Its an important question and one that only recently DNA has been able to answer.
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Well it turns out there was a LOT!
A LOT! more than has been previously suggested.
"Genetic variation is related to long-term population size," Dr Palumbi said. "The International Whaling Commission estimates that past population sizes of humpback whales numbered no more than 115,000 before whaling."
His analysis of humpback whale DNA, however, led him to estimate that the past population size of breeding females alone must have been between 125,000 and 250,000 individuals
"Mature breeding females make up about one sixth to one eighth of a whale population, so these numbers suggest a global humpback whale population size [in the past] of about 750,000 to 2 million animals," he said.