You might think that my contrarian view of the limited power of adaptation by natural selection would mean that I am “over” Darwin, that I am ready to denigrate the cultural/scientific personality cult that surrounds Darwin’s legacy. Quite to the contrary. I hope to celebrate that legacy but also to transform the popular understanding of it by shedding new light on Darwinian ideas that have been neglected, distorted, ignored, and almost forgotten for nearly a century and a half.Read more at location 307
The philosopher Daniel Dennett referred to evolution by natural selection—the subject of Darwin’s first great book, On the Origin of Species by Means of Natural Selection—as “Darwin’s dangerous idea.” Here I propose that Darwin’s really dangerous idea is the concept of aesthetic evolution by mate choice, which he explored in his second great book, The Descent of Man, and Selection in Relation to Sex.Read more at location 316
Darwinian mate choice really is dangerous—to the neo-Darwinists—because it acknowledges that there are limits to the power of natural selection as an evolutionary force and as a scientific explanation of the biological world. Natural selection cannot be the only dynamic at work in evolution, Darwin maintained in Descent, because it cannot fully account for the extraordinary diversity of ornament we see in the biological world.Read more at location 320
“The sight of a feather in a peacock’s tail, whenever I gaze at it, makes me sick!” Because the extravagance of its design seemed of no survival value whatsoever,Read more at location 324
The insight he eventually arrived at, that there was another evolutionary force at work, was considered an unforgivable apostasy by Darwin’s orthodox adaptationist followers.Read more at location 327
Aesthetic evolution by mate choice is an idea so dangerous that it had to be laundered out of Darwinism itself in order to preserve the omnipotence of the explanatory power of natural selection.Read more at location 329
the two great biological discoveries he revealed in Origin: the mechanism of evolution by natural selection, and the concept that all organisms are historically descended from a single common ancestor and thus related to one another in a “great Tree of Life.”Read more at location 355
In confronting the fierce attacks that were mounted against Origin after its publication, Darwin had three gnawing problems. The first problem was the absence of any working theory of genetics. Not knowing the work of Mendel, Darwin struggled and failed to develop a functioning theory of inheritance,Read more at location 359
Darwin’s second problem was the evolutionary origin of human beings, human nature, and human diversity.Read more at location 361
Darwin’s third big problem was the origin of impracticable beauty. If natural selection was driven by the differential survival of heritable variations, what could explain the elaborate beauty of that peacock’s tail that troubled him so much?Read more at location 364
In 1871, with the publication of The Descent of Man, and Selection in Relation to Sex, Darwin boldly addressed both the problem of human origins and the evolution of beauty. In this book he proposed a second, independent mechanism of evolution—sexual selection—to account for armaments and ornaments, battle and beauty. If the results of natural selection were determined by the differential survival of heritable variations, then the results of sexual selection were determined by their differential sexual success—Read more at location 374
Within sexual selection, Darwin envisioned two distinct and potentially opposing evolutionary mechanisms at work. The first mechanism, which he called the law of battle, was the struggle between individuals of one sex—Read more at location 379
second sexual selection mechanism, which he called the taste for the beautiful, concerned the process by which the members of one sex—often female—choose their mates on the basis of their own innate preferences. Darwin hypothesized that mate choice had resulted in the evolution of many of those traits in nature that are so pleasing and beautiful.Read more at location 382
Courage, pugnacity, perseverance, strength and size of body, weapons of all kinds, musical organs, both vocal and instrumental, bright colors, stripes and marks, and ornamental appendages, have all been indirectly gained…through the influence of love and jealousy, through the appreciation of the beautiful…and through the exertion of a choice.Read more at location 397
The most notable and revolutionary feature of Darwin’s theory of mate choice is that it was explicitly aesthetic. HeRead more at location 408
described the evolutionary origin of beauty in nature as a consequence of the fact that animals had evolved to be beautiful to themselves. What was so radical about this idea was that it positioned organisms—especially female organisms—as active agents in the evolution of their own species. Unlike natural selection, which emerges from external forces in nature, such as competition, predation, climate, and geography, acting on the organism, sexual selection is a potentially independent, self-directed process in which the organisms themselves (mostly female) were in charge.Read more at location 409
Note: STRANO: DARWIN POSTULA UN'ESTETICA FINE A SE STESSA O AL PIACERE DEL PARTNER. ERGO: NOI CON I NOSTRI GUSTI CONTRIBUIAMO A SELEZIONARE CIO' CHE SAREMO Edit
The first implication of Darwin’s language was that animals are choosing among their prospective mates on the basis of judgments about their aesthetic appeal. To many Victorian readers, even those sympathetic to evolution, this was patently absurd. It seemed impossible that animals could make fine aesthetic judgments.Read more at location 430
By using the words “beauty,” “taste,” “charm,” “appreciate,” “admire,” and “love,” Darwin was suggesting thatRead more at location 440
mating preferences could evolve for displays that had no utilitarian value at all to the chooser, only aesthetic value. In short, Darwin hypothesized that beauty evolves primarily because it is pleasurable to the observer.Read more at location 441
Darwin’s views on this issue developed over time. In an early discussion of sexual selection in Origin, Darwin wrote, “Amongst many animals, sexual selection will give its aid to ordinary [natural] selection by assuring to the most vigorous and best adaptive of all males the greatest number of offspring.” In other words, in Origin, Darwin saw sexual selection as simply the handmaiden of natural selection, another means of guaranteeing the perpetuation of the most vigorous and best-adapted mates.Read more at location 443
Note: IL PRIMO DARWIN: LA SCELTA SESSUALE è UN MEROP PROLUNGAMENTO DI QUELLA NATURALE. LA POSIZIONE OGGI PREVALENTE. POI PERò DARWIN CAMBIA IDEA E RENDE LA SCELTA SESSUALE INDIPENDENTE Edit
“The case of the male Argus pheasant is eminently interesting, because it affords good evidence that the most refined beauty may serve as a sexual charm, and for no other purpose [emphasis added].”Read more at location 450
Another distinctive feature of Darwin’s theory of mate choice was that it was coevolutionary. Darwin hypothesized that the specific display traits and the “standards of beauty” used to select a mate evolved together, mutually influencing and reinforcing each other—asRead more at location 456
animals are not merely subject to the extrinsic forces of ecological competition, predation, climate, geography, and so on that create natural selection. Rather, animals can play a distinct and vital role in their own evolution through their sexual and social choices.Read more at location 468
autonomy is the capacity of an individual agent to make an informed, independent, and uncoerced decision. So, sexual autonomy is the capacity for an individual organism to exercise an informed, independent, and uncoerced sexual choice about whom to mate with.Read more at location 483
In Descent, Darwin presented his hypothesis that female sexual autonomy—the taste for the beautiful—is an independent and transformative evolutionary force in the history of life.Read more at location 488
Upon publication in 1871, Darwin’s theory of sexual selection was swiftly and brutally attacked.Read more at location 497
the biologist St. George Mivart wrote, Under the head of sexual selection, Darwin put two very distinct processes. One of these consists in the action of superior strength or activity, by which one male succeeds in obtaining possession of mates and in keeping away rivals. This is, undoubtedly, a vera causa; but may be more conveniently reckoned as one kind of “natural selection” than as a branch of “sexual selection.”Read more at location 500
Mivart’s review of Descent also established another enduring intellectual trend. He was the very first person to portray Darwin as a traitor to his own great legacy—a traitor to true Darwinism: “The assignment of the law of ‘natural selection’ to a subordinate position is virtually an abandonment of the Darwinian theory; for the one distinguishing feature of that theory was the all-sufficiency of ‘natural selection’ [emphasis added].”Read more at location 544
In contrast to Darwin’s always polite and understated expression of his views, Wallace’s attack on evolution by mate choice grew ever more strident after Darwin’s death and continued until his own death in 1913. Ultimately, Wallace was so successful that the subject of sexual selection was almost completely marginalized and forgotten within evolutionary biology until the 1970s.Read more at location 565
Wallace articulates the idea that sexual displays constitute “honest” indicators of quality and condition—an entirely orthodox view in sexual selection today.Read more at location 577
today’s mainstream views of mate choice are as stridently anti-Darwinian as Wallace’s critiques.Read more at location 580
Wallace was the first to propose the now exceedingly popular BioMatch.com hypothesis, which holds that all beauty provides a rich profile of practical information about the adaptive qualities of potential mates. This view of evolution has become so pervasive that it even found its way into the 2013 Princeton University graduation speech by the Federal Reserve chairman, Ben Bernanke, who admonished the graduates to “remember that physical beauty is evolution’s way of assuring us that the other person doesn’t have too many intestinal parasites.”Read more at location 581
During the century-long dark age of mate choice theory, however, one man did make a fundamental contribution to the field. In a 1915 paper and a 1930 book, Ronald A. Fisher proposed a genetic mechanism for the evolution of mate choice that built on and extended Darwin’s aesthetic view. Unfortunately, however, Fisher’s ideas on sexual selection would be mostly ignored for the next fifty years.Read more at location 615
Fisher permanently reframed the sexual selection debate with a critical observation: Explaining the evolution of sexual ornaments is easy; all other things being equal, display traits should evolve to match the prevailing mating preferences.Read more at location 625
The more critical scientific question is, why and how do mating preferences evolve? This insight remains fundamental to all contemporary discussions of evolution by sexual selection.Read more at location 627
The first phase, which is solidly Wallacean, holds that preferences initially evolve for traits that are honest and accurate indices of health, vigor, and survival ability.Read more at location 630
But then, after the origin of mating preference, Fisher hypothesized in his second-phase model, the very existence ofRead more at location 632
mate choice would unhinge the display trait from its original honest, quality information by creating a new, unpredictable, aesthetically driven evolutionary force: sexual attraction to the trait itself. When the honest indicator trait becomes disconnected from its correlation with quality, that doesn’t make the trait any less attractive to a potential mate; it will continue to evolve and to be elaborated merely because it is preferred.Read more at location 633
Fisher hypothesized that a positive feedback loop between the sexual ornament and the mating preference for that ornament will evolve through genetic covariation (that is, correlated genetic variation) between the two.Read more at location 643
Fisher asserted that mating preferences do not continue to evolve because the particular male that the female chooses is any better than any other male. In fact, sexually successful males could sometimes evolve to be worse at survival or poorer in health or condition.Read more at location 692
This evolutionary mechanism is rather like high fashion. The difference between successful and unsuccessful clothes is determined not by variation in function or objective quality (really) but by evanescent ideas about what is subjectively appealing—the style of the season.Read more at location 699
Around the centennial of Darwin’s Descent of Man, the concept of sexual selection began to return to the evolutionary mainstream. Why did it take so long? Although it would require an extensive historical and sociological study to investigate my hunch, I don’t think it was a coincidence that evolutionary biologists finally began to reconsider mate choice, particularly female mate choice, as a genuine evolutionary phenomenon at precisely that moment when women inRead more at location 712
the United States and Europe began to organize politically and to protest for equal rights, sexual freedom, and access to birth control. It would be nice to think that the insights from evolutionary biologists had an influence on these positive cultural developments, but unfortunately history shows that the opposite was true.Read more at location 716
example, a male may have the optimal tail length for survival (that is, favored by natural selection), but if he is not sexy enough to attract even a single mate (that is, disfavored by sexual selection), he will fail to pass on his genes to the nextRead more at location 725
generation. Likewise, a male may have the perfect tail size for attracting mates (that is, favored by sexual selection), but if he is so sexually extravagant that he cannot survive long enough to attract a single mate (that is, disfavored by natural selection), he will also fail to pass on his genes. Lande and Kirkpatrick confirmed the intuition of Darwin and Fisher that natural and sexual selection on display traits will establish a balance between the two opposing forces. At this equilibrium, the male may still be quite far from the natural selection optimum, but that’s the cost of doing business with sexually autonomous, choosy females.Read more at location 727
In the 1970s and 1980s, the chief proponent of the neo-Wallacean view of adaptive mate choice was Amotz Zahavi, a charismatic and energetic Israeli ornithologist with a fierce independent streak.Read more at location 779
is a costly burden to the signaler—literally, a handicap. By its very existence, the ornamental handicap demonstrates the superior quality of the signaler because the signaler has been able to survive it.Read more at location 788
In what way was the handicapped male better? To Zahavi, it was clear that he could be better in any imaginable way.Read more at location 794
Zahavi promoted the handicap principle with a single-minded fervor. But his idea had one big flaw. If the sexual advantage of an ornament is directly proportional to its survival costs, then the two forces will cancel each other out, and neither the costly ornament nor a mating preference for it can evolve. In a 1986 paper boldly titled “The Handicap Mechanism of Sexual Selection Does Not Work,” Mark Kirkpatrick provided a mathematical proof of this evolutionary trap.Read more at location 809
sketch on Saturday Night Live in the 1970s: JANE CURTIN: And so, with a name like Flucker’s, it’s got to be good. CHEVY CHASE: Hey, hold on a second, I have a jam here called Nose Hair. Now, with a name like Nose Hair, you can imagine how good it must be. MMM MMM!! DAN AYKROYD: Hold it a minute, folks, but are you familiar with a jam called Death Camp? That’s Death Camp! Just look for the barbed wire on the label. With a name like Death Camp, it must be so good it’s incredible! Just amazingly good jam! From there the names got worse and worse. John Belushi promoted a jellyRead more at location 822
called Dog Vomit, Monkey Pus, and then Chevy Chase returned with yet another new jelly named Painful Rectal Itch. The competition culminated with a jelly whose name was so repulsive it induced nausea and could not be spoken on the air. “So good, it’s sick making!” Jane Curtin proclaimed, before signing off with “Ask for it by name!”Read more at location 831
The Smucker’s principle further demonstrates that Zahavi’s handicap principle is fundamentally incompatibleRead more at location 837
with the aesthetic nature of sexual display. Sexual displays actually evolve because they are attractive, not disgustingly informative or repulsively honest.Read more at location 838
In 1990, Alan Grafen at Oxford came to the rescue of the failing handicap principle.Read more at location 846
Grafen showed mathematically that a nonlinear relationship between display cost and mate quality could salvage the theory. In other words, if lower-quality males pay a proportionally higher cost to grow or display an attractive trait than do higher-quality males, then the handicap could evolve.Read more at location 848
Having established a way to salvage handicaps, Grafen then asked how we should decide between two plausible evolutionary alternatives, the Zahavian handicap and the Fisherian runaway as elaborated by Lande and Kirkpatrick:Read more at location 852
Grafen’s reasoning struck a chord. Although personal comfort is not a scientifically justifiable criterion, many people, including scientists, do want to believe that the world is filled with “rhyme and reason.” So, even though Grafen merely demonstrated that there were conditions under which the handicap principle could work, he so discredited the Fisherian theory that most evolutionary biologists concluded that the handicap principle not only could work but would work—all the time. If belief in the alternative hypothesis is “wicked,” there’s little choice to make. Adaptive mate choice has dominated the scientific discourse ever since.Read more at location 865
Matt Ridley brought this distinction to vivid life in his 1993 book, The Red Queen: The split between Fisher and Good-genes began to emerge in the 1970s once the fact of female choice had been established to the satisfaction of most. Those of a theoretical or mathematical bent—the pale, eccentric types umbilically attached to their computers—became Fisherians. Field biologists and naturalists—bearded, besweatered,Read more at location 874
Ironically, I find that I have been written out of the historical narrative of my own discipline. I have spent cumulative years of my life in tropical forests on multiple continents studying avian courtship displays. I have been as “bearded, besweatered, and booted” as any field biologist. Yet I have also been an ardent and inquisitive “Fisherian” since the mid-1980s. According to the Grafen and Ridley narrative, I do not exist. Neither does Darwin, a naturalist who certainly put in his time in the field. Odder still, neither does Grafen, who is primarily a mathematician. Unfortunately, Ridley’s scenario also eliminates from consideration all female field biologists and naturalists. (Sorry, Jane Goodall and Rosemary Grant!)Read more at location 879
scientific and intellectual bias toward simplicity and unification.Read more at location 920
In his 1867 antievolution tract, The Reign of Law, the Duke of Argyll cited the “ball and socket” designs of the Great Argus wing feathers as a sign of God’s hand in creation. Darwin countered that the Great Argus is evidence of the evolution of beauty by mate choice, concluding that “it is undoubtedly a marvelous fact that the female [Great Argus] should possess this almost human degree of taste.”Read more at location 1092
Given his low opinion of the cognitive and aesthetic capacities of female pheasants, Beebe simply could not accept the idea of sexual selection: “It seems impossible to conceive, much as we would like to believe in it, and personally, I should be willing to strain a point here and there to admit this pleasant psychologically aesthetic possibility; but I cannot.” Then how did Beebe explain the evolution of the male Great Argus? He could not. He concluded, “It is one of those cases where we should be brave enough to say, ‘I do not know.’ ” Ironically, a man who spent years of his life tracking down the displays of this fabulously beautiful creature, and many other pheasants, found Darwin’s explanation for its beauty “impossible.”Read more at location 1098
What biologists don’t agree on is whether mating preferences evolve forRead more at location 1110
those ornaments that provide consistently honest, practical information—about good genes or direct benefits like health, vigor, cognitive ability, or other attributes that would help the chooser—or whether they are merely meaningless, arbitrary (albeit fabulous) results of coevolutionary fashion. Actually, most biologists are in agreement with the former hypothesis. I am not. More precisely, I think that adaptive mate choice can occur but it is probably rather rare, whereas the mechanisms of mate choice envisioned by Darwin and Fisher, and modeled by Lande and Kirkpatrick, are likely to be nearly ubiquitous.Read more at location 1110
In 1997, I submitted a manuscript to the American Naturalist, a first-class science journal in ecology and evolutionary biology.Read more at location 1118
Through a comparative examination of the display behaviors of multiple species within the group, I described how the males of one of theRead more at location 1122
species, the White-throated Manakins, evolved a novel bill-pointing posture that replaced an ancestral tail-pointing posture that had been a routine part of the standard display repertoire. It was as though evolution had edited out the old posture with a cookie-cutter and pasted in the new one in the same exact position within the behavioral sequence. I proposed that this change was unlikely to have evolved because it provided better information about mate quality—if it did, then all of the manakin species would have evolved it—and more likely to have evolved in response to arbitrary, coevolved aesthetic mate preferences.Read more at location 1123
I had not tested whether the bill-pointing White-throated Manakin males were revealing their superior vigor or disease resistance. I responded that standing motionless in one posture as opposed to another was unlikely to be able to communicate any additional information about vigor or genetic quality, unless we were to hypothesize that the tail-pointing posture in the ancestral birds had evolved in order to reveal whether they were infested with butt mites, and the bill-pointing posture must have evolved in order to reveal theRead more at location 1132
possibility of some more recent problem in evolutionary history, such as infestations of throat mites. This seemed unlikely to me, but the reviewers insisted that the burden of proof was on me to demonstrate that the display traits were arbitrary. Of course, this made it impossible to “prove” my point,Read more at location 1135
How many of these adaptive hypotheses, I wondered, would I have to test before I could conclude that any given display trait was arbitrary—that is, that it lacked information about any quality other than its attractiveness?Read more at location 1139
Because there would be no end to the creative imaginations of the reviewers, there would be no end to the process of trying to demonstrate that any specific trait is arbitrary. I was trapped.Read more at location 1143
I realized that it was Alan Grafen’s standard of evidence that had put me in this bind: “To believe in the Fisher-Lande process as an explanation of sexual selection without abundant proof is methodologically wicked.”Read more at location 1146
Carl Sagan claimed, “Extraordinary claims require extraordinary evidence.”Read more at location 1149
Pierre-Simon Laplace, who wrote, “The weight of evidence for an extraordinary claim must be proportioned to its strangeness.”Read more at location 1150
Thus, whether Grafen’s abundant proof standard should be invoked depends on our perceptions of the strangeness of the Darwin-Fisher theory of mate choice.Read more at location 1151
Of course, it’s human nature to want to believe in a universe that is rational and orderly. No less a scientist than Albert Einstein backed away from quantum mechanics—Read more at location 1156
In rejecting quantum mechanics, Einstein famously wrote, “God does not play dice.” But eventually quantum mechanics triumphed despite its enduring strangeness, because the predictive power of the theory was too great to ignore.Read more at location 1158
When we test a scientific hypothesis, we must compare a conjecture—say, that a specific mechanism is responsible for producing the observations that we have made of the world—with a more general conjecture that nothing special is happening; that is, no specific, or special, explanation is required to account for the observations we have made. In science and statistics, this “nothing special is happening” hypothesis is known as the null hypothesis,Read more at location 1165
Thus, before we can assert that some specific process or mechanism of interest is happening, we must first reject the null hypothesis that nothing special is happening.Read more at location 1173
as Fisher observed, the null hypothesis is intellectually asymmetrical. One can find evidence to reject the null hypothesis, but one can never really prove it.Read more at location 1175
Unfortunately, there are fundamental reasons why humans, including professional scientists, are biased toward thinking that something special must be happening. The human brain gets lots of rewards for detecting hard-to-see patternsRead more at location 1182
in the flow of sensory information and cognitive details. Being able to figure out what’s going on when it’s not obvious is perhaps the most fundamental advantage of intelligence.Read more at location 1183
Lots of people indulge in their irrational desires for meaningful explanations of our chaotic world,Read more at location 1190
For example, “cigarettes do not cause lung cancer” is a null hypothesis.Read more at location 1203
After years of struggling against Grafen’s abundant proof standard, I came to realize that the field of evolutionary biology had become like the financial market news reports. Evolutionary biologists have become convinced that a special kind of rhyme and reason—adaptive mate choice—must be happening everywhere and all the time. Why are they so convinced? When you examine it, it is mostly just a belief that the world must be that way.Read more at location 1210
If the Lande-Kirkpatrick mechanism is the appropriate null model for evolution of traits and preferences, then itRead more at location 1221
Note: IL GUAIO DI SELSEX: NON PUO' ESSERE PROVATA PER DEFINIZIONE PERCHE' DISCENDE DALLA MANCANZA DI ROVE DELLE ALTERNATIVE Edit
cannot be proven. Thus, Grafen’s demand for “abundant proof” of the Fisher-Lande process was so rhetorically effective precisely because it demanded the impossible. Checkmate! This was the trap I experienced when I realized that I could never satisfy my reviewers. And this is why, nearly 150 years after The Descent of Man and 25 years after Grafen’s 1990 paper, there are still no generally accepted, textbook examples of arbitrary mate choice. Period. Grafen’s gambit triumphed.Read more at location 1222
model. In the absence of a null model, adaptive mate choice is unscientifically protected from falsification.Read more at location 1227
When a trait can be shown to be correlated with good genes or direct benefits, the adaptive model is declared to be correct. When no such correlation is found, the result is interpreted merely as a failure to try hard enough to establish how the adaptive model is correct. In this framework, the ultimate research goal for every young scientist or graduate student is to demonstrate what everyone already knows to be trueRead more at location 1228
