The Best Australian Science Writing 2014 (27 page)

Not to mention
Homo domestica bestia alitura
, the pet-keeping species.

The baby schema evolved because in normal circumstances it works. Any big-eyed, short-faced fluff-ball a mammal parent runs into usually is indeed its offspring. If it's not, other FAPs based on scent or behaviour commonly weed the impostor out. Yet as those Congolese bonobos show, every now and then, when species collide, the baby schema can make things get weird. It seems, for example, to trigger the parenting FAP in chimps and bonobos, at least occasionally, no matter what species it's on. And intriguingly, although apes can identify which young are not their own through smell (as can we), even that doesn't seem to stop them. They not only play with these cross-species pets, but also frequently adopt non-related chimp or bonobo infants, so strong is their baby schema FAP response.

However cute some FAPs are, though, they also have a sinister side. Because they're fixed and instinctual (meaning the animal can't stop doing them, even if they're compromised), FAPs are a prime target for parasites. Parenting FAPs, for example, are often exploited by brood parasites, who trick the host into raising the parasite's young by hacking that host's FAP's releaser code. The classic examples are the cuckoos, who exploit the ‘worm-dropping' FAP of their reed warbler and cowbird hosts – their compulsion to drop food into the nearest gullet when they see it gape and hear its owner cheep. When a cuckoo smuggles its egg into the host's nest, of course, the cuckoo chick's superb mimicry of the ‘gaping, cheeping' releaser allows it to divert a portion of those worms to itself.

We humans turn out to be every bit as prone to FAPs provoked by infant releasers (in our case, the baby schema) as other animals. Just glancing at a human baby's cute, big-eyed little face, for example, provokes immediate, involuntary activity in our zygomaticus major – our smiling muscle. The activity also
gets more intense, not less, the longer we look. Baby faces similarly provoke an involuntary change in our voices. We start talking in high-pitched, phonically exaggerated ‘baby talk'. Infant faces have also been shown to completely bypass our normal visual processing system and instead directly access the most basal reward regions of the brain: the cingulate cortex, basal ganglia and thalamus.

To top it all off we're also just as easily fooled by brood parasite impostors as those befuddled reed warblers. Studies show, for example, that exposure to the cute faces of our pets triggers parental FAP reactions in us indistinguishable from the authentic thing. (If anything, we're even less discriminating since our cuteness sensor can even be stimulated by inanimate, baby-faced objects like car fronts.) We're not faking it, either: urinary tests show we get the same surge of bonding hormones, predominantly oxytocin, from patting pets that we do from touching human babies. That's probably why around 83 per cent of us, in one recent survey, confessed that we do secretly view our pets as actual children.

This is a remarkable feat of brood parasitism. How have our pets pulled it off? Their secret seems to lie in the ‘supernormal' releasers they have evolved – FAP triggers so powerful they make a host prefer its brood parasite's young to its own – to keep us in thrall. Dogs' and cats' faces, for example, do not grow out of the baby schema the way ours do; even old cats and dogs still look a little baby-like. They are, what's more, becoming more so the longer they live with us. Dogs' snouts, for example, have been getting shorter, their skulls broader, and their eyes proportionally larger and more forward facing over the last 30 000 years – even before we created faux-baby breeds like chihuahuas. Behaviourally, too, dogs out-baby real babies. They're hyper-responsive to human gestures and expressions. Experiments show, for example, that they study human faces intently for problem-solving hints,
and understand pointing gestures better even than chimps. Crucially, they never stop doing so, while all human parents eventually face the trauma of becoming invisible to their kids. Exposed to supernormal stimuli like these, is it any wonder many of us report feeling more empathy for pets than for children, and that many married pet owners admit to secretly loving their pet more than their spouse?

So has human history since the Pleistocene possibly been nothing but a succession of pats along the road to our animal companions' rise to the status of parasitic master race? Were we done for the moment that first
Homo habiline
or erectine stooped down to pluck that first cuddly fur ball from its nest, den or burrow? I say yes. For a while, a million and a half years or so, we were protected by our sparse population. We were still too few to form a real niche in which our proto-pets could diverge genetically from their wild relatives and evolve into obligate human parasites (species that can't live without us). Instead they almost certainly did what captured full-blood dingoes do today: spent their youth in camp before melting back into the wild as adults. Our real, headlong plunge came when we started living in semi-permanent settlements around 20 000 years ago. It was only then that the wolves and wildcats, which would become our dogs and cats, could settle down for their whole lives too and begin their evolution into the most successful love parasites the world has ever seen. And once they'd done that the rest, like us, was history.

This is Peter McAllister, last survivor of the planet of the pets, signing off.

The carnivorous platypus

Uniquely human

Penis size may be driven by women
(Oh, and it matters …)

Rob Brooks

How important is penis size? Authors from the Australian National University, Monash and La Trobe recently provided the most complete answer yet: the size of a flaccid penis can significantly affect how attractive a man's body is to women.

Writing in the
Proceedings of the National Academy of Sciences
(a journal commonly known by its initials as ‘PNAS'), Brian Mautz, Bob Wong, Richard Peters and Michael Jennions use a clever experimental manipulation of computer-generated imagery (CGI) to test the effects of variation in penis size relative to height and torso shape (shoulder width relative to waist width) on the attractiveness of male bodies to women. While they found that torso shape was by far the most important determinant of attractiveness, penis size has about as much influence on attractiveness as height.

It's the kind of science made for easy-reading hundred-word news-porn in the tabloid press (‘Size really
does
matter'). Or for wowser columnists to work up a morning's indignation that a scientist somewhere did something interesting when everybody knows the rules: scientists should be finding new ways to extract
coal-seam gas or cure the cancers that tend to afflict late-middleage columnists (as in the controversy in March 2013 when Fox News attacked Patricia Brennan's research on duck penises). If Tom Waterhouse wasn't so busy swotting for Friday night football, he'd have already installed Mautz as hot favourite for the next igNobel Prize (for science that makes you laugh and then makes you think).

And yet for such a tabloid-ready topic, the paper itself is a study in how science should proceed in sober and restrained steps.

* * * * *

Genitalia tend to vary more dramatically than almost any other physical trait. And evolutionary biology has made stunning progress in resolving why.

For the most part, studies of animal penis size and shape have focused on the effectiveness of various structures in delivering sperm to where it needs to be, in removing sperm that a female had received from previous mates, in stimulating the female to use that male's sperm, or even inflicting damage on the female so she would not mate again.

One of the more striking features of the human penis, when compared with other primates, is its length. Relative to body size, the human penis dwarfs that of bonobos, common chimpanzees, gorillas and orangutans. And our erect stance and face-to-face social interactions make the penis a highly conspicuous feature.

That conspicuousness has led anthropologists and popscientists alike to speculate on the potential for penises to act as a sexual signal. Some have even suggested that a large penis may be a signal of more general health and vigour, and that the evolutionary loss of the human baculum (penis bone) may make the penis an honest signal because size and arousal can't be faked.

The function any preferences for penis size serve remains, for now, largely in the province of hypothetical speculation. Because much murkiness surrounds whether such preferences exist and, if so, just how important those preferences are.

* * * * *

Titillating news stories, fictional references and even song lyrics speak to a persistent fascination with properties of the penis. That fascination hints at a deeper, largely unspoken obsession with the links between size, virility, masculinity and attractiveness. Some might say that penis size presents an exclusively male obsession, pointing to the importance of embellishments such as Renaissance codpieces and New Guinea phallocarps in male– male interactions. Are not men at least as obsessed about questions of size as women?

Unfortunately for this line of argument, men are expected to obsess about
precisely
the traits that women – overtly or subtly – use to discriminate among their mates. And a strong whiff of male insecurity about how women are likely to judge their equipment inheres to most public discourse about penis size.

Consider what I call the Goldilocks cop-out. Most media stories on the topic of penis size conclude that as long as the penis in question isn't way too big or way too small, it's likely to be ‘just right'. Within the large zone of ‘just-rightness', few commentators are willing to claim that size really matters. The Goldilocks cop-out mollifies male insecurity.

If evolutionary psychologists are right – and I believe they are – then men's obsession with paternity presents a tectonic force shaping behaviour and societies. It doesn't take much imagination to see that part of that insecurity can be bound up in fears about penile inadequacy.

Makers of penis enlargers promising ‘extra inches' and
purveyors of nasal snake-oil guaranteeing ‘longer-lasting sex' exploit those fears. Fears that they will never attract a mate. And fears in those who already have a mate that they might inadvertently be raising another man's progeny.

* * * * *

If one accepts that women may have preferences for penises of a certain size, one is left with the not-inconsiderable challenge of how to measure such preferences. Asking people doesn't always work. Women – and men – have all sorts of reasons to prevaricate, or to grow indignant that the question has even been asked.

In earlier work, my UNSW Australia colleague Barnaby Dixson used a series of five line drawings, manipulated to have different sized flaccid penises, to study women's preferences in Cameroon, China, New Zealand and the USA. He found that slightly larger than average penises tend to be favoured by women. Important as this study was, it cannot illuminate how important penis preferences are relative to other preferences – such as for muscular torsos or for taller men. If the only thing that varies among stimuli in an experiment is the trait of interest, then we shouldn't be surprised to find it has an effect.

And subjects quickly cottoned on to what the experiment was about. Also, the smallest and largest penises may have just looked strange, relative to the body on which they had been drawn.

In this new work, Mautz and his colleagues used a higher tech method, building three-dimensional computer models – 343 models in all – that varied in torso shape, height and flaccid penis size. They then showed each female subject a subset of 53 bodies, one at a time, projected life-size on a wall, and asked them to rate the attractiveness of each on a seven-point scale.

According to Mautz, the life-size projection of the images was important:

While using small figures can provide important insights into how mate-choice might affect particular traits, I think responses will be affected by the size of the pictures (or stimuli if you will). Ever wondered why they do so many close-ups in pornographic videos?

Well, no. But moving right along.

For me, the stroke of genius was the independent manipulation of three traits, two of which (height and torso shape) are already well known to influence attractiveness. This allowed Mautz and his colleagues to calculate that penis size affects attractiveness – of CGI models at least – about as much as height does.

It also allowed them to test for interactions between penis size and the other traits. While well-endowed models tended to get the best ratings, they did so especially in taller men who had more masculine bodies.

That is to say the effects of all three traits – height, torso shape and penis size – were not independent; rather, models who were tall, broad-shouldered and with large members did particularly well.

Critics of this type of study love to point out that women usually decide if they will have sex with a man well before ever sighting his genitals. And, if so, then how can penis size influence choice?