Are these the same evolutionary biologists who advised Hitler?
Actually, Hitler drew on preDarwinian sources like Martin Luther as well as on people who may have been influenced by people who were influenced by a German mistranslation of the Origin of Species. But I want to discuss a less-serious case of falsely attributing incorrect ideas to evolutionary biologists.
"Evolutionary biologists, the experts on the theory of aging, have strong reasons to suppose that human life span cannot be altered in any quick and easy way. But they have been confounded by experiments with small laboratory animals, like roundworms, fruit flies and mice. In all these species, the change of single genes has brought noticeable increases in life span."This confounded quotation is from Nicholas Wade's recent New York Times article. Actually, "the change of single genes" isn't so "quick and easy" in humans yet. Even so, I don't know who these unnamed evolutionary biologists are who claim human lifespan can't be altered easily. Swimming with crocodiles usually works.
But perhaps Wade meant "increased" rather than "altered." Increasing lifespan doesn't seem to be that hard either. Exercise and protection from infectious disease (vaccines, clean water supplies, antibiotics) both seem to help. Where are the evolutionary biologists who supposedly deny this? What evolutionary biologists have said is that there are trade-offs between potential longevity and potential reproduction, most recently confirmed for macaques.(1) George Williams' classic paper on these tradeoffs(2) is discussed here by John Dennehy.
The relative importance (i.e., fitness benefit) of current reproduction vs. longevity allowing later reproduction depend on whether population size is increasing or decreasing.(3) If population is increasing, offspring produced later contribute genes to a larger gene pool, where they will have proportionally less effect. Conversely, if population is likely to decrease, forgoing current reproduction may increase fitness, if it significantly increases the chances of reproducing later. This is because each offspring produced later will be added to a smaller gene pool, thereby having a greater evolutionary effect. We recently suggested that many species have therefore evolved the unconscious ability to predict population declines and delay reproduction, thereby increasing longevity.(4) Our hypothesis explains some otherwise-puzzling results:
1) soft drinks with artificial sweeteners are just as likely to cause metabolic syndrome as those with sugar(5,6) - "food is plentiful, so population will increase, so I should reproduce now, so adjust insulin levels etc. accordingly, whatever the long-term consequences"
2) food odors reverse the longevity increase otherwise seen with food deprivation(7) - "even though I'm not eating, someone nearby is, so population isn't likely to decrease after all; cancel plans to sacrifice current reproduction to increase longevity"
3) many plant toxins improve health in low doses, a phenomenon known as "hormesis"(8) - "if I'm eating these bitter leaves, there must be a famine in progress; this will lead to population decrease, so I should switch the reproduction/longevity switch to the longevity position; I'll wait until after the famine, when the gene pool is smaller, to reproduce"
A key point is that delaying reproduction can increase fitness even without increasing the number of offspring produced. This is because fitness is a relative measure, with increasing per-offspring impact in smaller populations.
If our hypothesis is correct, what are the practical implications for increasing human longevity?
"My rule of thumb is to ignore the evolutionary biologists -- they're constantly telling you what you can't think," Gary Ruvkun of the Massachusetts General Hospital remarked.He can think whatever he wants, but the FDA should check antiaging drugs for their effects on fertility. As predicted by our hypothesis, resveratrol, a naturally occurring chemical that extends lifespan in some species, has already been shown to decrease early fecundity.(9) This wouldn't necessarily be a bad thing in humans, however.
1. Blomquist, G. E. Trade-off between age of first reproduction and survival in a female primate. Biology Letters 5, 339-342 (2009).
2. Williams, G. C. Pleiotropy, natural selection, and the evolution of senescence. Evolution 11, 398-411 (1957).
3. Hamilton, W. D. The moulding of senescence by natural selection. Journal of Theoretical Biology 12, 12-45 (1966).
4. Ratcliff, W. C., Hawthorne, P., Travisano, M. & Denison, R. F. When stress predicts a shrinking gene pool, trading early reproduction for longevity can increase fitness, even with lower fecundity. PLoS One 4, e6055 (2009).
5. Dhingra, R. et al. Soft drink consumption and risk of developing cardiometabolic risk factors and the metabolic syndrome in middle-aged adults in the community. Circulation 116, 480-488 (2007).
6. Lutsey, P. L., Steffen, L. M. & Stevens, J. Dietary Intake and the Development of the Metabolic Syndrome: The Atherosclerosis Risk in Communities Study. Circulation 117, 754-761 (2008).
7. Libert, S. et al. Regulation of Drosophila life span by olfaction and food-derived odors. Science 315, 1133-1137 (2007).
8. Mattson, M. P. & Cheng, A. Neurohormetic phytochemicals: low-dose toxins that induce adaptive neuronal stress responses. Trends in Neurosciences 29, 632-639 (2006).
9. Gruber, J., Tang, S.Y., & Halliwell, B. Evidence for a trade-off between survival and fitness caused by resveratrol treatment of Caenorhabditis elegans. Annals NY Acad Sci 1100:530-542 (2007)