Scientists have long wondered why the planet's first complex organisms emerged in the cold, dark depths of the ocean, where oxygen, food, and sun are in short supply. According to a new study, researchers now think that the deep ocean offered the animals more stable temperatures.

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Scientists have long wondered why the planet's first complex organisms emerged in the cold, dark depths of the ocean, where oxygen, food, and sun are in short supply. According to a new study, researchers now think that the deep ocean offered the animals more stable temperatures.