The Best Australian Science Writing 2013 (12 page)

In 2009, the Vatican released a statement condemning the release of contraceptive pill hormones into the water through human female urine, and blaming male infertility in the Western world on the pill. And while oral contraceptives are a significant source of hormone pollution, to be consistent the Vatican may have to consider adding the following to their list of sinful practices: washing the dishes, eating yoghurt, going boating, being a woman, being a man, and being a cow.

Dairy cows are an equally significant source of endocrine-disrupting chemicals. Cows naturally produce large quantities of oestrogens and progesterone, the female pregnancy hormone, which go directly into the soil through their urine and faeces, and eventually find their way into waterways.

And while cows produce the bulk of natural endocrine-disrupting hormones, we can't excuse ourselves. Our own bodies also produce these hormones. Oestrogen has a reputation as a female hormone, but while reproductive-age women have the highest levels, men also produce estrogen – about the same amount as non-reproductive women. The Pope himself contributes a small amount of oestrogen pollution.

Bizarrely, some industrial chemicals are similar enough to hormones to cause problems. These substances, known as xenoestrogens, are found in certain plastics, detergents, and pesticides. Some xenoestrogens mimic male hormones. Tributyltin, a substance that is applied to the surface of boats to prevent algal growth, makes some female shellfish develop a great big gonopodium. Which, as you may have guessed, is a shellfish penis.

It's not only our fellow animals that are at risk from endocrine disruption. Tests of sex hormones on plants have shown
that some species are vulnerable to the effects of oestrogens. The growth of alfalfa, for instance, is reduced by oestrogens, while both male hormones and progesterone increase the growth of wheat plants. Oestrogens, on the other hand, cause abnormal structural development in broad bean, tomato, wheat and lettuce plants.

While these effects occur at concentrations of hormones much higher than those currently found in the environment, there is some irony in the fact that our hormones are affecting plants. Most readers have probably heard about the benefits of soy products for menopausal women. Plants such as soy contain phytoestrogens, which are similar enough to human-produced oestrogens to relieve symptoms caused by falling oestrogen levels in the body.

However, current thinking is that plants do not produce these uncannily human hormones as a helpful, selfless hot-flush remedy. Rather, experiments on both mammals and birds have shown that phytoestrogens are plants' way of offering pesky herbivores a contraceptive-laced snack, as a way of keeping our numbers down. This was dramatically demonstrated in China during the 1930s and '40s, when regions of Jiangsu province switched to phytoestrogen-rich cottonseed oil as a staple food – and watched their birth rate drop to zero. It seems that eating large quantities of oestrogen really messes with male fertility.

The many illegal drugs derived from plants are also believed to be weapons in the vegetable kingdom's passive–aggressive arsenal. For example, the compounds in opium poppies may have evolved to make herbivores inclined to wander fearlessly into open spaces, where they can be picked off and eaten. That our species can currently indulge without being cleaned up by wolves may be a point for us on the great evolutionary scoreboard, but tests for illegal drugs in our waterways suggest plants may still have the last laugh.

Last year, Spanish scientists tested the water of the Llobregat River and found traces of cocaine and amphetamines. In 2008, tests of a Welsh waterway showed that the load of both these drugs skyrocketed in July, which suggests the locals may have been partying hard during their Northern Hemisphere summer. And just as being exposed to a cocktail of therapeutic drugs is unlikely to improve the health of aquatic animals, there is also reason to suspect that our mollusc and crustacean friends do not necessarily enjoy getting inadvertently wasted.

So far, it appears no one has tested for the effects of cocaine or amphetamines on aquatic animals, but it might be useful to consider a notorious experiment conducted by NASA in 1995. It seems that the brains at NASA, having already massively benefitted humankind by jabbing an American flag into the topsoil of the moon, decided it was time to do something even more useful. The obvious choice was to get hold of a lot of drugs and test them on spiders to see how this affected their ability to construct webs.

This experiment, apparently designed to see if spiders could be used in toxicity tests, was a repeat of a similar study done in the 1940s. It showed that animals could indeed be affected by our illicit drugs. While spiders on LSD and mescaline produced approximately normal webs, those on marijuana and the sleeping tablet chloral hydrate were unable to finish theirs. Spiders on speed worked very rapidly, but left large gaps in the structure.

Perhaps part of the reason this experiment has found a place in popular culture has something to do with its widely quoted punchline. While the webs of spiders on most of the drugs retained a semblance of normal structure, one drug produced webs so asymmetrical and eccentric that they would barely have been functional. That drug was caffeine.

Just as phytoestrogens are not produced for human benefit, so plants do not generously produce caffeine to help sophisticated urban dwellers kickstart their mornings. Caffeine is believed to
have evolved as a natural pesticide. And while it is effectively metabolised by the human body, and therefore not peed out like other drugs, some caffeine does find its way into waterways, possibly through being tipped down the sink, or when cups are washed.

What would the South African clawed frogs make of all this? Modern medicine has come a long way. The frogs have retired from their busy lives of international travel and being injected with human piss. Perhaps now they can sit back and relax with their girlfriends – of which they will have many more now that endocrine disrupters have feminised the species – and enjoy swimming in waterways that human beings have thoughtfully laced with a sophisticated coffee-pharmaceutical blend.

Aquatic lifestyles

Going, going, gone

Dreamtime cave

Elizabeth Finkel

A small Aboriginal woman peers through the microscope at the sliver of rock. Perched precariously on a stool, her feet barely touch the ground. ‘Do you want us to go on, Auntie?' asks archaeologist Bruno David. ‘Yes,' she says emphatically in a low quiet voice. ‘I want my grandchildren to know about our culture.'

It's an unusual gathering for the archaeology lab at Melbourne's Monash University. ‘Auntie' is Margaret Katherine, an elder of the Jawoyn people; David is the lab's co-director. Then there is carbon-dating expert Fiona Petchey from New Zealand's University of Waikato, archaeologist Mark Eccleston – with his shiny steel X-ray fluorescence gun – from Aboriginal Affairs Victoria, plus documentary film-makers Bentley Dean and Martin Butler, and me.

We are all focused on Margaret Katherine, whose attention is on a triangular piece of quartzite measuring close to 4 centimetres across its greatest length. Under the microscope its treasure becomes clear: a very finely painted black cross whose lines seem to continue beyond the edges, as if it were part of a larger image. The black pigment is charcoal, meaning it might be possible to scrape off a tiny bit to carbon-date the miniature painting. This is an extraordinary artefact, recovered by David's colleague Bryce
Barker from the University of Southern Queensland during a recent dig of the floor of Gabarnmung cave.

Gabarnmung has been rewriting world pre-history since its 2006 ‘rediscovery' by the Jawoyn. The cave is perched on a sandstone escarpment high in southwestern Arnhem Land, east of Darwin. Arnhem Land is wholly owned by Aboriginal tribes and much of the escarpment lies within the 50 000 square kilometres ancestral lands of the 600-member-strong Jawoyn. The escarpment's unusually hard quartzite rock is the canvas for one of the world's most spectacular collections of rock art – an archaeologist's utopia, its diverse styles preserve a sequential record of a people who have occupied this landscape for more than 50 000 years.

Much remains to be learned about this art. Archaeologists are uncertain about the age of the paintings and their precise meanings. It's safe to say some tell stories of the Dreamtime – the Aboriginal telling of the creation of the world – and also serve to mark clan territories, since different clans recognise different spirit-beings.

‘We know this from what Aboriginal elders have told anthropologists over the last 100 years,' says David.

Others may simply be works of art – expressions of the quintessential human urge to leave one's mark. Tens of thousands of years ago, Margaret Katherine's ancestors, nicely sheltered from the rain and wind, would have been cooking a meal on the floor of Gabarnmung and, no doubt, occasionally gazing up at the art work on the ceiling. Some of the art was old, even then, and a fragment broke off, landing on the ground to become buried by the cave's fine dust, rich in charcoal soot. But ever so slowly, at a rate of centimetres per millennia. Elsewhere, in the lowlands, artefacts are buried at a rate of metres per millennia.

In mid-2011, six months prior to the Monash University gathering, Barker fished that fragment out of an excavation trench
just 50 centimetres below the floor of the cave. When he had wiped off the dust to reveal the black cross, he realised he was holding archaeological gold. Now it's hoped that a tiny bit of the pigment can be extracted from the painted cross in an attempt to get a carbon date. The process will partly destroy the tiny painting but, for Margaret Katherine, it will be worth it.

A lot is riding on this little rock art fragment. It's clearly very important for Margaret Katherine and the rest of her people. Science is helping the Jawoyn flesh out their deep history. In the few months of seasonal digging at the cave, which commenced in May 2010, the international team headed by David has made extraordinary finds. ‘We are rewriting human prehistory,' Ian McNiven, a Monash University archaeologist and team member, told me.

David has assembled an illustrious team. As well as the Australians and New Zealander, there is a French contingent headed by Jean-Michel Geneste, from the Université de Bordeaux 1. Geneste is curator of France's national treasure, the prehistoric Lascaux Cave. He also directs the international research program at Chauvet Cave, where dynamic charcoal paintings of ponies, rhinos, bison and lions evoke the technical mastery of a Japanese brushstroke artist. Human eyes had not viewed this labyrinthine gallery for tens of thousands of years until 1992 when a trio of cavers felt an updraft in the cliffs of the Ardèche river canyon in southern France, and lowered themselves in. A steel door now protects the cave from the public and each year only a handful of researchers may enter, under Geneste's direction. Among Chauvet's treasures is the world's oldest known painting, depicting two battling rhinoceroses. Tiny scrapes of charcoal pigment gave it a carbon date of 36 000 years old.

But people lived at Gabarnmung for thousands of years before Chauvet was occupied: charcoal deposited above the very bottom layers of the Arnhem Land cave has been carbon-dated at 48 000 years old. For Europeans this is the stuff of pre-history;
they have no direct connection to this era. Not so for the Jawoyn. The paintings, tools, spears, ochre-anointed skulls and bones, are their history.

The 2010 dig at Gabarnmung also unearthed a piece of a basaltic stone axe 4 centimetres long and 2.5 centimetres wide, lying about 50 centimetres below the cave floor. It was not so startling to find a stone axe. Ancient people have been smashing two rocks together to produce stone tools for more than two million years. What was different about this axe was that someone had sat down with a stone and skilfully ground it until a sharp edge was made. Under the microscope the parallel striations wrought by the patient toolmaker are evident. Stone toolmaking was, like writing, one of those technological milestones that evolved independently in different civilisations. But the Gabarnmung axe supports evidence that it was people in Eastern Asia, New Guinea and Australia who got there first. Throughout Australasia ground axes are found at ages greater than 20 000 years; in Europe, Africa and West Asia, the oldest ground axes are 8000– 9000 years old.

Perhaps the Gabarnmung axe was used to chop pieces of goanna for the cooking fire. When its owner left the cave for the season, the axe must have slipped into the charcoals – the same charcoal now carbon-dated to 35 500 years old. This is a very, very old ground axe – older than ancient ground axes previously found in New Guinea, China or Japan. It is, in fact – for now – the world's oldest ground axe. The Jawoyn ancestors were the innovators of their time.

In 2011, returning to the Gabarnmung dig in July – after that time it becomes impossibly hot or impossibly wet – the archaeologists excavated a trench on the opposite side of the cave and unearthed the painted rock fragment we're now looking at in the Monash Uni lab. The charcoal layers which bookended it have been dated at 20 000–30 000 years old. Geneste, who knows
a thing or two about ancient rock art – having spent 15 years dating the charcoal pigments at Chauvet Cave – thinks it might be something very special. The Chauvet rhinoceroses are, so far, the world's oldest record of modern human beings ‘socialising their environment', Geneste explains. But he suspects some of the Gabarnmung art is likely to be just as old, probably older.