Friday, September 24, 2010

Recent critique of Darwin's original writing - The Genial Gene by Dr. Joan Roughgarden

An example of the vigor of current research and debate around Darwin's enduring ideas on Natural and Sexual Selection:

In her 2009 book, The Genial Gene, Stanford University researcher, Dr. Joan Roughgarden outlines her team's critique of Darwin's sexual selection outlined in The Descent of Man, and Selection in Relation to Sex (1871).

Darwin's idea of sexual selection (dramatized in class on 16 Sept 2010):

  1. Male ornaments (such as peacock's tail & deer's antlers) evolved because females preferred them.
  2. Males fight other males as females prefer the victors as mates.
  3. Males are 'passionate' whereas females are 'coy'. Males have lower reproductive costs than females.
  4. Females have a common (rather than individual) aesthetic ranking of males - all females would prefer the same type of male.

Roughgarden argues that sexual selection is wrong because

1) The sexual selection template offered by Darwin is violated by many species. Female selection exists, but its purpose is not to choose beautiful & well-armed males.

2) Many species previously thought to support Darwin's theory, do not, upon thorough investigation. For example, peahens (covered in lecture) were thought to prefer peacocks with big, fancy tails. Research now suggests that both sexes once had brightly coloured tails, but the ground-nesting females lost the bright plumage (shown to be inhibited by female hormones).

3) Contradictions exist between sexual-selection and population-genetic theories


Dr. Roughgarden's book also takes aim at neo-Darwinism (natural selection synthesized with genetics) as well. Her term: 'genial gene', responds to & aims to replace the concept of the 'selfish gene' (put forward by Richard Dawkins) with one including cooperation & teamwork. As Professor Ogden showed in lecture on September 8, Darwin's theory of natural selection is Whigism applied to evolution. Similarly, perhaps Dr. Roughgarden's cooperative theory reflects current political sensibilities applied to sexual selection.

Sexual & Social selection as applied to people...

Of direct relevance to the Humanities, Roughgarden specifies four topics related to human behaviour alone and compares sexual & social selection head-to-head:

1) Attractiveness:

  • SeS (sexual selection): women attracted to men displaying traits representative of their genetic quality; men promiscuous.
  • SoS (social selection): men & women choose each other equally based on factors promoting effective raising of children

2) Brain

  • SeS: brain is secondary sexual character "the counterpoint of the peacock's tail, an ornament used by men to attract women ... females need big brains to appreciate the brains of men"
  • SoS: brains needed to participate in social infrastructure & successfully raise children

3) Rape

  • SeS: allows rejected men to reproduce, by force
  • SoS: form of domination against males or females; not related to reproduction

4) Extra-Pair Paternity (women having children by men other than husband)

  • SeS: women mating with men "genetically superior to their husbands, provided they can retain their husband's parental investment"
  • SoS: "procuring a distributed commitment to protection, safety, and resource sharing through political alliance"

Propagation of errors in classic research on Darwin's Sexual Selection...

As an example of the need for scientific rigor when testing theories, even those put forward by scientific giants like Darwin,

(Also an example of genetic fallacy: 'mistaking an account of something's [i.e. a theory's] origin as an explanation of its truth or fallacy' [Dr. Stephen Ogden, lecture 23 Sept. 2010])

Roughgarden documents the results of various reappraisals of classic research by Bateman previously thought to decisively confirm sexual selection.

Roughgarden reports that one reappraisal group finds:

"subsequent 'dogmatization' of Bateman's findings. They observe that key researchers in the field... as well as textbook authors... present data only from the graph that is claimed to support sexual selection, while ignoring the other
... in some cases, Bateman's data and methodology was misrepresented and embellished when doing so strengthened preconceived notions of male and female behavior."

Another group made these statements about Bateman's research:

"his methods had flaws, including the elimination of genetic variance, sampling biases, miscalculations of fitness variances, statistical pseudo-replication, and selective representation of data."

"We conclude that Bateman's results are unreliable, his conclusions are questionable, and his observed variances are similar to those expected under random mating...[but we] do not intend this article as a criticism of Bateman"

Roughgarden comments:

"I admire the thoroughness of these reviewers and appreciate their circumspection. Still, I wonder whether the delicacy of phrase apparent in their conclusions serves the public's need to know the truth. These three critiques of Bateman and later workers have been devastating. There's simply no justification for continued adherence to the sexual-selection narrative on the basis of Bateman's work."

Caution urged in treating sexual selection as fact...

Roughgarden summarizes her view on the state of the sexual selection theory:

"The sexual selection narrative has been widely and uncritically adopted as axiomatic by these disciplines [psychology, anthropology, sociology, philosophy, ethics, and theology] as a scientific and true account of biological nature ... the sexual-selection area of evolutionary biology is not settled science, is in considerable flux, and is not ready for export. I hope, too, that journalists and science writers will withhold, or at least greatly qualify, their speculations and sound bites about the evolution of human social behavior."

Response from an authority on sexual selection, Dr. Tim Clutton-Brock...

In a rebuttal to Roughgarden's theory, Dr. Tim Clutton-Brock of Cambridge concedes the following:

  • parental care is not a direct consequence of gamete size
  • sexual selection strength is not necessarily higher in males than females
  • females may compete with other females (for parental-care resources) as strongly as males compete with other males for mates

He also comments on the general lack of clear knowledge about sexual selection:

"where females compete directly with each other, it is often unclear precisely what they are competing for. Where females have developed obvious secondary sexual characters, it is often uncertain whether these are used principally to attract males or in intrasexual competition for resources and how their development is limited is unknown. And, where males show consistent mating preferences for particular categories of females, we do not yet know whether they are selecting for heritable differences in female quality or for nonheritable variation in fecundity for for both"

However, in the final analysis, he insists:

"the theory of sexual selection still provides a robust framework that explains much of the variation in the development of secondary sexual characters in males, although ... [the whole topic is] more complex than was originally supposed. The recognition of these complexities helps to refine the assumptions and predictions of the theory of sexual selection but does not undermine its basic structure."

Darwin's attitude to criticism...

Darwin himself noted, upfront, the problems he saw with his theory of natural selection:

Long before the reader has arrived at this part of my work, a crowd of difficulties will have occurred to him. Some of them are so serious that to this day I can hardly reflect on them without being in some degree staggered (The Origin of Species, 6th ed. p.207)

In the sixth and final edition of The Origin of Species, he spends chapters specifically addressing objections to his theory. For example, Chapter Six is entitled: Difficulties of the Theory. Darwin did not shy away from criticism from colleagues, but rather faced it head on. Those researchers who unfortunately chose to promote Darwinism at the expense of good science could take a lesson from Darwin.

In fact, the theory of sexual selection is an additional mechanism Darwin suggested to try to overcome a specific problem he saw with natural selection [Dr. Stephen Ogden, Hum 321 lecture 16 Sept. 2010]. Namely, the difficulty that some traits appear to be injurious to an individual, yet continue to be inherited - seeming to violate the principles of Natural Selection.
Darwin used Sexual Selection to explain this apparent contradiction, indicating that secondary sexual characters are useful in the struggle between males for possession of females [Dr. Stephen Ogden, Hum 321 lecture 16 Sept. 2010].

On the veracity of sexual selection, Darwin himself admits: "I am aware that much remains doubtful" (The Descent of Man, p608). Roughgarden's alternative theory of social selection includes a 26 point chart of direct comparison with sexual selection, directly engaging Darwin's theory, and showing the great weight that his theory has in current research. Supporting Darwin's general theory of natural selection, Roughgarden concludes in her final chapter of The Genial Gene:

the 200 years since Darwin's birthday have confirmed ... Darwin's hypothesis about descent and common ancestry. (p.235)

Darwin trusted in the scientific process, of which criticism, peer review, and reevaluation are a part:

ignorance more frequently begets confidence than does knowledge: it is those who know little, and not those who know much, who so positively assert that this or that problem will never be solved by science. (The Descent of Man, p.2)

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