When the Gulf of Siam docked in Sydney in May 1892, the ship鈥檚 surgeon signed off. Robert Broom, a young doctor from Glasgow, was about to start a new life in Australia. Hidden in his luggage, away from the prying eyes of customs officers, were two rifles and enough ammunition to shoot the animals he needed for his investigations into the origins of mammals. Broom had no intention of paying duty on the guns. After all, he was going to use them to further the sum of human knowledge.
Forty years later, Broom鈥檚 conscience still wasn鈥檛 troubling him much. He hit the headlines in the 1930s when he discovered some of the first fossil australopithecines in the caves at Sterkfontein 鈥� breaking every rule in the book to get at them. But Broom had always done what he wanted first and asked permission afterwards. It was a strategy he had learnt back in the limestone hills of New South Wales, when he found the first of his important fossils, this little jaw with the puzzling teeth.
ROBERT BROOM relished the idea of running a rural medical practice in Australia. For a start, there wouldn鈥檛 be too many patients. Better still, he would have to ride about the country to see them. Broom had trained as a doctor, but medicine was just a way to make a living while he sorted out one of the great riddles of evolution.
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Australia, with its egg-laying monotremes and pouched marsupials, was a place where he could untangle the origins of mammals. Had they sprung from the amphibians, as some argued, or from the reptiles as others believed? Or had mammals arisen twice, with the reptiles giving rise to the egg-layers and the marsupials, and the 鈥渉igher鈥� mammals springing from frogs and their kin? As Broom travelled between patients he would be able to shoot a few animals for his collection. Even more to his liking, he would have the chance to hunt for fossils.
After Broom had smuggled his rifles safely through customs in Sydney, he sailed north to Queensland where his brother worked as an assayer for the mines. Disappointed by the fossils there, he moved south again until eventually he found what he wanted in a tiny township in New South Wales: Taralga, population 450. It was a dull and dusty place but the Taralga Progress Association was offering a subsidy to any doctor prepared to set up practice there. Not many patients, lots of limestone 鈥� it was perfect.
Not long after Broom arrived, he was invited to a picnic at the nearby Wombeyan caves. Pottering about the hillside during the afternoon, Broom stumbled across a deposit of tiny fossil bones. 鈥淭he deposit is evidently the remains of the floor of a cave,鈥� he wrote later. Some 15,000 years earlier, owls roosting in the cave had regurgitated the remains of their meals. A pile of bones had built up over time, and calcium-rich water flowing over the cave floor eventually entombed the remains in lime. Later the cave collapsed and the walls and roof weathered away.
Broom carried home as much of the deposit as he could, returning several times to refill his saddlebags before settling down to tease out the bones. He wanted to learn about the evolution of early mammals, and here were piles of some of the most primitive examples 鈥� marsupials. 鈥淢ost of the marsupials belong either to extinct species or to species not now living in the district,鈥� he wrote. He needed more material. But the Ministry of Mines was responsible for the caves and had a caretaker to watch over them. Broom did the proper thing and wrote to ask for permission to cart off a load or two of fossil deposits. The ministry refused.
It was Broom鈥檚 first encounter with bureaucrats who didn鈥檛 appear to appreciate the importance of the discoveries he felt sure he would make. Broom decided to ignore them. He continued to trek back and forth to the Wombeyan caves, removing buggy-loads of fossils while the caretaker obligingly turned a blind eye.
It wasn鈥檛 long before Broom discovered something that he believed justified his deception. Among the fossils from Wombeyan were some tiny marsupial jaws with huge grooved premolars unlike anything he had seen before. He sent specimens to the Australian Museum hoping someone might identify their owner. No one could. It was a new species, which Broom called Burramys parvus. Broom was convinced that the little marsupial was some sort of missing link, a member of an ancestral group that had given rise to kangaroos and gliders.
With this intriguing find under his belt, Broom decided he should again ask permission to excavate at the caves. This time he tried to enlist the support of Robert Etheridge, director of the Australian Museum. Surely Etheridge would back him now that his research was so obviously going to enrich the scientific world. He was wrong. If the ministry had said no, Etheridge told Broom, then what was he supposed to do? 鈥淚 am afraid I am quite powerless in the matter,鈥� he replied. However, he had influence enough to organise a sneaky visit to Wombeyan to collect his own samples. During the trip, he passed twice though Taralga. He didn鈥檛 call on Broom.
Broom felt slighted, and his attitude to the authorities hardened. From now on, he would do what he wanted regardless of whether he had permission. It became a lifelong philosophy. By now, though, Broom was giving up on Australia: it didn鈥檛 look as if he was going to unravel the origins of the mammals here. In May 1896 he left the country, leaving little behind but a hollow in the hillside at Wombeyan.
A few months later Broom was in South Africa鈥檚 Karroo, a region rich in the fossils of mammal-like reptiles. Over the next 40 years Broom showed how the mammals had sprung from reptiles like these.
Then in 1924 Raymond Dart discovered the first fossil of an australopithecine 鈥� the skull of the 鈥淭aung Child鈥�. Broom was fascinated and switched his attention from the transformation of reptiles into mammals to the evolution of modern humans from ancient apemen. Broom already had a reputation for arrogance and a habit of defying authority. Now he really began to chance his arm. He was growing old 鈥� pushing 70. The rocks were hard. So he dynamited them, scattering fragments of rock and bone all over the place. In 1936 he found his first man-like ape, which turned out to be an adult australopithecine.
From then on, 鈥渉e left no likely stone unturned鈥�, wrote Dart. 鈥淎t Sterkfontein, Kromdraai and Swartkrans, he wrenched and blasted out a series of unique fossils bearing upon the earliest phase of human prehistory.鈥� Appalled by his methods, South Africa鈥檚 Historical Monuments Commission banned him from the fossil sites. He ignored the ban, carried on blasting and discovered more hominid fossils.
Broom died in 1951, famous for his fossil apemen. Few remembered that he had ever been to Australia. But 15 years later, his little fossil from the Wombeyan caves was suddenly in the spotlight. A strange rat-sized marsupial showed up one night in 1966 in a ski hut on Mount Hotham in the Great Dividing Range. It had fine, dense fur, a long tail and massive grooved teeth. Broom鈥檚 Burramys was alive and well.
The mountain pygmy possum, as it is now called, was not a missing link but it was certainly different. Burramys is the only marsupial that lives above the snowline, leading a secretive life in the tunnels and cracks between broken boulders, and protected from the winter cold by a blanket of snow. If the temperature drops too low, Burramys hibernates. The possums were more widespread during the Pleistocene, when the climate was far colder, but as the climate warmed, they retreated uphill. Today they survive only among the jumbled screes where the ancient mountain plum pine grows.
And the explanation for those huge teeth? Although in summer the possums feast on the soft, fat-rich bodies of the bogong moths that migrate to the mountains to breed, at other times they eat insects, fruits and seeds. The big, grooved premolars are perfect for cracking open tough seed coats and the crunchy exterior of insects such as beetles, allowing the possum to scoop out the softer insides.
Burramys鈥檚 transformation from extinct to extant may be short-lived. Only around 3000 survive, and they are threatened by introduced predators such as cats, dogs and foxes, the development of ski resorts and global warming. Burramys has already retreated to the mountaintops. If the snow melts, it will have nowhere else to go. And Broom鈥檚 possum will be gone for good this time.