Science is Golden

by Karl Kruszelnicki

  ‘I usually proceeded till only the bottom piece—too thick to break with the teeth—was left.

  ‘There were always wise guys who challenged me to eat that too, to which my response was “when you eat as much as I have, I will eat the bottom too, ha, ha, ha”.

  ‘I must stress; this is NOT hearsay. This is my personal experience.’

  Physiology of Gut

  The gut is a very dynamic organ, continually writhing around as it processes your food in the space between the bottom of your lungs and the top of your legs. The gut is also dynamic internally—both the wall thickness of the gut, and the internal diameter of the gut change continually in a coordinated fashion. These movements are generally called ‘peristalsis’. So your gut both grinds your food very finely and pushes it along the 8-metre-or-so length of the gut, before it finally emerges into your toilet bowl.

  Long, fat, sharp splinters of glass would definitely cause problems as they were shoved along your gut—but you would certainly notice such splinters as you chewed your meal.

  And yes, chunks of jagged glass the size of match heads would cause bleeding as they rubbed against the soft interior of your gut. But with a chunk of glass in your mouth, you would certainly notice the unexpectedly rough texture of your meal.

  You would even notice the glass if it were ground as finely as sand. (Ever had a picnic on a windy day at the beach?) And if the glass were ground so finely that you didn’t notice its presence in your mouth, then neither would your gut.

  It would seem that ground glass as a murder weapon would transparently reveal your murderous relative as a Pain in the Glass…

  References

  Barham, Andrea, The Pedant’s Revolt: Why Most Things You Think Are Right Are Wrong, London: Michael O’Mara Books Limited, 2005, pp 22–23.

  Jackson, Caroline M., ‘Glassmaking in Bronze-Age Egypt’, Science, 17 June 2005, Vol 308, No 5729, pp 1750–1752.

  Lyle, D.P., Murder and Mayhem: A Doctor Answers Medical and Forensic Questions for Mystery Writers, New York: St Martin’s Press, 2003.

  Rehren, Thilo, et al., ‘Late Bronze-Age glass production at Qantir-Piramesses, Egypt’, Science, 17 June 2005, Vol 308, No 5729, pp 1756–1758.

  Shattock, S.G., ‘The Traumatic Causation of Appendicitis’, The Proceedings of The Royal Society of Medicine, London, 1915–16, ix., Pathological Section, pp 26–27, 2 May 1916.

  Smith, Dr F.J. (Editor), Taylor’s Principles and Practices of Medical Jurisprudence, Fifth Edition, 1905, Vol ii, p 847.

  Hyena Horribilis

  Luckily we don’t need to be zoologists to have three ‘facts’ about the Spotted Hyena (Crocuta crocuta) at our fingertips. One, they are some kind of dog. Two, they have the most powerful bite for their weight. And three, they are loathsome and cowardly scavengers.

  These three ‘facts’ are wrong—but it gets even weirder. Not only does the female Spotted Hyena outrank the male, but she also has an organ that looks exactly like the male’s penis. Even stranger, she gets pregnant and even gives birth through this organ.

  Cats or Dogs?

  First, hyenas are not members of the dog family. They are more closely related to cats.

  Both cats and dogs are carnivorous mammals with spinal cords. They belong to the same Kingdom—Animalia; the same Phylum—Chordata (creatures with spinal cords); the same Class—Mammalia (which breast-feed their young); and the same Order—Carnivora (meat eaters).

  However, about 50 million years ago, there was a parting of the ways—dogs splitting off along a pathway that led to the Family Canidae (which today includes dogs, wolves and foxes). The line

  that led to cats, mongooses and hyenas continued on into the Suborder Feliformia, which split and resplit over the next ten million years.

  About 30 million years ago, hyenas split off along a pathway that led to the Family Hyaenidae. They flourished, and by 15 million years ago, there were at least 30 different species of hyena.

  The Family of Hyaenidae then split off into various Subfamilies, two of which survive today—the Protelinae (the Aardwolf Hyena, 6–10 million years ago) and the Hyaeninae (which include Spotted, Striped and Brown Hyenas).

  So the hyenas of today are very closely related to civets and mongooses, closely related to cats—and distantly related to the Canids (which include dogs, wolves and foxes).

  Early Hyaenidae species did not have the bone-crushing molars of today’s hyenas—they evolved into existence about 5–7 million years ago. The largest known hyena was the 200-kg Pachycrocuta. It lived from three million to half a million years ago and had massive teeth that could crush the bones of elephants.

  Hyena Horribilis

  No real laughing matter

  Hyenas are not, as commonly thought, a variety of dog. They are actually closer to the cat family.

  They live in Africa, the Middle East, Pakistan and India.

  Hyena Species

  All hyena species tend to be nocturnal.

  The Aardwolf Hyena (Proteles cristatus) (the name means ‘earth wolf’ in Afrikaans) looks like a small Striped Hyena. Its diet is so specialised that it will eat only two types of termites. Apart from the canines, its teeth have dwindled to mere pegs that can no longer chew meat. These solitary animals will lick up to 30,000 termites each night.

  The Striped Hyena (Hyena hyaene) inhabits scrubland and arid and semiarid open country from Morocco to Egypt and Tanzania in Africa. It is also found in Asia Minor, the Caucasus and India. It weighs 30–40 kg, has pale grey long hair with black fur on the throat, and stripes on the body and legs. The crest that runs from the ears to the tail is erectile. There is a three-month gestation period, the cubs being weaned at 10–12 months of age.

  The Brown Hyena (Hyaena brunnea) is found in South Africa and along the western coastal deserts of Africa. It has pointed ears, a shaggy dark coat, with an erectile white mane over the neck and shoulders and horizontal white bands on the legs.

  The gestation period is three months, weaning of the cubs occurring at 15 months. This species is smaller and lighter (40 kg) than the Spotted Hyena and inhabits much drier areas. These hyenas do not sniff each other’s genitals as a greeting, but instead sniff heads, faces, necks and bodies.

  The Spotted or Laughing Hyena (Crocuta crocuta) lives south of the Sahara, in rainforests, deserts, swamps and mountains and is the most numerous predator in the Serengeti. It is the largest hyena species—weighing up to 85 kg. The females are larger than the males, measuring up to 100 cm high at the shoulder and 2 m long, with a massive neck. They are also about 6.6 kg heavier. They have a ginger colour and a unique pattern of spots. Their ‘laugh’ is a signal of fear, excitement, or being chased. The gestation period is approximately four months, the young being weaned at 12–16 months, which is exceptionally late compared to other mammals.

  Bite Club

  Mentioning teeth brings us to the second myth about hyenas—that, weight for weight, they have the most powerful bite of any animal. A fascinating paper by Stephen Wroe from the University of Sydney, entitled ‘Bite Club’, compared the Bite Force Quotient of various animals (alive and extinct, mammal and marsupial), as it related to their body weight. It was higher in marsupials and in animals that consistently attacked animals larger than themselves. The Spotted Hyena came in at 117—only slightly ahead of the lion at 112, but behind the tiger (127), the African Hunting Dog (142) and well behind the Tasmanian Devil at 181. The all-time winner was the Australian Marsupial Lion at 196.

  By the way, while the favourite food of Spotted Hyenas seems to be zebra, they will eat anything.

  On one hand, a pack of hyenas will entirely devour a 180-kg zebra in less than 25 minutes, leaving behind only bloodstained earth. They will later vomit up the hooves and the hair. In another example of Big Eating, a pack of 35 hyenas ate an adult zebra and her two-year-old foal (with an estimated total weight of 350 kg) in less than 30 minutes. A single Spotted Hyena can eat over 18 kg at a single meal—more than one-third of its we
ight. It is one of the very few animals that can eat every part of a carcass, including the bones. (In fact, their droppings are often white and crusty, thanks to the amount of bone in their diet.) This may explain why they are associated with gluttony, uncleanliness and even cowardice.

  On the other hand, Spotted Hyenas will also happily eat rotten meat that would make other animals quite sick. Scientists are studying the immune system of the Spotted Hyena to try to work out why they are unaffected by eating tainted flesh, and why they do not seem to suffer from any major infectious diseases.

  Hyena vs Lion

  Surprisingly, lions and hyenas seem to hate each other, lions going out of their way to kill hyenas. Indeed, lions will do this even when they are not hungry, leaving the hyena carcasses uneaten.

  Some 60% of hyena deaths are caused by lions.

  Scavenger

  As mentioned, hyenas will sometimes eat meat that has been hanging around for so long that it has gone rotten. Doesn’t this surely mean that they are scavengers?

  After all, in the Disney movie The Lion King they are described as ‘slobbery, mangy, stupid poachers’, while Ernest Hemingway saw them as a ‘devourer of the dead…sad yowler, camp-follower, stinking, foul’. The Encyclopaedia Britannica acknowledges this common belief with, ‘The Spotted Hyena, widely known as a scavenger, has heavy jaws equipped for crunching bones.’

  So let’s look at this so-called scavenging behaviour.

  For one thing, no sensible carnivore is going to let a perfectly good meal of edible meat go to waste. After all, they don’t even have to expend energy to chase it—it’s just lying there for the taking. So tigers, lions, cheetahs, jaguars and yes, hyenas, will all eat carrion.

  In addition, the noted wildlife biologist George Schaller, after several decades of observing these animals, claimed that lions scavenged more kills than Spotted Hyenas. And zoologist Dr Kay Holekamp, who has been studying Spotted Hyenas for a few decades, agreed, saying ‘it is far more frequent that the lion will steal a kill from the hyenas’ than vice versa.

  She also noted that hyenas are excellent hunters, catching about 95% of what they eat.

  So if lions aren’t accused of being scavengers, why accuse hyenas?

  Spotted Hyena 101

  Spotted Hyenas have long legs, and a powerful neck, jaw and shoulders for carrying and ripping apart their prey. They are tireless trotters and have been observed travelling at 60 kph for 3 km.

  The naturalist, Hans Kruuk, spent three and a half years observing the Spotted Hyenas of the Serengeti. He was impressed by these sophisticated hunters living in complex clans—he had originally expected to find solitary scavengers.

  Spotted Hyenas live in clans of up to 80 members, but beyond this, they split into smaller groups. They live in communal dens—a collection of underground tunnels with many above-ground entrances. They come together only for three occasions—kills, defending their territory and socialising at the communal den. Their territory ranges from 40 to 1,000 km2.

  They are very intelligent—possibly as smart as primates. When zoologists put a hyena into a small metal cage with a latch, the animal quickly learnt how to flip open the latch.

  Like primates, they have a high social intelligence and learn and follow the relevant rules of their society, form temporary and permanent coalitions within their clans and can understand the importance of some relationships over others.

  They can solve social problems using sophisticated mechanisms, such as conciliation, distraction and even deception. For example, a hungry, low-ranking hyena might give the Alarm Cry while higher-ranking members of the clan are feeding. When the other hyenas leave the area to respond to the nonexistent danger, the low-ranking hyena moves in to eat its fill.

  Confused Sexuality—History

  It’s been known for a long time that there was something special about the sexual anatomy and physiology of the Spotted Hyena.

  Quite a few ancient writers declared that the Spotted Hyena was a hermaphrodite with the genitals of both sexes in one body, or that it could change its sex. The Greek philosopher Aristotle (384–322 BC) mentions these claims but says that they are untrue. The Roman poet Ovid (43 BC–17 AD), who was famous for his love poems, thought that the hyena could change its gender. A few centuries later, the great Roman thinker and scientist Pliny the Elder (23–79 AD) also refers to Aristotle’s claims. St Clement of Alexandria (c. 150–211/216 AD) wrote in his Paedogogus that the hyena was ‘quite obsessed with sexual intercourse’. He believed that male hyenas could have sex with each other. But the Roman writer Claudius Aelianus (c. 175–c. 235 AD) preferred the hermaphrodite theory, claiming that the Spotted Hyena could change its sex in alternate years.

  Quite frankly, there was very little real knowledge about this species until the autumn of 1935, when the zoologist L. Harrison Matthews chartered a truck at Arusha, in Tanganyika Territory in East Africa.

  He set off on safari, killing about 103 Spotted Hyenas either with poisoned baits or bullets. He dissected them as soon as he could after they died. He examined them closely in the field, and then stored their genital tracts for later re-examination in England. He finally wrote up his results in 1939.

  Confused Sexuality—Anatomy

  According to Harrison Matthews the females are truly astonishing. They have a clitoris that looks just like a penis, and through which they give birth! The technical term for this is ‘extreme masculinisation of the external genitalia’.

  The clitoris is so enlarged that it looks just like the male hyena’s penis—zoologists call it a ‘pseudopenis’ or a ‘peniform clitoris’. It even has a narrow channel running through it to the outside world. Like the male hyena’s penis, the pseudopenis has two ‘corpora cavernosa’ and a single ‘corpus spongiosum’. This means that the female Spotted Hyena could have a genuine erection of its pseudopenis, as does the male with his penis. The clitoris is also as long as the male’s penis—about 17 cm.

  The female’s labia are fused together, and because it has two fatty pads, it looks almost identical to a male’s scrotum.

  So thanks to the pseudopenis and the fused swollen labia, sometimes even hyena specialists cannot tell the difference between boy and girl hyenas. On a few occasions, Dr Holekamp was surprised when a ‘male’ she had known since birth suddenly delivered cubs, proving that ‘he’ was actually a ‘she’. Perhaps this is how the misinformation about Spotted Hyenas being hermaphrodites came about.

  Female Spotted Hyenas do have a vagina, but it does not open directly to the outside world. Instead, it communicates with the outside world via the pseudopenis. It is a true vagina both in its appearance to the naked eye—and under a microscope.

  Only Spotted Hyena females have the pseudopenis. The females of other hyena species have ‘regular’ female genitals.

  Confused Sexuality—Physiology

  Female Spotted Hyenas urinate, copulate and give birth through the pseudopenis.

  Mating is impossible without the full cooperation of the female. The male has to balance himself very precariously, because of the orientation of the pseudopenis.

  The reproductive tract runs from the vagina, past the opening of the bladder and through the pseudopenis to the outside world. This means that the sperm have a long way to travel. Thanks to the position of the urinary bladder, she can flush out the sperm, if she changes her mind after mating.

  The reproductive tract has a hairpin turn along its length, as well as a small opening to the outside world. This means that it’s hard to give birth. Indeed, according to Harrison Matthews ‘lacerations to the margin of the opening are not uncommon’. Birth is a very uncomfortable process that kills one in ten mothers, and suffocates 60% of the first-born cubs.

  Hyena Cubs

  The pregnant Spotted Hyena goes off by herself to give birth. When the cubs are one month of age, she moves them back to the communal den, where they stay for eight months. She has only two nipples, so if she has three cubs, the least aggressive o
ne will starve.

  The cubs have only their mother’s milk for the first six months. Meat is then added to the diet until they are weaned at 12–16 months of age. By this time, they have a full set of adult teeth. But because their massive jaws and skulls take a few more years to mature, the mother must take care of them for 2–4 years. The mothers are very caring, tolerant and affectionate.

  Hyena in Human Society

  In Africa, the hyena was associated with divination, and thought of as a tool of demons and witches, much like the black cat in medieval European society.

  Witches and sorcerers were thought to travel either by riding on its back, or by turning into a hyena.

  It was also believed that the `laughter’ of the Spotted Hyena could not only closely imitate the human voice, but could also call the potential victims individually by name.

  Even though the Masai of Africa traditionally despise the hyena, they will leave out their dead for the hyenas to eat.

  Hyena Society—Women First

  There are very few female-dominated societies.

  Spotted Hyenas live in such a society. The lowest status female outranks the highest status male. The females are more aggressive than the males.