White bread, which was once reserved only for the elites of Europe, has now become the Wonderbread plague. Chocolate, once reserved for Mesoamerican elites, is now the bane of the overfed multitude...Fat-rich meats, which formerly were used only for special occasions or for the highest ranks of society, are now commonplace for all but the poorest and produce coronary and arterial diseases on a wide scale. Wines and spirits that played crucial roles in feasts for elites have now become the profane intoxicants of households throughout the industrial world. [2003: 459]
Hayden’s point in all this is that foods now taken for granted as everyday fare were once costly delicacies; however, his tirade hints at another process that may be at work in the evolution of human food choices. While modern food production methods have ensured that food is abundantly available in the industrialized world, we continue to crave the rare, fat-rich, ultra-satisfying commodities of our ancestors to the extent that our consumption of them becomes excessive. According to some evolutionary-minded human scientists, our now-unhealthy taste for salt, fat and sugar may be the result of an especially large “adaptive lag” among modern humans. Proponents of the adaptive lag hypothesis explain that, because humans have cultures and technologies that change environments extensively and quickly, biological evolution cannot keep up with current selective pressures. Therefore, modern “human minds are predominantly suited to an ancestral habitat” (Laland and Brown 2006: 103).
Kevin N. Laland and Gillian R. Brown have a problem with this viewpoint (“Niche Construction, Human Behavior, and the Adaptive-Lag Hypothesis,” 2006). While they admit that our continued taste for salt, fat and sugar is probably the result of an adaptive lag in our tastes, and that human behaviour will sometimes be maladaptive, they do not think that humans have a larger adaptive lag than any other species. Laland and Brown argue that recognizing niche construction as a cause of evolutionary change (rather than as an end-product of evolution) is the key to recognizing that modern humans live adaptively, not discordantly, with their environments. For three reasons, the authors propose that niche-constructing activity generally “increases the match between an animal’s behaviour and its environment” (2006: 98):
(1) Both humans and other animal species construct and reconstruct their worlds with intention.
(2) Humans—more so than animals—are able to buffer adaptive lag through cultural niche construction.
(3)When humans are unable to buffer adaptive lag full through further cultural niche construction, natural selection on genes will ensue.
According to the authors, the most compelling proof that adaptive modern human behaviour is the norm, and maladaptation the exception, can be seen in human global population growth during the Holocene. “Growth in human populations provides the clearest indication that a major proportion of human characteristics remains adaptive even in modern constructed environments, which share hidden commonalities with those of our ancestors” (2006: 102). However, one could argue that the simple fact of continued population growth—which, in evolutionary terms is a measure of success for a species—is indicative of a well-adapted human species, but what about when we take into account the negative effects of this population growth on the environment? The effects of dense industrial populations on the landscape have led to disease, pollution, and resource shortages worldwide. Should we still see the behaviours that led to these developments as “adaptive”?
Laland and Brown say “yes,” because we have also developed the vaccines, and new technologies for harnessing resources which alleviate the effects of negative pressures. This is the strength of niche construction. The adaptive lag hypothesis assumes, as does standard evolutionary theory, that adaptation is unidirectional: environments select, organisms adapt. However, as Laland and Brown clearly demonstrate, organisms can change their environments and regulate the conditions which act on them, creating a cycle of causation and feedback...So don’t be too quick to blame your ancestors when you over-imbibe!
References Cited:
Hayden, Brian. 2003. Were Luxury Foods the First Domesticates? Ethnoarchaeological Perspectives from Southeast Asia. World Archaeology 34(3): 458-469.
Laland, Kevin N. and Gillian R. Brown. 2006. Niche Construction, Human Behavior, and the Adaptive-Lag Hypothesis. Evolutionary Anthropology 15: 8-10.
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