Skin color can also be a factor in sexual selection, so it isn’t necessarily an adaptation to environment. For example, as Jared Diamond points out in “Guns, Germs, and Steel,” African populations that have been living for many millenia in jungle/forest areas, where sun exposure is minimal, are often very dark-skinned even though there’s no environmental advantage for it. (Melanism can change rapidly in a population, in only a few thousand years. Humans have a number of genes for diverse results, and it only takes a minor mutation or two to regulate them differently.)
True but that doesn’t affect the original argument, which is that most skin cancer tends to happen long after significant reproductive success. It’s not a particularly strong evolutionary force.
You said this in response to a discussion of “most of history”, so it’s apropos, but most human evolution happened in prehistoric times. Hunter-gatherer societies are pretty much classless, so your point isn’t really applicable to the main question here.
Also note that more recent research that the real “whitening” of European skin occurred more recently, casting doubt on the vitamin D hypothesis:
http://mbe.oxfordjournals.org/content/early/2012/08/25/molbev.mss207.abstract%20[open%20access
I guess I was wrong about how long our ancestors live but I would still maintain that there isn’t much evolutionary pressure from skin cancer as the trend for most of humanity is to reproduce at a young age it is more recent that people have been becoming parents at older ages and also some cancers such as Basal Cell Carcinomas may take years and years to metastasize to a dangerous level and would probably not usually develop until late middle age or beginning of old age so I don’t believe either way it has much of an effect on passing on one’s genes.
The first Europeans were hunter-gatherers, then herders. White skin was only selected for after grain-based agriculture took hold, in the Neolithic. If anything, that discovery supports the theory.
Per the paper I linked to above that occurred 11,000-19,000 years ago, which was well before grain-based agriculture took hold in Europe.
It has been suggested (I can’t find the research) that melanin has a similar protective effect in climates where skin infection is a bigger problem.
I argued many times that in fact, it was, taking as example the kings of France (living on average to their late 40s, and only one to 60) and England (living on average to their early 50s, and only 2-3 living to 60) between 1000 and 1500. I recently found actual data in a book by medieval historian Georges Duby, giving a life expectancy of 25 years at 20 in the 13th century (IOW, people who reached 20 were dying, on average, at 45).
People in the past were having shorther lives. Not as short as what appears based on raw figures including infant mortality, but much shorter than now even if they reached adult age in the first place. Making it to 60 was uncommon. Think of all the untreated diseases, accidents, parasites, hard work, poor hygiene, poor food, deaths in childbirth…
And that also is wrong. The average age of marriage varied a lot historically, depending on a number of factors. A study done about 15th century rural France indicated an average age for first marriage in their early 20s for men, late teens for women. The typical marriage would have been something like a 24 yo man marrying a 19 yo woman.
Matthew Henson’s Inuit descendants are probably dark-skinned.
I’m sure (I hope) you meant that as a joke, but let’s nit pick it anyway…
His only son was born in 1908, and died in 1987. Since MH’s living descendants (you said “are” not “were”) are, at most, 1/4 African American, it’s unlike they are particularly dark skinned.
Don’t know where you got the impression that Scandinavians don’t tan. The vast majority of scandinavians tan just fine.
And hunter-gathers had better life expectency than farmers. They had a more varied diet and less disease pressure. Farmers out-competed hunter-gatherers in all the good agricultural areas because their vast production of calories/acre allowed them to breed like rabbits and support armies. But early farming is a much worse life-style in almost every way than being a hunter-gatherer.
It’s possible that sunburn is a more important evolutionary factor than skin cancer. But it’s a mistake to think that longevity in humans carried no benefit to the gene-line. As someone else, said, there’s a reason we routinely survive menopause – in fact, the evolution of menopause suggests that there is evolutionary value in surviving after prime childbearing years. In traditional societies, grandparents provide extra calories, babysitting, and valuable wisdom (where is the waterhole that remained useful during the last big drought?) to their descendants. Tribes probably did best if they didn’t support too many people who become too frail to forage and hunt, but having a few old people, even past the age of direct economic production, added value to a tribe due to the accumulated wisdom.
And there’s some pretty prominent theories that the reason they gave up that easy, healthy life in exchange for drudgery, disease, and bad nutrition was that agriculture was the only way to guarantee a steady supply of beer.
I’d like to see a cite for all of that, as I don’t believe it to be correct. I believe, for one, you are confusing average life expectancy at birth with average life expectancy once age “X” is reached.
And there is no such thing as “early farming”, as if some H/Gs just stopped hunting and started farming. People didn’t give up H/G lifestyles to farm. They did both until farming was able to sustain them.
“Early farming” means farming as typically practiced in the first several millennia after the advent of agriculture and the estanlishment of fixed communities primarily supported by farming. The presumed first-ever, part-time farmers are not the focus of the point about lifespans and general health.
Citations… That’s hard. Let’s see. The first place I ran into the idea that farmers and civilizations in general have more disease pressure was in Plagues and Peoples
But the core ideas are pretty intuitive. Infectious disease tends to die out among scattered bands of people, but can burn through a densely-settled population center because every person who is exposed has a chance to expose so many other people. Also, sedentary people have more issues with hygiene, because they can’t just move away from their wastes until they fully decompose.
I’ve seen comments on the work-load and nutrition of hunter-gatherers vs. early farmers (by which I just mean pre-industrial age) in numerous places. Farmers tend to rely heavily on a single, starchy staple crop for a lot of their calories. Hunter-gatherers eat a greater variety, including more protein. I’ve also read that during colonial days a lot of people compared the lifestyle of the Native Americans on the east coast with that of farmers in England, and few would have chosen to be English farmers. Similarly, farmers ALWAYS have work that ought to be done to improve the farm, whereas hunter-gatherers tend to have more leisure time. Lazy, Godless people, dontchno.
Hmm, good web-based references are hard to find, because of the popularity of the “paleo diet”. And a lot of the references I can find are regarding modern (or near-modern) hunter-gatherers who mostly live on the lands that farmers don’t want, not re pre-farmers. But here are two. Neither is a great reference, but both tell persuasive stories:
http://www.proteinpower.com/drmike/low-carb-diets/nutrition-and-health-in-agriculturalists-and-hunter-gatherers/
http://www.ditext.com/diamond/mistake.html
Not something I can give a reference to, but a friend is an amateur archeologist and has studied some of this stuff. He tells me that farming spread across Eurasia extremely slowly. Basically, it appears that no one chose to become a farmer. Instead, children of farmers cleared new lands each generation, as their population grew. There is no doubt that farmers get more calories per acre than hunter-gatherers, and when the groups clash the more populous farmers tend to win. He says you can see the same pattern of farmers slowly taking over in the patterns in which the Greek islands were settled. A group of newcomers would show up in a boat, and start farming. The natives reacted in various ways, but most didn’t immediately commit genocide on the newcomers. Those newcomers outgrew their initial settlements in a few generations, and soon took over.
The health consequences of early agriculture were significantfor several reasons:
The general principle is that early agriculture provided more calories and thus more population density but provided less complete nutrition and created more infectious disease.