What kind of Darwinian are you? (ritual, evolution, America, theist)

[Victor]

What kind of Darwinian are you?
Figured this would make for a good dialogue.

As a fairly enthusiastic Darwinian myself, I can attest to the fact that "Darwinism," no less than "Christianity," is a notion with many meanings. Again, I will propose three grades. In a sense, these correspond to my three grades of Christian. I feel a bit diffident. however, about referring to an ardent Darwinian as a "conservative Darwinian." That is a misnomer, if not an oxymoron. Hence, I shall speak of the ultra-Darwinian, the moderate Darwinian, and the restrained Darwinian. These are not necessarily the most elegant terms, but they will serve.


All three Darwinians are evolutionists, believing that organisms, including ourselves, came by a process of development from a few simple forms. The ultra-Darwinian thinks that the sole cause was Charles Darwin's mechanism of natural selection working on random (not uncaused) variations. This factor suffices to explain all. There are no other causes at work, nor are other causes needed. This means that all organic features are to be considered adaptive, even though we may not at present know precisely the nature of the function of these adaptations.

The classic problem case is that of male nipples. What function could these possibly serve? The ultra-Darwinian thinks that they have to have some end, like sexual attractiveness. An explanation in terms of being a byproduct of other features, or some such thing, will not do. I do not know how many people are ultra-Darwinians of this extreme ilk today, but they have certainly existed in the past. Alfred Russet Wallace, the co-discoverer of natural selection, was one before his conversion to spiritualism. The turn of the century biometrician, Raphael Weldon, was another.
The moderate Darwinian thinks that natural selection is the mostimportant mechanism of evolutionary change. But he or she is unwilling to give selection complete and exclusive causal authority over evolution. The moderate thinks that there might well be other causes of change which, in their way, could be very important included here are genetic drift, correlation of parts, and perhaps even "hopeful monsters." No one today believes in Lamarckism, in the old-fashioned sense of the direct inheritance of acquired characters. Some today think that non-Darwinian factors might be very important at the molecular level.
The restrained Darwinian thinks that selection is certainly at work and may have important effects. However, he/she does not think it the most important cause of change, We must look for other factors of change to explain the overall pattern. In the past, someone like the American paleontologist Henry Fairfield Osborn would have come under this heading. Today one might include the Harvard paleontologist Stephen Jay Gould in this category, although I myself think he is more properly labeled a moderate. (As with Christianity, I do not intend to imply that the categories of Darwinism are sharp and exclusive; some people will fall on the boundaries.)

http://www.leaderu.com/orgs/fte/darwinism/chapter5.html

[Jayhawker Soule]

Originally Posted by Victor

The classic problem case is that of male nipples. What function could these possibly serve?

You know, Victor, ignorant statements such as that have been repeatedly challenged on this board.

[Jayhawker Soule]

Why do Men have Nipples?
ANDREW M SIMONS Scientific American Online 13jan03

Andrew M. Simons, a professor of biology at Carleton University in Ottawa, Ontario, explains. Like all "why" queries, the question of why men have nipples can be addressed on many levels. My four-year-old daughter, always suspicious of a trick when asked such obvious questions, answered: "because they grow them." In search of the trick answer, she quickly added that "chests would also look pretty funny with just hair."

Evolutionary biologists, whose job it is to explain variety in nature, are often expected to provide adaptive explanations for such "why" questions. Some traits may prove—through appropriate tests—to be best explained as adaptations; others have perfectly good evolutionary, but nonadaptive, explanations. This is because evolution is a process constrained by many factors including history, chance, and the mechanisms of heredity, which also explains why particular attributes of organisms are not as they would be had they been "designed" from scratch. Nipples in male mammals illustrate a constrained evolutionary result.

A human baby inherits one copy of every gene from his or her father and one copy of every gene from his or her mother. Inherited traits of a boy should thus be a combination of traits from both his parents. Thus, from a genetic perspective, the question should be turned around: How can males and females ever diverge if genes from both parents are inherited? We know that consistent differences between males and females (so-called sexual dimorphisms) are common--examples include bird plumage coloration and size dimorphism in insects. The only way such differences can evolve is if the same trait (color, for example) in males and females has become "uncoupled" at the genetic level. This happens if a trait is influenced by different genes in males and females, if it is under control of genes located on sex chromosomes, or if gene expression has evolved to be dependent on context (whether genes find themselves within a male or a female genome). The idea of the shared genetic basis of two traits (in this case in males and females) is known as a genetic correlation, and it is a quantity routinely measured by evolutionary geneticists. The evolutionary default is for males and females to share characters through genetic correlations.

The uncoupling of male and female traits occurs if there is selection for it: if the trait is important to the reproductive success of both males and females but the best or "optimal" trait is different for a male and a female. We would not expect such an uncoupling if the attribute is important in both sexes and the "optimal" value is similar in both sexes, nor would we expect uncoupling to evolve if the attribute is important to one sex but unimportant in the other. The latter is the case for nipples. Their advantage in females, in terms of reproductive success, is clear. But because the genetic "default" is for males and females to share characters, the presence of nipples in males is probably best explained as a genetic correlation that persists through lack of selection against them, rather than selection for them. Interestingly, though, it could be argued that the occurrence of problems associated with the male nipple, such as carcinoma, constitutes contemporary selection against them. In a sense, male nipples are analogous to vestigial structures such as the remnants of useless pelvic bones in whales: if they did much harm, they would have disappeared.

In a now-famous paper, Stephen Jay Gould and Richard C. Lewontin emphasize that we should not immediately assume that every trait has an adaptive explanation. Just as the spandrels of St. Mark's domed cathedral in Venice are simply an architectural consequence of the meeting of a vaulted ceiling with its supporting pillars, the presence of nipples in male mammals is a genetic architectural by-product of nipples in females. So, why do men have nipples? Because females do.

[ source ]

[Scuba Pete]

Originally Posted by Victor

The classic problem case is that of male nipples. What function could these possibly serve?

See? God does have a sense of humor! As a fairly enthusiastic evolutionist myself, I don't have a problem with the existence of nipples. As a fairly enthusiastic theist, I can only smile!

[Victor]

Originally Posted by Jayhawker Soule

You know, Victor, ignorant statements such as that have been repeatedly challenged on this board.

I was aware of it. The article was pasted for the intent noted on the OP. Next time I will do a <snip> to avoid this.

[Æsahættr]

Originally Posted by Victor

The ultra-Darwinian thinks that the sole cause was Charles Darwin's mechanism of natural selection working on random (not uncaused) variations. This factor suffices to explain all.

I realise this thread has been dead for a few days, but in the name of pedancy, this is a ridiculous classification system. Surely an "ultra-Darwinian" would be someone who adhered strictly to Darwin's ideas. Yet Darwin himself isn't an ultra-Darwinian under this sytem (he came up with the idea of sexual selection as a seperate mechanism to natural selection).

[Victor]

Originally Posted by Æsahættr

I realise this thread has been dead for a few days, but in the name of pedancy, this is a ridiculous classification system. Surely an "ultra-Darwinian" would be someone who adhered strictly to Darwin's ideas. Yet Darwin himself isn't an ultra-Darwinian under this sytem (he came up with the idea of sexual selection as a seperate mechanism to natural selection).

It's a classification because behind every approach there is a world view/philosophy that affects how you see it and interpret it.