Marian Stamp Dawkins, an animal behavior expert at the University of Oxford, has championed the idea that aspects of sensory processing can influence the evolution of communication signals; for example, a nocturnal species whose predators are color-blind would not evolve colored warning splotches. Our idea complements hers but takes it further, by arguing that higher-order principles of perception may also play a role.
Another principle that may affect evolution is known as grouping. The visual system has an obsessive desire to make whole objects from fragmentary evidence—such as a lion largely obscured by leaves and shadows. Like-colored fragments are interpreted as bits of a single object that is partially hidden by another, closer object. As naturalists have long recognized, this tendency is cunningly exploited by reef fish, which evolved bold colored splotches that “break” their outlines and confuse predators seeking continuous contours.
Proofs of Concept
If perceptual laws influence the development of species, what would evolutionary biologists expect to see? For one, the progressive “caricaturization” of easily recognizable physical traits over time. And indeed, such trends are commonly seen in the evolution of mammoths, ankylosaurs, titanotheres and other animals.
Another prediction from the theory is that unseen parts—internal organs—would not be subject to perceptual selection pressures and hence should diverge considerably less. Overall, this appears to be true. A rhesus monkey’s liver doesn’t look much different from a human one.
Finally, because plants do not have sophisticated sensory systems, they should vary less in appearance than animals do, except when selection has been done for them by animals. This would explain why leaves and trunks look much alike, whereas flowers, which “compete” to be visited by insects and hummingbirds, are stunningly conspicuous and variable. There is even one species, the bee orchid, whose flower perfectly resembles a caricature of
a female bee—a superbee—to attract pseudocopulation and cross-pollination by male bees.
Ultimately, our hypothesis is not a mechanism outside Darwin’s theory but an unexpected interaction within it. His principle of natural selection leads to the emergence of brain mechanisms that enable an animal to quickly detect healthy sexual partners of the same species. But inevitably these cognitive processes have side effects. They evolved to increase a species’ fitness but may lead to perceptual quirks that do not promote fitness—and may even work against it. Thus, the study of visual illusions—and the laws they exploit—offers clues to certain otherwise mysterious trends in evolution.
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3 Comments
Add CommentI believe that the Ramachandrans hypothesis proposed in Carried to Extremes also has ramifications in the development of extreme behavior in cults. Leaders like Jim Jones do not usually start out being as bizarre as we later find them. The group selects a behavior that is deemed to represent the ideal of the cult. Those who demonstrate higher levels of dedication to that behavior are elevated to leadership. As they struggle to retain their influence they will tend to exhibit extreme degrees of said behavior to the continued admiration of their followers. As the trend continues more and more bizarre behavior is seen until the situation becomes untenable and comes crashing down.
Reply | Report Abuse | Link to thisThe red spot doesn't just identify the mother, it tells the mother there's a chick there that's hungry. The mother's job is to keep the dot near the chick so it doesn't go picking at a different beaklike structure or beak of some predatory species, etc. I can see a lot of other things wrong with this article's analysis, but I'll pass on them for now.
Reply | Report Abuse | Link to thisOk, I'll bite. Very interesting article. At first I thought they were attempting to counter the influence of natural selection, as if this was a rival theory, and then I read that they were suggesting it was just an additional force influencing the origin of species. I think they may be right, however this theory may be difficult to apply or prove for several reasons. Application of this theory may be limited to those animals, such as mammals, with visual systems like that of our species. If they use the strict criteria of animals noticing visual differences in a way similar to we, humans, do, then I think they could be extrapolating human thought patterns to the reaons for behavior of other quite different life forms. But of course, they say they are not. But even if they were to enlarge the criteria and not limit it to just visual differences, but rather those of smell, chemical stimuli, etc, it would still be limited to certain life forms, namely those who reproduce sexually. Obviously an ant may not be subject to this influence, a jellyfish even less likely, a plant even less likely, and a bacterium probably not likely at all. Nonetheless, among species where the theory does apply, it probably does input some influence. However, proving it would be difficult. Using the giraffe example in the article, there could be evolutionary forces based on those in the article, distinct from classic natural selection based on ability to reach for food supply. However, these two forces cannot be realistically looked at independently, because the other force is always present, filtering the gene pool. But then I thought, maybe the two are not mutually exclusive. Maybe the two forces could be part of the same process for survival. For example, if there were two species of antelope who looked quite similar, but were genetically distinct enough to be unable to reproduce if they were to mate, then the theory in this article may be applicable, but when you think about it, it may be only a means of selection itself. If the two antelope species couldn't tell themselves apart, then every time one were to court or mate with the opposite species, it would be a wasted effort. Even males sparring off against males in the other species could happen and would be a further waste of effort. The species that can distinguish apart in one or more distinct ways would be more efficient at breeding, and passing along its genes. Hence, the genes that conferred the ability to differentiate based on exaggerated recognition of others' traits would find themselves more commonplace over time, and would dominate in a gene pool. So, the theory in the article may not be a force in its right, but may be a further criterion around which individuals must compete for natural selection. Our abilities to do this peak-shifting visually may have evolved long ago in the earliest mammals or even before. And before that, perhaps it was exaggerating the chemical differences between one worm and another. But far enough back, when we were non-sexually reproducing "species", the entire environment, whether competing rivals from within the same species, others outside the species trying to compete within the same niche, or non-living hazards, were a danger to the individual. Recognition of which type of hazard would have been useful, but not in the same manner as it would be among sexually reproducing species. So, all in all, this article's theory seems to me actually a criterion for selection within the classical theory of natural selection, rather than a new independent force co-acting upon species.
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