The geologists handed over their find to Andrew Foote, evolutionary ecologist at the Norwegian University of Science and Technology in Trondheim. Foote, an expert on ancient DNA, seized the opportunity.
A famous example of Darwin's theory are the finches of the Galapagos archipelago. Starting from one ancestral species, the birds on the different islands have produced quite different beak shapes, depending on what food they used. Such a split is what evolutionary biologists call an adaptive radiation.
The prehistoric bone find opened up completely new possibilities for the Tübingen researchers and their collaborators: For the first time, they had an ancestor of the freshwater stickleback in front of them, and this fish, which had lived around 12,000 years ago, also revealed genetic information.
The comparison showed that the Ice Age fish was genetically very similar to its modern-day marine conspecifics: "The bones mainly contained gene variants that are advantageous for life in salt water," says Melanie Kirch, a doctoral student in Felicity Jones' research group, who analysed a large part of the genome data.
For the freshwater sticklebacks, this bottleneck was momentous: genetic variation is the material from which evolution produces new adaptations. If many different gene variants are available, it can draw on the full resources.