Humans evolving 100 times faster than historical levels.
latimes.com
latimes.com
Now that's interesting. Any theories?
Resistance to cancer would likely have little evolutionary value. Most mating and child rearing is done before the average age of cancer, particularly in past societies. I would similarly wager that cancer would not a be a strong enough force (it would usually hit people randomly rather than the entire group simultaneously) to ruin the ability of a tribe to defend itself.
If anything, cancer resistance (which would probably mean less cell mutation ability) would be disadvantageous from an evolution standpoint because you would have less variation and consequently may have trouble adapting.
The grandmother hypothesis [http://well.blogs.nytimes.com/2007/10/05/evolutions-secret-w...] supports cancer resistance as an evolutionarily beneficial gene. You also miss the obvious unstated point that cancer resistance itself may just be a side effect of another characteristic, such as more efficient mitochondria.
Your third paragraph fails to support any of its assertions; cancer resistance takes many forms, and most mutations are negative in nature: some math would likely be necessary to support a (carefully worded) argument in either direction.
but re your last point, being prone to cancer could speed up evolution but at the same time could wipe out a sub population? infact- that (probably) holds for anything that speeds up evolution - but again math models would be needed to prove that.
Evolution doesn't work that way. It doesn't favor mutation because mutation is "good" for evolution. You have to look at it from individual genes, and there the story is just the opposite.
Evolution happens in spite of, not because of genetic predisposition to mutation, because it's vastly more likely for a mutation to be pointless or harmful than beneficial. If you have a gene that makes mutation in the genepool overall less likely, that gene will be more successful at spreading itself, because the mutants have, on the whole, far less chance of success than the originals (which have already proven their worth in a long chain of ancestor individuals carrying them). Of course every so often a mutant gets lucky and is more successful (or at least not less successful) than the original -- this is what selection is all about -- but statistics are against them.
To elaborate your scenario: suppose the environment changed very rapidly, and adaptation in some direction were necessary to survive it. If by some stroke of luck a gene that increased the mutation rate happened to be there at that moment, defying the odds, it would find a favorable environment, but only for as long as the rapid change is required. Generalizing this: a successful genepool is one where the mutation rate is "just right" for adapting to the environment. Too much mutation and the genepool isn't stable and will eliminate itself, too little mutation and the genepool will be eliminated by the environment. In this balance, the odds are stacked in favor of avoiding mutation.
And all this is orthogonal to the discussion of how cancer (the uncontrolled reproduction of cells) is related to the capacity for mutations (infidelity in the copying process). Cancer resistance and mutation resistance are related, but by no means the same thing. To borrow a computer image: your computer has copy processes with very high fidelity (only the occasional alpha particle to spoil the fun) but this doesn't protect it against worms, which copy themselves unwantedly but with the same high fidelity. This analogy is badly flawed in obvious ways (regular programs are not designed to copy themselves, cells are), but I hope it gets the point across.
If you are talking about prehistory, how can you know this?
As it stands, culture encourages promiscuity under the guide of empowerment (whether this is positive or negative is a longer argument) and legislation certainly doesn't discourage cheating (e.g. fault-free divorce, child maintenance to support the female partner even in cases where the male partner ends up not being the actual father, alimony in the U.S.).
My reaction is that he misspoke here or he overstated his claim to make a point.
I know nothing about the proportion of people with blue eyes back then or right now for that matter. But I think at the very least, you could only make that claim with a tiny, tiny, tiny amount of confidence.
Maybe the proportion of humans with blue eyes was smaller back then, maybe it was larger, or maybe it was the same. I don't know. But to claim nobody 10,000 years ago had blue eyes is an impossible point to prove unless you have DNA samples from every human alive 10,000 years ago. We might be able to say that all the people alive today with blue eyes descended from one ancestor, but we can't claim to know about the population of people with blue eyes back then. For all I know, half the population 10,000 years ago could have had blue eyes but then got wiped out by swine blue.
That's like saying no one 100 years ago was over 7'6" tall. I know a bit more about height and think that this statement may be true. But it would be real hard to prove. Now shift the timespan back by 2 orders of magnitude, and I think it'd be harder to prove.
I'm not saying that the general idea is wrong, but I'm just it would be a good idea to question that claim a lot before thinking about reasons why that might be the case.
-- exactly.
And, if you follow the science of using mitochondrial DNA to date genetic changes..
http://www.dailymail.co.uk/sciencetech/article-511473/All-bl...
Although I'm not convinced from the results of one study, now I understand what the genesis of the original comment was.
Evolution is a fascinating subject. I think it would be neat if all our schools taught 12 years of Reading, Writing, Arithmetic and Evolution.
I did find a different source that would tend to support the randomness of mutations, and that also indicates that there are two different mutations that can lead to blue eyes, and as such, it is unlikely there is only one ancestor. http://www.thetech.org/genetics/ask.php?id=160
Sexual preferences are pretty strong drivers and combined with periods of harsh environments (e.g. where either of the sexes die off early in life) can create really fast evolution.
(1) Perhaps less pigment in the eyes improves vision in certain conditions (especially those in colder latitudes).
(2) As a recessive trait, blue-eyed mating limited a woman's ability to pass off offspring from other (dark-eyed) fathers as that of a blue-eyed father. This greater confidence in paternity won greater fatherly support, and in some eras/places (inheritable property?) this dominates the advantages of promiscuity. (This effect may fade or even reverse depending on proportion of eye colors.)
(3) Handicap principle -- even if blue-eyes are a disadvantage in some dimensions (sun-robustness, alien look), sometimes a conspicuous disadvantage is effective as a signal that fitness in other harder-to-measure dimensions is better. ( http://en.wikipedia.org/wiki/Handicap_principle )
(4) I suspect just about any unique visible characteristic, advantageous or mildly disadvantageous, can find some reinforcement as a quick signal of genetic kinship against outside competitive groups that look different. So just, "different enough to tell closer-cousins from distant-cousins" could be a sufficient explanation.
Either that, or consult with your milkman/gardener.
My wife is from a part of China that is not very likely to have any genes for blue eyes (or red hair) in the indigenous population. The overwhelming probability is that she is homozygotic for both black hair and brown eyes.
The fact that your children have blue eyes means she does have genes for blue eyes
There is a reading problem here, because I never said anywhere in my post that any of my children have blue eyes. (In fact, these days I am startled whenever I see a child with blue eyes, even though I grew up with siblings with blue eyes, because all my children and my wife look at me with brown eyes. I see blue eyes and ask myself, "Do they make eyes in that color too?")
You also are well advised to do more reading about the genetics of human eye color and hair color
http://en.wikipedia.org/wiki/Eye_color
http://en.wikipedia.org/wiki/Human_hair_color
and human genetics in general. Genes can recombine from one generation to the next. My red-haired dad, by the usual assumption that you made in your reply, was homozygotic for red hair, making me presumptively heterozygotic for red hair, while my wife presumptively is not a carrier of that trait at all, on population genetics probabilities. But two of my children have hair that is "brown" at a glance but also includes red pigment (as can be seen when their hair is backlit by sunlight or when strands of their hair are observed under a microscope). Sometimes children can inherit a double copy on one gene from just one parent, as anyone who has carefully studied human genetics knows.
Edit: posted this before I saw the other thread and the excellent answer here - http://news.ycombinator.com/item?id=824543 My mistake.
And melanin has many roles, sun protection being just one, the other is as a structural protein. Just compare how black skin ages vs. how a redhead of the same (advanced) age looks.
And why would Caucasians have a mutation which deposits less of such a useful protein? Vitamin D.
It is produced when UV light hits the skin. In northern climates with less sun, and skin being covered or you die of exposure, often even when the sun is up, people get a lot less vitamin D.
Inuit get more due to their diet, and modern man also gets much more again because of diet. And yet most people living in the north even today lack vitamin D.
Also, I thought all of the above is common knowledge which makes me question the whole article.
More than you ever wanted to know about eyes: http://en.wikipedia.org/wiki/Eye_color
Also, this is neat: A 2002 study found the prevalence of blue eye color among Caucasians in the United States to be 33.8 percent for those born from 1936 through 1951 compared with 57.4 percent for those born from 1899 through 1905.[10] Blue eyes have become increasingly rare among American children with only 1 out of every 6 – 16.6 percent which is 49.8 million out of 300 million (22.4% of white Americans) of the total United States population having blue eyes.[33][34] The plunge in the past few decades has taken place at a remarkable rate. A century ago, 80 percent of people married within their ethnic group. Blue eyes, a genetically recessive trait, were routinely passed down, especially among people of Scottish, English, Irish, Welsh, Western and Northern Slavic, and Northern European ancestry.[33][34][35] In the 1930s, eugenicists[citation needed] used the disappearance of blue eyes as a rallying cry to support immigration restrictions. They went so far as to map the parts of the country with the highest and lowest percentage of blue-eyed people.[citation needed]
Blue eyes are most common in Northern Europe and Central Europe and to a lesser degree in Southern Europe,North America and southern Central Asia; Afghanistan is a notable example.[30] They're also found in parts of North Africa,[31] West Asia, and South Asia[32], in particular the northern areas of India and Pakistan. It can rarely occur as far south as Sri Lanka. However blue eyes are not found within the population of East Asia, due to the major pre-dominance of the brown eye gene in the area.
Central Asians, people from the Caucasus, Afghans, Pakistanis, and even Indians darker then many an African are considered Caucasian. They are Caucasians. And North Africa is full of Caucasians, hell even German tribes, Goths if I recall correctly, settled there during Roman times.
So only Caucasians have Blue eyes. Again because of a gene mutation which control how much melanin is deposited in hair, skin, and irises.
Someone with a lot of melanin could have blue eyes, but they wouldn't appear blue do the the melanin. That's why blue eyes contain low amounts of melanin.
And low amounts of melanin are related to vitamin D, which is related to living in northern climates.
Depends who you ask, as race is purely a social construct.. http://en.wikipedia.org/wiki/Craniofacial_anthropometry
Some mongoloids do have blue eyes, but yes this is a result of interbreeding with descendants of the common ancestor.
A friend told me that in baseball, batters have a higher tendency towards blue eyes, and pitchers to brown, but I couldn't find any references.
Does anyone know if this has any scientific basis?
Greater population = greater opportunity for mutation. Sounds right...
After edit: Here is a link to a more recent article on a closely related subject:
http://pritch.bsd.uchicago.edu/publications/pdfs/CoopEtAl09....
1) This blows my mind -- am I reading it right that there was virtually no variation in skin color 20,000 years ago? I assumed there was always variation in skin pigmentation, with darker skin colors predominating until we expanded into northern latitudes where lighter colors made sense.
2) What about Neandertals? I always imagined them being light-skinned, since they were adapted to northern climates. I wonder if they evolved genes for light skin tens of thousands of years before modern humans did. If so, that must have made them look even more freakish to modern human eyes, and vice-versa.
I think the correct statement is as you say in another part of your post: there has always been variation in skin color in the human population. It was geographically segregated (forming "races" in the biological sense) only very recently. And even today there is a lot of variation among individuals in skin color within each continental subpopulation of human beings.
The usual view of evolution of skin color is that the ancestral condition was white skin under dark hair (as we still see in chimpanzees). Then at some unknown time, human ancestors became less hairy, and darker skin pigmentation became necessary. Then as human beings (Homo sapiens) migrated to latitudes with less sunlight (VERY recently) gene frequencies changed again in favor of lighter skin in some areas. (Inuit people are quite dark skinned for people who live near the North Pole and usually wear heavy clothing.)
100 what?! You're making my brain frustrated.
EDIT: Ahh FTA: 100 times historical levels.
Dark skin means more light is absorbed, and therefore doesn't bounce back at the viewer's eyes.
the only explanation I can think of is that the rules are somehow different for light outside the visible range?
Perhaps the question is more complex because sunlight is not all in the visible wavelengths and skin is actually translucent and light reaches different level through the skin, melanin prevents parts of the light to reach deeper levels in the skin and also converts parts of light.
Melanin inhibits the above reaction, so blacks need more sun to get the same amount of vitamin D.
More details: http://www.cholesterol-and-health.com/Vitamin-D.html
Dawkins, with his gene-centered view of Darwinian evolution, refutes this, explaining that evolution by natural selection is gradual.
People say he refutes this. According to him, he never said anything to refute this. In either case, you have to be specific about what "gradual" means. Dawkin's evolution is more gradual than intelligent design, but not so gradual that it is inconsistent with Stephen Gould's claim.
I'm not implying that they have a hostile personal relationship, but their academic disagreements were significant. Examples include the gradual view of evolution, and also Gould's claim of NOMA, which Dawkins (detests).
http://cogweb.ucla.edu/Debate/CEP_Gould.html
(I have studied some related subjects but not evolutionary biology, so I don't really know the research papers. But I do know that political/religious idealists are often dishonest to influence public opinion.)
One thing to remember is that evolution != progress
And Cochran and Harpending, the "Utah colleagues" mentioned in the article, have already written a book about this accelerated human evolution: http://www.amazon.com/000-Year-Explosion-Civilization-Accele...
(Pure joke)