Liz Harper

speaker

123 appearances 1 recordings 1 series first heard Jul 2026 last heard 30 Jul

Liz Harper’s voice in public audio — every appearance, attributed to the second.

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Recordings per month over the last 12 months — 1 in all, peaking in Jul 2026 with 1.

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In Our Time · Seashells · 30 Jul 2026 podcast

Well, that's a very interesting question.

We don't really know terribly much about the very earliest shells because we're dependent on the fossil record.

So it's been life on Earth for over 3.5 billion years.

But the first proper shells start about 540 or so million years ago during this Grand Cambrian Explosion.

So that's when we see our first mollusks.

Everything before that had soft bodies, so they don't preserve very well anymore.

So there's a sense that we've almost missed the first shells because they don't fossilise, because they're probably very fragile and thin.

Or maybe actually they've cheated, making them out of particles rather than laying down a shell.

But we know that when they do start, that's the start of a sort of massive explosion, not just for the rest of animal life, but the mollusks themselves actually diversify more.

and become more and more abundant from that time.

So the big question really is, well, why do they start?

Helen's mentioned many of the different uses these organisms make for their shell.

It's somewhere safe to live.

Whether that's the first reason for having one is difficult to test.

But it's clear that it is a form of armour, both from, if you like, storms and what have you.

But most attractive to most people like me is predation.

And at that time, you do see the first evidence of predatory groups and the first evidence that predation is happening to these shells.

So it's a popular idea at any rate, if maybe not the initial idea of having a shell, but very soon afterwards became co-opted to being useful in that way.

So shells of mollusks are made of calcium carbonate.

And on the face of that, that's really good material.

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