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

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.