July 18, 2014

Upcoming talks in NY and Washington states

Both talks are part of symposia with other interesting speakers.

August 18: Student Organic Seed Symposium, NY Finger Lakes Region

October 28: minisymposium (with Emma Marris, author of "Rambunctious Garden: Saving Nature in a Post-Wild World") on "Saving Nature and Improving Agriculture: Where does Nature's Wisdom Lie?" Washington State University, Pullman

July 19, 2013

Weed evolution in the New York Times

Carl Zimmer, author of several evolution-themed books and an interesting blog, published an article on weed evolution in Tuesday's New York Times. He used one of my favorite examples of rapid evolution of complex traits (flooding tolerance and crop mimicry in Echinochloa barnyardgrass/watergrass in <1000 years) to make the point that evolution of herbicide resistance (a much-simpler trait) in only a few years shouldn't have been a surprise.
(Left) Under selection pressure imposed by farmers with hoes, Echinochloa watergrass evolved to resemble rice more than it resembles its own recent ancestor, barnyardgrass (Barrett, 1983). I discussed this example near the end of this lecture at the International Rice Research Institute.

Glyphosate-resistant weeds are becoming increasingly common, just before the expiration of Monsanto's patent on Roundup-Ready soybeans. What does the US Constitution say about patents?

"The Congress shall have Power To...promote the Progress of Science and useful Arts, by securing for limited Times to Authors and Inventors the exclusive Right to their respective Writings and Discoveries...."
If the original intent was to give inventors short-term monopolies, in exchange for long-term benefits to society, should the duration of patent protection be shorter for inventions whose useful life is likely to be limited by evolution? For example, 17 years with a really good resistance-management plan, 5 years with no resistance-management plan.... Of course, the Patent Office might need to hire an evolutionary biologist or two.

I agree with the statement from David Mortensen that adding another resistance gene to glyphosate-resistant crops, and spraying with both herbicides, will be only "a short-lived solution," although it might last long enough to be worth patenting. If they had put two different herbicide-resistant genes into soybean from the start, and if evolution of resistance requires two or more independent mutations -- this isn't always true -- and if farmers growing that herbicide-resistant crop were somehow required to use both herbicides (so that mutants resistant to just one of the herbicides wouldn't have increased in frequency), evolution of resistance might have taken much longer.

Zimnmer quoted me and mentioned my book on Darwinian Agriculture, depleting Amazon's stock, though they still have a few copies left. You could try your favorite independent bookstore or library.

October 8, 2012

Darwinian Agriculture reviewed in Science

Allison Snow, whose publications have included some of the best work on gene flow from transgenic crops to weeds, has reviewed Darwinian Agriculture in the journal, Science. Like an earlier reviewer, she noted that I can sometimes be repetitive, but the review was very positive overall. That may explain why Amazon's listing suddenly went from "in stock" to "usually ships within 1 to 3 weeks." You can also order from your local bookstore, Barnes & Noble, or directly from Princeton University Press, whose latest mailing offers a discount.

See also the two-part review by Jeremy Cherfas at the Agricultural Biodiversity Weblog. And if, after reading the book, you agree with Professor Snow that "the book is perfect for discussion-based seminar courses", I may be able to help.

September 26, 2012

Diversity of Opinions on Diversity

Cedar Creek plots weeded to maintain low diversity have low plant cover, explaining their low productivity. But why does that space stay open?

Part two of the mostly positive review by Jeremy Cherfas, on the Agricultural Biodiversity blog, argues that my Darwinian Agriculture book understates the benefits of mixing varieties (e.g., with different disease-resistance genes) within a field.

I added a comment there, noting that I had included a comparison of this strategy to an alternative way of deploying the same amount of genetic diversity. But his overall point remains valid. I think I over-reacted to what I see as a tendency to think about crop diversity mainly at fine spatial scales, while ignoring diversity at larger spatial scales and over time.

While I'm on the subject of plant diversity, I talked to Dave Tilman about the suggestion in the book that the low plant cover (see above) in his low-diversity treatments could be an artifact from their weeding protocol. He apparently has data showing that seedlings of the one "resident" species in his monoculture plots do poorly, relative to seedlings of other species. I've seen the same mechanism as an explanation for high tree-species diversity in the tropics -- species X doesn't do well near species X, perhaps due to disease.

The fact remains, however, that photons hitting soil, rather than leaves, drive water loss without contributing to photosynthesis. So it's not surprising that low-cover plots have low productivity. Crop monocultures, however, usually achieve full cover, limiting the relevance of this work to agriculture.

If I get to do a second edition, I will try to correct these flaws. Meanwhile, I see thoughtful negative comments as positive, consistent with my goal of stimulating more-insightful discussion.

September 25, 2012

Blogs discussing Darwinian Agriculture

The bloggers and commentators at Agricultural Biodiversity set the standard for insightful discussion of many agricultural issues, so I was hoping they would review my book. Jeremy Cherfas has just posted the first half of a two-part review.

Tyler Cowen also mentions my book, briefly, in the web version of his op-ed on world hunger in the New York Times, posted on his blog, Marginal Revolution.

Cherfas's review and Cowen's mention are both positive. Both are reasonable summaries. Both somewhat over-state my doubts about biotechnology's potential, however. Yes, many of the approaches suggested or tried by biotechnologists have already been tested and rejected by natural selection. But some tradeoffs rejected by natural selection may be acceptable to us. Less-bitter cucumbers may attract rabbits, but we can build fences.

Eventually, we may learn how to design and implement improvements so radically different from anything that exists now that they have never been tested by natural selection. Radical innovations may carry unknown risks, however.

September 24, 2012

Comments on Forbes article on biomimicry

Steven Kotler, at Forbes, recently posted a story titled "Move Over Genetic-Engineering; Biomimicry Seems The Better Bet For Solving Global Hunger."

The Forbes site said I could comment using my Google identity, if they could just have access to my contact list. No thanks. I"m amazed it's even legal to ask, if it is.

So I'll comment here. Biomimicry is a major theme of my recently published book, Darwinian Agriculture -- but biomimicry of what?

The adaptations of individual plants, animals, and microbes have been improved (by the criterion of Darwinian fitness in past environments) through millions of years of competitive testing against alternatives. But larger-scale patterns we see in nature, such as the total number of species in a forest, or how trees are arranged, haven't been tested competitively. Trees compete against trees, but forests don't compete against forests.

If we copy individual adaptations of trees, we are copying the winners of many past rounds of competition. A forest may have persisted for thousands of years, so it's probably not too dysfunctional. But it hasn't been tested through repeated competition, so there's likely to be plenty of room for improvement.

I would have expected a writer at Forbes -- do they still call themselves "a capitalist tool?" -- to understand how competition is key to improvement, but apparently not.

Now, what about the specific examples in the Forbes post? Spiders compete against spiders and sharks compete against sharks, so it's not surprising that spider silk and shark skin are awesome.

But his "favorite" example is that wildlife corridors that mimic electric circuits work better. I'm not sure what point Kotler is trying to make here -- did he not notice that this is biomimicry in the opposite direction? Although caribou have competed against caribou, curved and straight wildlife migration corridors haven't competed against each other. (OK, maybe they have competed for caribou and their manure, sort of, but the winning corridors don't produce "offspring" with the same degree of curvature.) So this case calls for intelligent design by humans, not mimicry of large-scale patterns seen in nature.

And then there's the endophyte example. Some fungi that live inside plants can provide major benefits to those plants. We will be reading and discussing journal articles about this in a couple weeks, in our graduate seminar.

If there were only one fungus per plant, fungi that benefit their hosts would thereby benefit themselves. But mixed infections seems to be common. With mixed infection, a fungus that invests resources to benefit the host is like someone who pays taxes when nobody else does. Admirable, perhaps, but not likely to be very successful. It's a variation on the classic "tragedy of the commons."

One benefit often provided by endophytes is chemical defense against a plant's enemies. This case isn't too hard to understand. Maybe the various fungi make toxic chemicals to attack each other, since they're competing for the same plant resources, and those same toxins also protect against insects that might otherwise eat the plant.

But how and why do endophytes improve drought tolerance? Unlike mycorrhizal fungi, which extend out into the soil, most endophytes are entirely inside the plant. So it's not as if they can pull more water out of the soil. Sure, they can produce chemicals that mimic plant hormones, thereby manipulating the plant to make more (or fewer) roots or to open (or close) the stomata through which water evaporates from leaves.

But it's hard for me to believe that:
1) a fungus infecting a plant is a better judge of how many roots a plant needs than the plant is
2) that the fungus would put the plant's interests ahead of its own.

It's a mystery. But that's what science does: solve mysteries. Stay tuned.

September 11, 2012

Somebody liked my book

The first customer review on is positive, aside from the statement that the book is "at times a bit repetitive." I have to agree. I thought repeating some key points would help those who just read particular sections, but I may have overdone it.

Amazon's US branch doesn't have any customer reviews yet, just reviews from two experts contacted by the publisher.

September 5, 2012

Biomimicry of forests or trees?

A colleague is teaching a class on biomimicry and asked whether I had a short summary of evolution as background. I gave him part of "Evolution 101", Chapter 3 of my book on Darwinian Agriculture, but also some material the editor made me leave out. Here it is:

A brief analogy with engineering may be useful. Imagine that a pair of ideas-from-nature experts were asked to help engineers improve a bicycle safety helmet. Ideally, they would like to increase fracture resistance, while decreasing weight. Here's how the discussion might go.

Ideas-from-nature expert #1: "Consider mimicking the structure of conch shells. I don't know anything about their structure, but I do know that sting rays have been eating conchs for millions of years, by crushing their shells. Whichever conchs had the toughest shells were most likely to survive and reproduce, all else being equal, because the rays would give up on them and go crack a weaker conch. Whenever mutations arose that made shells stronger, those mutants would have tended to survive longer, so their descendants have displaced those who made slightly weaker shells. This process has been repeated for millions of years, so the structure of conch shells is probably pretty good by now."

Engineer (one week later): "We tested conch shells and their fracture-resistance is indeed amazing (Kamat,S. 2000). Microscopy reveals that conch shells have alternate layers of hard minerals and stretchy organic material. We have some man-made materials with similar properties, but I think we can improve on the conch-shell design. In particular, we could make each of the two kinds of layers thicker. Thicker layers will probably make the material even stronger."

Ideas-from-nature expert #1: "Maybe, but surely mutant conchs with thicker layers must have arisen repeatedly. If thicker layers are better, why didn't conchs with thicker layers in their shells displace conchs with thinner layers?"

Engineer: "Interesting question. Maybe thinner layers actually give better interaction between the two materials. Also, thicker layers would be heavier, for a given number of layers."

Ideas-from-nature expert #1: "And a conch with a heavier shell couldn't swim as fast. Natural selection balanced the tradeoff between strength and weight. Evolution is all about such tradeoffs. We can't be sure that conchs have evolved the best possible compromise between shell strength and weight, but it's probably better than most slightly different alternatives. That's because alternatives that are only slightly different have probably arisen via mutation, and tested through indirect, sting-ray-imposed competition."

Engineer: "OK, but our bike helmets will also be exposed to ultraviolet light from the sun. Conch shells didn't have that additional challenge."

Ideas-from-nature expert #1: "Right. Some of the challenges that shaped conch-shell evolution are the same as those we're facing in designing a bike helmet. Other challenges are different. I can see that you recognize the difference, so I'll leave you to your work."

Ideas-from-nature expert #2 (arriving out of breath): "Sorry I'm late. I just heard the last part of that. I have a different idea. Instead of copying conch shells, what about copying rocks? They've been tested over thousands of years. I know where there's some obsidian that's been exposed to ultraviolet light and erosion for millennia, and it's still there. Maybe your helmet shells should mimic the glass-like structure of obsidian."

Engineer (one week later): "We tested the obsidian. The conch shell is hundreds of times stronger."

Ideas-from-nature expert #2: "Well, how about this sedimentary rock? It's been around for millions of years, so it must be really strong. It has particles of different sizes; maybe you could copy that structure."

Engineer (one week later): "We tested the sedimentary rock, and it's also much weaker than the conch shells."

Ideas-from-nature expert #2: "Hmmm... Why not combine our best ideas? Here's a sedimentary rock that contains conch shells, embedded in inorganic materials. It's been around for millions of years, so it's probably great. We could make bike helmets with little bits of conch-like material, embedded in some rock-like material."

Ideas-from-nature expert #1: "This illustrates two different kinds of testing over time. The structure of the conch shells in the sedimentary rock has been tested and improved by millions of years of indirect competition among conchs having different shell structures. But the organization of the sedimentary rock (the ratio of conch shell to other materials, or whether the conch shell is uniformly distributed or clumped) hasn't been improved by competition with other rocks. By simply persisting over millions of years, the rock passed a weaker kind of test than that imposed on conch shells through competition over millions of years. If reasonable durability were all we needed, it would be safe to conclude that the rock meets that minimum standard. But, in the absence of data, we have no reason to assume that the rock is more durable than some manmade material, like concrete. We would have to run lots of expensive tests to find out. The conch shells, on the other hand, have already been subject to millions of years of comparative tests by sting rays."

Ideas-from-nature expert #2: "OK, then what about land-snail shells? Their structure has been tested by competition (like conch shells), yet they're sometimes exposed to ultraviolet light (like rocks)."

Ideas-from-nature expert #1: "Good idea. Let's explore that option."

Natural selection has tested the adaptations of trees competitively, like conchs. Forests have only been tested by their ability to persist, like rocks. Nature's wisdom may be found more in trees than in forests.

August 27, 2012

Another route to drought-tolerant crops?

My book, Darwinian Agriculture, argues that the quickest route to crop genetic improvement is to identify tradeoffs that were rejected by past natural selection, but which we are willing to accept. Tradeoffs between individual-plant competitiveness and the collective performance of the whole crop are particularly promising. "MAT kinase", the Scientist Gardener suggests that this is the key to Monsanto's DroughtGard corn:

"From what I've heard, the yield gain of this variety under drought occurs because it slows its growth specifically under drought stress such that existing soil moisture is saved for the critical period surrounding flowering, resulting in less kernel abortion, higher harvest index and greater yield. This is certainly ironic given the expectations of many field physiologists and breeders. It also occurs to me that this is consistent with the thesis of Denison's Darwinian Agriculture - that evolution has already maxed out our crops' ability to deal with most stresses and environments, and that the greatest potential for improvement exist in traits that only work in an ecosystem (such as a farm field), where plants aren't in competition with their neighbors. "

This drought-tolerance-via-slower-growth would be quite interesting, if true, and similar to an idea I discuss in the book in the context of drought-tolerant Drysdale wheat.

In a recent post, I had suggested an alternative idea, that the bacterial gene they transferred to corn might result in a phenotype so radically different that natural selection had never had a chance to test it, in corn or its wild ancestors. I like The Scientific Gardener's hypothesis better. The problem with radically new phenotypes, of course, is that it's very hard to predict all of their effects and side effects.

August 10, 2012

Fossils, convergent evolution, cooperation, and "groundwater footprints"

New fossils from Koobi Fora in northern Kenya confirm taxonomic diversity in early Homo "The new fossils confirm the presence of two contemporary species of early Homo, in addition to Homo erectus, in the early Pleistocene of eastern Africa."

A transitional snake from the Late Cretaceous period of North America "...snakes evolved from burrowing lizards. The skull is intermediate..."

Community-wide convergent evolution in insect adaptation to toxic cardenolides by substitutions in the Na,K-ATPase The same molecular change to a sodium pump, previously seen in Monarch butterflies, was found in four insect species (separated by 300 million years of evolution) feeding on plants making the same natural insecticides.

Heterogeneous networks do not promote cooperation when humans play a Prisoner's Dilemma "1,229 volunteers chosen among last year's high school students"

Water balance of global aquifers revealed by groundwater footprint" "80 per cent of aquifers have a groundwater footprint that is less than their area" but "the global groundwater footprint is currently about 3.5 times the actual area of aquifers", putting water supplies for 3.5 million people at risk. My book briefly compares the ecological footprints of conventional and organic farms.

August 9, 2012

Darwinian agriculture and Darwinian medicine: beyond resistance management

DarwinianMedicine.jpg Thumbnail image for BookCover.gif

Evolution happens. Careless use of antibiotics selects for antibiotic-resistant pathogens, careless use of insecticides (including crops that make their own insecticides) selects for pesticide-resistant insect pests, and careless use of herbicides selects for herbicide-resistant weeds.

Many people seem to assume that this well-known problem, evolution of resistance, is all there is to "Darwinian medicine" or "Darwinian agriculture." But check the tables of contents of the books above. You'll only find one chapter on the "arms race" between pathogens and their hosts and one chapter (titled "Stop Evolution Now!") that focuses on slowing the evolution of resistance to pesticides and other pest-control measures.

Both books (Nesse and Williams, 1994, Denison, 2012) and the earlier review articles on which they were based (Williams and Nesse, 1991, Denison, et al., 2003) devote much more space to the implications of past evolution.

"If evolution by natural selection can shape sophisticated mechanisms such as the eye, heart, and brain, why hasn't it shaped ways to prevent nearsightedness, heart attacks, and Alzheimer's disease?"

Similarly, biotechnology allows us to increase the expression of crop genes that enhance drought tolerance, but

"mutations that increase gene expression happen all the time, and natural selection maintains those that are beneficial to the plant. So why does corn normally have lower expression of this gene than was obtained by genetic engineering?"

We don't have definite answers to these questions. Both books present hypotheses with various amounts of supporting data, but additional research is needed. With aging populations and rising food prices, maybe there will even be some money available to fund that research.

Should evolutionary biologists working on fundamental problems and/or wild species consider adding applied work to their research portfolios? If so, you or your students might get some useful ideas from Nesse and Williams or from my book, just published by Princeton University Press.

Literature Cited

Denison RF. 2012. Darwinian agriculture: How understanding evolution can improve agriculture. Princeton: Princeton University Press.

Denison RF, Kiers ET, West SA. 2003. Darwinian agriculture: when can humans find solutions beyond the reach of natural selection? Quarterly Review of Biology 78: 145-168.

Nesse RM, and Williams GW. 1994. Why we get sick: The new science of Darwinian medicine. New York: Vintage Books.

Williams GW, Nesse RM. 1991. The dawn of Darwinian medicine. Quarterly Review of Biology 66: 1-22.

July 30, 2012

Page 99 test

Thumbnail image for Thumbnail image for BookCover.gifYou can't judge a book by its cover, but Ford Madox Ford supposedly claimed that:

"Open the book to page ninety-nine and read, and the quality of the whole will be revealed to you."

The website Page 99 test has an excerpt from page 99 of my book, along with some context.

Someone must have bought a copy from, since it moved up from the two-millionth most-popular to 200,000th. No reviews yet, though.

July 26, 2012

This View of Life

A press release about my Darwinian Agriculture book is circulating and ended up at This View of Life, "a new online general interest magazine in which all of the content is from an evolutionary perspective." They have a wide range of content (much of it from other sources) including evolutionary perspectives on economics and religion as well as biology.

July 24, 2012

Using "Darwinian Agriculture" for a seminar class?

Thumbnail image for BookCover.gif

Although my just-published book is...

* More profusely illustrated than The Origin of Species
* Better-referenced than Collapse
* Somewhat cheaper than the Encyclopedia Galactica's probably too opinionated and not comprehensive enough to work well as a textbook. But a few people have suggested that they might want to use it for a seminar. I think that could work well and am wondering what sort of help from me might be useful.

Within reason, I would be happy to :
* Supply images (pictures and graphs) that could be useful in discussions.
* Answer questions from instructors via email.
* Host Google Hangout discussions (if 3-4 seminars could agree on a time).

Any interest in these or other ideas? I'm assuming that even people who might be interested mostly haven't read the book yet, so this may be premature...

July 20, 2012

The Macroecology of Sustainability

That's the title of a recent open-access paper in PLoS Biology by Joseph Burger and colleagues. They argue that "sustainability science" has focused too much on local issues, ignoring the importance of large fluxes of materials and issues of global supplies. For example, Portland, Oregon is considered "sustainable" because more residents ride bicycles than in other US cities, yet the city imports and consumes fossil fuels and other resources at rates similar to other cities of similar size. So we need to ask whether those imports can be sustained.

Their Figure 3 is particularly interesting. Global use of land for agriculture, withdrawal of fresh water from surface and underground sources, harvest of wild fish and wood, and mining of phosphorus are all similar today to what they were 20 years ago. Is this because we all decided to conserve scarce resources or because we are reaching the limits of what can be obtained at reasonable cost? Increasing production of coal and copper seem inconsistent with the "conservation hypothesis."

I learned of this paper by reading a post by Jeremy Cherfas in the always-interesting Agricultural Biodiversity Weblog. Some of these issues are discussed in my just-published book on Darwinian Agriculture, particularly in Chapter 2.

July 19, 2012

Grok Science interview -- limitations of transgenic drought-tolerant crops and, uh, learning from wild potatoes, etc.

Grok Science has posted a lengthy podcast interview with me about my just-published book, "Darwinian Agriculture." Some of their other interviews look interesting, too.

If you want to hear more, Carl Zimmer interviewed me for Microbe World in 2010. That interview is also still available. I was still writing the book, but I mention a 2003 paper in Quarterly Review of Biology, also titled "Darwinian agriculture," written with E. Toby Kiers and Stuart West. Much of Zimmer's interview focuses on the evolution of cooperation and conflict between legume plants and the rhizobia bacteria that live inside their root nodules and, to varying extents, provide them with nitrogen.

July 18, 2012

At least they spelled my name right

Science is listing my just-published book as "Darwinian Architecture." I suppose that could expand my potential audience, at the risk of disappointing readers who expected something about the survival of the fittest buildings or northern Australian landmarks.
A PDF of the first chapter is available on the Princeton University Press page, here.

July 9, 2012

Sold out!

Thumbnail image for BookCover.gif
The Princeton University Press table has sold all the copies of my Darwinian Agriculture book they brought to the Evolution meetings. They didn't have that many, but apparently it's out-selling their other books here. You can still order from them or your local independent bookstore.

June 28, 2012

Evolutionary tradeoffs and drought-tolerant crops

The Union of Concerned Scientists recently sent me a link to a report arguing that "Genetic Engineering is not Solving Agriculture's Drought Problem." This is an issue I address in detail in my book on Darwinian Agriculture, which will be available at the upcoming Evolution Meetings in Ottawa and more widely by the end of July.

Briefly, my argument is that mutant plants with greater or less expression of existing genes must have arisen repeatedly over the course of evolution. Some of those mutants were presumably more drought-tolerant than their parents, while others were less drought-tolerant. If there were no disadvantages to a given drought-tolerance gene, then plants with that gene took over. Repeat this process of natural selection for millions of years, and there may be few remaining opportunities for further improvements that are both simple (i.e., achievable by the sort of mutations that arise reasonably often) and tradeoff-free (never having negative effects on fitness, at least in past environments). My book therefore raises doubts about increasing the expression of existing plant genes to improve drought tolerance.

This argument applies to conventional breeding, not just genetic engineering. Another key point is that some tradeoffs rejected by past natural selection may be acceptable in an agricultural context. In fact, accepting acceptable tradeoffs may often be the fastest route to progress.

It's not entirely clear, however, whether my concerns above apply to the particular transgenic crop discussed in the Union of Concerned Scientists report. Monsanto's "DroughtGard" corn (maize) contains a gene derived from bacteria. Does this gene result in a phenotype very different from any seen in the recent evolutionary history of corn? If so, then we can't assume that this approach to drought tolerance has been repeatedly rejected by past natural selection. It may never have been tested by natural selection. Rather than rejecting it on theoretical grounds, therefore, we would need actual field data to determine the advantages or disadvantages of this transgenic variety.

Of course, those data would need to come from independent tests, not run or paid for either by Monsanto or by one of their commercial competitors. Agricultural universities run such tests every year, comparing crop varieties developed by different companies and by public-sector plant breeders. I look forward to seeing how DroughtGard does in such tests.

April 19, 2012

A taste of Darwinian Agriculture

My book on Darwinian Agriculture should be available in June. If you think you might want to read it, Princeton University Press has information, including a PDF of the first chapter.

June 3, 2011

Darwinian agriculture: health benefits of organic vegetables

I'm making final revisions to my book, "Darwinian agriculture: where does nature's wisdom lie?" [they made me change the title, too] and my editor, at Princeton University Press, has asked me to cut two chapters. I agree that doing so will give the book a narrower focus, but I think some people might find them interesting. So here's the first of the missing chapters.

Beneficial toxins, evolutionary tradeoffs, and the health benefits of organic vegetables

"Early births are worth more than late in an increasing population, and vice versa in a decreasing one." -- Hamilton. 1966

What about food quality?

Early in 2011, a majority of the world's population could afford to buy enough food to meet their basic needs for protein and food energy, although this may not always be true in the future. But some diets are better than others. Vegetables appear to be particularly health-promoting.

Some of the income from my brother Tom's family's organic farm (near Corvallis, Oregon) comes from "community supported agriculture" subscriptions, where families pay an annual fee for a weekly food box from his farm. I once asked him whether people save money by buying these subscriptions.

"They save money on their medical bills," he explained. This is because one of his boxes contains more vegetables than most families would otherwise eat. Rather than waste vegetables they've already paid for, they eat them, presumably improving their health.

Why are vegetables so good for us? They provide fiber, vitamins, and antioxidants, all apparently beneficial, but can these explain all of their health benefits?

Continue reading "Darwinian agriculture: health benefits of organic vegetables" »

February 5, 2010

Tradeoff-free drought resistance?

I'm working on the last chapter of my book, Darwinian Agriculture: where does Nature's wisdom lie?, and will be sending it to Princeton University Press soon for their review process. So I'm alert for any information that might make me change my main conclusions.

One theme of the book, and also of my recent talk at the Applied Evolution Summit, is that past natural selection is unlikely to have missed simple, tradeoff-free improvements. So I'm always skeptical when someone speculates that we could double crop yield just by increasing the expression of some newly discovered "drought-resistance gene." My rationale is that mutants with greater expression of any given gene are simple enough to have arisen repeatedly over the course of evolution. (This contrasts with more-complex adaptations, like the ability to form a symbiotic relationship with nitrogen-fixing bacteria, which natural selection may have had fewer opportunities to test.) If past natural selection has repeatedly rejected these "drought-resistant" mutations, then they must have been some negative effects on fitness, at least in past environments.

But could some mutations repeatedly rejected by past natural selection still be beneficial in agriculture? Maybe. Tradeoffs that constrained past natural selection need not always constrain us, as discussed below. But, I suggested at the meeting, we can't just ignore them.

However, someone called my attention to Drysdale wheat, developed in Australia, and reported to have higher yield under drought than older varieties, without any apparent yield penalty under wetter conditions. Is this an example of a tradeoff-free improvement missed by past natural selection?

The answer can be found in a very interesting paper, Breeding for high water use efficiency, published in Journal of Experimental Botany in 2004 by A.G. Condon, R.A. Richards, G.J. Rebetzke and G.D. Farquhar. If you are at all interested in this topic, the entire paper is well worth reading. But here are some key points....

Continue reading "Tradeoff-free drought resistance?" »