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Comment by mynameishere | Hacker News Reader

Traits tend to go away when not needed. Pigment is essentially an appendix.

EDIT: Okay, wisdom teeth then. Or teeth in general, which are gradually disappearing.

...in that the appendix was recently discovered to have a useful function as a backup store for intestinal bacteria in case something killed off all the good stuff in your gut?

(Slightly off topic, but isn't the benefit of the appendix outweighed by how often if becomes infected, etc?)

Only with the "western" diet. You'll see much fewer cases of appendicitis amongst those who don't eat the overly-rich western diet. So in my opinion, this is cultural, not genetic.

My father had appendicitis before the age of 25, despite a relatively simple diet. His father, who lived through WWII food rationing, had appendicitis, too. He wouldn't have survived without being cut open and treated with penicillin. For obvious reasons, I wish this were caused by culture, but genetics is almost certainly at work.

Culture saved them in this case.

Are we really at liberty to disagree with the replicators on that one? If it really outweighed it, it would have been the end of the line.

Removing the appendix would presumably take multiple mutations that would have other, possibly harmful effects as well. So it can't really happen overnight.

In order for it to happen at all the appendix needs to become so troublesome that everybody dies before they can reproduce. My son was born 3 weeks ago. My appendix could do me in tomorrow and the genes that express for it will likely go on.

In order for it to happen at all the appendix needs to become so troublesome that everybody dies before they can reproduce.

Not at all; it just needs to reduce the average number of children the average person has. Any mutation that makes it "less troublesome" on average would be favoured.

Fair point. I thought it would be fun to compare the mortality rate with an issue with another organ that has slim chance of going away: the pancreas. It looks like the appendix is more-or-less a trouble-free organ in comparison. I wouldn't place any bets on the emergence of an appendix-free homo sapien offshoot any time soon.

http://www.wolframalpha.com/input/?i=pancreas+cancer http://www.wolframalpha.com/input/?i=appendicitis

> Any mutation that makes it "less troublesome" on average would be favoured.

That's correct, but, from my understanding, revolutionary mutations are orders of magnitude less likely to happen than evolutionary mutations.

Everyone has an appendix, so there's no natural selection pressure where non-appendix people are breeding to further the spread of non-appendix humans. Just thinking out loud here - I reckon the way it would have to go would be if the appendix was a significant disadvantage, and people with a less sensitive/smaller/less prominent/something-like-that appendix were able to survive more easily or have more children on average, then you might selection pressures moving towards a less prominent and eventually no appendix.

It could happen, but it'd take a long time. Actually, one that fascinates me is what effect modern medicine and technology will have on evolution. Greater mobility is seeing children with a more mixed and diverse hereditary mix. Beyond that though, longer life cycles and better medical treatment might mean both slower and less evolution. I'd expect a lot of positive effects from interbreeding of different peoples over the next 500 years, but I reckon, sadly, that things like aggression won't be genetically bred out of us any time soon by being selected for less. Interesting stuff to think about.

Not if your not being there reduces your son's chances of growing to reproductive age...

[Citation Needed]

[1]: http://www.msnbc.msn.com/id/21153898/

I doubt it; isn't it providing protection from UV-caused skin cancer and such?

[Edit: I took you to mean that pigment was generally not beneficial, but probably you meant only in certain environments, which would be fair enough.]

Other way around. Darker skin in North America is correlated to more cancer, due to the consequent vitamin D deficiency.

Most of the population is now vitamin D deficient because people don't spend much time outside.

I said specifically skin cancer. Naturally there's a balance between getting vitamin D and avoiding harmful UV. So the best skin tone to have differs in different environments (hence the gradual cline in skin tones over the world).

I don't have details at hand to cite, but I recall encountering some recent news of research that may place in question equating a simple measure of sun exposure to elevated risk for skin cancer. (I didn't look at in depth, and my memory could be somewhat faulty.)

It may not be simple quantity of exposure, but rather severe sunburns that most elevate risk. If one is outside regularly and acclimatized, these severe burns are less likely to occur.

Perhaps someone else will have a more detailed comment on this.

Of course, one's pigmentation will also influence the likelihood of sunburn, although dark pigmentation does not entirely prevent burning.

EDIT: Just read InclinedPlane's comment, above, which mentions the same concern with sunburn.

Actually you have it backwards. Melanin is considered extremely important by the body, some people have high latent melanin levels but all people regardless of race are able to darken their skin color via tanning (exposure to the sun triggering melanin release). Darker skin protects you from being sun burned, which is harmful and can even be fatal (leading to heat exhaustion, heat stroke, etc.) The body considers melanin production so important that some of the natural checks and balances against cancer are inhibited in melanin generation cells, which is why skin cancer is fairly common compared to other types of cancer.

In my defense:

"Melanin helps protect the skin against effects of the sun such as skin cancers and premature aging. In African American skin, melanin provides a sun protection factor (SPF) approximately equivalent to 13.4, compared to 3.4 in white skin. This discrepancy illustrates why skin cancer is more prevalent in Caucasian people"

http://www.skincancer.org/skin-cancer-and-skin-of-color.html

Quite. Folks with the recessive MC1R gene for red hair, like myself, are at much higher risk for skin cancer since we don't really tan, only freckle. Interestingly, this gene is also linked to a vitamin K deficiency, lower tolerance for thermal pain and has implications for anaesthesia and post-operative pain management.

Inexplicably it also correlates with a higher tolerance for electrical pain, which might be a useful adaptation for hackers :)

I don't know where I heard or read this, wearing sunglasses tricks your body into thinking it is dark (no surprise).

In response to that, your thymus (?) which is influenced by light levels now diminished because you covered your eyes with dark glass, releases less melanin which makes your skin more susceptible to UV light. It's weird, your skin is more likely to burn because you are wearing sunglasses.

I believe it was CBC Radio quirks and Quarks where I heard it.

Also, (I mentioned over at Reddit) another interesting thing is the ability of the majority (95%) of adult northern Europeans to be able to digest milk. the next closest group are people from India where 50% of adults are able to digest milk.

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