Here is a review of pansteatitis (and other diseases) in farm raised crocodiles (and ostriches), including a picture of the hardened yellow fat in crocodile tails. This hardening of the fatty tissue in crocodile tails impairs their mobility and therefore their ability to hunt. Crocs with pansteatitis therefore waste away and die of starvation. There is no specific indication in the articles of the state of the crocs bodies. Are they emaciated? Another posting on ProMedmail, including some details of the dam that may be a source of pollutants is here. The moderator asks the important question: Is anything else affected? No mention is made in any of the news articles. What about other aquatic organisms in the Olifants River? For example, what about Cape Clawless Otters (Aonyx capensis)?
Monthly Archives: July 2008
Crocodile Die-Off in Kruger National Park
Crocodiles have been dying in large numbers on the Olifants River in Kruger National Park, the crown jewel of the South African Parks System. The article rather casually states that the die-off is attributable to environmental pollutants:
There is growing consensus that the croc die-off is a result of a confluence of low level toxins, which has lead to endocrinal [sic] abnormalities (that is, hormonal changes) in croc tissues.
As the moderator for the promedmail wrote, however, it would be nice to have some specific details explaining why this consensus is apparently growing:
The article does not specify chemicals, pesticides, or heavy metals, or their amounts, yet the article boldly states, "Long term exposure to these and other toxins may well be conspiring towards the crippling condition suffered by Olifants River crocodiles." So apparently, the specifics of the chemicals, pesticides and/or heavy metals are known. It would be much more beneficial to publish what has been found and the levels of those alleged toxins, then those doing research or having experience in the area would be able to suggest a possible solution.
It certainly seems possible, particularly given the diversion of water from the Olifants River and from new mining operations in Mozambique, but it would still be nice to have some more details. One of the striking features of the dead crocs is the fact that they have hardened yellow fat deposits in their tails. The article suggests that cause of death is pansteatitis, a disease caused by excessive consumption of unstabilized polyunsaturated fatty acids (often found in rotting fish). There is no evidence of correspondingly large fish die-off, which could complete the causal story. How the environmental contamination story fits in with pansteatitis seems an important missing link in understanding this problem.
Cattle that eat threadleaf groundsel can die of a disease that induces hard yellow liver, providing more suggestive evidence that an environmental poison might be responsible for the croc die-off. Maybe...?
This is a disturbing story, the resolution of which I will follow closely.
Bush Justice and Sex Trafficking
George W. Bush needs all the help he can get with his historical legacy. It's shameful that the Bush Justice Department is trying to scuttle tough new anti-trafficking legislation, particularly considering that this is an issue Mr. Bush actually cares about. It seems that lawyers in the Justice Department believe that girls and women endure the humiliations and dangers of sex work because they want to be doing it. They have made a choice to join the oldest profession as it were. Sounds an awful lot like the she-was-asking-for-it defense. It's not often that I agree with the opinion of a Discovery Institute fellow, but Miller's Op-Ed piece calling out the inexcusable position taken by the Justice Department is something I can get behind.
Value of Human Life Declining Dramatically
An AP story suggests that, according to the EPA, the value of a human life has declined from $8.7 to $6.9 million since 2004 (in 2008 dollars). That is an annual decline of 5.5%. This means that if this decline continues at a constant rate, a human life will be worth one dollar in just under 272 years!
On the Conditions for Natural Selection
Olivia Judson's piece in today's New York Times makes the important (and chastening) point that too many contemporary biologists have not actually read Darwin in the original. As usual, she is terrific and generally right on. I do have one small issue with a comment she makes:
Natural selection will operate whenever all of three conditions are met. These are: (1) some of the differences between individuals are inherited differences, not due to differences in their environments; (2) more individuals are born than can survive; and (3) part of the reason at least some of the survivors make it is owing to the traits — a longer-than-average beak, say — that they inherited from their parents. For natural selection, then, what is important is that some differences are inherited; and this, Darwin could show.
The problem with this statement is that it's not actually correct. But it's incorrect in an interesting way, given Judson's point that there is value in understanding the history of our science. In the Origin, Darwin was clearly influenced by another foundational document, Thomas Mathus's Essay on the Principle of Population. Indeed, the Malthusian insight that populations, human or otherwise, can easily outstrip their resource base proved to be a critical link in Darwin's formulation of the idea of natural selection.
The key about Judson's statement is that point (2) is not necessary. If it were true, it would imply that natural selection can not act in growing populations. The necessary and sufficient conditions for natural selection acting on a trait are: (i) variation in the trait, (ii) heritability of the trait, and (iii) differential reproductive success as a function of the trait. So a trait can increase even in the absence of differential mortality as long as there is differential fertility. Darwinian fitness is a relative concept. A trait with higher fitness is one that increases in frequency relative to other traits. This increase in relative frequency can come about because of differential mortality or differential fertility or a combination of the two.
It turns out that models of selection are more mathematically tractable when one assumes only viability selection and so this is what is most commonly employed in theoretical work. This relates to the fact that fertility selection works at the level of the breeding pair and not the individual. The equations describing selection in this context thus become rather more complex. But this is more technical than most sane people would care to get. A good review of models of fertility selection can be found in Feldman et al. (1983).
Judson is essentially correct though. We should all have a better understanding of the history of Evolutionary Biology (and, I should add, Anthropology). A major part of this is reading the classics: Darwin, Malthus, Wallace, Fisher, Dobzhansky, Wright, Lorenz, Tibergen, Hinde... I could go on for a while, of course. When I teach my class in life history theory, almost all of the readings are (20th century) classics. My experience in the field is that lots of people cite Hamilton (1966) or Cole (1954), for instance, but very few people have actually read them.
References
Cole, L. C. 1954. The Population Consequences of Life History Phenomena. Quarterly Review of Biology 29 (2):103-137.
Feldman, M. W., F. B. Christiansen, and U. Liberman. 1983. On Some Models of Fertility Selection. Genetics 105 (4):1003-1010.
Hamilton, W. D. 1966. The Moulding of Senescence by Natural Selection. Journal of Theoretical Biology 12:12-45.
WALL-E, the Anthropocene, and the Future of Humanity
My kids are away for the month and my wife is in the hospital, recovering from a recent surgery. So what do I do with my first free Saturday night in, say, ten years? I go see a children's movie. Having read the rave review by A. O. Scott in the New York Times and heard the similarly glowing review by David Edelstein on Fresh Air, I didn't think that I could wait until my kids come back from a month of camp and grandparents. Somehow, the idea of a story set on a post ecological-apocalyptic Earth seemed to resonate with my my mood.
The movie was, indeed, terrific. The narrative is very straightforward and sweet. Robot meets robot. Robot falls in love with robot. Robots take off for distant nebula where they undergo a series of trials and tribulations in an effort to save the descendants of humanity and Earth. You know...
It's the backdrop of the movie that is so stunning. The bleak vision of a dead Earth, strewn with the detritus of a decadent consumer society, where toxic dust storms ravage the deadened landscape and a lone mutant cockroach appears to be the extent of life. And when we meet what has become of humans... In just 25 generations, humans have evolved to become passive, obese, infantile receptacles of mindless consumption. Deriving all nutriment from Big Gulps. Too fat and weak to even walk, they scoot around (seemingly endlessly) on floating sleds, interacting with the world only through the video screens constantly in front of their faces. Hmmm, a distorting mirror for our society that my recent travels up and down American highways suggests is not all that distorting.
And yet, there is hope in the movie. Athletic physiques may be extinct in the 28th century, but not the human spirit. All it takes is a little robot in love to jump start a new communitarian will to power.
About the time I went to see WALL-E, a reference to this article appeared in my inbox. Mike Davis, author of City of Quartz: Excavating the Future in Los Angeles, writes a dark essay on the state of our planet. I don't always agree with Davis, but there is little doubt that he is a provocative and compelling writer who makes you think. In this essay, Davis describes the recent suggestion by the The Geological Society of London that human agency has led to the dawning of the newest geological epoch, The Anthropocene.
The term "Anthropocene" was coined by Dutch Nobel Laureate Paul Crutzen and has been used casually for a number of years now. Recent work, however, has suggested that there might truly be scientific utility to the term. Zalasiewicz and colleagues ask in the Geological Society of America's publication, GSA Today, Are We Now Living in the Anthropocene? In a recent issue of the journal Ambio, Steffen and colleagues describe the Anthropocene in terms of trends in atmospheric carbon dioxide. This work suggests that humans have changed the environment to such an extent that it is geologically durable. Future geologists (perhaps from another planet?) could recognize the human ecological footprint in Earth's stratigraphy. In the words of Zalasiewicz et al.,
Earth has endured changes sufficient to leave a global stratigraphic signature distinct from that of the Holocene or of previous Pleistocene interglacial phases, encompassing novel biotic, sedimentary, and geochemical change. These changes, although likely only in their initial phases, are sufficiently distinct and robustly established for suggestions of a Holocene–Anthropocene boundary in the recent historical past to be geologically reasonable.
The untimely passing of the Holocene may seem an obscure and uninteresting event, but it is troubling when you think that everything that has happened in human civilization has happened in -- and because of -- the Holocene, a period of warmth and climatic stability otherwise not seen in the recent geological history of Earth. You know, little things like the origin of agriculture, complex societies, writing, the Red Sox. All because of the stability of the Holocene.
So the Anthropocene may bring with it increased climatic volatility and create a potentially more hostile world, less buffered to further perturbations. But just as global warming doesn't mean that all places on Earth get noticeably warmer, so too, the environmental sequelae of the Anthropocene will not be felt equally by all. Once again, the poor are likely to lose. And if we really manage to bring upon ourselves the environmental apocalypse envisioned in WALL-E?
This question bugged me as I basked in the glow of WALL-E. Are there non-Americans on the Axiom, the space cruise ship that is the home away from home for humanity? Did the Buy N Large Corporation, which seems to have taken over the world when humanity bugs out, see fit to bring poor people from, say, Sub-Saharan Africa or Central Asia to space? Everyone on Axiom seems pretty American in their accent, gluttony, and shape. But who knows? It emphasizes the likelihood that in the Anthropocene world of potentially increasing climatic instability, differences between those who have and those who don't will be magnified. As Davis writes,
But global warming is not War of the Worlds, where invading Martians are dedicated to annihilating all of humanity without distinction. Climate change, instead, will initially produce dramatically unequal impacts across regions and social classes. It will reinforce, not diminish, geopolitical inequality and conflict.
If we foul our home to the point that our only option is to emigrate to space, who will be invited to the party? Let's hope that we never need to actually answer that question. You see, the ability to transport all of humanity to a space ship to wait out the environmental end-of-days is not really an option. In his book, How Many People Can the Earth Support?, Rockefeller University demographer Joel Cohen writes about the space option for dealing with over-population and resulting ecological collapse. Cohen's simple calculations show how spectacularly out-of-the-question the space colonization solution is, even if the technology that would allow space colonization existed.
So I guess we had better take care of our home. We're stuck here. Let's hope that we can galvanize some of that enduring human spirit that shows itself in WALL-E to change the potentially disastrous path we have set out for ourselves. Davis is clearly right when he rails against the pie-in-the-sky "Spontaneous Decarbonization" that is implicit in most climate change scenarios. Checking global warming will require active, politically difficult, interventions to be undertaken. I'm not exactly overflowing with confidence that we can pull this off, but then again, life can take hold in the most unlikely of places.
Salmonella Outbreak: Is It Really Tomatoes?
An outbreak of Salmonella serotype Saintpaul has sickened 943 people since April. Nearly 14% of these cases required hospitalization. It has been hypothesized that tomatoes have been the vehicle for this food-borne infection. Here in Palo Alto, certain types of tomatoes (e.g., Roma and beefsteak) were taken off store shelves for a while. The latest report from CDC suggests that tomatoes may not, in fact, be the culprit. CDC epidemiologists are expanding their investigations to include food items that are "commonly consumed with tomatoes."
Epidemiological evidence indicates that while people of just about any age can contract the infection (age range of cases is <1-99 years), the most likely age group to contract the infection are 20-29 year-olds. The least likely age classes are 10-19 year-olds and people over 80. What food do young adults commonly eat with raw tomatoes that is less commonly eaten by the young or very old? I'd say salad greens but if that were the case, I'd expect a sex bias in infections. 50% of the infections are women and my informed guess (based on my experience with largely middle-class college students) is that 20-29 year-old women eat more salad than 20-29 year-old men.
So what is it if it's not tomatoes? Something having to do with consumption of alcohol? Some salsa ingredient like jalapeños or scallions? (note: another thing consumed in bars)
Swingin' on the Extemporaneous Flippity-Flop
While running seemingly interminable errands this past Saturday, I listened to NPR's Wait, Wait Don't Tell Me. Sub Pop Records president, Jonathan Poneman, was the guest for the Not-My-Job segment and related a story in which a heroic employee at Sub Pop, Megan Jasper, simply made up a lingo when a New York Times reporter called to ask how the kids were talking in Seattle back in 1992. Listen here. Beautiful. As someone who spent a lot of time in the Pacific Northwest throughout the nineties but lived in the rather more uptight Northeast, this story provided particular amusement for me. The original NYT piece is here. See page three for the Lexicon. Score. (though a harsh realm for the reporter who couldn't be troubled to go to Seattle to fact check)
Until next time, rock on you dishes and lamestains alike...
Fife and Drum
Man, this is something pretty amazing that I missed when I lived in Mississippi briefly in 1991-1992. I heard fife and drum every 4th of July growing up in a New England town with a strong sense of its colonial heritage. It didn't sound like this. This amazing film produced by Bill Ferris, Judy Peiser, David Evans in 1972 and distributed by the Center for Southern Folklore is available in its entirety on folkstreams.net.
Biofuels Place Price Pressure on Food
A recent story in The Guardian reports on an unpublished World Bank study that suggests the conversion of food crops to biofuels, and the resulting economic pressures entailed in this process, is responsible for most of the steep price increases in food this year. The World Bank report has not been published, though it was completed in April, and speculation is that the delay is meant to avoid embarrassing the Bush administration, who maintains that biofuels have had only a minor impact on food prices. For example, the report contradicts statements by US Agriculture Secretary Ed Schafer and Energy Secretary Samuel Bodman made in a letter sent to the Senate Energy Committee last month. The World Bank report attributes fully 75% of the increase in food prices to biofuels in contrast to the official US estimates of just 3%.
Biofuel development distorts food markets in three ways, one of them obvious, the other two less so: (1) it diverts grain production for food to the production of biofuels, (2) it creates incentives for farmers to set aside more land for biofuel crop development, and (3) it induces speculation on the commodities market, driving up grain prices.
The results of this report (at least as reported in The Guardian) resonate well with my own intuitions about biofuels. It seems like a very bad idea to me to make fuel for SUVs out of food. It's all too easy for people in the developing world, where the leading dietary problem is obesity, to forget that a substantial portion of the world (somewhere in the vicinity of 800 million) is still regularly hungry. I remain open to the idea of generating biofuels from organic waste, but the consequences of growing grain and other basic foodstuffs for biofuels on commodity prices, and therefore the price that people pay for food, should be obvious to anyone who has taken an introductory economics class. Price increases with demand and decreases with supply, remember? Given that world population is still growing and that some formerly poor parts of the world are rapidly developing (and therefore increasing their demand for grain both directly and indirectly through increased demand for meat), there is no way that demand for grain as food is going to decrease. This can only mean that increasing crop production for biofuel is bound to decrease supply for food in the absence of large expansions of crop land. Generating demand for biofuels through legislation requiring a certain proportion of biofuel use (as is the case in the EU) or marketing ethanol-burning SUVs as somehow environmentally friendly is similarly going to increase demand for biofuels. This means that prices for grains (and substitutable commodities) are bound to increase. Or am I missing something here?