• Question: Why cant we be born with purple hair? or green? Or Blue? Or Red? Or pink?

    Asked by anon-181139 on 5 Jun 2018.
    • Photo: Alex Haragan

      Alex Haragan answered on 5 Jun 2018:

      Hair colour, and indeed any complex “trait” is made up of both genetics and environment.
      When I say a trait I mean anything about a person that is part of defining them – so it might be something physical, like height or hair colour, or something personal like preference for music.

      Some traits are more determined by genetics, and some more by what you experience. Nature vs nuture.

      Hair colour is a good example – we are all born with a certain hair colour (well, many babies are born bald but the hair grows in a certain colour) but of course things like sunlight can change its colour and you can dye it any colour you like.

      But the hair colour you’re born with is entirely dependent on genetics. Every gene in your body can hold a number of different configurations – that is, for example, a gene coding for hair colour can code for brown or blonde. We call these different choices alleles.
      Now I’m sure you’ve been taught or will be taught about dominant and recessive genes, and incomplete and semi-dominant expression (hence all the other hair colours) – although even that isn’t the whole story – there is more than one “hair colour gene”.
      We don’t fully know – but it is likely several genes code for hair colour. However, the alleles that determine what colour hair is only come from a limited range of choices – brown, ginger, blonde, black etc.
      Although mutations in genetics can result in unpredicted change – hair colour is actually quite a complicated trait, and there is only a certain range of pigment/colour that the human body can literally produce. So even if you had really bizarre mutations – the body cannot make green hair pigment.
      So if you want green hair you’ll just have to dye it!

    • Photo: Joanne Sharpe

      Joanne Sharpe answered on 5 Jun 2018:

      This is such an interesting question! I didn’t know the answer, but having read Alex’s answer it makes sense!

      Colour is simply the wavelength of light that is reflected by something. In a rainbow you see all the colours in a spectrum because white light is split up into those colours by passing through water. If something is white, it reflects all the colours, if something is pink it absorbs some wavelengths so you see the pink colour. What wavelengths an object absorbs/reflects are down to its chemical structure – you can’t see this! So the pigments in your hair all have different structures which reflect different wavelengths of light so your hair may appear different colours. Our body doesn’t make any pigments that reflect only blue light so we can’t have blue hair! If you choose to dye your hair blue, you’re putting on an artificial pigment that has a structure which reflects blue light.

    • Photo: Laura Hemming

      Laura Hemming answered on 6 Jun 2018:

      This is SUCH a good question! Sorry I don’t know the answer, but just wanted to have a nosey to find out what the answer is! Haha

    • Photo: Claire Donald

      Claire Donald answered on 7 Jun 2018:

      Just like Alex and Joanne said, its about genes. But you can also think about it from an evolutionary perspective. Dark hair is good for places that get a lot of sun. When early people moved to areas with less sun, their hair got lighter. Our hair gets its colour from the pigment, melanin which unfortunately doesn’t come in bright colours. Having brown/black/yellow/red pigments probably helped our ancestors to blend in with their surroundings and therefore avoid being eaten by predators. Bright pink wouldn’t have been so helpful for that. Thankfully, now we can dye it whatever colour we fancy and don’t need to worry about being gobbled by a hungry lion.

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