Evolution 101
"White" skins only evolved in Europe since the end of the last ice age!
This suggests a powerful evolutionary selective pressure against dark skins!
Britain's industrial and port cities had sizeable Black populations in the mid 19th century, by the early 20th they had mostly died out (There were of course other factors involved but chronic Vit-D deficiency would have been a major factor)
In evolutionary terms, "White" people cannot live in Australia! The Abbos didn't come directly from Africa you know! They evolved from far paler central Asian diaspora!
Rest assured Octonaught that in 2014 scientists have treatment for Vit D deficiency and we can cure it. It is therefore no longer a selection pressure and will not be a factor in human evolution.
(The treatment is Vitamin D and eggs, oily fish, margarine, breakfast cereal, powered milk - not necessarily all at the same time).
When we look for evidence to support our views peer reviewed scientific journals lead the way rather than internet sites.
Looking for a correlation between race and ethnicity and illness is problematic, see sections here on 'Race' 'Ethnicity'
http://www.ncbi.nlm.nih.gov/books/NBK44246/#A1150
Our genetic make-up and the genes we have do increase the likelihood of us developing a disease if those genes are active.
But it is very complex, we can't conclude it is just one factor e.g. skin colour at play. For instance the risk factors of developing a mental illness (excluding reading this thread) may be:
Individual
Genetic vulnerability
Gender
Low birth weight
Neuropsychological deficits
Language disabilities
Chronic physical illness
Below-average intelligence
Child abuse or neglect
Family
Severe marital discord
Social disadvantage
Overcrowding or large family size
Paternal criminality
Maternal mental disorder
Admission to foster care
Community or social
Violence
Poverty
Community disorganization
Inadequate schools
Racism and discrimination