World's Oldest Fossils Found On Australian Beach

sciencehabit writes "Researchers say they have discovered the fossils of 3.4-billion-year-old cells in between the cemented sand grains of an ancient beach in Western Australia, possibly the oldest fossils ever found (abstract). Chemical analyses of the minerals near the cells suggest the microorganisms depended on sulfur for fuel. Such a beach might have been life's first breeding ground, one author says."

Comments

Closer and closer to the earliest chance

[JoshuaZ]

TFA notes that this work was done by Martin Brasier's team and that Brasier has generally been a strong critic of a lot of the claims about early fossilized life. That may be strong evidence that this claim should be taken seriously. However, there have been times before where scientists have criticized claims coming from other groups even as they've made nearly identical claims. It looks like Brasier et al. have done much more careful chemical work than some of the other early life claims which makes this look promising but this probably won't be completely clear until a bit more work by other groups is done. It is also important to note that it is extremely unlikely that we are finding the very first life. Most likely, life had to be pretty common already in order for it to have a decent chance to leave fossils. This means that one can tentatively guess that life arose at least a few million years before when these fossils were formed.

We keep pushing farther and farther back in time when life arose on Earth. This is important since it helps us figure out just how likely life is to arise in general. The argument goes that if life is easy to start then we should expect to see life arise soon after heavy bombardment of Earth begins. And that's what we do seem to be seeing. This suggests that life may be plentiful. There's a substantial very recent argument against this line of reasoning by David Spiegel and Edwin Turner http://www.physorg.com/news/2011-07-astrophysicists-logic-downplay-probability-extraterrestrial.html. Spiegel and Turner argued that if it generally takes a lot of time to get intelligent life to develop then intelligent life will have an observer bias since it will only arise on the planets where life started very early. This means that seeing life early on in our history might be something which we should expect even if life arises really rarely.

Re:Closer and closer to the earliest chance

[Anonymous Coward]

Spiegel and Turner's argument based on observer bias leaves out other key necessary events leading to intelligence, most notably multicellularity and the emergence of large, complex (eukaryotic) cells. After the origin of life, it took at least 2 billion years to make this major leap in complexity to eukaryotes, and over 1 billion years after that until multicellular, developmentally complex (e.g., metazoan) organisms evolved. As these two necessary events are singular, unlikely, and highly contingent on specific existing physiologies and selective pressures (i.e., there was nothing stopping something like eukaryotes from emerging much, much earlier if the right endosymbioses happened), then the 4 billion years that have passed before the emergence of intelligence largely reflects the rarity of these events, and does nothing to inform us about the minimum necessary time for intelligence to emerge, or the abundance of life expected in the universe. Additionally, the role of mass extinctions in severely diminishing biodiversity and curtailing the largest, most successful groups of animals during each event also cause an over-estimation of necessary time to technological intelligence, with the observed time, even since multicellularity emerged, being largely a product of the frequency and intensity of these random events.

Take home message: Evolution is both a mechanistic and historical science, and one has to take both kinds of processes into account to draw any general conclusions from the timing of events.

IAAEBAPS (I am an evolutionary biologist and planetary scientist).

 

Re:Mars has lots of sulfur

[ColdWetDog]

If Mars has a biology, it may involve sulfur a lot more than the Earth's does, so this is very interesting from the standpoint of seeding life between the two planets.

Or it just might be that hot sulfur conditions might be a good way to start life rolling. Convergent evolution.

Re:probably wasn't a beach...

[Anonymous Coward]

4.5 billion years ago, probably not. At least not for long, any water probably getting vaporized by gigantic collisions on a regular basis. But by 4.4 billion years ago, there is evidence for detrital (i.e. eroded on the surface and redeposited) zircon mineral grains in what are now highly metamorphosed sedimentary rocks. The original rocks did not survive unaltered from that period, but the recycled zircons did, implying there had to be some process to erode them from the rock in which they initially crystallized and redeposit them, likely water. Refer to this web page and this paper. They're kind of technical, so good luck if you don't have some familiarity with geology and isotope geochemistry, but if you google "cool early Earth hypothesis", you'll find more general accounts from media reports too. It's fair to say that these interpretations are relatively new and thus tentative, but if they are correct it would mean the Earth wasn't the completely lava-covered hell that most geologists used to think it was when they named the pre-4-billion-year period of its history the Hadean Era. So, you have the right idea and it's a legitimate question to wonder whether there was water so early, but the science has changed in recent years.

By 3.4 billion years (the estimated age of these new fossils), there's plenty of unambiguous evidence for oceans having been around for quite a while before.