Take a look at your partner, if you have one - notice anything similar? Well, you definitely would do if you're a crow, according to new research from scientists at Uppsala University in Sweden. Writing in the journal Science, the team have discovered that crows pick partners that look like themselves, and that this behaviour is rooted in their genetic makeup.
Crows come in two colours - black and grey, and they tend to pick partners that are the same. The scientists focused on black carrion crows and grey hooded crows, which both seem to be extremely similar on a genetic level, but are obviously different colours. But there's a small strip of land across Europe and Asia where they interbreed, allowing researchers to study how the populations split.
Through careful studies of the two crows' genomes and developing feathers, the researchers discovered that out of more than 1 billion DNA 'letters', the two crows genomes differed significantly in only 82 key regions, 81 of them in genes involved in colour and visual perception. The scientists suggest that the crows' colouring is coupled to their ability to detect it, so they pick similar-coloured mates and help to maintain the differences between the populations. The finding helps to answer the puzzle of how new species emerge and become established from slight genetic changes, allowing populations to split into new species over time that can then evolve independently.