Whales reach their maximum size
Glacial upwelling concentrates krill into dense patches, and filter feeders grow to the largest size in Earth's history.
- When
- —
- Duration
- 1.8 million years
- Known to
- ± 300 thousand years
- Era
- Early Pleistocene, Quaternary
Baleen whale body size increases sharply in the Pleistocene, and the blue whale — at up to 30 metres and 150 tonnes, the largest animal ever known to have existed, exceeding any dinosaur — belongs to this interval. The driver is the ice ages themselves: glacial cycles intensify coastal upwelling and produce extremely dense, patchy, seasonal concentrations of krill. Very large size pays only when food comes in patches worth travelling to and rich enough to gorge on.