In 1985, the International Whaling Commission (IWC) placed a controversial moratorium on whaling which banned the hunting of whales until their populations recovered to pre-whaling numbers. One subject on which scientists, conservationists, and the whaling industry disagree, is exactly how many whales there were before whale hunting started.

A recent study suggests that pre-hunting whale populations numbered 12 times greater than previously thought. This means that populations have to recover further than expected to reach the levels they were before whale hunting commenced.

Stephen Palumbi and his research team at Stanford University measured the diversity of mutations in whales' DNA today. By comparing the results to the estimated mutation rates, they were able to extrapolate how many whales existed in the past. Their results suggest that there were once 240,000 humpbacks in the North Atlantic.

Today, there are about 10,000 humpbacks inhabiting the waters of the North Atlantic. Previous population estimates suggested that there were historically 20,000 whales in that region. Researchers and whaling proponents are now both scrutinizing the validity of the new estimates Stephan Palumbi and colleages have set forth.

Find out more: Whales' Recovery 'Vastly Overestimated' (BBC News)

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