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ELEANOR HALL: US researchers say they've found the oldest animal fossils ever discovered
and they uncovered them in the Flinders Ranges in South Australia.
The findings challenge the theory of when animal life began on earth.
Princeton University's assistant professor of geology Adam Maloof told Timothy McDonald
that scientists had previously assumed that life did not exist before a catastrophic ice
age.
ADAM MALOOF: They're younger than 659 million years old and older than 635 million years
old. So I frequently will say they're about 650 or 640 million years old.
TIMOTHY MCDONALD: And these animals are a kind of sponge. I mean what would it look
like if you were to see it today?
ADAM MALOOF: Well it's pretty important to be careful here and say that they're sponge-like.
So I wouldn't want to say for sure that they're a direct ancestor of the sponges living today.
But they do seem to share a few characterises.
These are centimetre-sized objects and they have an internal network of canals, about
a millimetre in diameter. And we think if they are a sponge-like organism that these
canals were used to filter water - in other words to get carbon out of water to eat -
and then exhale that water out of their body.
TIMOTHY MCDONALD: So the real discovery here you're suggesting is that it's I guess a fairly
complicated animal for how old it is.
ADAM MALOOF: Yeah, exactly. It's very surprising to find them in rocks or soil.
Now one of the reasons it's surprisingly - this is another important thing to note
- is that it's not only the absolute age. It's also that they are older than the Marinoan
ice age, this event in Earth's history that many people consider catastrophic to life.
And yet our evidence and other people's work suggests that maybe even animals could have
survived this kind of ice house catastrophe.
TIMOTHY MCDONALD: But is there any suggestion that these creatures might have survived the
ice age?
ADAM MALOOF: Well that's a really good question. If our interpretation is correct that these
are sponge-grade animals I think many people would argue that animals did not evolve twice.
So what it doesn't mean that our critters themselves survived the snowball, but what
it means is that animals evolved before the snowball and some form of animal likely survived
the snowball. So I think that the take home message is simply that the kingdom animalia
likely evolved before the snowball.