Ummm...about that "evolutionary impact statement"...04 May 2005
MSNBC is running a series on the "future of evolution," featuring Peter Ward's book Future Evolution and others. Today (5/4/05) was my last lecture day in my introductory course, and I tend to spend time talking about the future direction of human evolution, so the future is on my mind.
The speculations about the future evolution of animal species are frippery, but certainly entertaining:
In "The Future is Wild," [Dougal] Dixon, the British geologist, and co-author John Adams create an animal kingdom in which humans no longer reign.
Dixon and Adams give whimsical names to the creatures they dream up, aiming not so much to predict the future but to show some possibilities.
In their vision, humans become extinct in an Ice Age 5 million years from now. "Shagrats," or giant rodents, and "gannet whales," large aquatic birds, have evolved during this stretch of time.
The Ice Age melts away 100 million years later, marking the beginning of the end of large mammals and giving rise to creatures like the "ocean phantom," a jellyfish the size of a truck; the "swampus," a relative of the octopus that emerges from swamps to feed; and the "toraton," a reptile bigger than dinosaurs.
The more relevant predictions are those of Ward, who envisions the consequences of continued high-density human society on natural environments:
Gone will be the vast grasslands that gave rise to large mammals. "I bet we'll never see a large animal species ever again," Ward says. "Give it a million years," he says, and lions, tigers and bears might all be gone.
Probably true. Even if the current area and density of human habitation was maintained without further increase, the megafauna are probably doomed. Their population sizes and geographic extents are small enough now that a pathogen could easily devastate their population. They might survive this for thousands of years with human help, but large-bodied mammals are definitely not a growth industry. The only way they will be is if we start to farm them. Of course, in light of their natural lean content, this might be a good idea.
The article also talks to Stephen Palumbi (Stanford University)
"Anything that works we like to do more and more and more of," he said in an interview, noting that in the case of vaccines, insecticides and herbicides, that means short-term gains against disease and pests only to see them develop a resistance and come back even stronger.
Palumbi does see a "movement towards greater awareness" of such dangers and suggests that society take them into account much as it does significant environmental changes that come with development. "There's no reason we couldn't do an 'evolutionary impact statement,'" he says.
This idea appears to be focused on the impact of transferring genes across species barriers. Of course if we could rationally estimate unforeseen consequences of such transfers, they wouldn't be unforeseen. And there is no sense at all in trying to estimate "worst-case scenarios" if no regulation is ever shaped around preventing the worst possible cases from happening.
In the case of genetic engineering, the main problem appears to be that it is fast. The MSNBC article raises the point that dog breeds have evolved tremendous diversity under human influence. Any population geneticist knows that with a few hundred generations of strong selection, it is probably possible to make anything that a genetic engineer could conceivably manufacture. Sure, a genetic engineer could in principle replace many hundreds of genes and create major phenotypic reorganizations, but in practical terms this is almost certainly not going to create a functional organism. Our problem isn't that we can't make the breeds we want through old-fashioned selective breeding, it is that we want results faster, and implanting a bacterial gene into corn is the fastest way to go. If the resulting seeds can't be saved and replanted but need to be bought every year from the supplier, more the better. So filing an "impact statement" for evolutionary changes is a little overwrought, unless we are going to send federal agents to the Westminster Dog Show to stop the breeding of Ch. Miss Fuzzies Snoop of All Doggz.
Lead with your gut
Another article in the series focuses on diet changes and obesity in an evolutionary context. This one is straightforward science, citing Loren Cordain, whose work I have previously described. Cordain is the author of The Paleo Diet, a health book focused on the qualities of hunter-gatherer diets. It's a NeanderThin for the new generation (except of course that NeanderThin is the NeanderThin for the new generation). There's also The Origin Diet, if you're counting.
Modern life may have solved most of our food-gathering problems, but human evolution has not kept up. Our bodies are still wired for hunter-gatherer biology: Eat all the food you can and store it -- in body fat -- in case your supply of food runs out, as in the case of famine. A dangerous configuration for a society with all-you-can-eat buffets.
Somehow people never seem to mention that the great "caveman" diet that kept us so healthy in the Pleistocene HAD EVERYONE DYING BEFORE 50! Instead of French Women Don't Get Fat, we could just as easily be buying Erectus Women Didn't Get Fat, which would almost certainly omit the likelihood that THEY LIVED WITH CONSTANT HUNGER AND FREQUENT STARVATION.
Bill Leonard makes an appearance:
"What I think we can say conclusively, is that the evolutionary success of our species is ultimately a nutrition story," says Bill Leonard, chairman of Northwestern University's anthropology department.
A high caloric intake isn't so much to blame as an imbalance between calories in and calories out. Though developing nations generally consume fewer calories than industrialized nations, Leonard found subsistence societies that match developed societies calorie for calorie. The reindeer-herding Evenki people of Siberia consume more than 2,800 calories a day, and far more animal foods than the typical American, yet have lower cholesterol and body mass indicators.
As does Henry Bunn:
Along with nearly universal access to food, the modern economy has allowed an unprecedented number of Americans to survive using our big, evolved brains and little else. We're getting fat off our own evolutionary success and, says University of Wisconsin paleoanthropologist Henry Bunn, "I don't think biological evolution has really had a chance to react."
It's a very nice piece of journalism, really, citing most of the right people. I recommend it.
Disease in the future
As for my class, what prediction came up today about the future of humanity? Disease load. Compared to historic levels, today we have a pretty low pathogen and parasite load. We accomplished this by eliminating pathogens directly (smallpox), by changing the circumstances that allows pathogens and parasites to spread (sanitation), by killing pathogens directly (antibiotics), and by training our immune systems with foreign antigens (vaccination). These changes have had a pretty radical effect in increasing human survivorship, especially for kids. Assuming that technology continues to get cheaper, these changes will continue to spread to the developing world and cause great improvements in human health.
The evolution of resistance is a never-ending problem. Not only can bacteria become resistant to antibiotics, but mosquitos become resistant to pesticides. And commensal species like H. pylori and E. coli are affected by the same antibiotics that treat disease, leading to changes in their populations and the potential spread of pathogenic variants.
The outcome of this technological battle is likely to be the increased tolerance of pathogen load in humans. We are already seeing this with treatments for HIV infection. The drug cocktails that delay or prevent the progression of the disease don't cure it or eliminate the pathogen. Instead they restrict the pathogen population to low numbers that the body can tolerate as a chronic infection. This is the goal of many medical treatments--making chronic conditions manageable with medication, rather than curing them. It is what leads many people to take long-term courses of antacids for their chronic H. pylori infections, and why people are looking for pathogens that influence heart disease, diabetes, and other chronic conditions.
The thing is that we have already figured out how to fight most of the pathogens that have immediate impacts on health (if imperfectly in many cases). The ones we are encountering now have greatly delayed health impacts, and not always for the worse. The story with H. pylori is an example in point: although some strains present a higher risk of gastric ulcers or cancer, they may also have benefits in regulating acid levels. So the medical problem is finding the best balance of benefits and drawbacks, and that involves not antibiotics to eliminate infections entirely, but other kinds of medications to regulate the microbial signaling interactions.
In other words, we are no longer defeating most diseases; we are using our technology to live with them, and in some cases to exploit them. And we face every likelihood of seeing many new pathogens in the future, through human-animal interactions (avian flu), through the emergence of resistant pathogen strains (Staphylococcus) and perhaps through the deliberate introduction of bioengineered pathogens in to human populations (anthrax?). It is even possible that we will see the reemergence of viral genomes that have long been incorporated into the human genome as a product of our evolution.
I predict that these changes will mean that future people will live with greatly increased pathogen loads compared to today. This will be a return to what for many human populations was the Pleistocene norm: long-term, low-impact infections. Except instead of being regulated by selection and consequent mortality, the system will be regulated by chemicals and biotechnology.
Other predictions are welcome, and I'll be happy to post the best ones!
I can't end better than Peter Ward, though:
'"I get tired of futurists so missing the mark, or so it seems to me," he says. "First, there is the sense that humans will soon be gone, or second, that we will produce some 'Blade Runner' world that is all pollution and Michael Jackson mouth masks."