Since the late 1970s, however, a new generation of biologists has begun to peek behind this suspect veil and, using fresh analyses, to reveal quite a different story, one summed up by the title of a seminal paper, “The Energetic Egg.” In this new account the egg, no longer a slumbering princess, becomes an active agent, directing the growth of microvilli (small finger-like projections on its surface) to capture and tether the sperm. Here the egg and sperm are partners, co-activators in the process of conception.

What is particularly noteworthy is that while the egg’s cone of microvilli was discovered in the 1890s, it was not thought worthy of serious scientific attention until 80 years later — a time when women’s roles in society were themselves being reconceived.

But before we cheer too loudly for this liberation of a core biological function from the rhetorical trappings of millennia-old sexism, it is worth stopping to reflect that the new tale itself is rife with gendered cultural overtones. As Schiebinger notes, in this new account the egg and sperm have come to resemble nothing so much as the high-powered dual-career couple of the ’80s and ’90s.

Like the contemporary corporate woman, the new “energetic egg” is valued precisely because it is now seen to be more like its male counterpart. Like the business exec with her power suit, the new egg has been “masculinized.” And just as the female exec risks accusations of aggressiveness, so too the new egg is all-too-easily seen as a “femme fatale, threatening to capture and victimize sperm.” The point is that while the new story may have stripped away the old sexist overtones, the egg and sperm remain gendered, essentially reflecting the pattern of current social arrangements between men and women.

This saga of transformation in one of our premier biological narratives raises a question that has become central to the current discussion about science: Can science ever be free of cultural influences? To put it another way: Can science ever be purely objective, an inquiry into the unsullied “truth” about the “real” world, or will it always be prey to the vagaries of subjective experience?

This is the question that resides at the heart of the so-called “science wars” that have rocked the academy for the past several years, and which show little sign of abating. On the one side are the objectivists (sometimes called realists), who believe that science is an ever-progressing ascent toward an ultimate picture of the-world-as-it-really-is. On the other hand are the subjectivists (sometimes known as relativists), who believe, to varying degrees, that science will always carry the stamp of the culture from which it springs. For this camp, prevailing views about gender, race, class and the like inexorably influence scientific theories, so that we can never (even in principle) see the world as it really is. To this camp, that very notion is a fiction that must be abandoned.

Many, though by no means all, scientists fall into the first camp — Stephen Jay Gould is an eminent exception. Likewise, many, though not all, historians, philosophers and science-studies scholars fall into the second camp.

The question of whether science can ever be culture-free is also at the heart of a number of new books. One of the best is Schiebinger’s provocatively titled “Has Feminism Changed Science?” If science is, as the objectivists claim, a culture-free activity, then the answer must be no. But as the changing narrative of the egg reveals, it is not so easy to strip away the cultural subtext from our scientific theories.

The science wars have been simmering for the past decade, but in 1996 they moved from sort of a cold war standoff phase into active engagement. The catalyst was the publication by a little-known physicist named Alan Sokal of an article in the cultural studies journal Social Text. In his now infamous piece Sokal purported to present a postmodern critique of physics in which, using lashings of trendy French philosophy and deliberately nonsensical postmodern jargon, he suggested that quantum mechanics could be seen to support the view that all knowledge is culturally relative. Immediately after the piece came out he gleefully exposed it as a hoax designed to show that cultural studies types know naught about science and ought to lay off pronouncements on the subject.

Whether one regards this as a brilliant exposi or as a petty frat-boy prank, the fallout has driven a deep wedge between the community of scientists and the community of science-studies scholars (those who study how science fits into the social, cultural and historical landscape.)

One way of looking at this divide is suggested by Canadian philosopher Michael Ruse in his new book, “Mystery of Mysteries: Is Evolution a Social Construction?” Ruse divides the two camps, roughly speaking, into the Popperians (following the Austrian philosopher of science Karl Popper), and the Kuhnians (following the American philosopher of science Thomas S. Kuhn). For Popper, science was a progressive activity, getting us ever nearer to a true picture of reality. Although Popper acknowledged that we could never find ultimate truth, he insisted on an objective view of science as an exploration of the world as it really is.

Kuhn, in his 1962 book “The Structure of Scientific Revolutions,” famously declared that all science proceeds according to “paradigms” — mental constructs or theoretical frameworks which inevitably change as our society changes. For Kuhn, science is not an ascent towards any God’s-eye view, and the science of one age must be considered no better or worse than the science of any other.

Kuhn’s book sparked its own revolution, not in science but in science studies, and it became a flash point for even more revolutionary views of science, which have culminated in the radically relativist views that Sokal and the objectivists so deplore.

The two extremes in the debate may be characterized as follows: For radical objectivists, nature is the only voice, with human culture playing no role. For radical relativists, nature has no voice of its own, and all scientific knowledge is the production of humans. In reality, most people fall somewhere in between. Even Einstein, that arch-realist, recognized that we can only know nature through the prism of our theories — we can never see it naked, as it were. Glad news it is, then, to see Ruse and Schiebinger trying to find a middle ground.

Both Ruse and Schiebinger approach the question — and both books are indeed framed as questions — from the vantage point of a particular case study. For Ruse the case study is the theory of evolution, and the ways that ideas about evolution have themselves evolved over the past two centuries. For Schiebinger the case study is feminism, and the way that both female practitioners of science, and feminist theories about science, have affected (or not) various scientific disciplines — from cell biology to primatology, archeology, medicine, mathematics and physics.

Feminist science scholars, it must be noted, make up one of the key groups to have claimed science as a culture-laden activity. As such, they are seen by objectivists as a key battalion of the enemy. In the post-Sokal era, Schiebinger is aware of the need for caution, and she approaches her subject with the hyperalert acuity of a lion tamer encountering a large, wild cat. The big surprise for many objectivists will be that Schiebinger lays to rest to the notion that women in and of themselves change the nature of science simply by becoming scientists. The culture of science is not rooted in the chromosomes of its practitioners, she assures us — a conclusion all objectivists should applaud.

But if women do not necessarily do science differently, the historical record suggests that feminist perspectives have indeed made an impact on both the culture and content of science. The saga of the egg is just one example Schiebinger gives in which women’s involvement in a field has opened up new lines of inquiry that have led to significant new discoveries. Another case in point is primatology. For more than a century primatologists, who were almost exclusively male, focused almost exclusively on male primates. Once a new generation of primatologists — again beginning in the 1970s, and who by then included women — started to pay attention to the females of the species, they found that previous views were clearly distorted. Other cases can be found in genetics, archeology and medicine.

Some of the female scientists who made these discoveries were avowed feminists, but many were not. Yet, as Schiebinger shows, it is no coincidence that so many of these insights came to the fore at a time when women’s own role in society was changing, and when the very nature of “femininity” and “womanhood” was so much a subject of debate. In short, you do not have to be a feminist to be influenced by feminist cultural movements.

One example of this trend that has struck me forcefully over the past few years is the way in which the whole question of embodiment has become a hot topic in fields like artificial intelligence and cognitive science. After decades during which intelligence was seen to be a purely mental phenomenon, suddenly there is talk of it being ineluctably rooted in the physical reality of a body. Most of the current scientists and philosophers making this claim are men who would not (I am sure) identify themselves as feminists; nonetheless, feminist philosophers have been making just this claim for decades.

We are all a part of a cultural matrix, which, even if unconsciously, affects the way we think. As Schiebinger puts it “We cannot free ourselves of cultural influence; we cannot think or act outside a culture. Language shapes even as it articulates thought.”

Reluctant though he seems to be to admit this, Michael Ruse comes to a similar, if more guarded conclusion regarding evolution. Tracing the evolution of evolutionary theory through a half-dozen of its major proponents — from Charles Darwin to contemporary practitioners such as Richard Dawkins, Stephen Jay Gould and E.O. Wilson — Ruse reveals how their views of evolution were influenced both by the culture of their time and by their own upbringings.

Wilson, for example, perhaps as a legacy of his Southern Baptist childhood, is still essentially looking for some kind of fundamental truth. As he acknowledges in his own recent book, “Consilience,” at university he traded in his religion for science. Given the indelible traces of each man’s culture on his scientific theories, Ruse frankly admits, “I see the influence of culture on scientific ideas as something that is here to stay.”

That said, Ruse also wants to claim victory — and for him it is the most significant victory — for objectivism. The course of history has shown, he says, that although in the beginning evolutionary theory was almost purely a cultural construction, over the past two centuries it has been increasingly cleansed of such intrusions. While individual practitioners may still reveal the hallmarks of their culture, particularly in their use of metaphors to describe their ideas to non-scientists, in the final analysis the theory has been born out by objective, empirical validation.

In the end Ruse wants to have his cake and eat it, too: He sees evolutionary theory as essentially objective, but with an overlay of metaphorical subjectivity. Not everyone will feel satisfied with this resolution, but it is a heartening testimony to our times that this avowed champion of Sokal is at least prepared to acknowledge that the other side is not entirely wrong.

There are some male mammals without nipples, a fact I was alerted
to by Aristotle, who wrote “Such, for instance, is the case with
horses, some stallions being destitute of these parts.”

Since Aristotle’s medical facts were sometimes a bit wobbly — he
said cabbage cures hangovers — I called an equine veterinarian. “I
have never seen a stallion with nipples,” she declared flatly. “And
I have looked around down there.” As far as I know, she’s never
seen a bald stallion, either, so that’s how they avoid being called
reptiles.

The veterinarian pointed out that a mare’s two nipples are located
toward the tail end of the body, as opposed to the chic head-end
location in humans. This, she daintily hinted, might be why
stallions don’t exhibit nipples. “There’s no room.”

These shocking facts sent me on a quest for other data on animal
nipples or, as medical types have long preferred to say, mammae.
Male nipples? Mammae masculinae. (If you need to be even more
obscure you can also call a nipple a mamilla or a thelium.)

My mother, when I told her of my research, may have been hinting
that there were more hard-hitting stories I could be working on by
bringing up the folk analogy “as useless as tits on a boar hog.” My
research appears to indicate that boar hogs do in fact have tits.
Which they are not known to use.

Not only do male platypuses not have nipples, neither do females.
The milk simply flows out through pores and is licked up by baby
platypuses. And while platypuses are not actually categorized as
reptiles, you’ll notice that people are always talking about how
“primitive” they are and making fun of their noses.

I would have assumed that nipples were only available in even
numbers had I not learned that female possums, for example, have
between seven and 25 nipples. The delightful Virginia opossum, which
inhabits the middles of American roads and highways, usually has
13, efficiently arranged in an open circle with one in the center.
This information should not tempt you to snicker and point the next
time you see a possum: They also have 50 teeth.

Most mammals, however, stick to even numbers of nipples, and often
the males get to have them too. In addition to boar hogs, dogs,
cats, all primates and many other animals feature the mamma
masculina.

It seems that human embryos develop mammary tissue before they
bother to check on whether they’re going to be male or female and
start modifying the basic plan with surges of this or that hormone.
After only a few weeks, milk ridges form — two stripes of tissue
that start in the armpits, curve out over the chest, go straight
down the stomach and then veer in toward the groin, ending
somewhere high on each thigh. Later the milk ridges regress to some
extent, usually leaving us with just two nipples.

Quite a few people end up with an extra, or supernumerary nipple
somewhere along the trail of the milk ridge, however. (One man had
five.) Sometimes they can’t be mistaken for anything but a nipple,
and other times they look like a mole. In fact, many people with
supernumerary nipples don’t know they have them until some
officious and informative person starts examining their moles.
Extras often run in families — Darwin cites two brothers who each
had a supernumerary nipple. Anyone who thinks that’s weird should
immediately leave the room and go check his or her torso for moles. How
do you know you’re not head-to-foot extra nipples and we’ve all
just been too polite to mention it?

What of male nipples as erogenous zones? You know they are, or why
would they be banished from the chest of Ken? (To avoid inflaming
Barbie.) I have looked into the matter of G.I. Joe: I never owned a
G.I. Joe, though I recall liking his accessories, particularly the
canteen. (Don’t take that the wrong way. Sometimes a canteen is
just a canteen.)

I asked a friend, who indicated with some annoyance that her
childhood G.I. Joes were just as smooth-chested as Ken. But it
seems that over the years G.I. Joe bulked up, and from being an
average Joe with an average physique became an eerily burly
muscle man who apparently never leaves the gym except to go to the
rifle range. Somewhere along the line some G.I. Joes acquired
nipples to go with their superior muscle definition and popping
veins. The effect is not particularly erotic: I suspect they’re
just there to give the viewer a reassuring landmark among all the
unfamiliar ripples of the bodybuilder’s torso caused by out-of-control delts, pecs, abs, intercostals and other oddities.

(In addition to the mute testimony of dolls, many actual men state
emphatically that male nipples are erogenous zones.)

Of course, the principal reason for the nipple’s enduring
popularity is its function as a food delivery device. Ask any baby.
Ask any father who has held his child in his arms and suddenly had
said infant jerk its head to the side and latch optimistically onto
a nipple. After a moment, the baby gives the father the reproachful
look of an innocent child betrayed: You’re no fun!

Darwin, who thought about everything, naturally wondered about
nipples. He collected case reports of men and women with extra
nipples (which he called mammae erraticae), including the case of
a woman who allegedly nourished a child via an extra nipple on her
thigh. (Why? Why not use the ones on her chest? Pure showboating,
that’s my guess.) This led him to suspect that we are descended
from creatures with more than just the two mammae.

He also pondered male nipples. In “The Descent of Man,” Darwin
suggests the possibility that “long after the progenitors of the
whole mammalian class had ceased to be androgynous, both sexes
yielded milk, and thus nourished their young; and in the case of
marsupials, that both sexes carried their young in marsupial
sacks.”

Darwin defended mammae masculinae: “The mammary glands and nipples,
as they exist in male mammals, can indeed hardly be called
rudimentary; they are merely not full developed, and not
functionally active.” He suggested that ancestral males gave up the
practice of nursing, after a prolonged period, perhaps because
litters were smaller. When “the males ceased to give this aid,
disuse to the organs during maturity would lead to their becoming
inactive; and … this state of inactivity would probably be
transmitted to the males at the corresponding age of maturity. But
at an earlier age these organs would be left unaffected, so that
they would be almost equally well developed in the young of both
sexes.”

Surely this is why everybody loves Darwin. Who else was thinking up
ancestral father animals suckling pouches full of thirsty babies?

I asked mammalogist Douglas Long, collections manager for
ornithology and mammalogy at the California Academy of Sciences,
whether there’s any new thinking on this particular suggestion of
Darwin’s. “Unfortunately, the fossil record doesn’t give much of
a clue at all,” Long said. “It’s very intriguing.”

While there’s no evidence to refute or support Darwin’s hypothesis,
Long points out that of the thousands of species of living mammals,
“Not a single one has a male that is able to lactate in any way.”
Why all the male nipples, then? Long cites the embryologic process
that creates mammary tissue and also notes that, evolutionarily
speaking, “It’s a lot more difficult to lose an organ than develop
an organ … It could be that males still have nipples because
there’s nothing deleterious about nipples. There’s no real need to
get rid of them. Why do we still have toenails, for example? Other
animals use them for digging, scratching or fighting, but we
don’t. They’re useless but at the same time they don’t distract
from the business of living.”

Pigeons and a couple of species of fish do something similar to
suckling their young, a task they split down the middle. Male and
female pigeons and doves feed their nestlings “pigeon’s milk,” a
cheesy substance they manufacture in their crops. Discus and orange
chromide fish feed their young with a nutritious mucus from the
sides of their bodies.

(Which reminds me. I do not want to hear about the breast being
just a modified sweat gland one more time, OK? That was a long
time ago and it was a pretty radical modification. Milk isn’t
sweat. Do you ever hear people say “the sweat of human kindness,”
“She rode a sweat-white horse” or “got sweat?” There’s a reason:
Milk is different from sweat. Until I hear you describe your hand
as a modified flipper, there will be no more talk of sweat glands.)

Male humans look pretty unhelpful next to pigeons. Newborn babies,
still pumped full of maternal hormones, usually lactate slightly,
producing a few drops of “witch’s milk.” Medical conditions like
acromegaly (excess growth hormone) can induce male lactation.

Dr. Miriam Stoppard, author of “The Breast Book,” agrees with
Darwin that male nipples are more than rudimentary, cheerfully
suggesting that “men could develop fully functional breasts given
the right hormonal conditions.”

That’s right. If men would just submit themselves to an intense
barrage of hormone therapy, affecting every organ system of the
body in unknown ways, maybe they would be able to suckle their
young and throw off the charge of reptilianism once and for all.
But where is the research? Where is the funding? Where is the will?

Whither the male nipple? Is it ever likely to stomp off in an
evolutionary snit over not getting any respect (“Enough about boar
hogs!”) and leave male humans as smooth-chested as stallions or
bulls? It seems unlikely. They’ve managed to hang in there all
these millennia, and many guys speak well of their nipples and
would clearly vote to retain them. Ask any boar hog and he’ll
tell you the same.

The Net is where the intelligent action will be. In the Dysonian schema, fragments of software replicating across the Internet are analogous to strings of DNA replicating in living cells. Evolutionary pressure provides the drive: What works survives; what doesn’t gets deleted, either by us or on its own.

So be prepared — there’s a new primordial soup in town, bubbling over with restless code, seething right toward the boiling point of sapience. And this new sapience won’t be purely digital; the emergent new order will be defined by a commingling of the silicon and the biological, by a collective merging of human and hardware. That’s both a promise and a threat.

Dyson was to the computer manner born. As a child he grew up on the campus of the Princeton-based Institute of Advanced Studies, where his mathematical physicist father, Freeman Dyson, hobnobbed with such luminaries of the computer world as John von Neumann, and where abandoned fragments of the earliest known computers rusted away in nearby barns. Dyson’s sister, Esther, is the publisher of Release 1.0, a pricey newsletter that reports from the cutting edge of current digital developments.

Freeman Dyson is perhaps most famous for his theory that all intelligent species will inevitably progress to a point where they enclose their home sun with a vast shell — a “Dyson sphere” — in order to maximize living space. On their face, George Dyson’s theories about emergent global intelligence might sound equally fantastic. No matter how persuasive the arguments, it’s never clear how routers, high-speed telecommunication lines and torrents of data add up to a new intelligent species.

But that doesn’t harm the book, because “Darwin Among the Machines” is as much a work of history as of speculation. In a phone interview from his kayak repair workshop in western Washington state, Dyson himself called it “a catalog of beginnings.” Dyson explores the roots of computer design, of distributed networks and of the very concepts of artificial intelligence and even evolution.

It’s a sound strategy. Just attempting to define terms such as “life” or “intelligence” can confound the most brilliant of minds. Since, as Dyson notes on several occasions, the only thing that can truly describe a complex system is the system itself, it makes sense to focus one’s attention on first steps, rather than the goal line.

“You can only sort of hint at things,” says Dyson. “How do you explain the explanations? You have to rely a great deal on analogies … But what it all comes down to is that the more we understand about the way our brains work the more we find that evolution has a lot to do it.”

And we also find, when we start at the beginning, that there is nothing new under the sun. From the earliest days of evolutionary theory, Dyson shows, fascinated observers speculated on the possibility that the same evolutionary laws that determined natural development might also shape emergent machine intelligence. As early as 1865, Charles Darwin’s contemporary Samuel Butler wrote that “although we grant that hardly any mistake would be more puerile than to individualize and animalize the at present existing machines … yet we can see no a priori objection to the gradual development of a mechanical life, though that life shall be so different from ours that it is only by a severe discipline that we can think of it as life at all.”

From Butler onward, Dyson traces the history of the notion that it’s possible to bridge the gap between nature and machine. It’s all a matter of changing one’s frame of reference.

In Dyson’s view, complex living organisms evolve out of the symbiotic
cooperation of simpler organisms — “symbiogenesis.” Symbiogenesis “assumes
that the most probable explanation for improbably complex structures
(living or otherwise) lies in the association of less complicated parts.”

“All intelligence is collective,” writes Dyson. “This intelligence –
whether that of a billion neurons, a billion microprocessors, or a billion
molecules forming a single cell — arises not from the unfolding of a
predetermined master plan, but by the accumulation of random bits of wisdom
through the power of small mistakes.”

The Net is the ultimate forum for collective intelligence, as well as
for unlimited experimentation. It has long passed the point, as a complex
system, at which it could be definitively mapped or succinctly summed up.
And every signpost points the way to increasing volatility — toward an
environment in which increasingly mobile and autonomous conglomerations of
code migrate from node to node, constantly mutating and reshaping
themselves in response to circumstantial demands.

Just as natural selection resulted in the range of highly adapted
species existing in the world today, so too will evolutionary pressure
ensure that tomorrow’s mobile code exhibits capabilities that will astound
and baffle us. Indeed, the packet-switching protocols of the Net itself
are, writes Dyson, a “particularly virulent strain of symbiotic code …
Successful code is now executed in millions of places at once, just as a
successful genotype is expressed within each of an organism’s many cells.
The possibilities of complex, multi-cellular digital organisms are only
beginning to be explored.”

The possibilities are not confined to digital limits, either. “The Net
wouldn’t function for a minute if there weren’t all those people sitting at
their desks,” says Dyson.

The Net is as much flesh-and-blood as it is chips and fiber optics.
Humans are indispensable to the new intelligence equation. The emergent
collective intelligence isn’t just hardware and software — it includes us.

And why not? If all of life up to now has been a series of ever more
intricate joint ventures, who is to say this latest synthesis is
unworkable? The principle has been well illustrated; all that’s changed is
the speed at which it can all happen.

“The cooperation between human beings and microprocessors is
unprecedented, not in kind, but in suddenness and scale,” writes Dyson.
“Now, in the coalescence of electronics and biology, we are forming a
complex collective organism composed of individual intelligences.”

Some humanocentric nativists might well be dismayed at the prospect.
They wouldn’t be the first to eye the yoke of the machine with suspicion.
Again, Samuel Butler staked out the territory. In an 1863 essay titled
“Darwin Among the Machines,” Butler noted that “the machines are gaining
ground upon us; day by day we are becoming more subservient to them; more
men are daily bound down as slaves to tend them; more men are daily
devoting the energies of their whole lives to the development of mechanical
life.”

Submission to the machine — from “Frankenstein” to “The Terminator,”
it’s a recurring nightmare. But from Dyson’s symbiogenetic perspective,
Butler misses the point. We’re not necessarily bound to become slaves, but we
could well be partners. We’re all in this together. There is no Net without
humanity, no global intelligence without cooperation.

We could have an important role to play. Then again, we could be written
out of the script.

“For the single-celled organisms, the advent of multi-cellular
organisms, such as the nervous system, was the end of freedom,” says Dyson.
“We’re at that stage now. Whether it is good or bad completely depends on
how you look at it.”

“Sure, we feel threatened,” he adds. “We’re loyal to our own life form.
Americans feel threatened by foreigners, Earthlings feel threatened by
Martians, and protoplasmic forms of life ought to feel threatened by other
forms of life.”

The real danger is not necessarily that machines will grow too smart but
that human intelligence may atrophy. Evolution isn’t necessarily on our
side. Just because we are intelligent now doesn’t mean that we always will
be. Even as we get subsumed into a greater intelligent cooperative,
individually, we may become dumber.

Evolution, argues Dyson, moves forward by constantly dispensing with
unnecessary baggage. He is fond of pointing out that human babies are born
with more neurons than a fully grown adult. As they grow older, they shed
irrelevant neurons, while reinforcing the connections and neural pathways
that make sense.

From babies, Dyson jumps to kayaks. It seems his true passion is
repairing Inuit watercraft. It’s part of a struggle to ensure that the
human race doesn’t get dumber. “There’s a 10,000-year-old tradition
of kayak design which is in danger of being lost,” he says. “I want to
prevent that if I can.”

“To build a kayak,” he writes, “you assemble a skeleton and then give it
a skin that allows it to float, just as the architectural framework of a
computer is fitted, by evolution or by design, with an envelope of code. To
build a dugout, you grow a tree and then remove everything, one chip at a
time, except the boat. This is how nature creates her intelligences, by
spawning an overwhelming surplus of neurons and then selectively pruning
them to leave a network that, if all goes well, becomes a mind.”

The Net is a new spawning ground for software code proto-neurons. There
is no limit to the possibilities it may engender. But we should beware lest
our own intelligence, through willful ignorance or simple inaction, becomes the
part that gets pruned.

It’s de rigueur for women in country music to declare in song after song that no man, no thwarted love affair, no crumbling marriage can get the better of them. Vulnerability is permissible if it ends with the singer realizing that, gee, she turned out to be stronger than she thought she was. The sound of country music right now — the arrangements sweetened with strings, the preponderance of mid-tempo ballads — derives from country’s early-’60s “countrypolitan” makeover, a fagade of nouveau respectability designed to forever banish images of hicks and hillbillies from the minds of pop music fans. One contemporary performer, Bobbie Cryner, on last year’s “Girl of Your Dreams,” a tough set of songs about the compromises of married life, used the slickness of current country to turn the empowerment ethos on its head. For the most part, though, we’re talking about a genre whose current finest practitioner, Alison Krauss, is considered too country for country radio.

All this may explain why listening to Martina McBride’s fourth album, “Evolution” (RCA), is such a schizophrenic experience. Here’s a set of empowerment songs delivered by a singer with the chops — and, more importantly, the passion — to plumb romantic loss and confusion and resentment. McBride may be capable of more genuine emotion than any female singer working in country pop right now. Just hearing them, I couldn’t tell Tricia from Shania from Deana if they up and bit me in the John Deere. Even at her most slicked-up and professional, McBride has the simple ability to never sound less than a real person. The numbers are typical Nashville hit-factory fodder, the band trades in Adult Contemporary Country Licks 101 (Biff Watson’s acoustic guitar work, like a loaf of home-baked bread that mistakenly wound up on the shelf at the Qwik Mart, is a notable exception), and still McBride doesn’t sound like she’s phoning it in. And she’s one of the few female singers in any genre of Adult Contemporary Pop who doesn’t show off with vocal gymnastics. When McBride wants to express a rising emotion, her voice simply gets bigger and freer. That’s what happens on “Broken Wing,” a testament to how an emotionally committed performance can transform a trite central metaphor.

McBride’s voice can get you listening to songs you’d otherwise avoid like the plague. It took about five listens for me to realize that “Happy Girl,” with its lyrics about giving up the party crowd and letting your soul break free, is a piece of dread Christian Contemporary pop — I was hooked by the forthright ebullience of McBride’s vocals. And “Keeping My Distance” is the good side of female role-model country. There’s no nonsense, no suffering in the way McBride tells the guy she’s singing to that she’s going to stand her ground until he gets his shit together. There’s even a sexualized challenge in the hard way she asks, “Will you ever try anything new?”

But that same sensibility is what demands an upbeat ending be grafted onto “Wrong Again.” There’s an unforced ache to McBride’s vocal on this number. She’s singing as a woman who’s tried to remain optimistic about her crumbling marriage (and there’s enough ambiguity in the way she sings, “It’s somethin’ that each man goes through” that she could be singing about infidelity or impotence) only to end each verse with the realization “wrong again.” Of course, what she has to be proven wrong about in the last verse is her certainty that she’ll never find anyone who loves her for her. See, this little object lesson of a song says, you’re much stronger than you thought you were, and it makes hash of the emotion that’s gone before. It may be more adult, more well-adjusted to sing, “Let’s learn to give/let’s talk things out” as McBride does in “Some Say I’m Running,” but it can’t hold a candle to “Let’s say things we’ll regret, smash up the furniture, screw like bunnies and hate ourselves in the morning.”

It may be that McBride will never match her 1995 hit “Independence Day.” The story of a woman remembering the Fourth of July fire that killed her abusive drunk of a father and the mother that set it to escape him, “Independence Day” was one of those performances that called everything into question. There was irony and bitterness and triumph and unresolvable contradictions in the way McBride opened each chorus with the declaration “Let freedom ring,” acknowledging both the cost of freedom and the lip service America pays it. By querying the bedrock patriotism that country music rests on, McBride even called into question the music itself. Like the punks did with rock ‘n’ roll, she was asking how country served to reinforce the oppressive structure she was decrying. “Independence Day” was a black hole of a song, sucking in everything that surrounded it on the radio. The independence celebrated on “Evolution” is false independence, depending on an enforced restriction of the emotional palette. The album’s irony is that you can’t detect any falseness in McBride’s singing. “You think I’m always makin’/Something out of nothin,’” she sings on “Whatever You Say.” And that’s the success of “Evolution” — the aftertaste is the knowledge of how McBride has made somethin’ out of somethin.’