Jonathan Sarfati

Response to the PBS-TV series Evolution

Episode 5: Why Sex?


This episode was one of the most revealing about the conflicts between evolution and Christianity. The usual propaganda is that ‘science’ (stipulatively defined as evolution) is about facts/evidence or ‘how’ questions, while religion deals with values/faith/morals or ‘why’ questions. As explained in the Rebuttal to Episode 1, this is a faulty distinction, and this episode demonstrates this. Here, evolutionary psychology directly affects questions of sexual morality.

The program also spends much time discussing the advantages of a fully functional sexual reproductive system, but misleadingly implies that this is sufficient to explain its origin.

Sex is said to be more important than life itself, since it enables genes to be passed on to succeeding generations. Rutgers University evolutionary geneticist Robert Vrijenhoek even said:

‘That’s our immortality. That’s what connects us to humans on into the future. That’s what’s connected us to all our ancestors in the past. That’s what connects us to the ancestors that were fish, the ancestors that were protozoans, and the ancestors that were bacteria.’

Of course thus far the series has merely asserted this connection, apart from dubious implications from some common features (see Rebuttal to Episode 2). It’s also important to note how evolution directly impinges on ‘religion’ despite the claims that they are compatible (see Rebuttal to Episode 1). Vrijenhoek implies that immortality has nothing to do with survival of the individual.

Asexual vs sexual reproduction

The program shifts to Texas, where scientists investigated lizards that were entirely female. They laid eggs that hatched into lizards that were clones of the mother. This is called parthenogenesis, from Greek parthenos (virgin) and Latin genesis (from Greek gignesthai [to be born]). They seemed to do very well, so what’s the point of sex?

Disadvantages of sexual reproduction

Indeed, the program acknowledges that sex has many disadvantages, e.g. only 50% of the genes are passed on to an offspring. This means that there is a 50% chance of losing a beneficial mutation. And in a stable population (i.e. not changing the number of individuals), there is on average one surviving offspring per parent, so asexual reproduction is twice as efficient at passing on genes to the next generation. Sex also means that an optimal gene configuration can never be passed on in its entirety.

It is also biologically costly to maintain the sex organs, and to maintain mechanisms to stop the male’s immune system destroying his own (genetically different) sperm, and stop the female’s immune system destroying incoming sperm or the offspring she carries (in viviparous organisms). And as will be seen in the sexual selection section below, sometimes sexual displays can be cumbersome and make the organism more vulnerable. Females obviously expend a lot of time and energy if they must bear live young. It takes energy to find a mate, otherwise the organism will die without passing on its genes, and if one sex is eliminated, the species will become extinct. It’s a lot of trouble, considering that asexual organisms such as bacteria reproduce very quickly.

Because of these lizards, the narrator posed the question, ‘Are males really necessary?’ Males eat about half the food, and it means that only half the members of the population (females) are involved directly in bearing young. In an asexual population, all its members bear offspring directly.

Advantages of sexual reproduction

Since sexually reproducing species do well, males must have their uses. The program then shifts to a pool in Sonora, Mexico, inhabited by a species of minnows, both asexually and sexually reproducing ones. But they are infested with a parasite that causes black spot disease. Vrijenhoek says that the sexually reproducing minnows are more resistant than the asexual ones.

The researchers invoked the ‘Red Queen Hypothesis’, invented by Lee van Valen; Alice (in Wonderland) raced the Red Queen, and exclaimed that they had to keep running just to stay in the same relative position. Evolution is supposed to be a race, and the asexual minnows produced clones, so stopped evolving, so are easy targets. But the sexually reproducing minnows produced lots of variation, so presented a moving target. But other evolutionists say:

‘The Red Queen idea is simply a cute name for a zoological myth.’1

This neat hypothesis seemed to be questioned when a drought eliminated the minnows. When the pool was naturally recolonised, the parasites killed the sexually reproducing ones faster. But it turned out that human-introduced sexually reproducing minnows were still the most resistant of all. The natural colonizers turned out to be inbred, so lost the advantage of variability.

So it seems that the variability is a major advantage, and well worth paying the price of transmitting only 50% of the genes, and the other disadvantages of males. Sexual reproduction also has a 50% chance of losing a harmful mutation without cost to the population (death of an individual).

Advantage doesn’t explain origin!

Creationists can explain the origin of fully functioning sexual reproduction, from the start, in an optimal and genetically diverse population. Once the mechanisms are already in place, they have these advantages. But simply having advantages doesn’t remotely explain how they could be built from scratch. The hypothetical transitional forms would be highly disadvantageous, so natural selection would work against them. In many cases, the male and female genitalia are precisely tuned so one could fit the other, meaning that they could not have evolved independently.

Evolution of sex?

This episode features a cute cartoon of two single-celled creatures with eyes kissing and exchanging genes. Then the narrator intoned:

‘Random change produced a creature that was small and fast, which turned out to be an evolutionary advantage. Organisms with reproductive cells like that are called males. Their goal is to find organisms with a different speciality—providing the nutrients life requires. They’re called females. These early pioneers evolved into sperm and eggs.’

Hang on—not only is slick animation no substitute for evidence, but somewhere along the line this program jumped from alleged male and female single-celled creatures to multicellular organisms containing cells like them. Then the narrator continued:

‘Males produce sperm by the millions—with so many potential offspring, it doesn’t pay to be fussy about eggs. A better strategy is to try to fertilize as many eggs as you can. Eggs are more complex than sperm and take a larger investment of energy. Females make a limited number of them. Fewer eggs mean fewer chances to pass on genes, and that means that females—unlike males—do better if they’re choosy. At a deep biological level, males and females want different things, regardless of how things appear on the surface. … Small sperm vs large eggs. … Quantity vs quality.’

At about the same time, the program showed a man and woman under a sheet, probably naked but not showing too much of that, indulging in sexual foreplay, then lots of sequences of animals having sex. Is this program really meant for young schoolchildren?

Then the program explains male competition for mates and ornate sexual displays, while females exercise choice.Supposedly the concept of female choice was often discounted in Victorian England (with a female head of state who ruled for more than 60 years).

But the program shifts to a role-reversing bird in Panama. Supposedly the crocodiles ate so many chicks that females leave the males in charge of the eggs while they try to reproduce again. The females are the ones who keep harems, and kill chicks and break eggs of other females. The narrator says:

‘So now it’s the females who care more about quality than quantity. Now it’s the females who fight over mates. Over time, they take on traditionally male characteristics. … So here is an evolutionary revelation about gender. Male and female roles are not set in stone. They’re largely determined by which sex competes for mates, and which invests in the young.’

But before, it was the relative size and speed of sperm and egg that caused males to compete and females to invest more time with their offspring, and other behavioural differences. Now, competition and investment in young are no longer effects but are themselves causes that overturn the roles expected from the differences in gametes. What this really means is that evolution as an explanatory framework is so plastic that its proponents can explain mutually contradictory states of affairs, if they have enough imagination to create plausible just-so stories.

In line with the rest of the PBS series, this episode aims to indoctrinate readers to think that the origin of sex is well explained by evolution. A decent documentary would not have censored evidence against this view. In reality, evolutionists really have no idea how sex could have evolved. Even the atheist Richard Dawkins says:

To say, as I have, that good genes can benefit from the existence of sex whereas bad genes can benefit from its absence, is not the same thing as explaining why sex is there at all. There are many theories of why sex exists, and none of them is knock-down convincing. … Maybe one day I’ll summon up the courage to tackle it in full and write a whole book on the origin of sex.2

The smug assurances of this episode are also contradicted by the journal Science: ‘How sex began and why it thrived remain a mystery.’3


Darwin is most famous for the idea that natural selection is a driving force behind evolution. But he realised that this would not explain a number of features that seem to be a hindrance, e.g. the peacock tail. So Darwin invoked the idea of sexual selection, where choice by the opposite sex played a huge part in determining which individuals were able to pass on their genes. Later on, sexual selection is invoked to explain the human brain.

Creationists deny neither natural nor sexual selection. For example, we think it’s likely that sexual selection augmented natural selection in producing the different people groups (‘races’) from a single population of humans that were isolated after Babel. See Where did the human races come from?

The difference is that creationists recognize that selection can work only on existing genetic information. Evolutionists believe that mutation provides new information for selection. But no known mutation has ever increased genetic information, although there should be many examples observable today if mutation/selection were truly adequate to explain the goo-to-you theory. See Beetle bloopers. Even a defect can be an advantage sometimes.4

Chimps and bonobos

The common chimpanzee Pan troglodytes and the bonobo (or pygmy chimp) Pan paniscus hybridize so are the same Biblical kind. Sometimes they are classified as the subspecies Pan troglodytes troglodytes and P. t. paniscus respectively within the same species. Although they look similar, live in similar environments and eat similar food, their behaviour is different.

Chimps are violent, and bonobos are peaceful. The program shows the San Diego Wild Animal Park, and displays bonobos having ‘every imaginable’ type of recreational copulation, both heterosexual and homosexual, with a running commentary worthy of a hyper-testosteronic adolescent schoolboy.

So how is their behavior explained? Supposedly by female solidarity: they ‘can form alliances and cooperatively dominate males’ whereas the chimp males abuse females. So how to explain female solidarity? ‘A relatively simple change in feeding ecology was responsible for this dramatic difference in social behavior.’ Female bonobos forage on the ground, so have opportunities for social interaction. Female chimps can’t do this because gorillas eat the food on the ground, so females must forage on fruit trees alone. Supposedly a drought 2 million years ago killed the gorillas, and enabled a population of chimps to forage on the ground and evolve into bonobos. What a pity, says the program, that we didn’t have a similar history and evolve ‘to be a totally different, more peaceful, less violent, and more sexual species.’

As usual, we shouldn’t expect actual evidence for this story. From the available evidence, it’s impossible to prove cause-effect. I.e., how can we disprove that it was the other way round, i.e. that female solidarity didn’t generate ground foraging behavior, or even that a gorilla invasion didn’t cause bonobos to devolve into chimps?

Sexual morality vs evolutionary psychology

A female may well want the male with the best genes to ensure that her offspring are the ‘fittest’. But her best strategy for offspring survival could be finding a male who will stick around and help her care for the young. The male’s best strategy is to make sure the offspring are his, so monogamy would have a selective advantage.

But other evolutionary forces threaten monogamy. E.g. songbirds are monogamous, but sometimes a female will lust after a male with stronger genes. But this is risky—if the ‘husband’ finds out, he could kill the offspring.

Concepts from animals are applied to humans in the new field of evolutionary psychology. Geoffrey Miller claimed that our brain is too extravagant to have evolved by natural selection. He claimed, ‘It wasn’t God, it was our ancestors,’ via sexual selection, that shaped our brain ‘by choosing their sexual partners for their brains, for their behavior, during courtship.’ Art, music and humor played the part of the peacock tail.

Supposedly this is borne out by tests of human attraction. Men prefer women’s faces with full lips, indicating high estrogen; and other facial features, indicating low testosterone. Both are indicators of fertility. So now males do make choices despite having fast and small sperm? Once more, evolution explains any state of affairs, so really explains nothing.

Women looking for a short-term fling, or who are ovulating, prefer more masculine faces, indicating ‘good’ genes. But they prefer more feminine ‘gentler’ men for a long-term relationship, because they will be more likely to help care for her children. But appearances can be deceptive. We also wonder whether a face of a person from a different people group would be picked as often, although there is no disadvantage to the offspring’s genes from so-called inter-racial marriages.

While there’s a fleeting disclaimer that evolutionary psychology is controversial even among evolutionists, this program presents Miller’s ideas uncritically and unchallenged. But a review of his book The Mating Mind in New Scientist said:

‘How does one actually test these ideas? Without a concerted effort to do this, evolutionary psychology will remain in the realms of armchair entertainment rather than real science.’5

A leading evolutionary paleoanthropologist, Ian Tattersall, was equally scathing of Miller’s book:

‘In the end we are looking here at the product of a storyteller’s art, not of science.6

Why this episode?

In searching for explanations as to why evolutionists would feel passionately enough about their belief system to spend so many millions foisting it upon the public as in this series, one may not have to look much further than this segment. It is as if those looking for justification of an ‘anything goes’ approach to sexual morality have had a major hand in this segment. With humans already portrayed as just an advanced species of ape, and sex as a mere tool for propagation of genes, the way the program dwelt on the random hetero/homo ‘flings’ of our alleged bonobo ‘cousins’, and the association with an allegedly superior, more peaceful lifestyle, was telling.


  1. Margulis, L. and Sagan, D., What is sex? P. 121, Simon and Schuster, NY, 1997. Return to text.
  2. Dawkins, R., Climbing Mt Improbable p.75, Penguin Books Ltd. Harmondsworth, Middlesex, England, 1997. Return to text.
  3. Wuethrich, B., Why sex? Putting the theory to the test, Science 281:1980–1982, 1998. Return to text.
  4. Note that even if such a mutation were ever discovered, evolutionists would still need to find hundreds more to give their theory the observational boost it desperately needs. See Spetner, L, Not by Chance, Judaica Press (available through CMI). Return to text.
  5. Birkhead, T., ‘Strictly for the birds’, review of The Mating Mind by Geoffrey Miller, New Scientist pp. 48–49, 13 May 2000. Return to text.
  6. Tattersall, I., ‘Whatever turns you on’, review of The Mating Mind by Geoffrey Miller, New York Times Book Review, 11 June 2000. Return to text.
Published: 14 February 2006