at how CERTAIN people are about theories for which there is NO clear cut empirical evidence...


Whenever you read an article you seem to look for ways to find people making claims of certainty. There is none in this one.

And by the way it is pretty certain that life started in oceans. There is no certainty as to where in the oceans. Some think around undersea vents others the tidal regions. I go for the tidal regions as that gives chemistry a chance to undergo an iterative process. Drying out and then getting a fresh batch of ocean water. It remains speculation but sea vents looks like crap in comparison for me.

This article was about ANIMAL life. We can certain that all fish came from freshwater, for instance, because all fish have kidneys and the rest of salt water life doesn't have an equivalent.

There is one quibble I have with the article.

In their research, the authors focused on South China's Doushantuo Formation, one of the oldest fossil beds that houses highly preserved fossils dated to about 600 million years ago. These beds have no adult fossils. Instead, many of the fossils appear as bundles of cells interpreted to be animal embryos.


Do they think animal life started with adults? It had to start with little more than collections of cells. Edicarian life was little more than that and it started earlier than this. Somewhere a basic intestinal system developed. Most likely it had one entrance-exit combination. Basically just a hollow in a surface, much like primitive eyes, only specialized to process food.

The development of adult and larva stages has to come after basic cellular specialization. Maybe they found what came at beginning of that development. The Cambrian Explosion took place less than 80 million years later but there had to be some pretty basic developments first.

Ethelred

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