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."

Comments

*At least* once...

[jemenake]

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".

Re:Life fills a space defined by its environment

[commodore64_love]

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.