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[Bobby Isosceles]

I have trouble characterizing a genetic difference that allows one to do something additional as a "defect".  That's kind of like calling the opposible thumb a "defect".  

Whatever your position on eating meat or drinking milk, I can do something that a most people in the world can't -- digest lactose.  How is it that I'm the defective one?

To be a wonk about it:

The question is whether lactose digestion arises from the creation of a new ability (what we call a "gain-of-function mutation") or the disabling of a previous ability (what's called a "loss-of-function mutation"). I don't actually know what's going on there, but you could posit a system in which what the mutation actually does is to disable the pathway that inhibits lactose digestion after infancy; in that case, you would probably call it a loss-of-function mutation, since you're "losing" the lactose-digestion-inhibition "function." However, given that lactose digestion is not apparently maladaptive or disruptive to reproduction, calling it a "defect" is at best misguided.

(I hasten to add that, in scientific terms, causing any mutation a "defect" is generally considered fallacious; more and more "disease" mutations are turning out to have advantageous functions when heterozygous, for example, or otherwise be around for a reason other than making our lives hell. Really heinous, embryonically-fatal-in-heterozygosity stuff, or stuff directly related to DNA damage, can still get called a "defect" with some justice, but most mutations can't be. Also, as a scientist*, I have to just say that technically all mutations are morally neutral. Until we track down that elusive "evil gene," at least.)

* "I'm a SCIENTIST -- I don't believe in anything!!"

I remember reading somewhere that the evolutionary benefit of lactose intolerance was a natural impetus toward weaning; in which case, a loss-of-function mutation as such could be seen as a defect from a genetic fitness perspective. Someone who is weaning far beyond the point where they absolutely have to is, at least to some degree, going to be less fertile for impregnation; thus, being part of a race of milk-lovers means you will breed less often.

This is a fair point, but you could argue just as strongly that later weaning results in a higher overall nutrititive intake for the child during early childhood, better development during that period, and thus greater viability. If the babies you have are more likely to live, that can cancel out the effect of having fewer babies, since children only "matter" for natural-selection purposes if they get to breeding age and breed themselves. I can't say which effect is stronger, but if we posit the suggested model (that somehow this mutation has spread throughout Europe and does not generally appear to be being outcompeted by Europeans without it) then it doesn't appear to be having measurable deleterious effects on the fitness of the carriers.

I agree with you; I was just challenging myself by trying to find a circumstance under which the term 'defect' could be apropos. For what it's worth, however, talk of genetic fitness in humanity IMO is bullshit after we started doing agriculture and actually had a net drop in our welfare, health and genetic fitness which didn't regain its former level until after the Industrial Revolution.  We just starting doing any old thing with the trophic web and hoped the good lord would provide.

I miss hunting and gathering. That's why I hunt hookers and gather cocaine.

[jough]

Ever notice how food allergies tend to only arise in areas where food is plentiful?  The number of people who are lactose intolerant and who receive food aid in Africa is almost zero.   It's not even an issue.

In the U.S., a ridiculously large number of people seem to be allergic to some food or another, like peanuts, milk, or seafood.

We could probably wipe out the lactose intolerance problem in a generation by just LETTING THOSE WHO HAVE IT DIE. That way they can't pass on the sissy gene to their offspring.

We're all about SCIENCE here.

[CortJstr]

I don't think the peanut allergy is spreading genetically though. The two most common theories are that children are being exposed to peanuts, peanut butter, and peanut oil too young (< 1year) or that we're coddling the kids too damn much and need to let them come into contact with things that aren't sterilized before they do to school.  Does anybody else remember than plastic that made the news a few years ago that claimed to have anti-bacterial substances mixed right into it?

[Bobby Isosceles]

Ever notice how food allergies tend to only arise in areas where food is plentiful?  The number of people who are lactose intolerant and who receive food aid in Africa is almost zero.   It's not even an issue.

In the U.S., a ridiculously large number of people seem to be allergic to some food or another, like peanuts, milk, or seafood.

We could probably wipe out the lactose intolerance problem in a generation by just LETTING THOSE WHO HAVE IT DIE. That way they can't pass on the sissy gene to their offspring.

We're all about SCIENCE here.

If you're talking about SCIENCE try getting it straight. Lactose intolerance isn't a food allergy. Lactose intolerance has symptoms such as diarrhoea and stomach upset, which would be indistinguishable from cholera, which most of the developing world still suffers.

As for food allergies, there's a school of thought (and it's not new -- I remember Discover Magazine mentioning it as established in the late eighties) that allergies are the result of an immune system that is expecting parasites and such. Our immune systems are turned to 11 in expectation of the immune-dampening secretions of trichinosis, whipworms, pinworms, tapeworms and the like.

Thus, in the absence of actual infiltrators, we're declaring war on an an abstract and innumerable enemy (pollen, food, etc), the entirety of which we can't possibly destroy. (sound like any presidential administrations you know?)

[wombat]

I'm mildly lactose intolerant. I can't have a milk shake without waking up in the middle of the night with terrible gas pains.

Are you sure this isn't the effect of eating massive amounts of fat, rather than lactose?

[CortJstr]

I'm mildly lactose intolerant. I can't have a milk shake without waking up in the middle of the night with terrible gas pains.

Are you sure this isn't the effect of eating massive amounts of fat, rather than lactose?

Pretty sure. Trips to Popeye's never seem to have this effect.

[Bozack]

All I know is, I can't eat 15 bacon double cheeseburgers, 25 twinkies and wash it down with buttermilk without having another coronary.

[Emergent_C]

I'm mildly lactose intolerant. I can't have a milk shake without waking up in the middle of the night with terrible gas pains.

Are you sure this isn't the effect of eating massive amounts of fat, rather than lactose?

Oh, hell no, it ain't. I get the same symptoms when I consume milk products, regardless of the amount of fat involved. In fact, the opposite is true...I can eat or drink things made with cream, since cream contains no (or very little?) lactose.