Friday 5 February 2016
A black eye to sexual selection?
Mating behavior in the natural world contradicts Darwin’s idea that females make the decisions, researchers find
Date:
January 28, 2016
Source:
McMaster University
What if Darwin was wrong?:
A provocative study by evolutionary biologists at McMaster University takes on one of Charles Darwin's central ideas: that males adapt and compete for the attention of females because it is the females who ultimately choose their mates and the time of mating.
Instead, new research using fruit flies as a representative species indicates that females do not have specific preferences, suggesting that 150 years of evolutionary theory around mating choice may need to be tossed out.
"Darwin's female-choice theory has become the foundation for explaining the presence of exaggerated secondary sexual traits in many males, such as the peacock's tail feathers," says evolutionary biologist Rama Singh, an author of a paper in the journal PLOS ONE that explains the findings.
"It has also led to a cottage industry based on the idea that female choice is based on the genetic quality of the males, known as the 'good gene hypothesis'," Singh says. "Sexually exaggerated traits are said to be male advertisements to females of their good genes, when in fact they may simply be a means of making the male more visible to females or intimidating other males."
Did Darwin get it right? Could it be that the Victorian values of his time, when men tipped their hats and made other exaggerated displays of sensitivity to women, subtly affected Darwin's scientific thinking, leading him to attribute a veto power to females in matters of sexual negotiations? Is female choice more apparent than real?
When a female seems to "choose" a large male over a small male, how do we know if she really prefers the large male or she is making the "choice" under coercion or threat, or if the large male has eliminated others from the competition?
Singh and his co-authors designed a simple trick to answer these questions. Using a garden variety of fruit fly, Drosophila, they sexually aroused a female with a male (large or small), then removed the male and offered the female two fresh males -- one small and one large. The results were clear-cut and unambiguous: the aroused females did not show any particular preference for large males and mated as if randomly, leading the authors to conclude that once sexually aroused, females have no preference in terms of mates.
The key to understanding the question of choice may be in the longer time it takes female fruit flies reach a state of arousal -- a lag that is often misinterpreted as females exercising mate choice.
In matters of mate choice and mating, there is no such thing as pure male charm, Singh says. All male moves can be seen as tinged with direct or indirect coercion or threat of physical force.
This may be so because the physical strength and aggressive behaviors that males develop through male-male competition can also be used in male-female sexual interactions, which are all lumped into "male sex drive" a term proposed by Singh as a complement to Darwin's "female choice."
In the case of humans, Singh says, things are different. Sexual behaviors are not hard wired; we assume that they can be modulated and moderated through rules of social interactions imposed by the brain's veto power over the body.
Journal Reference:
Santosh Jagadeeshan, Ushma Shah, Debarti Chakrabarti, Rama S. Singh. Female Choice or Male Sex Drive? The Advantages of Male Body Size during Mating in Drosophila Melanogaster. PLOS ONE, 2015; 10 (12): e0144672 DOI: 10.1371/journal.pone.0144672
Date:
January 28, 2016
Source:
McMaster University
What if Darwin was wrong?:
A provocative study by evolutionary biologists at McMaster University takes on one of Charles Darwin's central ideas: that males adapt and compete for the attention of females because it is the females who ultimately choose their mates and the time of mating.
Instead, new research using fruit flies as a representative species indicates that females do not have specific preferences, suggesting that 150 years of evolutionary theory around mating choice may need to be tossed out.
"Darwin's female-choice theory has become the foundation for explaining the presence of exaggerated secondary sexual traits in many males, such as the peacock's tail feathers," says evolutionary biologist Rama Singh, an author of a paper in the journal PLOS ONE that explains the findings.
"It has also led to a cottage industry based on the idea that female choice is based on the genetic quality of the males, known as the 'good gene hypothesis'," Singh says. "Sexually exaggerated traits are said to be male advertisements to females of their good genes, when in fact they may simply be a means of making the male more visible to females or intimidating other males."
Did Darwin get it right? Could it be that the Victorian values of his time, when men tipped their hats and made other exaggerated displays of sensitivity to women, subtly affected Darwin's scientific thinking, leading him to attribute a veto power to females in matters of sexual negotiations? Is female choice more apparent than real?
When a female seems to "choose" a large male over a small male, how do we know if she really prefers the large male or she is making the "choice" under coercion or threat, or if the large male has eliminated others from the competition?
Singh and his co-authors designed a simple trick to answer these questions. Using a garden variety of fruit fly, Drosophila, they sexually aroused a female with a male (large or small), then removed the male and offered the female two fresh males -- one small and one large. The results were clear-cut and unambiguous: the aroused females did not show any particular preference for large males and mated as if randomly, leading the authors to conclude that once sexually aroused, females have no preference in terms of mates.
The key to understanding the question of choice may be in the longer time it takes female fruit flies reach a state of arousal -- a lag that is often misinterpreted as females exercising mate choice.
In matters of mate choice and mating, there is no such thing as pure male charm, Singh says. All male moves can be seen as tinged with direct or indirect coercion or threat of physical force.
This may be so because the physical strength and aggressive behaviors that males develop through male-male competition can also be used in male-female sexual interactions, which are all lumped into "male sex drive" a term proposed by Singh as a complement to Darwin's "female choice."
In the case of humans, Singh says, things are different. Sexual behaviors are not hard wired; we assume that they can be modulated and moderated through rules of social interactions imposed by the brain's veto power over the body.
Journal Reference:
Santosh Jagadeeshan, Ushma Shah, Debarti Chakrabarti, Rama S. Singh. Female Choice or Male Sex Drive? The Advantages of Male Body Size during Mating in Drosophila Melanogaster. PLOS ONE, 2015; 10 (12): e0144672 DOI: 10.1371/journal.pone.0144672
Yet more on mindless intelligence.
Misunderstanding Wallace on "Intelligent Evolution"
Michael Flannery February 5, 2016 3:28 AM
As Evolution News pointed out here yesterday ("You Can't Ascribe Intelligence to an Unguided Process"), Alfred Russel Wallace never actually used the term "intelligent evolution" himself. Instead, I have used it as an accurate description of his idea of a thoroughly teleological form of evolutionary theory. This is in stark contrast to his counterpart, Charles Darwin, with whom he shares credit for discovering the theory of evolution by natural selection. Readers who would like to know more about my use of the term may go here. But since Richard A. Watson brings it up in his article, "Intelligent design without a creator? Why evolution may be smarter than we thought," I will add a few more thoughts on the subject.
Watson states that "intelligent evolution" prompted Wallace "to argue for divine intervention in the trajectory of evolutionary processes." Yet Watson adds, "If the formal link between learning and evolution continues to expand, the same term could become used to imply the opposite." This is Watson's claim for "intelligent design without a creator."
In addition to the important observations offered by Evolution News -- Watson's mischaracterization of ID, his misguided neural network argument, his questionable application of learning theory to evolvability, the conspicuous absence of information theory in his argument, and his anthropomorphizing of evolution itself -- I would suggest more broadly that Watson misses the point. Whether or not evolution by means of natural selection might have some limited capacity to "learn" doesn't really matter, especially if Watson is trying to save Darwinian evolution for naturalism. Alan Turing was right: it is now possible to create chess programs that over time can "learn" which moves produce winning games and drop those that create losing results. Over time, a machine can thus "learn" winning strategies. But it is important to bear in mind that the computer needed a programming language to do so and that came originally from a programmer. The computer's ability to develop winning chess moves and strategies is not a self-emergent property.
As this relates to Wallace, the capacity for learning is equally beside the point. Wallace's central argument was that certain attributes like love of beauty, art, dance, music, abstract thought, mathematical ability, religious and ceremonial expression are all inexplicable by natural selection or any other naturalistic mechanism. Wallace believed that it was unlikely for natural selection to somehow "learn" these things because there was no reason for it to do so. None of these enhance survival and they might even in some circumstances impede it. The question isn't "Can evolution learn?" -- but rather, how, by any naturalistic means entailed in Darwinian evolution, can we account for the true operations of a mind, namely, intentionality, foresight, purposive action involving choice, and tacit knowing (for more on this read Michael Polyani)?
Moreover, all these capacities must be demonstrated in Darwinian operations to really imply "intelligent evolution" as Wallace described it. For Wallace, the diversity of life meant the necessity of a "Mind," and in 1910 he wrote about it at length in The World of Life: A Manifestation of Creative, Directive Mind and Ultimate Purpose. Intelligent design without a creator? Wallace didn't think so.
Michael Flannery February 5, 2016 3:28 AM
As Evolution News pointed out here yesterday ("You Can't Ascribe Intelligence to an Unguided Process"), Alfred Russel Wallace never actually used the term "intelligent evolution" himself. Instead, I have used it as an accurate description of his idea of a thoroughly teleological form of evolutionary theory. This is in stark contrast to his counterpart, Charles Darwin, with whom he shares credit for discovering the theory of evolution by natural selection. Readers who would like to know more about my use of the term may go here. But since Richard A. Watson brings it up in his article, "Intelligent design without a creator? Why evolution may be smarter than we thought," I will add a few more thoughts on the subject.
Watson states that "intelligent evolution" prompted Wallace "to argue for divine intervention in the trajectory of evolutionary processes." Yet Watson adds, "If the formal link between learning and evolution continues to expand, the same term could become used to imply the opposite." This is Watson's claim for "intelligent design without a creator."
In addition to the important observations offered by Evolution News -- Watson's mischaracterization of ID, his misguided neural network argument, his questionable application of learning theory to evolvability, the conspicuous absence of information theory in his argument, and his anthropomorphizing of evolution itself -- I would suggest more broadly that Watson misses the point. Whether or not evolution by means of natural selection might have some limited capacity to "learn" doesn't really matter, especially if Watson is trying to save Darwinian evolution for naturalism. Alan Turing was right: it is now possible to create chess programs that over time can "learn" which moves produce winning games and drop those that create losing results. Over time, a machine can thus "learn" winning strategies. But it is important to bear in mind that the computer needed a programming language to do so and that came originally from a programmer. The computer's ability to develop winning chess moves and strategies is not a self-emergent property.
As this relates to Wallace, the capacity for learning is equally beside the point. Wallace's central argument was that certain attributes like love of beauty, art, dance, music, abstract thought, mathematical ability, religious and ceremonial expression are all inexplicable by natural selection or any other naturalistic mechanism. Wallace believed that it was unlikely for natural selection to somehow "learn" these things because there was no reason for it to do so. None of these enhance survival and they might even in some circumstances impede it. The question isn't "Can evolution learn?" -- but rather, how, by any naturalistic means entailed in Darwinian evolution, can we account for the true operations of a mind, namely, intentionality, foresight, purposive action involving choice, and tacit knowing (for more on this read Michael Polyani)?
Moreover, all these capacities must be demonstrated in Darwinian operations to really imply "intelligent evolution" as Wallace described it. For Wallace, the diversity of life meant the necessity of a "Mind," and in 1910 he wrote about it at length in The World of Life: A Manifestation of Creative, Directive Mind and Ultimate Purpose. Intelligent design without a creator? Wallace didn't think so.
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