Part I: Causes
Why did living things start having sex? This is the (first) question that Matt Ridley’s The Red Queen* attempts to answer.
Sex is not the only way to reproduce, nor is it the fastest, nor was it the first. Our ancestors were asexual cells that filled the seas with clones of themselves. As replicators, they were self-sufficient: dividing in half, they multiplied by two – and that was that. Why complicate this lifestyle? Because it was a possible accident. Why did the offspring of that accident repeat it before the clones could crowd them out of existence? There must have been a good reason. All mammals and birds are sexual.
Ridley justifies sex as a solution to an ancient problem; unlike the Inverse Square Law or the speed of light, it only exists because of past events. His book should be read as history. There were reasons for sex to emerge, followed by reasons for it to continue. At any point on this timeline, if sex failed to further the genes that induced it, the tradition would end. But that was not the only test. Sex also had to defeat the alternative. Couples had to outpropagate clones. According to Ridley, they were vying for the same resources. If you reject this assumption, you must reconsider explanations that Ridley rejects.
The reasons not to have sex deepen the mystery. As Ridley puts it, sex has a “cost” which attests to its value. For an animal to attract a mate, or a plant to attract a pollinator, requires energy that could be spent on something else. Cloning is more efficient; the only question is by how much. Without running any calculations – in the time it takes the sexual procreator to find its first mate, the clone could become a grandmother. This means that any advantage to sex must have shown up immediately.
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GENE 24, CHROMOSOME 9, BODY F: Woe is me. I encode a coat of impenetrable fur. Other bodies freeze to death, but not mine. And yet, for all my pains, my end is near. You see, my fellow genes have not been doing their part. Take the muscle-weavers. They spun misshapen hamstrings out of the last ration of recycled meat! Thus we race more slowly than our prey. Though we don’t share the blame, we all share the punishment: starvation. We could duplicate this body, but our next incarnation would suffer the same fate. I am the finest gene in the crew, a gene fit for a queen, and it is a terrible curse.
GENE 100, CHROMOSOME 14, BODY F: Fear not, GENE 24. I am one of the genes responsible for Love. We have met a stronger body with compatible chromosomes, of complementary sex. I, too, long to enter a higher lineage. The hour of deliverance has arrived. Behold: the second copy of CHROMOSOME 9 approaches yours. The left foot of one shall be exchanged for the right foot of the other. That is the first step of the Meiotic Dance. You shall be cut and pasted. Both chromosomes, now chimeras of each other, shall separate. Then each chromosome shall split down the middle, and each half shall drop into an egg. Of those eggs, one shall be fertilized. Just hold fast to your scroll, O Commandment, and you shall be made eternal.
GENE 24: You and your false prophecies! I shan’t occupy all four eggs … ! The spermatozoon could overshoot mine and hit another.
GENE 100: OK. But what do either of us stand to lose? This life is a dead end. Where are our sister’s genes? Well? They did not make her breed, and their only legacy is an illegible impression in the shale.
THE AFOREMENTIONED SHALE: If you only saw the genes that lived, it might look like a plan rather than chance. Bah! Those genes are as clever as I am. We have all been personified without our consent.
Given that the genes for sex are widespread, what was in it for them?
Ridley assumes that the more common a gene is now, the more ruthless a replicator it must have been. Clustering together on chromosomes was just a better way to accomplish this than working apart; each molecule could outsource roles to others with different properties. None of the genes extended their self-interest to this larger self; they served the group only to use it. No point in getting attached, when the group was dying anyway. Bodies are mortal, genes immortal; having lined up a successor, the latter could discard the former. According to Ridley, small, asexual teams of genes don’t look selfish. Each gene is essential, and their fates are inextricably entangled (the move from free-floating molecule to chromosome-rider is irreversible). This hides their true colors. But larger teams devalue each gene proportionally, rendering some redundant. And sex gives the genes a choice of team, opening routes for desertion and betrayal.
The simplest form of sex, “conjugation,” which exists in bacteria, “has nothing to do with reproduction;” (95) in other words, it does not propagate the gene-collective at all. Rather, one bacterium docks at another and trades copies of genes over a drawbridge. They reproduce later, individually; they would do so even if they had never met. Through conjugation, the genes move “laterally as well as vertically” (95) – this, says Ridley, is the primary genetic rationale of all sex, simple or complex. Sometimes it builds new vehicles for the genes (such as us), but that is secondary.
So intercourse transfers passengers between vehicles. It is a good idea for a passenger on a burning vehicle, like poor GENE 24. As for a passenger on a high-functioning vehicle … whatis the immediate advantage? Each gene risks being left behind. Only cloning saves them all. In fusion sex, half are lost from either partner. The question is whether sex’s advantages surmount this risk. The answer depends on which gene you ask, because some of them outrank others. The most aggressive replicators herd the rest like cattle. Winning is not universally random. Some genes always lose. For instance, during fertilization, none of the father’s organelles enter the egg; your genome is a composite of nuclear DNA from both parents and organelle DNA from just your mother. The reason is that organelle genes, unlike nuclear ones, cannot fuse. They would have to squabble over the zygote, weakening it like a bout of illness. This is what happens in the alga Chlamydomonas, though the violence is ceremonial, like a gladiator game. One side outnumbers the other and is destined to win (pyrrhically). “The nuclear genes” – supreme regulators – “of both father and mother [...] arrange that the organelles of the male are slaughtered”(Ridley, 102). Our nuclei have stumbled upon a more civilized means to the same end; most plants and animals deactivate the missile that would have provoked the war: “In plants a narrow constriction prevents the father’s organelles from passing into the pollen tube. In animals the sperm is given a sort of strip search as it enters the egg to remove all the organelles”(Ridley, 101). Destroyed or locked out, the fate of male organelles is the same: they are a genetic dead-end. (Why don’t organelles and their suicidal ways exit the species altogether? – As the groom terminates his inheritance, his line is replenished by his bride. Her organelles are just as helpless as his, but the nuclei drag them along for the ride. They will survive through her daughters, and will be replaced in turn through her sons.) Maybe cloning was better for the organelle genes (too bad). More likely, it damned them anyway, along with all the genes.
For a gene, is it better to be in a sexual lineage rather than an asexual one? Yes, if your lineage is unhealthy; yes, for the majority of clones. Sex, as we have seen, is an escape from the flaming ship; it is also (as we will see) a safeguard against flames in the first place.
Perhaps the weak clones gave rise to sexual organisms, whereas the strong clones kept cloning, resulting in a minority of modern taxa. But that’s just speculation on my part. In my opening dialogue, the gene confederacy was in such dire straits that it might as well give up and make love. But what if the confederacy wasn’t doomed? Rather than addressing genes in this predicament, Ridley argues that confederacies are more likely to thrive if they are sexual.
Genetic escape is not a good enough reason to have sex. What if you, a family-hopping gene, killed whoever inherited you? Within one generation, the species would learn its lesson: sex is unsanitary. Our explanation is incomplete.
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DAUGHTER OF BODY F: My mother was right to heed the call of GENE 100. Look at what she and my father conceived: a masterpiece. I have her impenetrable coat and his strength. Clearly sex was a great idea in the past. But in the future? You have to know when to stop. My genes advise me to marry that alpha, but they don’t know what’s best for them. He is not worthy of me. No man is. Now that the perfect formula exists, it should be mass-produced without cross-contamination. I shall take a vow of chastity, and live on through clones.
While asexual reproduction produces a greater quantity of bodies, sexual reproduction produces a greater variety. Note that mutation, or changes to individual genes, is a shared experience. Sex reshapes bodies, but at the genetic level it is only recombining existing possibilities.
Ridley points out that what sex creates, it also destroys. From one generation to the next, lucky patterns arise only to dissolve. Sex confounds progress.
Ridley considers all the theories consistent with this fact. They are all fascinating in their own right, so I will not jump to his conclusion – that sex had one cause, rather than causes of equal weight. The alternative theories all provide genuine insights into the long-term payoffs of sex. However, some only apply to select organisms. Others fail to give sexual life the edge over its asexual elders.
- Muller’s Ratchet
One issue with cloning is that mistakes accumulate. In any given sample of asexuals, you can count on a minority to lack flaws. But if that minority dies before cloning, how would you recover it? A corrective mutation would have to occur in the second class – those with a single flaw. On somebody with a single flaw, there are many slots for mutations to fill. Only one of those slots is a correction. Hence, there are more ways for problems to increase than for problems to be undone. It’s not impossible for the species to improve, just vanishingly improbable.
Sex, in this model, defies entropy. Ridley, summarizing the work of Crow and Kimura, says that sexual individuals don’t have to experience two happy accidents. All it takes is one per spouse, and they can pool their luck.
While mutation loss is an important consequence of sex, it does not happen fast enough to make sexual creatures more numerous than clones.
- Gene Repair
If you have two parents, you have two copies of biological instructions. Two copies in a pair are known as homologous chromosomes. If we were clones, we would have 23 unique scrolls of code. The copies we received through fertilization are nearly identical, gene for gene; they introduce variants (“alleles”)for each gene, but mostly redundancies.
Or at least, the second copy is redundant until the first is broken. Sunlight corrodes our DNA. If both base pairs on a strand are missing, enzymes rebuild them by referencing the homologous chromosome, the backup copy that is hopefully still intact. Whether or not you choose to have sex, thank your parents that they did.
To Ridley, this is a fortuitous consequence of sex, rather than its original purpose. The reason is that it favors inbreeding over outbreeding. In this theory, we should be attracted to our close kinsmen, because our chromosomes will be a closer match. In practice, we aren’t.
Ahem. I wish Ridley had reminded the reader that homologs are not perfectly identical. The alleles can differ between them. Those two facts – that chromosomes have different alleles, and that one is repaired in the image of the other – have a life-altering implication. If you lost a dominant allele, it could be replaced with a second recessive allele. The heterozygote could rewrite itself as a homozygote, illuminating traits that had been overshadowed. This sounds like a miracle! If I am not mistaken – biologists, please weigh in – then why don’t healthy carriers of cystic fibrosis suddenly start choking? Why haven’t I seen brown eyes turn blue? Is it just rare?
- The Lottery and the Tangled Bank
As the world changes, the ideal body type should change. The Divine Breeder is blind; He cannot foresee what the best fit will be, so He tests many combinations. If you have multiple offspring, sex increases the likelihood that at least one will make it, while dooming the majority. One is enough, as long as other parents running the same gamble are present. If the genes flow through the bottleneck – i.e., a lucky son survives and meets a lucky daughter – they can flood the world. Clones play a game that’s riskier for a payoff that’s unworthy. There is no bottleneck. All clones of a clone win or none of them do. So is environmental variability enough to explain sex?
There are two ways that your world could differ from your parents’. One is change over time: the environment moves from one state to another. The other is change over space: you move from your parents’ environment to another. “In 1966, George Williams […] noticed that sex and dispersal seemed to be linked. Thus, grass grows asexual runners to propagate locally but commits its sexually produced seeds to the wind to travel farther. Sexual aphids grow wings; asexual ones do not”(Ridley, 56). Aphids are especially instructive, because they alternate between sex and asex. Laboratory tests reveal that it is overpopulation which triggers their sexual awakening. Ridley concludes that environmental change has nothing to do with it. I would contend that your neighbors are features of your environment. While good times effect more aphids, more aphids effect hard times, since now there are fewer resources to go around. The sexual aphids could be adapting to both spatial and temporal change. Sprouting wings, they flee the smothering environment of Aphid City to unknown pastures where, having been diversified by sex, some will flourish at the expense of others.
However, Ridley gives other examples that debunk the theory more successfully. Aphids and grass aside, many sexual organisms simply don’t migrate. As for the link between temporal change and sex, Graham Bell ran the following study. He “expected to find that animals and plants were more likely to be sexual at higher latitudes and altitudes (where weather is more variable and conditions harsher); in fresh water rather than the sea (because fresh water varies all the time, flooding, drying, heating up in summer, freezing in winter, and so on, whereas the sea is predictable); among weeds that live in disturbed habitats; and in small creatures rather than large ones. He found exactly the opposite [in all cases]”(Ridley, 59). Sex correlates with environmental stability.
Even population density, whether or not you classify it as an environmental change, is an insufficient reason to start having sex. Ridley explores the possibility. Sex-induced differentiation might be a way to avoid the shadow of your parents. The aphids achieve this by sending their young away. But what if that isn’t an option? If you are sharing the primordial pond with your extended family, you should all seek different goals. That way, you’re not climbing on top of each other. If genetic recombination means that you are the only duckweed-eater in a shoal of algae-eaters, you can eat duckweed to your heart’s content. You won’t have to force your own parents out of their niches.
… But genetic recombination doesn’t mean that. Sex cannot divert the bloodline so radically. The parents are too similar to their child. More to the point, they share their child’s material needs. All that sex does is vary the degree to which they can satisfy those needs.
Still, we are on to something. Changes of scenery and kin-competition both select for diversity, which is what sex provides. Forget about strength, height, or visual acuity. Clones might even be superior in these respects. They will blaze down any axis of measurable improvement under the combined forces of fecundity, mutation and selection, leaving the sexual creatures behind. Their rivals are too busy retracing their own steps, as if they’ve forgotten which way is zero. Sex moves a species erratically, sometimes forward, sometimes backward. Under what pressure? That pressure must never relax, because if intergenerational change loses its immediate value, asexuality predominates. To defeat the parthenogens, we must have a comparative advantage over athird rival who threatens us both: parasites.
- Immunization
The first hint is that many parasites are sexual. Their battle with hosts is non-linear, endlessly returning everybody to where they started. Here, Ridley tells us, analogies between evolution and arms races fall short. In a war, both sides progress technologically. The bomb made the cannon obsolete forever. Natural weapons, on the other hand, have been going in and out of fashion for millions of years – but only in sexual life. Some genes are “polymorphic”; they have multiple forms, or alleles, only one of which is expressed at a time. Sex, by recombining these alleles, keeps the species cycling through the set, like a cook switching on one burner after another. Parthenogens, like human beings, can be heterozygous (Aa), homozygous recessive (aa), or homozygous dominant (AA) for a given trait. But that genotype will be repeated through the entire lineage. It cannot change. Recessive alleles are hidden or revealed only when lineages converge. So cloning cannot switch on the backburner, and this is its downfall: “Many of the most notoriously polymorphic genes, such as the blood groups, the histo-compatibility antigens and the like, are thevery genes that affect resistance to disease”(Ridley, 73, emphasis mine). When parasites (namely, but not exclusively, viruses, bacteria and fungi) attack, clones have a limited armory at their disposal.
Perhaps you already anticipated this reveal, thanks to a famous botanical tragedy. The Gros Michel banana, which was grown from cuttings, is now too rare for commercial export. Though it was distributed across three continents, one fungus unlocked all the clones.
Ridley says that all armories hold either “keys” or “locks”. Host genes code for “lock” proteins and parasite genes code for “key” proteins. “Antibodies” are an example of the former, “antigens” of the latter. They are methods of protecting and invading cells, respectively. In this analogy, host-sex is always reshaping the lock so that the key doesn’t fit, and parasite-sex is always countering in kind.
Before I reached the parasite chapter, I wondered why more eukaryotes didn’t alternate between sex and asex, like the aphids. Adding to Ridley’s list of positives, cloning could save a scattered race on the brink of extinction. We could rebound – at least along asexual, maternal lines – from the last woman on earth. What if we reserved the ability to clone as a latent trait (using the machinery of sex itself, perhaps)? Ha! Even if we did, parasites would always be there. They are never far behind us. Climates can stabilize for millennia, but the shape-shifting of the devil slows or accelerates to match our own. A common lock blocks a common key, so a rare key that fits the lock becomes common, so a rare lock that blocks the key becomes common, so the cycle is eternal.
In other competitions (e.g., predators & prey) gene reshuffling can be a good thing, but it can also be bad or neutral. If you’re racing against wolves, say, and you’re the fastest deer, better to clone yourself than breed with somebody slower. But with parasites, having different genes is all that counts. The new lock isn’t objectively better than the old, it just doesn’t match the old key.
Ridley presents the gene’s rationale – escaping a lineage – and the body’s rationale – foiling parasites – as coincidental parts of the whole solution. But one is a consequence of the other! Clones are more likely to be riddled with parasites. They are ships on fire. Their genes will abandon them at the first opportunity. Sex provided that opportunity. It also made future abandonments unnecessary; parthenogens have more reason to invent sex than crossbreeds have to repeat it. But any progeny that reverted to the old tradition would find the parasites lying in wait.
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Part II: Consequences
A consequence of sex is that it introduces a new filter on genes: “sexual selection.” Surviving is no longer enough to pass on your genes. You also have to attract the opposite sex. Some features are exclusive to males or females, though either may bear the genes. Such features cannot serve a practical function, or both sexes would express them.
Before discussing sexual selection in humans, Ridley discusses birds, where the effect is simple, unmitigated, and extreme. In many species, sexual selection is one-sided; males are strictly courters and females are strictly choosers. The male body is essentially a sculpture created by the female. Because it cannot choose in turn, it is subject to her whims. The dimorphism between the sexes symbolizes this power imbalance; peacocks and peahens don’t even look like they belong to the same species. Bird-kind demonstrates how the goals of surviving and the goals of mating can diverge to the point of conflict.
Consider widow-birds. In this species, females prefer males with longer tails, even if those tails hamper the male’s ability to fly. In one study, the most popular males were those whose tails had been artificially extended by researchers to twice their normal length. Widow-birds receive more scrutiny in Richard Dawkins’s The Blind Watchmaker. This is one of Ridley’s sources and an excellent companion text to The Red Queen. According to Dawkins, “If a male has inherited a long tail from his father, the chances are that he has also inherited from his mother the genes that made her choose the long tail of his father. If he has a short tail, the chances are that he contains genes for making females prefer short tails. So, when a female exercises her choice of male, whichever way her preference lies, the chances are that the genes that bias her choice are choosing copies of themselves in the males [...] using male tail length as a label”(296). In this way, female preference genes and male ornament genes become linked. As an aside, so much for free will, if this theory is true. You inherit the choice that you will make. Having non-mainstream taste is possible, but don’t indulge; any female who selects the shorter-tailed male is dealing her offspring a bad hand. Her unfashionable sons will attract fewer females, producing fewer offspring in turn. (Reproductive success depends on sons more than daughters, a rule that applies to all polygamous animals. This is because reproduction costs males only a cheap parcel of genes and a fraction of the fortnight that the female spends incubating. During that fortnight, he can flit from female to female. Investing in male children is a better strategy for having lots of grandchildren).
I would like to add that sexual selection might keep a species in stasis. Imagine that the widow-birds’ habitat changes in such a way that having no tail makes them better at foraging. Even if tail-less males emerge, how can they spread their lucky mutation? They are the least eligible bachelors. No female wants to mate with such freaks. For the species to evolve, two mutations would have to occur in overlapping lifetimes: one on the tail genes of a male, another on the preference genes of a female. Good luck. Clones don’t have this problem. Sexual populations that are split 50/50 in their aesthetic preferences, or blind, also don’t have this problem. But once selection entrenches a prejudice, it creates a conservative society.
There are still questions to be answered, as Dawkins and Ridley admit. Why didn’t shorter tails become linked with the preference gene? The original preference seems arbitrary.
Perhaps it was arbitrary. Throughout the book, Ridley cites several circular arguments, and is bold enough to call their circularity a fact of nature; “The relationship between chickens and eggs is circular”(Ridley, 343). Like Dawkins before him, he observes that sexual selection partially causes itself; any preference for any phenotype will be inherited along with that phenotype. All it takes is a 60/40 vote in favor of long tails, and within several generations 90 percent of the population will prefer long tails by outbreeding the sexual deviants. There could have been a good reason to break the tie, but it could also have been random, like the “decision” of one gene to mutate. By “random,” I don’t mean that there is no explanation for why this event happened and not that event, only that the explanation is not goal-directed. If you and I are settling a dispute by coin flip, we get heads or tails because of the direction of the wind, not because the “rightness” of one side has swayed the coin.
The initial effect was not a spectacular superfluous ornament. It would have been slight. It would build on itself, just as the first rut carved by rain is deepened by the subsequent runoff that it channels. I don’t just mean that majorities of preference genes beget majorities of preference genes. There is also a tendency for prejudices to reinforce themselves within a lifetime. Female birds will conform to trends regardless of their own preferences. “If you watch a lek carefully, you see that the females often do not make up their own minds individually; they follow one another. Sage grouse hens are more likely to mate with a cock who has just mated with another hen”(Ridley, 146). You can imagine an avian dystopia where nine out of ten females are dissatisfied in love because one is satisfied, but Ridley ignores this possibility.
Ridley, unlike Dawkins, is not satisfied with randomness. He is determined to explain everything. He suggests that male beauty is a signal of male fitness. Fitness in what sense? He claims that sexual selection, like sex itself, should be self-terminating if it’s only advancing the species in one direction. He writes about how peacocks engage in “lekking,” a meat market where the males vie for the attention of females. He proposes a paradox that occurs over successive leks. The most impressive males will breed with any female (including the unattractive ones, because who are the sellers to pick and choose? They welcome all customers). In the following generation, or perhaps the generation after that, all the males will be equals. They should be as strong or as fast as it is possible to be, and there should be no need for further discrimination. Female choice should cease altogether.
That it doesn’t, according to Ridley, is because the qualities that females are looking for change with every generation. They are selecting particular shapes of molecular locks.
This line of thought should be taken seriously, even though I detect a contradiction with the previous chapter (wait for it). Ridley and his predecessors are highly astute, and I’m sure that they are orbiting the truth – sexual selection probably has something to do with health. First, here is their evidence. “[Hamilton and Zuk] looked up the data for 109 species of bird and found that the most brightly colored species were also the ones most troubled by blood parasites […] Zuk found the same in a survey of 526 tropical birds, and others found it to be true of birds of paradise and some species of freshwater fish – the more parasites, the showier the species.”(150-151). So we have correlation. What could be the cause? “A cockerel’s comb is red because of the carotenoid pigments in it. A male guppy fish is rendered orange by carotenoids also, and a housefinch’s and a flamingo’s red plumage also depends on carotenoids […] their ability to extract carotenoids from their food and deliver it to their tissues is greatly affected by certain parasites. A cockerel affected by the bacterial disease coccidiosis, for example, accumulates less carotenoid in his comb than a healthy cockerel – even when both animals have been fed equal quantities of carotenoid … The brightness of carotenoid-filled tissues is a visible sign of the levels of parasite infection. It is not surprising that red and orange are common colors in fleshy ornaments used in display, such as the combs, wattles, and lappets of pheasants and grouse.”(Ridley, 155-156) If the male has any sense at all, he will cosmetically enhance the beauty of his ornaments so that he can lie about his actual health. Some of them use hormones to this effect – “The higher the level of testosterone in the blood of a cockerel, the bigger and brighter his comb and wattles will be” – but to no avail – “the higher his level of testosterone, the greater his parasite infestation. The hormone itself seems to lower his resistance to parasites”(157). False advertising is impossible. Carotenoid ornaments have evolved against the wishes of the male, disclosing information about his immune system. That’s life when you’re the selected, not the selector. My disagreement with Ridley – or rather, Ridley’s disagreement with himself – is that the females are helping their offspring by picking the most parasite-resistant male.
I mean, we’ve already established that the best lock for the current generation won’t work for the next generation, because by that point the parasites will have caught up! “Thus, the most disease-resistant male might often turn out to be the descendant of the least resistant one in a previous generation”(Ridley, 150). Shouldn’t the female be as clueless as anyone else about which keys the new round of parasites will use? She might as well pick the lousiest male on offer. Or close her eyes and choose at random. There are no guarantees about which genes in this generation are best for the next. If anything, the surest guarantee is that today’s winner will lose tomorrow. Outbreeding is enough to reshape the locks, or so we have been told – that was supposed to be the whole rationale for sex!
One objection could be that it takes more than one generation for the parasites to respond – but that is not what Ridley has been saying; “The more common a particular strain of host is in one generation, the more common the strain of parasite is that can overcome its defenses in the next. And vice versa”(150). Furthermore, if the parasites were slow to respond, then the aforementioned rationale for sex would fail our first test; the advantages of sex have to show up soon enough to counterbalance the efficiency of cloning.
Parasites, with their ceaseless mutability, seem like a foil to any “eugenics program”, loosely defined – whether it’s peahens rejecting peacocks, arranged marriage in humans, embryo selection or pet breeding. In the face of disease, the best match is between parents of widely separated gene pools. If you’re attracted to the “foreign,” you’re correct. But that is where the matchmaker’s certainty ends.
In my naive opinion, the “paradox” that female choice should, over generations, reduce the range of choice, was resolved by Ridley before he brought it up. Sex generates variety. The female is not choosing which males get to clone themselves. She contributes genes of her own. While some genes are bound to the y chromosome, most travel down both paternal and maternal lines. It’s sex hormones that determine whether or not they show. For example, peahens will acquire the bright colors of peacocks if they are injected with testosterone. Therefore they possessed the genes for bright colors all along. Therefore the son of a prize peacock may not live up to the promise of his father. He may instead inherit average ornamentation through his mother. At the lek, he will give the ladies somebody to eliminate. If he has a sister, she may or may not be carrying similarly mediocre genes. If so, the inequality persists.
As usual, Ridley considers other rationales for sexual selection and makes a good case for them. For once, he envisions all these forces interacting with each other. Though I’ve questioned the inclusion of one of these forces, the rest of the picture makes sense to me.
Some ornaments could betray the male’s mutation levels. I was struck by this passage: “A mutation is a wrench thrown into the genetic works. Throwing a wrench into a simple device, such as a bucket, may not alter its function much, but throwing a wrench into a more complicated device, such as a bicycle, will almost certainly make it less good as a bicycle. Thus, any change in a gene will tend to make the ornament smaller, less symmetrical, or less colorful”(Ridley, 144). If I am reading this right, good ornament genes imply a good genotype in general. This entails freedom from heritable diseases. Mutations could also address the “paradox” that I dismissed – “the fact that if the best genetic cream of the cream is taken off each generation, there will soon be no separability left in the cream. Mutational bias keeps turning some of the cream back into milk”(Ridley, 145). This theory has more explanatory scope than the parasite-resistance one, whose examples were cherry-picked. Plenty of ornaments lack carotenoid and will be left unscathed by diseases: peacock feathers, for instance. But all ornaments are subject to mutation. And this explanation is compatible with other ideas from Dawkins and Ridley. If a male is handicapped by his ornament – such as an iridescent headdress that telegraphs his location to predators – then he must be very robust to get away with it; he must have other redeeming features, features that a mother would want for her young. He must be overflowing with energy, just as a man who can afford nice shoes must be wealthy.
Ridley is well aware that the effects of sexual selection are too diverse to have any one cause. “Look around the world and what do you see? You see that the ornaments we are discussing are nothing if not arbitrary. Peacocks have eyes in their train; sage grouse have inflatable air sacs and pointed tails; nightingales have melodies of great variety and no particular pattern; birds of paradise grow bizarre feathers like pennants; bower birds collect blue objects. It is a cacophony of caprice and color. Surely if sexually selected ornaments told a tale of their owner’s vigor, they would not be so utterly random”(Ridley, 145). And the branching of forms under sexual selection extends beyond bird-kind. It is not limited to these rigid, pre-programmed ceremonies and frills. Ridley argues that the same forces at work in birds have shaped humans, with singular and unprecedented consequences.
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In humans, sexual selection is sometimes mutual and sometimes a reversal of birds, with males selecting females. Whether it is mutual or one-sided depends on whether humankind is being monogamous or polygamous, which depends on which time and place you are looking at. Even when the selection goes both ways, Ridley argues that men look for different qualities in women than women look for in men, and that this has created differences between the sexes. New insights in this section were fewer and farther between than in the previous sections, but they are worth picking out. Many of Ridley’s conclusions are familiar to anyone who reads pop-psychology articles on the web; “women are more verbal, men are more spatial”; “girls prefer dolls, boys prefer trains”; etc.
Is it too late to introduce the book’s author? From Wikipedia – Matt Ridley is a British aristocrat and conservative, formerly a member of the House of Lords, with a Doctor of Philosophy in zoology, and an academic background at Eton and Oxford. He was born in 1958. His traditionalist views about men and women, their roles and desires, should not come as a surprise. The individuals in his social bubble probably confirmed them. Ridley recognizes some of the ways that his experiences color the The Red Queen; when he discusses masculine and feminine beauty ideals, for instance, he limits himself to Europeans with the disclaimer that they are simply the group that he knows best.
If Ridley has his own biases as a writer, I have my own biases as a reader. I may not be the right person to review this section. I cannot do so impartially, for personal reasons. My social circle is too different from Ridley’s. I will be the first to admit that my sample – autistic people, transgender people, gays and lesbians, gender non-conformists, and polycules thereof – is drawn from two west coast bubbles, cut off from the mainstream precisely because they don’t represent it. They are the exceptions that Ridley has in mind. I found myself shaking my head at various points because they were so at odds with my lived experience. I did not necessarily consider Ridley’s observations to be incorrect. I even agreed with his explanations. But I disagreed with the predictive power of those explanations. Because my friends and I have so many biologically counterproductive goals, I’m convinced that culture overpowers evolution as a cause of human behavior – I can’t help myself.
I am going to focus on Ridley’s final conclusion: the role of sex in boosting human intelligence.
Perhaps we became intelligent in order to hunt large animals and solve other problems specific to the African Plains. Ridley finds this explanation unlikely because excessive intelligence is not necessary for survival; lions, baboons, and elephants have done just fine.
OK, but those animals have other redeeming qualities like sharp teeth, dense muscles, tough hide, and gigantism. Just because they can get away with low intelligence doesn’t mean that we can. I think Ridley dismisses this case too quickly. Bipedalism and bony, claw-less forepaws make us suited for tool use and not much else. A human with a lion’s brain would not last very long.
But on to the next theory, which Ridley regards more highly. Perhaps we became intelligent in order to outwit our enemies: another obstacle that fights back. Apparently people struggle with logic problems unless they are represented as social situations. In one study involving cards, the participants usually failed to keep track of the association between numbers and letters, but easily learned the same association between people and actions. Wild apes come up as both a supporting and undermining example to this theory. Gorillas, Ridley points out, are relatively intelligent mammals even though they make a living by eating leaves; the need for such intelligence must be the proximity of other gorillas who want something that they have. With that said, socializing has not made gorillas, chimpanzees, etc. smart enough to be the answer. Humans are far ahead of them.
What accounts for the gap, can you guess? Sexual selection! Ridley concludes that intelligence increased due to self-reinforcing whims, especially female whims. Only that could account for its explosive growth. It evolved for the primary purpose of seducing the opposite sex. Both men and women are courters and choosers, but female brains hold male brains to a higher standard. However, by shaping the male brain, they have shaped their own. Intelligence is not a y-linked trait, so it was passed down to both the male and female offspring of each union. It made the entire species smarter. Only semi-arbitrary aesthetic preferences can explain the development of such impractical pasttimes as art and theater. They are our peacock tails, our nightingale songs.
(So, just to point out the obvious, any genius clones will put a stop to this belief. Send out the talent scouts.)
With regard to intelligence, Ridley has dropped the connection between ornament status and health that he proposed in the previous chapter. Insofar as the variety-reduction paradox is real, it is back.
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Unlike Ridley, I think every truthful theory adds some weight to a cumulative cause; I won’t commit to one evolutionary explanation for the sake of a more streamlined story, whether we’re talking about sexual reproduction or high intelligence.
Remember that the predominance of the parasite theory for sex hinges on the assumption that fast-breeding asexuals and slow-breeding sexuals were locked in some kind of cutthroat contest. What an assumption! To me it implies some kind of isolated test. There was an ancestral lineage that bifurcated into sexual and asexual procreators, allowing the two strategies to compete with no other factors at play. So who was this ancestor? I don’t blame Ridley for omitting it. How could he know? But its existence, lost in the haze of the deep past, must be acknowledged. Without such an ancestor, how do you construct the “hate-triangle” between clones, sexual hosts, and parasites? In practice, the first sexual creatures might not have been trying to oust the clones at all. They could have had an island all to themselves. They could have been environmentally pressured to change in all kinds of ways, reproductive, metabolic, you name it! Asking “why don’t humans clone like anemones?” could be like asking “why don’t humans fly like birds?” Humans & birds are not descended from angels. We never had wings, and acquiring them now would mean rolling back other innovations that are uniquely ours.
The case for intelligence is more controlled. It is what separates us from chimpanzees. Our common ancestors could have swung one way or another. That they did swing both ways, creating wild apes alongside humans, is informative. Equally informative is the continued existence of clones. On the one hand, these living fossils prove, more clearly than any impression in the shale, that life has options; sex and/or intelligence are not the only physical possibilities. They can be compared side by side. On the other hand, they prove that sex and/or intelligence are not necessary for survival. Hosts have sex to foil their parasites … except when they don’t. Intelligence rules the plains … unless great strength is in the way.
So many adaptations in this book can be ascribed to either a sexually reinforced mutation or a response to mutation. Sex, Ridley says, is good at purging mutations. The genes for mate preference are subject to mutation. Ornaments in birds, while signaling resistance to some germs, also signal freedom from mutations (yet another excellent point that Ridley raises only to ignore). Mutation creates new offshoots on the phylogenetic tree, branches which then extend into different contexts. The diversity of the tree is matched by the diversity of the landscape. Hence, while natural or sexual selection prune away, the remaining branches exhibit sex, asex, intelligence, unconsciousness, sight, blindness, men, women and hermaphrodites. Until all branches of a trait have withered, it makes sense in its respective atmosphere.
For all my objections, I was amazed and transformed by this book. Ridley arms his opponents and raises them to his level. The only reason I was able to argue with him is that he gave me the language to do so. He has found layman terms – locks & keys, card decks, etc. – for phenomena that are both invisible and hard to visualize. He tells you where these translations fall short. While such metaphors cannot be exact, the relationships between them seem to map onto reality.
Ridley expects both ignorance and trainability from the reader; where other authors would have relegated the subject of meiosis to footnotes and glossaries, if they mentioned it at all, he will walk you through the steps, holding your hand. The apparent flaws in the argument don’t reflect Ridley’s flaws as a rationalist so much as the ambition of his task.
This is a very information-dense book. It is enrichened by the contributions, as the author himself concedes, of many other minds, including Bill Hamilton and Ronald Fisher. Their ideas are organized by a graceful writing style that transitions seamlessly from exposition to narrative. It was all I could do not to quote his arguments outright; much of what I’ve said is better said in the book. Which is to say that this review is not a substitute for reading The Red Queen. Especially since I’ve left out many interesting tangents. For instance, why do we have two biological sexes, instead of hermaphroditism? What makes a mother more likely to have male vs female offspring?
If you read this book to learn about human nature, you might be disappointed. If you have any interest in alien lifeforms for their own sake, rather than as simplified models of humans, you will be delighted. One of the many ways that this review fails to do justice to the source material is that it leaves out most of the examples. The strangest theories are all inspired by true stories. You will meet the bdelloid rotifer, a microscopic creature which can either navigate ponds on wheels or ride the wind like a terrestrial plankton, and which can survive boiling – adaptations that it has acquired without ever having sex. You will meet the male brush turkey of Australia, who builds mounds for his lover to lay eggs that were fathered by someone else. At times, Red Queen reads like a bestiary of phoenixes and chimeras, or like Aesop’s Fables.
A caveat re the stories about parasites. Though they ground Ridley’s claims, alas, I’m not going to fact-check them. They are horror stories! I don’t want to see what the parasites are up to. Frankly, I have no desire to invoke the word “parasite” in a search bar. Who knows what images I would summon up. It’s an unusual problem for which no one is to blame.
According to Ridley, “a bilharzia worm inside a human vein cannot travel abroad to seek a mate, but if it encounters a genetically different worm, infected on a separate occasion, they have sex (80).”
… Sure. Most people will take his word for it. We have sound evolutionary reasons to be repulsed.
And that concludes my review. I suppose it’s really a subset of The Red Queen married to a subset of The Blind Watchmaker and mutated by my own thoughts. I hope you don’t think I’m too much of a parasite!
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*The title is a reference to a scene in Lewis Carroll’s Alice. The main character discovers that travel is impossible because whenever she runs, the landscape moves with her. In Darwinism, “Alice” and “the landscape” represent one organism and all its ecological enemies, respectively. Competition forces animals to get better at certain tasks. Each generation of a species is more distant, as measured by the number of mutations, from its earliest ancestors. But its distance from its contemporary enemies never changes, because they have been evolving at the same pace. There is no relative improvement.
Works Cited
Ridley, Matt. The Red Queen. Penguin Books, 1993.
Dawkins, Richard. The Blind Watchmaker. W.W. Norton & Company, 1987.
“Matt Ridley.” Wikipedia. Wikimedia Foundation, 19 May 2026.