The history of today’s cichlid abundance in Lake Victoria began with a disaster. Towards the end of the last ice age, about 20,000 years ago, Lake Victoria dried up. Remnants of its previously presumably rich fish life survived the almost 4,000-year drought phase in isolated swamps that were left over from Africa’s largest lake.

When the lake basin filled up with water once again, the survivors also returned. Using over 7,000 fish teeth from sediments dating back almost 17,000 years, the researchers were able to identify five different families of carp-like catfish and cichlids. Only one of these families, however, the cichlids, has since rapidly split into different species with as many as 500 today.

But why do some families tend to speciate quickly while others do not? Two teams led by Ole Seehausen from the Swiss aquatic research institute Eawag and the University of Bern investigated this question. They discovered answers in the genomes of the fish and in fish fossils from the lake sediments. These finding have just been published in the “Science” and “Nature” journals.