by Tim Flannery
Before I could grapple with this question our convoy left the place in the brightness of a wet-season dawn. We had not gone fifty kilometres when my bike suddenly yawed on the road and skidded to a halt, its rear tyre shredded by sharp iron lying on the track. There was no choice but once again to hide my beautiful machine in the bushes, and continue on the back of Bill’s to Halls Creek, 250 kilometres away, in search of a spare.
We arrived in Halls Creek on New Year’s Eve, and found everyone busily preparing for the big dance at the town hall. It was a dour affair—all white—with the hall starkly lit, barely decorated and enlivened only by a country and western band plucking away in the corner. The young men who had come from miles around made it clear that they wanted no competition for the few eligible girls, so Bill and I avoided a onesided fight by retiring early.
The next morning I discovered that in all of Halls Creek there was not a motorcycle tyre that fitted my Guzzi. I would have to order one in from Darwin, which meant further delay. To safeguard my bike I would also have to truck it to Halls Creek, but with the wet season setting in this was not going to be easy. I began by calling the police station in Fitzroy Crossing, inquiring whether they could help me locate a truckie willing to load the bike. ‘You mean that Italian bike up the track?’ the policeman who answered the phone said. ‘Too late, mate. It’s burned to a crisp.’ When I asked how it happened, he replied, ‘Abos, mate. Would have burned it just for the clothes in the panniers.’ I was still numb when I told the garage owner I would not be needing a tyre after all, and when I explained why he replied, ‘Yeh, that cop at Fitzroy’ll really teach ’em a lesson, take his shotgun down to the camp. Least you’ll get yer clothes back.’ And so I didn’t pursue the matter. Instead I went with Bill to Darwin from where, like any teenager, I phoned Mum and asked for money for an airfare home. The city had been hit by Cyclone Tracy the year before, and most of it was little more than a forest of concrete house supports. I felt about that flat too.
I still don’t know what happened to my bike. And it was only much later that I learned who those people were camped around the hotel at Fitzroy Crossing. Many were Walmatjarri tribesmen and women from Noonkanbah station. From the time their land had been appropriated by Europeans in the late nineteenth century until the 1960s, the Walmatjarri had worked as cattlemen, being paid by the owners partly in flour and sugar. The life they lived was not so different from the one they had known before the European invasion, for they were still living on their traditional land, visiting its sacred sites and eating plenty of bush tucker. When we granted them equal wages in the 1960s, the station owner couldn’t afford to pay union rates, so he kicked them off the place. They had retreated to the only refuge they knew—Fitzroy Crossing.
In 1976—a year after I heard their sad corroboree—the Walmatjarri got their land back, the transfer of title marked by the passing of a handful of soil to a tribal elder. It was one of the earliest acts of reconciliation to take place in Australia, but still the Walmatjarri had a long fight ahead of them. The mineral exploration company CRA wished to explore for oil in the area—mineral exploration was not allowed, while looking for oil was. After several confrontations between the Walmatjarri and CRA, in 1981 a hole was drilled right next to a sacred site. Not surprisingly, no oil was ever discovered, and having established the primacy of their right to explore, the mining company moved on, leaving a punctured land and people in its wake.
By the time I returned to Melbourne in the summer of 1976 I had discovered that I lived in the most astonishing, harsh and beautiful country on Earth; and that the kangaroo, in all its enigma and mystery, lay at the heart of Australia. I still had several years of my humanities degree before me, but now I knew what I must do. Somehow I would become a biologist so that I could better understand this country and its extraordinary creatures. It was a tortuous career path, involving many catch-up courses, a Master of Science in geology at Monash University, then a shift to zoology and the University of New South Wales, where I completed a doctorate in 1984. By a stroke of great good fortune I then found a job—in November 1984—as technical officer in the mammal section of the Australian Museum in Sydney. Now I could study kangaroos to my heart’s content.
6
Kangaroo Essence
When the gentlemen of Hobart met in 1829 to form Australia’s first scientific society, they took as their motto Quocunque aspicias hic paradoxus erit. ‘Whatever one examines here will seem a paradox.’ It was a phrase that well captured the received British perception that everything in Australia was, contra naturam, novel to the point of being ridiculous. The kangaroo, as symbol of the newly discovered land, bore the full brunt of this preconception. Phrases such as ‘kangaroo court’—a court where there is no justice—entered the language via America and reinforced the sense that things get turned on their head in Australia and can’t be taken seriously.
For anyone who has watched a red kangaroo with her joey in the dawn light of the Australian desert, such glosses are manifestly inadequate. The crisp air lends a gossamer-thin softness to the landscape whose pastel shades are all the more precious for the knowledge that in an hour or so they will be gone, and in its stillness wafts the delicate scent of dust and saltbush that is the essence of the outback. Not
A whimsical artistic rendering of the first kangaroo, as it was imagined by Rudyard Kipling.
knowing that you are there she rests, the mother, her eyes half closed as the first weak rays of the sun warm her, while her offspring tries out his new legs in flailing investigations of every bush, insect and stone in his expanded world. They are frail living things in an awesome wideness of environment that, like the open ocean, offers no refuge from the forces of nature. Yet they will survive. They always have. Unless of course we disrupt the subtle web of relationships that life is attuned to in this country.
So what, in essence, are kangaroos? While manners may make the man, the outer form does not make the kangaroo, for members of this family are astonishingly varied—being mistaken for cats, rats, deer and raccoons by early European observers. Their variety continues to confound non-expert observers, and yet no matter whether they be tiny rat-kangaroos or the giant red, kangaroos share a suite of characteristics that make them utterly different from all other living things. These kangaroo essentials, so to speak, underpin the creature’s great success, and involve the way kangaroos reproduce, eat and get about. Because they evolved with the earliest kangaroos, they tell us a lot about the ecological challenges that faced the first kangaroos in a long-vanished Australia. In effect they form a sort of family blueprint, an ‘anatomical fossil’ dating to the Eocene period, around 35 to 55 million years ago.
Kangaroos have no close relatives among living marsupials, yet their anatomy bears the indelible stamp of having evolved from small, tree-dwelling ancestors. One of the first people to speculate on what that original creature might have looked like was Rudyard Kipling, who in 1908 published the ‘Sing-song of Old Man Kangaroo’:
Not always was the kangaroo as now we do behold him, but a Different Animal with four short legs. He was grey and he was woolly, and his pride was inordinate: he danced on an outcrop in the middle of Australia… saying, ‘Make me different from all other animals; make me popular and wonderfully run-after by five this afternoon.’
When biologists rather than poets try to picture the creature kangaroos evolved from, the living pygmy possums—mouse-sized omnivores that lurk in dense scrubs in southern and eastern Australia—offer the best guide, for they share a few odd characteristics with kangaroos. Hopping, however, is not one of them, and the ankles of these possums make one realise how extraordinary it is that kangaroos—and hopping—ever evolved at all. Possums have the most flexible ankles of any living mammal, allowing the foot to be ‘dislocated’ so that it can swing through 180 degrees and point backwards—something unimaginable outside the
From left to right: 1) The foot of a musky rat-kangaroo, the only species to have a graspin
g great toe. 2) A forest wallaby. In all kangaroos two toes (here, those on the right) are encased together in skin for grooming. 3) A rock-wallaby, whose short claws and fingerprint-like gripping pads are useful when leaping among rocks. 4) The tree-kangaroo’s broad foot and long, curved claws help grip tree-trunks.
torture chamber for humans and kangaroos alike—but a very necessary ability for an animal that climbs down tree-trunks head-first. To convert this most flexible of ankles into the rigid structure required to withstand the extreme forces generated by hopping is an engineering feat akin to converting a bicycle into a bulldozer.
The flexibility in a possum’s foot is facilitated by the shape of its joints, which are rounded—rather like ball-and-socket structures—and loose-fitting. The joints in the kangaroo foot are, in contrast, all sharp angles and closely opposed linear facets. In extreme cases bones have become fused together to exclude all movement except in a forwards–backwards direction. The evolution of the kangaroo foot is so distinctive that a single bone is usually all you need to identify its owner. Indeed the kangaroo family, Macropodidae (meaning ‘big foot’) takes its name from this part of the anatomy.
We have little idea how long it took for this radical re-engineering to be effected, but we do know one thing—the changes were not driven by the requirements of hopping, but rather a shift from an arboreal to a terrestrial lifestyle. This is because it is evident from the fossil record that hopping was not achieved until long after the distinctive features of the kangaroo foot first appeared. For millions of years—possibly tens of millions of years—after the group first arose, it seems all kangaroos got about by bunny-hopping.
Feet are important, for unless one belongs to a shoe-wearing species they provide the interface between a land mammal and its environment, and that determines where one can go, how fast, and at what expense. Another anatomical feature of the kangaroo every bit as odd as its feet are its genitals. Contrary to any sense of good use—and as noted by many early settlers who took this as further proof that everything was paradoxical in Australia—in the male the usual order of appearances is reversed—the scrotum hangs in front of the penis. Unless you have seen an excited male kangaroo you may not have noticed this remarkable fact, for most of the time its penis lies hidden inside a pouch in the cloaca (appropriately meaning ‘sewer’ in Latin, for it is the common opening for both urine and faeces). The kangaroo penis is slender, S-shaped, pink, and very long. It needs to be, for to be of use it must snake around the prominent scrotum.
All marsupials share this strange anatomy, and if you have the necessary equipment and are so inclined, palpation of your own wedding tackle may convince you that your ancestors possessed a similarly inconvenient arrangement. To prove that the reverse order is the primitive condition for mammals, trace your penis posteriorly until you find its base, very near the anus (a more specialised offshoot of the cloaca). The ensheathing of the organ in skin and tendons so that it exits the body well forward of this point has been the work of untold millions of years of evolution.
The original, forward position of the testes in our ancestors can also be demonstrated by our anatomy. Gently pinch your abdominal wall just to the sides and in front of your penis’s point of entry into the world. You should be able to feel the cords from which the testes are suspended. Before you were born your testes migrated through your abdominal wall then took a downward turn to enter the scrotum, there to reside in sensible placental manner behind the business end of the penis. But in our distant ancestors, which lived before this migration occurred, they clung to the stomach wall below the belly button. This is pretty much what you see in kangaroos, except that they have evolved a capacious scrotum to house them.
Do not, incidentally, believe everything you see in museums, for sometimes confused taxidermists have effected a kind of evolutionary sex-change operation upon the unfortunate marsupials in their care. The most spectacular example I know of resides in Oxford University’s zoology museum—the very place where Thomas Huxley took on Bishop Wilberforce in the first public and fiery debate on evolution. When mounting their stuffed male thylacine, a deluded don (or a don’s assistant) fabricated a whole new three-piece set for the animal, modelled precisely upon the genitals of an alsatian and crafted (as far as I can tell) out of deer fur! If you wish to see real male thylacine genitals travel to Leiden in the Netherlands, in whose Naturalis Museum resides the only surviving thylacine penis I know of. It is a splendid organ—albeit like that of the kangaroos a little on the slender side, but just as long, and double-headed (or at least cleft) to boot.
While the reproductive anatomy of the male kangaroo may be mostly a reflection of the ancestral mammalian condition, that of the female is packed with novelty. Let me give you a riddle. What has two vaginas, yet gives birth through neither? If your answer is a female kangaroo, congratulations, you are correct. Her two vaginas, which open into her cloaca, are a relic of a time when the entire female reproductive system was divided into left and right sides, a condition that can still be seen in reptiles. But the fact that kangaroos do not give birth through either vagina is entirely original. Instead, as her time nears, a canal forms in the flesh between her vaginas, and it is through this unique anatomical structure that the young enters the world.
Like all mammals the young kangaroo begins life as a fertilised egg. At one tenth of a millimetre in diameter it is tiny, but as with the eggs of chickens (and unlike our own eggs, which lack the outer layers) it is enclosed in a full set of shell membranes. It is out of this tiny egg that, during the last week or so of pregnancy, the kangaroo hatches. Its egg-yolk membranes then form a sort of placenta, delivering nutrients directly from the mother’s uterus, allowing the embryo to grow rapidly. After a pregnancy of thirty-three days the red kangaroo is born, having grown to the size of a raisin and weighing just under a gram. That such a minuscule being can breathe, climb and suckle is a marvel to many people, but the young kangaroo is born in an advanced state compared with the young of other marsupials, which have shorter pregnancies and smaller young, even when adult body size is taken into account. Some bandicoots are pregnant for only eleven days, while many marsupial newborns are the size of a grain of rice.
As befits a species that, relative to other marsupials, invests so much in pregnancy, the mother kangaroo lavishes resources on young that are born singly or, rarely, as twins. Again this contrasts mightily with the basic marsupial pattern, of which the American opossum is a fine example. An opossum mother has thirteen nipples—the one making up the baker’s dozen sitting in the middle of a circle created by the rest—but she gives birth to as many as fifty-six young, thus dooming most to lose at the first lotto-draw of life. The production of throwaway embryos in this manner is common among marsupials, but is utterly foreign to the kangaroo.
The kangaroo possesses a remarkable (at least from a human perspective) capacity to switch on and off the development of her growing young. Were women so endowed they could conceive whenever they wished, then tailor the baby’s birthdate to suit their calendars. While there is still much mystery about the origins of this amazing capacity, kangaroos use the ability to maximise their reproduction. Once she reaches sexual maturity the female kangaroo is, quite literally, forever barefoot and pregnant.
The system works as follows. A few hours after the female kangaroo gives birth and houses her new baby joey in her pouch, she seeks a mate, copulates and once again falls pregnant. Having sex on the birthing bed, so to speak, might seem to be in bad taste and contrary to common sense—so why would any creature do it? The answer lies at least in part in energy efficiency, for pregnant and lactating mammals must maintain a higher body temperature than normal, which costs extra food and energy. If you can be pregnant and lactate at the same time, you shorten the length of time an elevated temperature is required, thus saving on energy.
Following conception the embryo develops normally until it is about a third of a millimetre across, then it abruptly stops. A chemic
al ‘order’ has been sent for it to cease growing, and it enters a state of suspended animation in which it can remain for almost a year. Inevitably a signal to resume development is sent, and within a few weeks—usually on the very day that the older young leaves the pouch permanently—a new kangaroo is born. Two other Australian marsupials possess a similar capacity, the thumb-sized honey possum of the southwest of Western Australia, and at least one species of pygmy possum, which is one reason why scientists posit an evolutionary link between kangaroos and these creatures. Several kangaroo species have modified this reproductive heritage—the female eastern grey kangaroo does not copulate until three or four months after the birth of her young—but the pattern outlined above seems to have evolved with the earliest kangaroo, and it is retained in the majority of her descendants today.
Interestingly, the puppet-master controlling the development of the embryo is not the mother at all, but her joey. While it sucks hard and steadily, the embryo will remain in suspended animation. But if the suckling eases—perhaps an accident befalls the joey or it starts to eat solid food—the quiescent embryo recommences its growth. And while the older young is shut out of the pouch by the mother’s powerful pouch muscles on the day of its sibling’s birth, the mother does permit the older joey to put its head into the pouch to suckle from its nipple (joeys remain faithful to a single nipple, despite the fact that they have four to choose from) which after many months of sucking has become enormously elongated.
The mother must now suckle two young of very different sizes—one weighing a gram and the other up to four kilograms—and because their nutritional needs are very different she must provide milk with differing chemical formulas. To her smaller young she must provide the proteins needed to grow fur when it is ready, while the larger young may need more water. Just how she performs this miracle of mammary discretion no one understands, and few fields in the natural sciences offer more promise of fundamental discovery than that of marsupial lactation.