Evolution usually works by diversiﬁcation, but sometimes a similar solution is reached by different routes
Oceans near the North and South Poles are a challenge for life. How do animals such as ﬁsh survive in temperatures around zero Celsius?
Key to survival are antifreeze proteins, which stop ice crystals forming and destroying cells. Antifreeze proteins have been seen in ﬁsh from both the Arctic and the Antarctic – but the proteins are completely different. (Read our Exploring antifreeze proteins article for more on this topic.)
Antifreeze proteins are an example of convergent evolution. An environmental challenge has been overcome in a similar way but independently in different species. Wings are another obvious example.
Many of the same genes are used to build eyes in both octopuses and humans.
Eyes are an interesting contrast. The compound eyes of insects and mammalian eyes are completely different, but the eyes of octopuses and mammals are startlingly similar – even though they evolved independently.
It turns out that many of the same genes are used to build eyes in both octopuses and humans. Remarkably, many of these genes are also important in insect eye development – notably Pax-6, which seems to be a ‘master gene’ for building eyes.
This suggests that the common ancestor of all these organisms had a core set of genes involved in light detection. Over time, this core set has been added to and trimmed in the different lineages, as animals developed better ways of seeing their external world.Lead image:
Drosophila melanogaster adult eye: David Strutt/Wellcome Images; human eye: Kate Whiteley/Wellcome Images