Natural selection at work

“This new forage has great insect resistance”, effused a former colleague, “we just need to eliminate the toxins that keep sheep from eating it.”

Genetically engineered drought-tolerant crops are introduced with great fanfare, only to disappear when they turn out to have low yield under nondrought conditions.

Fascinating post from R. Ford Denison, about how silly old natural selection (apparently) fails to make simple changes that would “obviously” be good for the organism concerned. Denison is very clear, in this post and elsewhere on his blog, about just how hard it is for even clever people to improve on the countless experiments that natural selection has had to work on, especially in agriculture. That’s why I for one am not holding my breath waiting for anyone anywhere to transform a C3 plant into a C4 plant.

5 Replies to “Natural selection at work”

  1. I agree with your prediction that humans will find it difficult or impossible to convert C3 into C4, even though natural selection has done this repeatedly. On the other hand, there are lots of cases where natural selection’s “goals” are different than ours. There, progress is much easier. I’ll be discussing both points in my book, “Darwinian Agriculture: where does nature’s wisdom lie”, which is about half done.

    Another point your readers might find interesting is a recent post (“The bitter fountain of youth“) suggesting a new explanation for the health benefits, for humans, of chemicals plants make to defend themselves against insects.

  2. I agree, Denison’s research is fascinating but I don’t buy his suggestion (bitter fountain of youth) that bitter foods are famine foods for humans. I wonder if we aren’t biased by our current day food habits, past food stories (ie. the bitter herbs in the desert), and loss of knowledge of what plants are edible, not to see how far we’ve moved away from what we used to know about how to eat in just the last few generations. Indigenous diets are often far more diverse in the range of flavors they seek out. They recognize flavors that in the western context, we would interpret purely as smells and include foods that are intentionally bitter, sour, astringent (ie. under ripe bananas), spicey, hot (as in creating heat), rich (oily or high in protein), bland, sweet, salty, pungent (like durian), what we might call foetid or just plain stinky (a sour green sort of smell-taste), and “off” (ie. turned the freshness corner or moulded) along with a few others. Recently, a visitor from South America commented that all our foods are way too sweet. In Southeast Asia, an ancient proverb “bitter is medicine, sweet is poison [aka will make you sick]” in relation to food plants is a guide of how to eat. Perhaps, our assumptions of sweet diets being the norm, or the reproductive signal, is not the norm but a result of reduced food biodiversity and corporate food producers and plant breeders making ‘sweet’ junkies out of the city masses?

  3. I agree that loss of food diversity is a problem, for many reasons, but I’m not sure how much our physiological responses to sweet vs. bitter foods, for example, are shaped by current or recent cultural differences, versus being inherited from ancestral populations whose dietary options were very different from now (prior to human use of fire, say). The question is: which foods were most reliably associated with population increases or decreases over the relevant periods in our evolutionary history? I don’t know the answer to this, but I’m guessing we’re talking about eating leaves vs. fruit or (raw) meat.

    Is there an explanation (other than sweet foods triggering physiological responses appropriate for increasing populations) for the association between diet soda and metabolic syndrome (Circulation 117:754) in the US? I wonder if results would be different in other cultures?

  4. Ah, you’d be wrong about “leaves vs fruits and meat”. That sounds so “primitive”. Even in US diets, spinach, kale and lettuce are leaves, brocolli are flower buds, green beans and tomatoes are a fruit. Culinary terms (fruit) vs botanical terms (fruit) might be what’s confusing the picture.

    But, I wonder as well if the results would be different in non-fast food diets. Or, how ‘awa (or kava), coffee, taro leaf, bitter melon, berry-type eggplants (Solanum trilobatum, S. torvum), bamboo shoots, gobo or cassava – all with bitter elements and mainstays in today’s diets figure into the chemical signal mix? It is very curious that metabolic syndrome in the US seems to be associated with sugars (false or otherwise). Has it effected other western countries or Japan in the same way?

    In 1984, Roy Rappaport (Pigs for the Ancestors) suggested an abundance of pigs played a significant role in population abundance (and tribal wars) in Papua New Guinea. Nabahm among the indigenous people of the Sonoran Desert 1982, and the work of Shintani and Hughes in the Hawaiian community in the 1990s also demonstrate how recently the change from traditional (not caveman) to “modern diets” has been (between 200,000-790,000 years ACUF – after controlled use of fire; Maybe, it’s the availability of meat/fat (a signal of fertility) and sugar is just the phermone tease that fools the body’s metabolism? The one striking element in the diets of traditional non-western cultures is how few refined sugar/carb sweets there are relative to whole food sweets such as fresh or dried frutis. And they warned us it was drug (Dufty 1975). Now we know.

  5. Of course I know that tomatoes are fruits, but “prior to the invention of fire” should have made it clear that the leaves and fruit could not have been domesticated species. If these physiological responses mainly evolved millions of years ago then human cultural differences we see today aren’t much of a guide. On the other hand, evolution is an ongoing process, so I don’t exclude the possibility that different human groups might respond differently.

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