1
$\begingroup$

I have read somewhere brown eyes have more melanin than blue eyes and as melanin protects our body from cancers, I thought that brown eyes are more healthier.

$\endgroup$
3
  • 3
    $\begingroup$ Where did you read this? $\endgroup$
    – kmm
    Jun 4, 2017 at 13:34
  • 4
    $\begingroup$ I am voting to close until more information has been given on the source of the claim. It is for the moment hard to tackle the truth value of a claim we don't know the origin of. $\endgroup$
    – Remi.b
    Jun 5, 2017 at 1:49
  • $\begingroup$ Might be that melanin in our irises protects our pupils' dilator muscles but not much more. $\endgroup$
    – lauir
    Jun 5, 2017 at 8:30

2 Answers 2

2
$\begingroup$

People conflate "Dominant" traits to mean "healthier" which is a huge misconception. The previous answer provided a good example of how what is adaptive in one environment can be Mal-adaptive in another. Many Disorders can be dominant for example Huntingtons disease or achondriplastic dwarfism.

$\endgroup$
2
  • $\begingroup$ You're right to draw this distinction. However, polygeny and pleiotropy allow evolution to render many deleterious alleles recessive, and still-dominant examples (including HD) usually affect the individual late in life, resulting in little effect on fitness. $\endgroup$
    – J.G.
    Jun 5, 2017 at 8:36
  • $\begingroup$ true: gene expression is often more like volume nobs than On/Off switches $\endgroup$ Jun 6, 2017 at 2:59
1
$\begingroup$

Not an answer (I hope an expert provides one), but too long for a comment.

Although I'm unfamiliar with this claim, it's conceivable the optimum melanin content in eyes is subject to a trade-off as it is in skin. In bright areas, skin is dark to prevent damage from ultraviolet light; in dim areas, skin is light to produce enough vitamin D to avoid rickets. Eyes are different in their details, but they too may have adaptive geographical variations (or the distribution of light irises may be due to something more mundane, such as genetic bottlenecks). In theory their optimum colour would trade visual acuity against retinal protection, though I'm dubious about that as light enters through the pupil, not the iris.

$\endgroup$
3
  • $\begingroup$ @JG I agree with your point regarding adaptive geographical variations. Is there any place wherewe can discuss this more? $\endgroup$
    – AScientist
    Oct 29, 2017 at 15:31
  • $\begingroup$ @AScientist I have no ideas about it besides those I wrote. $\endgroup$
    – J.G.
    Oct 29, 2017 at 15:50
  • $\begingroup$ Well,That's a bummer.Do you know anyone who knows this stuff? $\endgroup$
    – AScientist
    Oct 29, 2017 at 15:55

Not the answer you're looking for? Browse other questions tagged or ask your own question.