Evolving to handle grains? page

[HotfootinJoe]

Ok, so grains are pretty bad for us but since they have been with us since the dawn of civilization I think they're here to stay. If this is indeed the case, how long before we evolve to cope with the anti-nutrients in them and do our systems cope with them any better than the people 10,000 years ago?

[NorthernMonkeyGirl]

Interesting question.


Thing is, as long as someone survives long enough to reproduce, their genes will be passed on. That's why late-onset diseases such as dementia haven't been selected against. It's also the basis of the claim that humans have stopped evolving due to medicines and fertility treatments, but that's a whole other can of worms!


It does seem anecdotally that some people are more sensitive than others, but I couldn't tell you if that was genetic, or related to aaaaaall the other differences in life!

[rphlslv]

Probably in a million years or so. But do you think we, as a race, will even last that long? No chance.

[Griff]

From what I've read, it takes an organism about 500,000 years to adapt to a new dietary plan. We've had maybe 10,000 years. It's not going to happen anytime soon.

[lbd]

Actually, evolution only occurs when there is some pressure to do so. If there is no pressure forcing a change in the gene pool (where those better suited to survive, do so, and pass on their more-suited genes to their offspring), than there is no shift in the species. Because the cumulative effects of the CW way of eating tends to affect people later in life, after reproduction may have already occurred, chances are that any "favorable" CW-diet genes will not increase within the gene pool.


And Raphael is right in the sense that very few species really ever last that long. There are some hypotheses that many dinosaur species were eliminated due to their inability to adapt to the angiosperms (flowering plants) that over-ran the planet, pushing the gymnosperms northward. Most dinosaurs couldn't tolerate the colder temps as well. Before the final hit of possible meteor or volcanic eruptions occurred, the dinos were on their way out anyway.


It is funny how humans look at the planet as a place to preserve "as is" and "for us." This planet will likely go on without us very easily and species are likely to replace us just as has been done many, many times in the almost 5 billion years of its existence.


Sorry, I digress, but I do love to talk evolution (and not evolution vs creationism).

[Annika]

But Griff, what about evolving to digest lactose? That seems to have happened to Europeans in a fairly short time.

[rphlslv]

I think it's because lactose isn't as bad as what's in grains... besides, at one point in our lives (as babies) we could handle it very well. It's only a sugar.


Anyways, I don't know much, so I might be wrong. :P

[Pikaia]

Yep, the ability that some of us have to tolerate lactose in adulthood was a fairly simple genetic alteration. The changes required to more effectively digest grains would take a lot more time to evolve.


The gene for lactase, the enzyme that breaks down lactose, is switched on from infancy until sometime in childhood. Then it shuts off, because presumably you are no longer ingesting breastmilk, and your body would rather not waste resources making an enzyme that is not needed. But fairly simple mutations have occurred which can keep the gene from shutting off. Those changes allow some people to continue efficient digestion of lactose in adulthood.


However, I wouldn't go so far as to say we're now perfectly adapted for digesting cow's milk products. Sure, some of us can handle lactose, and that ability probably conferred a competitive advantage at some point in time. But some humans who have no trouble with lactose DO have significant trouble handling cow's milk proteins (caseins and/or whey). This can cause true allergies or dairy intolerance/sensitivity. The latter are often milder and may go completely unrecognized, but they can have significant negative impact on health.

[lbd]

You don't really evolve to digest lactose. All mammal babies are born with the ability to produce lactase, the enzyme to digest lactose. But the gene that makes the instructions for making lactase is turned off around the age of weaning in most mammals, probably triggered by the transition to other foods. We humans have decided to continue drinking/eating OTHER mammals' milk, so many of us keep producing the enzyme. This is more of a case of an environmental trigger (continuing to drink the milk) affecting the gene's expression. We don't have to develop new gene instructions to drink milk - just keep the ones we have working. My guess, and it is truly a guess, is that some cultures use dairy so prevalently that the gene mechanism to shut down may have been altered some, IF it gave those who could tolerate milk longer a reproductive capacity edge. This might be true in northern clime cultures who may have depended on milk products to get them through hard winters or through drought periods, etc. If children died early because they could not tolerate other mammal milk, then it is possible that there was some selection for those that kept the enzyme working longer.


Evolution can work quickly, but it can be harsh - you either survive or don't and you better hope there are some members in the group that will be able to pass on those survival genes to the next generation. If no one has the genes, the species is out of luck. Just ask the several million species or more that are long gone from this planet. Cheetahs, for example, are so genetically similar that if something comes along like a virus that kills one, it will most likely wipe the remaining population out because they have no genetic diversity.

[Pikaia]

Anyone interested in the genetics of lactase persistence can read all about it here -


http://www.ncbi.nlm.nih.gov/entrez/d....cgi?id=223100