I was going to note this (first learnt about it in Capra's "Web of Life", IIRC), but they did already:
>Abiotic, or nonliving, chemical processes can also form structures that look surprisingly similar to life, adds Rachel Wood, a carbonate geologist at the University of Edinburgh. "She [Turner] may be right. But I think you really have to explore and disprove all the other possibilities to make such a really strong claim like this." So for now, Wood says, "I don't think that she's really nailed that these are sponges."
>Only further analysis can resolve the debate. Wood notes that crafting three-dimensional models of the tube network would help give a more detailed look at the structures. And Riding hopes the new study will inspire more scientists to take a closer look at other stromatolites to search for more of these meshy structures.
I think about this often in relation to stromatolites[0]. The earliest evidence of life on Earth ranges from immediately after liquid water appeared on the surface to one billion years after, depending on whether or not you think the specific evidence is of abiotic origin.
That's a big range! If life appeared within a few million years of liquid water, it has huge implications for the probability of life elsewhere in the universe.
A relatively recent discovery points to macroscopic multicellular life as early as 2.1B years ago (1), right after the Great Oxidization Event. We only have fossils of a single specie. Given the complexity of the specimens, it's unlikely to have been the only specie in existence. The rest of the biota is probably lost to time.
The fossil record for Ediacarian biota (pre-Cambrian age) is also very sparse. It's only after the evolution of endo/exoskeletons that we start to get proper fossil records
Well, you can’t get fossils from rocks which have melted or metamorphised. If you try you might get lucky and find some relatively unscathed sediments, but I don’t know enough geology to say for sure how much of the plate would have escaped metamorphism.
Carbon dating is only supposed to be accurate to about 40,000 years ago. They must be using some other method to date it, but I didn't see in the article where they say what method was used.
In the study linked in the article, this is written: "depositional age is known through litho- and chemostratigraphic correlation with the 892 ± 13-Ma (Re–Os black shale) Boot Inlet Formation (Shaler Supergroup (Sg)), together with other geochronological constraints"
The "Re-Os" bit indicates that it was Rhenium-Osmium dating of black shale (a sedimentary rock commonly found on paleo-coastlines) in the formation.
One of the major differences between the paleontologists and archaeologists is their opinion of shale and other mudstones. Paleontologists love the stuff, archaeologists hate it.
Geologists and paleontologist usually use multiple methods to estimate age. Carbon works well for young deposits. Uranium dating can be used for much older materials. As AlotOfReading mentioned Rhenium-Osmium. Sometimes they can use Oxygen ratios in inclusions in Zircon crystals. There are other more specialized measures. Using multiple methods can help calibrate each other.
I don't like to enter random emails into forms. The company needlessly suffers with bad data going into their lists and ends up taxing other email providers with sends to non-existent inboxes. Unless you use a domain like example.com or something.
