Many black people I've met have bigger lips than white people, why?
Regard this one as a comment



I prefer to cite some text form this website instead of providing the link only (as it could be removed).


  In general, this pattern can be observed across the planet with the
  size of lips and nose decreasing as we move away from the equator
  towards the poles. So what could the reason be?
  
  For someone living in hot climatic conditions, cooling down the body
  is critical for their survival. Our body has many cooling mechanisms
  and one of them is simply disseminating heat when it comes in contact
  with colder air (simple thermodynamics). This however requires larger
  surface area so that more heat can be disseminated. 
  
  Given that a significant portion of breathing also happens through the
  mouth (especially when exposed to heat), lips are pretty much like the
  gateway for colder air being inhaled and exhaled. So, the larger the
  lips, the more heat that can be disseminated. Thus, people living in
  hotter climatic conditions gradually evolved to have bigger lips. 
  
  The opposite is true for people in colder climates. They get a
  survival advantage if they are able to retain as much heat as possible
  and so they gradually evolved to have smaller lips thus limiting the
  amount of heat that can escape when cold air brushes past their lips
  while inhaling and exhaling.


Notably, there was no scientific source provided for this claim, however intuitively this could make sense.