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Did Sea Life Arise Twice?
eldavojohn writes "Dr. Adam Maloof has found fossils of sea sponges in Australia from 650 million years ago. You might think this is no big deal unless you consider that sea sponges were thought to have arisen 520 million years ago. These fossils predate the oldest hard bodied fossils we have by a hundred million years. Dr. Maloof is now wondering if life might have arisen twice after the first attempt was quashed 635 million years ago: 'Since animals probably did not evolve twice, we are suddenly confronted with the question of how some relative of these reef-dwelling animals survived the Snowball Earth.' So how is it that life survived the Marinoan glaciation? The BBC has a video on the topic and Wikipedia has a time line of the Proterozoic Eon into the Paleozoic Era."
For that matter, maybe life has and continues to spontaneously emerge on our warm, wet, densely living planet in different nooks and crannies but hasn't found the right conditions to start sprouting in other places at all... as far as we can tell... yet. With the "chemicals for life" and every imaginable condition spread across the universe, the suggestion that life spontaneously emerged on the Earth implies that the universe has sprouted life millions or billions of other times; in other words, that the universe itself "is alive."
When I discuss evolution-vs-creationism with some folks, the discussion sometimes steers toward the notion that the coming together of amino acids to form life is this *incredibly* improbable thing, and that it certainly needed the hand of a creator to ensure that it happened on a planet which could support it.
I then point out to them that *all* we know is that life has been created on this planet *at least* once. It may have happened a million times, for all we know. Out in that vast ocean, there are countless chances for it to happen every day and it very well *may* be happening. Who the hell knows? Any life that we may find out there in the oceans gets attributed to being descended from the *first* occurrence of life... but that might not really be the case.
So, this notion that life may have arisen twice? I don't find it shocking at all. Okay, I guess I'm a little piqued by the fact that researchers think that they hold *evidence* of it (since that's a little harder to do) but, like I said, I have a hunch this has happened millions of times since the "first time".
But scientists can usually tell different species. They may look superficially identical, but they have unique organs which indicate if it's the same species, or a different species that discovered the same niche.
I think the likely explanation here is that (1) it's the same species at ~500 and ~600 million years ago, and it did survive the extinction because (2) Snowball earth wasn't as harsh as we believe.... there were probably warm zones around the equator for a few sponges to hang-on.
"I disapprove of what you say, but I will defend to the death your right to say it." - historian Evelyn Beatrice Hall
Yes. This. There is a certain amount of cognitive dissonance to be expected when a presumably scientific article is surrounded by such journalistic gems as "Brittany Murphy's mother 'shared bed with daughter's husband after her death'.
One's head asplodes, it does.
Faster! Faster! Faster would be better!
Despite the BBC article's title and the slashdot summary, this story is not about whether *life* evolved twice---it's about whether *animals* evolved twice. The issue here is that they have discovered relatively complex sponge-like organisms before a catastrophic event (snowball earth). This means either that 1) snowball earth wasn't that bad, didn't kill them off, and more complex animals (including us) might have evolved from them or 2) it killed them off, and animals evolved a second time once it was over.
Oh, and, attempting to stay on topic. "Snowball earth" likely did not cause all of the oceans to freeze solid. In fact, it is really unclear just how much glaciation actually occurred - other than the general statement of "a lot". It's not hard to imagine pockets of happy sponges in liquid water hanging around for millions of years (what else are sponges going to do anyway?).
According to the linked Wikipedia article, even the dating of the 'Cryogenian' period is pretty loose. People need to look at those solid lines separating geologic eras with a grain of salt or at least a Photoshop^HGimp gradient. It's not like God came down and said "OK it's now Cambrian time, lets pop out those hominids riding dinosaurs, and while your at it, lets change the color of the strata to mauve."
Right?
Faster! Faster! Faster would be better!
Ok, it seems there are two possibilities here: it could be that being "confronted by the question of how they survived" is a rhetorical device leading up to just such a hypothesis, even if they didn't publish it in the article. Or maybe you're just a lot smarter than the "idiot" (who's a paleontology PhD) quoted here. Which do you think is more likely?
Accurate smakurate! What we really need is a dating method that won't be rejected by anti-science types. Unfortunately, we all know that is impossible, because their objections are ideological, not scientific. So, we are left with only one option, which is to ignore the anti-science types.