The Deadliest Ice Age Ever

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0:01Over the last few billion years, species have appeared and disappeared from our planet like

0:05guests at an open-house party.

0:07Sometimes they’ve shown up in droves, making the party swell with new forms of life, and

0:12other times, the majority of the guests have headed for the exit virtually all at once.

0:17The first big swell came about 550 million years ago, when the earliest animals appeared

0:22and diversified into virtually all the basic body shapes we know today.

0:26One hundred million years later, the warm, shallow seas were packed with tiny plants

0:31and animals – essentially, hors d'oeuvres for a plethora of bigger creatures like trilobites,

0:35conodonts, brachiopods, and corals.

0:37But just a million years after that, four out of five of the world’s marine species

0:43were gone.

0:44Only the rock record can tell us what happened to them, but most ancient rocks have been

0:49scattered, buried, or destroyed over time.

0:51The best clues we’ve uncovered so far come from Northern Africa, which, 450 million years

0:57ago, was part of a supercontinent near the South Pole.

1:00Outcrops dating back to that time contain the track-marks of an ice sheet’s vast expansion,

1:05as well as piles of rocky debris left by its rapid melt.

1:08What’s more, the mass extinction appears to have unfolded in two distinct pulses, one

1:13in sync with the ice sheet’s growth, the other with its retreat.

1:17In other words, it seems that our planet’s first major party killer was an ice age.

1:22And yet, this revelation has created more questions than it has answered.

1:25Much of the life in the shallows probably perished as the growing ice sheet locked up

1:29more and more of the world’s water, but why did so many deep-water organisms disappear

1:34along with them?

1:35And why did some species survive the ice age, only to die as seas rose and temperatures

1:40warmed at its finish?

1:42And why did this particular ice age wreak more havoc on life than any cold snap since?

1:47The answers to these questions are probably all out there somewhere, just waiting for

1:51us to unearth them.

1:54Hey, this is Emily.

1:55I just wanna give a big shout out to all of our supporters on Patreon – we love making

2:00these videos, and we're really grateful to you for making it possible for us to keep

2:04making them!

2:05Thanks!

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