Do octopuses get cataracts?

Sir Martin Rees, distinguished scientist, Astronomer Royal and a churchgoing atheist, has just accepted the Templeton Prize. This is awarded by the Templeton Foundation, a charity set up by the late John Templeton, a wealthy merchant banker, enthusiastic Christian and fan of the big questions in life. It is £1 million – chosen I think to be at least equal in value to a Nobel prize. This has stirred up the usual storm in a teacup. Some people are concerned that the Templeton Foundation is using its wealth to mix science and religion. I would say that this not something to lose sleep over, but I am biased, I got money from the Templeton Foundation myself. Sadly only £100,000 and all for research, Sir Martin Rees gets to keep his £1 million.

A few years ago I got the money to do research into what is called convergent evolution. Essentially, this is when a feature of living organisms evolves independently more than once. The classic example is the so-called camera-like eye – the type of eye we have, as opposed the rather different type of eye that insects have. The evidence is strong that our eyes (those of mammals etc) evolved independently of the eyes of octopuses (and other cephalopods).

However, our eyes and those of octopuses are very similar – it is hard to prove this but one idea is that basically there is pretty much only one way to build a versatile focusing light sensor. This is basically a controllable focusing lens in front of a light sensor – the laws of physics essentially dictate this. Then, evolution has hit upon this solution at least twice, as have Nikon, Canon, Kodak, etc.

The beautiful thing, I think is not so much the similarity between our eyes and those of octopuses, but the small difference. In our eyes the optic nerve actually comes out in front of the retina (the bit of the eye that actually senses the light). This a bit back to front as part of the optic nerve actually obscures part of the retina, creating a blind spot in our vision. However, in octopuses it is in the apparently more sensible position of behind the retina.

It looks  like millions of years ago and early on in the evolution of our eye the optic nerve was positioned in front of the retina and it got stuck there, and so millions of years later we all have a blind spot – a small imperfection caused by the limitations of evolution. This brings me to my final thought, if octopus eys escaped that imperfection, do they also not suffer from cataracts?