An oft cited example of convergent evolution is the eye. The camera-style eye has evolved many times independently across different species. The commonly made comparison is between the human eye and that of an octopus.
The human eye is structurally similar to the octopus eye but our last common ancestor was 750 million years ago and this creature would likely have only had a surface layer of tissue able to detect presence or absence of light. The retina of the octopus eyes evolved more sensibly than humans; the light detecting cells are on the top of the retina facing forward. Human eyes have these cells on the bottom layer facing backwards and as a result we have what is known as the “optic blind spot”. Octopuses have no such blind spot.