I recall while reading The Journey of Man that Wells talked about various differences among people and the evolutionary reasons for them. For example, he talks about how Europeans evolved lighter skin (opposed to the darker skin of those from Africa) because there was less sunshine in Europe and the Europeans needed to be able to absorb more Vitamin D from the sun. Light eyes evolved, he suggested, evolved because there was less sunshine to deal with (this I can see- my friends with light eyes constantly bitch and moan about how much the sun hurts their eyes ). Nothing is conclusive of course, but he just offered up explanations for various adaptations*.
So, I was just thinking- is there a potential explanation for variations in hair type, particularly between people of African descent and people of European descent. For all intents and purposes, I think it’s fair to say that while there are certainly a ton of variations, on a whole black people have thicker, coarser, and dryer hair than their white counterparts. And, just my TOTALLY anecdotal experience with m friends, it seems that the hair of my black friends grows much slower than the hair of my white friends.
I hope no one thinks I’m being an ignorant racist or anything of the sort- that’s certainly, definitely not my intent (or me at all). I’m genuinely curious because I can’t really think of an advantage to having dryer, coarser hair in a hot, dry environment. If anything, I would think European people in colder environments would require thicker hair to deal with the cold.
*For those of you that are unaware, Wells is a big proponent (or founder?) of the theory that man migrated out of South Africa and moved throughout the world. In the book I link to above, he uses Y chromosome testing- as opposed to Mitochondrial testing- to find common genetic markers that people throughout the world share with the San Bushmen (according to him, the oldest group around).
The key to evolution is that the pressure subtracts traits, does not add them.
And it subtracts only those traits that cause death or disability before maturity.
Thus, we don’t have eyebrows for any reason. They are part of all mammals.
However, we may very well have reasons for bare bodies.
But it’s equally likely that there is no advantage or disadvantage to bare bodies, and they were simply never a fatal flaw, so once somebody had that and lived it became part of the genome, and perhaps increased by other factors such as separation of groups.
DiosaBellissima,
The main point to realise is that most traits are not completely independant, and that is almost certain to be the case with hair colour/shape as well. Skin and eye colour are controlled through melanin production, and melanin and melanin precursors play a role in huge numbers of biochemical processes including protein conformation. Also note that what you say doesn’t apply to all or even most black people, just those of recent sub-Saharan African origin.
So although nobody knows for sure it is most likely that African Blacks retain coarser hair because they also retain darker skin and eyes. People in other parts of the world have evolved lighter skin and eye colours because melanin production wasn’t as important or was outright detrimental. That effectively freed up all the metabolic pathways associated with melanin, including those pathways associated with the shape of the hair protien, and in turn allowed for the evolution of novel hair types. Basically non-African people tend to exhi9bitmore diveristy in hair shape becaue they also exhibit more diversity in skin and eye colour. The shape of the hair has no survival advantage as such, it’s simply that it has been allowed to change North of the Sahara. Whther it then also became a sexual trait that became reibnforced is another issue, but the initial conditions that allowed for different hair types to evolve were the evoloutionof lighter skin and eye colours.
Pressure neither adds nor subtracts traits. Pressure favours traits that are already in existence, it doesn’t produce them nor does it subtact them. Mutation adds traits and mutation subtracts them.
Not in any way true.
We have eyebrows because communication is extremely difficult without eyebrows. About 40% of human communictaion occurs via facial expression and a person without eyebrows loses the ability to produce most facial expression if the viewer is more than a few feet away.
It’s possible but it is an extremely slothful induction. All other savanna primates retain fur, humans do not. That alone means that the logical conclusion is that it is advantageous. Trying to argue that thetre is no reason is ignoring the elephant in the room.
Quite incorrect. Natural selection operates to cull the “weak” and favor the “strong”. Or more specifically, those individuals who possess traits which are advantageous to them, however minutely, will have a better than average chance of passing on those traits to future generations. Individuals who possess traits which are disadvantageous will have a lower than average chance to pass on those traits. Thus, the tendancy is for the population to accumulate the beneficial traits while the frequency of the particular disadvantageous traits decreases. That’s the essence of adaptation: building upon favorable traits.
As soon as you shave them off, alas, you realise that eyebrows are (or were) pretty effective at deflecting water and / or sweat running down the forehead away from the eyes. ETA: Not that I’ve ever done this or anything.
). Nothing is conclusive of course, but he just offered up explanations for various adaptations*.