Race of Turkish people

Also historical rather than current practices of humans

Having sex and having a family are two different things. Most children prosper in a family system. Offspring outside the family system tend to be despised as b**tards even within the same community. Half breeds of two different communities are despised by both the communities and find it difficult to start their own family. Most have their mixed genes lost from reproductive disadvantage - talking here of hundreds of years and more ago when such people would not find a marriage partner from either of their communities.

Sometimes a despised community amongst a multiethnic background is severely disadvantaged. The Hazara community of Afghanistan are an example, also Gypsies in most of history and tribes notified in colonial times as criminal tribes in India. 

In cities people dont really care much about caste. It is more a rich poor situation with all poor people having a tough time. Caste has little to do with race or skin color because all look more or less same. But the stereotype is that higher castes have slightly lighter skin tone and sharper ffeatures. 

Dark skin is better suited for India protecting against skin cancer. So those people who have evolved longer within India will keep getting darker.

So a person from a supposedly lower caste in Punjab would have more central asian features and skin than a person from a supposedly higher caste from Tamil Nadu, where apart from Brahmins (some of whom are more recent arrivals from 1200 to 1800 AD, being displaced from looted temples of North India by muslim invasion) everyone would look the same. 

Punjab was invased in succession by Aryans (1200BC), Persians (500BC), Greeks (300BC), Shakas (200BC), Parthians (150BC), Kushans (100BC), Huns (500AD), Afghans (1200 AD), Mongols (briefly and not in strength 1250-1300 AD), Tamerlane (1400 AD), Afghans (Mughals) 1500 AD and Persians (Nadir Shah) 1750 AD. 

(Just approximate dates)

Brahmins from southern states would have a longer tradition of learning than from other states, because the deep south was never invaded by the Muslims though most pre-British learning was religious in nature. Except for Malik Kaufar's raid of Kanchipuram and the brief occupation of Kanchipuram by Tipu Sultan, the deep south was relatively free of invasions, disruptions and looting of temples and centers of learning. Fighting between Hindus spared these centers as was the norm in north India as well until Muslim invasion. But a little north of Tamil Nadu, there were muslim invasions in north Karnataka and North Andra Pradesh.

However, people from Brahmin, Kshatriya and Business castes of north India will also have a long tradition of learning and do well in school, but being from invaded areas, will have a more practical and down to earth attitude on learning and many will be good in business, unlike the Brahmins of south India.

You need whiter skin to make vitamin d. So it is a trade off.

Blond people of norway and iceland with higher ultraviolet have greater tanning tendency to protect the skin