The Ancestor's Tale Part 9

Fruit flies and mice measure their generations in weeks and months, not decades as we do. In one experiment, Drosophila Drosophila fruit flies were split into two 'lines'. One line was bred, over several generations, for a positive tendency to approach light. In each generation, the most strongly light-seeking individuals were allowed to breed. The other line was bred systematically in the opposite direction, over the same number of generations, for a tendency to shun light. In a mere 20 generations, dramatic evolutionary change was achieved, in both directions. Would the divergence go on for ever at the same rate? No, if only because the available genetic variation would eventually run out and we'd have to wait for new mutations. But before this happens, a great deal of change can be achieved. fruit flies were split into two 'lines'. One line was bred, over several generations, for a positive tendency to approach light. In each generation, the most strongly light-seeking individuals were allowed to breed. The other line was bred systematically in the opposite direction, over the same number of generations, for a tendency to shun light. In a mere 20 generations, dramatic evolutionary change was achieved, in both directions. Would the divergence go on for ever at the same rate? No, if only because the available genetic variation would eventually run out and we'd have to wait for new mutations. But before this happens, a great deal of change can be achieved.

Maize has a longer generation time than Drosophila Drosophila. But in 1896 the Illinois State Agricultural Laboratory started breeding for oil content in maize seeds. A 'high line' was selected for increased oil content, and a low line simultaneously selected for decreased oil (see plate 17) (see plate 17). Fortunately this experiment has been continued far longer than the research career of any normal scientist, and it is possible to see, over 90 or so generations, an approximately linear increase in oil content in the high line. The low line has decreased its oil content less rapidly, but that is presumably because it is. .h.i.tting the floor of the graph: you can't have less oil than zero.

This experiment, like the Drosophila Drosophila one and like many others of the same type, brings home the potential power of selection to drive evolutionary change very fast indeed. Translate 90 generations of maize, or 20 generations of one and like many others of the same type, brings home the potential power of selection to drive evolutionary change very fast indeed. Translate 90 generations of maize, or 20 generations of Drosophila Drosophila, even 20 elephant generations, into real time, and you have something that is still negligible on the geological scale. One million years, which is too short to notice in most parts of the fossil record, is 20,000 times as long as it takes to triple the oil content of maize seeds. Of course this doesn't mean a million years of selection could multiply the oil content by 60,000. Quite apart from running out of genetic variation, there's a limit to how much oil a maize seed can pack in. But these experiments serve to warn against looking at apparent trends spread over millions of fossil years, and naively interpreting them as responses to steadily sustained selection pressures.

Darwinian selection pressures are out there, for sure. And they are immensely important, as we shall see throughout this book. But selection pressures are not sustained and uniform over the sort of timescales that can normally be resolved by fossils, especially in older parts of the fossil record. The lesson of the maize and the fruit flies is that Darwinian selection could meander hither and yon, back and forth, ten thousand times, all within the shortest time we can measure in the record of the rocks. My bet is that this happens.

Yet there are major trends over longer timescales, and we have to be aware of them too. To repeat an a.n.a.logy I have used before, think of a cork, bobbing about off the Atlantic coast of America. The Gulf Stream imposes an overall eastward drift in the average position of the cork, which will eventually be washed up on some European sh.o.r.e. But if you measure its direction of movement during any one minute, buffeted by waves and eddies and whirlpools, it will seem to move west as often as east. You won't notice any eastward bias unless you sample its position over much longer periods. Yet the eastward bias is real, it is there, and it too deserves an explanation.

The waves and eddies of natural evolution are usually too slow for us to see in our little lifetimes, or at least within the short compa.s.s of a typical research grant. There are a few notable exceptions. The school of E. B. Ford, the eccentric and fastidious scholar from whom my generation of Oxford zoologists learned our genetics, devoted decades of research to tracking the year-by-year fortunes of particular genes in wild populations of b.u.t.terflies, moths and snails. Their results in some cases seem to have straightforward Darwinian explanations. In other cases the noise of buffeting waves drowns out the signal of whatever Gulf Streams may have been tugging the undertow, and the results are enigmatic. The point I am now making is that such enigma is to be expected by any mortal Darwinian even a Darwinian with a research career as long as Ford's. One of the main messages Ford himself drew from his life's work was that the selection pressures actually to be found in nature, even if they don't always pull in the same direction, are orders of magnitude stronger than anything dreamed of by the most optimistic founders of the neo-Darwinian revival. And this again underlines the point: why doesn't evolution go much faster than it does?

THE GALAPAGOS FINCH'S TALE.

The Galapagos archipelago is volcanic, and no more than 5 million years old. During that brief existence, a spectacular quant.i.ty of diversity has evolved most famously among the 14 species of finches widely, though perhaps wrongly, believed to have been Darwin's princ.i.p.al inspiration.2 The Galapagos finches are among the most thoroughly studied wild animals in existence. Peter and Rosemary Grant have devoted their professional lives to following the year-by-year fortunes of these small island birds. And in the years between Charles Darwin and Peter Grant (who himself bears a pleasing facial resemblance to Darwin) the great (but clean-shaven) ornithologist David Lack also paid them a perceptive and productive visit. The Galapagos finches are among the most thoroughly studied wild animals in existence. Peter and Rosemary Grant have devoted their professional lives to following the year-by-year fortunes of these small island birds. And in the years between Charles Darwin and Peter Grant (who himself bears a pleasing facial resemblance to Darwin) the great (but clean-shaven) ornithologist David Lack also paid them a perceptive and productive visit.3 The Grants and their colleagues and students have been returning yearly to the Galapagos Islands for more than a quarter of a century, trapping finches, individually marking them, measuring their beaks and wings, and more recently taking blood samples for DNA a.n.a.lysis to establish paternities and other relationships. There has probably never been a more complete study of the individuals and genes of any wild population. The Grants know in minute detail exactly what is happening to the bobbing corks which are the finch populations, as they are tossed this way and that in the sea of evolution by selection pressures that change every year.

In 1977 there was a severe drought, and the food supply plummeted. The total number of individual finches of all species on the small island of Daphne Major dropped from 1,300 in January to less than 300 by December. The population of the dominant species, Geospiza fortis Geospiza fortis, the medium ground finch, dropped from 1,200 to 180. The cactus finch, G. scandens G. scandens, fell from 280 to 110. Figures for other species confirmed that 1977 was a finch annus horribilis annus horribilis. But the Grant team didn't just count the numbers of each species dying and living. Being Darwinians, they looked at the selective selective mortality figures within each species. Were individuals with certain characteristics more likely to survive the catastrophe than others? Did the drought selectively change the relative composition of a population? mortality figures within each species. Were individuals with certain characteristics more likely to survive the catastrophe than others? Did the drought selectively change the relative composition of a population?

Yes, it did. Within the G. fortis G. fortis population, the survivors were on average more than five per cent larger than those that succ.u.mbed. And the average beak after the drought was 11.07 mm long compared with 10.68 mm before. The mean depth of beak had similarly gone up from 9.42 mm to 9.96 mm. These differences may seem tiny but, within the sceptical conventions of statistical science, they were too consistent to be due to chance. But why would a drought year favour such changes? The team already had evidence that larger birds with larger beaks are more efficient than average birds at dealing with the big, tough, spiky seeds such as those of the weed population, the survivors were on average more than five per cent larger than those that succ.u.mbed. And the average beak after the drought was 11.07 mm long compared with 10.68 mm before. The mean depth of beak had similarly gone up from 9.42 mm to 9.96 mm. These differences may seem tiny but, within the sceptical conventions of statistical science, they were too consistent to be due to chance. But why would a drought year favour such changes? The team already had evidence that larger birds with larger beaks are more efficient than average birds at dealing with the big, tough, spiky seeds such as those of the weed Tribulus Tribulus, which were just about the only seeds to be found during the worst of the drought. A different species, the large ground finch G. magnirostris G. magnirostris, is the professional when it comes to handling Tribulus Tribulus seeds. But Darwinian survival of the fittest is all about the relative survival of individuals within a species, not the relative survival of one species compared to another. And within the population of medium ground finches, the largest individuals with the largest beaks survived best. The average seeds. But Darwinian survival of the fittest is all about the relative survival of individuals within a species, not the relative survival of one species compared to another. And within the population of medium ground finches, the largest individuals with the largest beaks survived best. The average G. fortis G. fortis individual became a tiny bit more like individual became a tiny bit more like G. magnirostris G. magnirostris. The Grant team had observed a small episode of natural selection in action, during a single year.

They witnessed another episode after the drought ended, which pushed the finch populations in the same evolutionary direction, but for a different reason. As with many species of bird, G. fortis G. fortis males are larger than females, and they have larger beaks, which presumably equipped them to survive the drought better. Before the drought there were about 600 males and 600 females. Of the 180 individuals who survived, 150 were male. The rains, when they finally returned in January 1978, unleashed boom conditions which were ideal for breeding. But now there were five males for every female. Understandably, there was fierce compet.i.tion among the males for the scarce females. And the males who won these s.e.xual compet.i.tions, the new winners among the already larger-than-normal surviving males, again tended to be the largest males with the largest beaks. Once again, natural selection was driving the population to evolve larger body size and larger beaks, but for a different reason. As to why females prefer large males, the Seal's Tale has primed us to see significance in the fact that male males are larger than females, and they have larger beaks, which presumably equipped them to survive the drought better. Before the drought there were about 600 males and 600 females. Of the 180 individuals who survived, 150 were male. The rains, when they finally returned in January 1978, unleashed boom conditions which were ideal for breeding. But now there were five males for every female. Understandably, there was fierce compet.i.tion among the males for the scarce females. And the males who won these s.e.xual compet.i.tions, the new winners among the already larger-than-normal surviving males, again tended to be the largest males with the largest beaks. Once again, natural selection was driving the population to evolve larger body size and larger beaks, but for a different reason. As to why females prefer large males, the Seal's Tale has primed us to see significance in the fact that male Geospiza Geospiza the more compet.i.tive s.e.x are larger than females anyway. the more compet.i.tive s.e.x are larger than females anyway.

If large size is such an advantage, why weren't the birds just larger in the first place? Because in other years, non-drought years, natural selection favours smaller individuals with smaller beaks. The Grants actually witnessed this in the years following 198283 when there happened to be an El Nino flood. After the flood, the balance of seeds changed. The large tough seeds of plants such as Tribulus Tribulus became rare in comparison with the smaller, softer seeds of plants like became rare in comparison with the smaller, softer seeds of plants like Cacabus Cacabus. Now smaller finches with smaller beaks came into their own. It wasn't that large birds couldn't eat small, soft seeds. But they needed more of them to maintain their larger bodies. So smaller birds now had a slight edge. And, within the population of medium ground finches, the tables were turned. The evolutionary trend of the drought years was reversed.

The differences in beak size between the successful and the unsuccessful birds in the drought year seem awfully small, don't they? Jonathan Weiner quotes a telling anecdote about this, from Peter Grant: Once, just as I was beginning a lecture, a biologist in the audience interrupted me: 'How much difference do you claim to see,' he asked me, 'between the beak of a finch that survives and the beak of a finch that dies?''One half of a millimetre, on average,' I told him.'I don't believe it!' the man said. 'I don't believe a half of a millimetre really matters so much.''Well, that's the fact,' I said. 'Watch my data and then ask questions.' And he asked no questions.

Peter Grant calculated that it would take only 23 bouts of 1977-style drought on Daphne Major to turn Geospiza fortis Geospiza fortis into into G. magnirostris G. magnirostris. It wouldn't literally be magnirostris magnirostris, of course. But it is a vivid way to visualise the origin of species, and how rapidly it can happen. Darwin little knew, when he met them and failed to label them properly, what powerful allies 'his' finches would eventually turn out to be.4 THE PEAc.o.c.k'S TALE.

The peac.o.c.k's 'tail' is not its true morphological tail (the true tail of a bird is the diminutive 'parson's nose'), but a 'fan' made of long back feathers. The Peac.o.c.k's Tale is exemplary for this book because, in true Chaucerian style, it carries a message or moral from one pilgrim, which helps other pilgrims to understand themselves. In particular, when I was discussing two of the major transitions in human evolution, I looked forward to when the peac.o.c.k would join our pilgrimage and give us the benefit of his (and I mean his in this case, not her) tale. It is, of course, a tale of s.e.xual selection. Those two hominid transitions were our shift from four legs to two, and the subsequent enlargement of our brain. Let's add a third, perhaps less important but very characteristically human feature: our loss of body hair. Why did we become the Naked Ape?

There were lots of ape species in Africa in the late Miocene. Why did one of them suddenly and rapidly start evolving in a very different direction from the rest indeed from the rest of the mammals? What picked out this one species and sent it hurtling at high speed in new and strange evolutionary directions: first to become bipedal, then to become brainy, and at some point to lose most of its body hair?

Rapid, apparently arbitrary spurts of evolution in quirky directions say one thing to me: s.e.xual selection. This is where we have to start listening to the peac.o.c.k. Why does the peac.o.c.k have a train that dwarfs the rest of its body, quivering and shimmering in the sun with glorious eye-spot motifs of royal purple and green? Because generations of peahens have chosen peac.o.c.ks who flaunted ancestral equivalents of these extravagant advertis.e.m.e.nts. Why does the male twelve-wired bird of paradise have red eyes and a black ruff with an iridescent green fringe, while Wilson's bird of paradise catches the eye with a scarlet back, yellow neck and blue head? Not because something in their respective diets or habitats predisposes these two species to their different colour schemes. No, these differences, and those that so conspicuously mark out all the other species of bird of paradise, are arbitrary, whimsical, unimportant to anybody except female birds of paradise (see plate 18) (see plate 18). s.e.xual selection does this kind of thing. s.e.xual selection produces quirky, whimsical evolution that runs away in apparently arbitrary directions, feeding on itself to produce wild flights of evolutionary fancy.

On the other hand, s.e.xual selection also tends to magnify differences between the s.e.xes s.e.xual dimorphism (see the Seal's Tale). Any theory that attributes human brains, bipedality or nakedness to s.e.xual selection has got to face up to a major difficulty. There is no evidence that one s.e.x is brainier than the other, nor that one s.e.x is more bipedal than the other. It is true that one s.e.x tends to be more naked than the other, and Darwin made use of this in his own s.e.xual selection theory of the loss of human hair. He supposed that ancestral males chose females rather than the other way around as is normal in the animal kingdom, and that they preferred hairless females. When one s.e.x evolves ahead of the other (in this case the female s.e.x towards hairlessness) the other s.e.x can be thought of as 'dragged in its wake'. It's the kind of explanation we more or less have to offer for that old chestnut, male nipples. It is not implausible to invoke it for the evolution of partial nakedness in man, dragged in the wake of more total nakedness in woman. The 'dragged in its wake' theory works less well for bipedality and braininess. The mind boggles recoils even when trying to imagine a bipedal member of one s.e.x walking out with a quadrupedal member of the other. Nevertheless, the 'dragged in its wake' theory has a role to play.

There are circ.u.mstances in which s.e.xual selection can favour monomorphism. My own suspicion, and Geoffrey Miller's in The Mating Mind The Mating Mind, is that human mate choice, unlike perhaps that of peafowl, goes both ways. Moreover, our criteria for choice may be different when we look for a long-term partner than when we seek a one-night stand.

For the moment, we return to the simpler world of peac.o.c.ks and peahens where females do the choosing and males strut around and aspire to be chosen. One version of the idea a.s.sumes that choice of mate (in this case choice by peahens) is arbitrary and whimsical compared with, for example, choice of food or choice of habitat. But you could reasonably ask why this should be so. According to at least one influential theory of s.e.xual selection, that of the great geneticist and statistician R. A. Fisher, there is a very good reason. I have expounded the theory in detail in another book (The Blind Watchmaker, Chapter 8) and will not do so again here. The essential point is that male appearance and female taste evolve together in a kind of explosive chain reaction. Innovations in the consensus of female taste within a species, and corresponding changes in male appearance, are amplified in a runaway process which drives both of them in lockstep, further and further in one direction. There is no overweening reason for this one direction to be chosen: it just happens to be the direction in which the evolutionary trend started. The ancestors of peahens happened to take a step in the direction of preferring a larger fan. That was enough for the explosive engine of s.e.xual selection. It kicked in and, within a very short time by evolutionary standards, peac.o.c.ks were sprouting larger and more iridescent fans, and females couldn't get enough of them.

Every species of bird of paradise, many other birds, and fish and frogs, beetles and lizards, zoomed off in their own evolutionary directions, all bright colours or weird shapes but different bright colours, different weird shapes. What matters for our purpose is that s.e.xual selection, according to a sound mathematical theory, is apt to drive evolution to take off in arbitrary directions and push things to non-utilitarian excess. The suggestion arose in the chapters on human evolution that this is just what the sudden inflation of the brain looks like. So does the sudden loss of body hair, and even the sudden take-off into bipedality.

Darwin's Descent of Man Descent of Man is largely devoted to s.e.xual selection. His lengthy review of s.e.xual selection in non-human animals prefaces his advocacy of s.e.xual selection as the dominant force in the recent evolution of our species. His treatment of human nakedness begins by dismissing more glibly than his modern followers find comfortable the possibility that we lost our hair for utilitarian reasons. His faith in s.e.xual selection is reinforced by the observation that in all races, however hairy or however hairless, the women tend to be less hairy than the men. Darwin believed that ancestral men found hairy women unattractive. Generations of men chose the most naked women as mates. is largely devoted to s.e.xual selection. His lengthy review of s.e.xual selection in non-human animals prefaces his advocacy of s.e.xual selection as the dominant force in the recent evolution of our species. His treatment of human nakedness begins by dismissing more glibly than his modern followers find comfortable the possibility that we lost our hair for utilitarian reasons. His faith in s.e.xual selection is reinforced by the observation that in all races, however hairy or however hairless, the women tend to be less hairy than the men. Darwin believed that ancestral men found hairy women unattractive. Generations of men chose the most naked women as mates.5 Nakedness in men was dragged along in the evolutionary wake of nakedness in women, but never quite caught up, which is why men remain hairier than women. Nakedness in men was dragged along in the evolutionary wake of nakedness in women, but never quite caught up, which is why men remain hairier than women.

For Darwin, the preferences that drove s.e.xual selection were taken for granted given. Men just prefer smooth women, and that's that. Alfred Russel Wallace, the co-discoverer of natural selection, hated the arbitrariness of Darwinian s.e.xual selection. He wanted females to choose males not by whim but on merit. He wanted the bright feathers of peac.o.c.ks and birds of paradise to be tokens of underlying fitness. For Darwin, peahens choose peac.o.c.ks simply because, in their eyes, they are pretty. Fisher's later mathematics put that Darwinian theory on a sounder mathematical footing. For Wallaceans,6 peahens choose peac.o.c.ks not because they are pretty but because their bright feathers are a token of their underlying health and fitness. peahens choose peac.o.c.ks not because they are pretty but because their bright feathers are a token of their underlying health and fitness.

In post-Wallace language, a Wallacean female is, in effect, reading a male's genes by their external manifestations from which she judges their quality. And it is a startling consequence of some sophisticated neo-Wallacean theorising that males are expected to go out of their way to make it easy for females to read their quality, even if their quality is poor. This piece of theory progression of theories, rather which we owe to A. Zahavi, W. D. Hamilton and A. Grafen, would take us too far afield, interesting as it is. My best attempt at expounding it is in the endnotes to the second edition of The Selfish Gene The Selfish Gene.

This brings us to the first of our three questions about human evolution. Why did we lose our hair? Mark Pagel and Walter Bodmer have made the intriguing suggestion that hairlessness evolved to reduce ectoparasites such as lice and, in keeping with the theme of this tale, as a s.e.xually selected advertis.e.m.e.nt of freedom from parasites. Pagel and Bodmer followed Darwin's invocation of s.e.xual selection, but in the neo-Wallacean version of W. D. Hamilton.

Darwin did not try to explain female preference, but was content to postulate it to explain male appearance. Wallaceans seek evolutionary explanations for s.e.xual preferences themselves. Hamilton's favoured explanation is all about advertising health. When individuals choose their mates, they are looking for health, freedom from parasites, or signs that the mate is likely to be good at evading or combating parasites. And individuals seeking to be chosen advertise their health: make it easy for the choosers to read their health, whether it is good or bad. Patches of bare skin in turkeys and monkeys are conspicuous screens on which the health of their possessors is displayed. You can actually see the colour of the blood through the skin.

Humans don't just have bare skin on their rumps like monkeys. They have bare skin all over, except on the top of the head, under the arms and in the pubic region. When we get ectoparasites such as lice, they are often confined to these very regions. The crab louse, Phthirus pubis Phthirus pubis, is mainly found in the pubic region, but also infests the armpits, beard and even eyebrows. The head louse, Pediculus huma.n.u.s capitus Pediculus huma.n.u.s capitus, infests only the hairs of the head. The body louse, P. h. huma.n.u.s P. h. huma.n.u.s, is a subspecies in the same species as the head louse which, interestingly, is believed to have evolved from it only after we began to wear clothes. Some workers in Germany have looked at the DNA of head lice and body lice to see when they diverged, with a view to dating the invention of clothes. They put it at 72,000 years, plus or minus 42,000.

Lice need hair, and Pagel and Bodmer's first suggestion is that the benefit of losing our body hair was that it reduced the real estate available to lice. Two questions arise. Why, if losing hair is such a good idea, have other mammals who also suffer from ectoparasites kept theirs? Those, such as elephants and rhinos, that could afford to lose their hair because they are large enough to keep warm without it, have indeed lost it. Pagel and Bodmer suggest that it was the invention of fire and clothes that enabled us to dispense with our hair. This immediately leads to the second question. Why have we retained hair on our heads, under our arms and in the pubic region? There must have been some overriding advantages. It is entirely plausible that hair on the top of the head protects against sunstroke, which can be very dangerous in Africa where we evolved. As for armpit and pubic hair, it probably helps disseminate the powerful pheromones (airborne scent signals) that our ancestors certainly used in their s.e.x lives, and which we still use more than many of us realise.

So, the straightforward portion of the Pagel/Bodmer theory is that ectoparasites such as lice are dangerous (lice carry typhus and other serious diseases), and ectoparasites prefer hair to bare skin. Getting rid of hair is a good way to make life difficult for these unpleasant and dangerous parasites. It is also much easier for us to see and pick off ectoparasites like ticks if we have no hair. Primates spend a substantial amount of time doing this, to themselves and to each other. It has become, indeed, a major social activity and, as a byproduct, a vehicle for bonding.

But I find the most interesting angle on the Pagel/Bodmer theory is one that they treat rather briefly in their paper: s.e.xual selection, which is why it belongs in the Peac.o.c.k's Tale. Nakedness is not only bad news for lice and ticks. It is good news for choosers trying to discover whether a would-be s.e.xual partner has has lice or ticks. The Hamilton/Zahavi/Grafen theory predicts that s.e.xual selection will enhance whatever it takes to help choosers tell whether would-be mates have parasites. Hairlessness is a beautiful example. On closing the Pagel/Bodmer paper I thought of T. H. Huxley's famous words: how extremely stupid not to have thought of that. lice or ticks. The Hamilton/Zahavi/Grafen theory predicts that s.e.xual selection will enhance whatever it takes to help choosers tell whether would-be mates have parasites. Hairlessness is a beautiful example. On closing the Pagel/Bodmer paper I thought of T. H. Huxley's famous words: how extremely stupid not to have thought of that.

But nakedness is a small matter. As promised, let's turn now to bipedality and brains. Can the peac.o.c.k help us to understand those two larger events in human evolution the rise onto our hind legs, and the inflation of our brain? Bipedality came first, and I shall discuss it first. In Little Foot's Tale, I mentioned various theories of bipedality, including the recent squat-feeding theory of Jonathan Kingdon, which I find very convincing. I said that I was postponing my own suggestion to the Peac.o.c.k's Tale.

s.e.xual selection, and its power to drive evolution in non-utilitarian arbitrary directions, is the first ingredient in my theory of the evolution of bipedality. The second is a tendency to imitate. The English language even has a verb, to ape, meaning to copy, although I am not sure how apt it is. Among all the apes, humans are the champion copyists, but chimpanzees do it too, and there is no reason to think australopithecines did not. The third ingredient is the widespread habit among apes generally of rising temporarily onto the hind legs, including during s.e.xual and aggressive displays. Gorillas do it to drum on their chests with their fists. Male chimpanzees also thump their chests, and they have a remarkable display called the rain dance which involves leaping about on the hind legs. A captive chimpanzee called Oliver habitually and for preference walks on his hind legs. I have seen a film of him walking, and his stance is surprisingly erect not a shambling totter, almost a military gait. So un-chimp-like is Oliver's walk that he has been the subject of bizarre speculations. Until DNA tests showed him to be a chimpanzee, Pan troglodytes Pan troglodytes, people have thought he might be a chimp/human hybrid, a chimp/bon.o.bo hybrid, even a relict australopithecine. Unfortunately Oliver's biography is hard to piece together, and n.o.body seems to know whether he was taught to walk as a trick for a circus or fair-ground sideshow, or whether it is an odd idiosyncrasy: he might even be a genetic mutant. Oliver aside, orang utans are slightly better on their hind legs than chimpanzees; and wild gibbons actually run across clearings bipedally, in a style which is not very different from the way they run along branches in trees when they are not brachiating under them.

Putting all these ingredients together, my suggestion for the origin of human bipedality is this. Our ancestors, like other apes, walked on all fours when not up in trees, but reared up on their hind legs from time to time, perhaps in something like a rain dance, or to pick fruits off low branches, or to move from one squat-feeding position to another, or to wade across rivers, or to show off their p.e.n.i.ses, or for any combination of reasons, just as modern apes and monkeys do. Then this is the crucial additional suggestion I am adding something unusual happened in one of those ape species, the one from which we are descended. A fashion fashion for walking bipedally arose, and it arose as suddenly and capriciously as fashions do. It was a gimmick. An a.n.a.logy might be found in the legend (probably false, alas) that the Spanish lisp sprang from the fashionable imitation of an admired courtier, or, in another version of the legend, a king of the Habsburg dynasty, or an infanta, who had a speech defect. for walking bipedally arose, and it arose as suddenly and capriciously as fashions do. It was a gimmick. An a.n.a.logy might be found in the legend (probably false, alas) that the Spanish lisp sprang from the fashionable imitation of an admired courtier, or, in another version of the legend, a king of the Habsburg dynasty, or an infanta, who had a speech defect.

It'll be easiest if I tell the story in a s.e.x-biased way, with females choosing males, but remember that it could have been the other way around. In my vision, an admired or dominant ape, a Pliocene Oliver perhaps, gained s.e.xual attractiveness and social status through his unusual virtuosity in maintaining the bipedal posture, perhaps in some ancient equivalent of a rain dance. Others imitated his gimmicky habit and it became 'cool', 'it', 'the thing to do' in a local area, just as local bands of chimpanzees have habits of nut-cracking or termite-fishing which spread by fashionable imitation. In my teenage years, a more than usually inane popular song had the refrain, Everybody's talking'Bout a new way of walking!

And, while this particular line was probably chosen in the service of a lazy rhyme, it is undoubtedly true that styles of walking have a kind of contagiousness and are imitated because they are admired. The boarding school that I attended, Oundle in central England, had a ritual whereby the senior boys paraded into the chapel after the rest of us were in our places. Their mutually imitated style of walking, a mixture of swagger and lumbering roll (which I now, as a student of animal behaviour and a colleague of Desmond Morris, recognise as a dominance display) was so characteristic and idiosyncratic that my father, who saw it once a term on Parents' Day, gave it a name, 'the Oundle Roll'. The socially observant writer Tom Wolfe has named a particular loose-limbed gait of American dudes, fashionable in a certain social sector, the Pimp Roll. At the time of writing, the abject sycophancy of the British Prime Minister to the US President has earned him the t.i.tle 'Bush's Poodle'. Several commentators have noticed that, especially when in his company, he imitates Bush's macho 'cowboy swagger', with arms held out to the sides as though ready to reach for two pistols.

Returning to our imagined sequence of events among human ancestors, females in the local area of the fashion preferred to mate with males who adopted the new way of walking. They preferred them for the same reason as individuals wanted to join the fashion: because it was admired in their social group. And now the next step in the argument is crucial. Those who were especially good at the fashionable new walk would be most likely to attract mates and sire children. But this would be of evolutionary significance only if there was a genetic component to the variation in ability to do 'the walk'. And this is entirely plausible. We are talking, remember, about a quant.i.tative shift in the amount of time spent doing an existing activity. It is unusual for a quant.i.tative shift in an existing variable not not to have a genetic component. to have a genetic component.

The next step in the argument follows standard s.e.xual selection theory. Those choosers whose taste conforms to the majority taste will tend to have children who inherit, from their mothers' choice of mate, skill in walking according to the bipedal fashion. They will also have daughters who inherit their mothers' taste in males. This dual selection on males for possessing some quality and on females for admiring the self-same quality is the ingredient for explosive, runaway selection, according to the Fisher theory. The key point is that the precise direction of the runaway evolution is arbitrary and unpredictable. It could have been opposite. Indeed, in another local population perhaps it was in the opposite direction. An explosive evolutionary excursion, in an arbitrary and unpredictable direction, is just the kind of thing we need, if we are to explain why one group of apes (who became our ancestors) suddenly evolved in the direction of bipedality while another group of apes (the ancestors of the chimpanzees) did not. An additional virtue of the theory is that this evolutionary spurt would have been exceptionally fast: just what we need in order to explain the otherwise puzzling closeness in time of Concestor 1 and the supposedly bipedal Toumai and Orrorin Orrorin.

Let's turn now to the other great advance in human evolution, the enlargement of the brain. The Handyman's Tale discussed various theories, and again we left s.e.xual selection till last, postponing it until the Peac.o.c.k's Tale. In The Mating Mind The Mating Mind, Geoffrey Miller argues that some very high percentage of human genes, perhaps up to 50 per cent, express themselves in the brain. Yet again, for the sake of clarity, it's convenient to tell the story from one point of view only females choosing males but it could go the other way: or both ways simultaneously. A female who seeks a penetrating and thorough reading of the quality of a male's genes would do well to concentrate on his brain. She can't literally look at the brain, so she looks at its works. And, following the theory that males should make it easy by advertising their quality, males will not hide their mental light under a bony bushel but bring it out into the open. They will dance, sing, sweet-talk, tell jokes, compose music or poetry, play it or recite it, paint cave walls or Sistine chapel ceilings. Yes, yes, I know Michelangelo might not, as it happens, have been interested in impressing females. It is still entirely plausible that his brain was 'designed' by natural selection for impressing females, just as whatever his personal preferences his p.e.n.i.s was designed for impregnating them. The human mind, on this view, is a mental peac.o.c.k's tail. And the brain expanded under the same kind of s.e.xual selection as drove the enlargement of the peac.o.c.k's tail. Miller himself favours the Wallacean rather than the Fisherian version of s.e.xual selection, but the consequence is essentially the same. The brain gets bigger, and it does so swiftly and explosively.

The psychologist Susan Blackmore, in her audacious book The Meme Machine The Meme Machine, has a more radical s.e.xual selection theory of the human mind. She makes use of what have been called 'memes', units of cultural inheritance. Memes are not genes, and they have nothing to do with DNA except by a.n.a.logy. Whereas genes are transmitted via fertilised eggs (or via viruses), memes are transmitted via imitation. If I teach you how to make an origami model of a Chinese junk, a meme pa.s.ses from my brain to yours. You may then teach two other people the same skill, each of whom teaches two more, and so on. The meme is spreading exponentially, like a virus. a.s.suming we have all done our teaching work properly, later 'generations' of the meme will not be detectably different from earlier ones. All will produce the same origami 'phenotype'.7 Some junks may be more perfect than others, as some paper-folders take more trouble, say. But quality will not deteriorate gradually and progressively over the 'generations'. The meme is pa.s.sed on, whole and intact like a gene, even if its detailed phenotypic expression varies. This particular example of a meme is a good a.n.a.logue for a gene, specifically a gene in a virus. A manner of speaking, or a skill in carpentry, might be more dubious candidates for memes because I am guessing progressively later 'generations' in a lineage of imitation will probably become progressively more different from the original generation. Some junks may be more perfect than others, as some paper-folders take more trouble, say. But quality will not deteriorate gradually and progressively over the 'generations'. The meme is pa.s.sed on, whole and intact like a gene, even if its detailed phenotypic expression varies. This particular example of a meme is a good a.n.a.logue for a gene, specifically a gene in a virus. A manner of speaking, or a skill in carpentry, might be more dubious candidates for memes because I am guessing progressively later 'generations' in a lineage of imitation will probably become progressively more different from the original generation.

Blackmore, like the philosopher Daniel Dennett, believes that memes played a decisive role in the process that made us human. In Dennett's words: The haven all memes depend on reaching is the human mind, but a human mind is itself an artifact created when memes restructure a human brain in order to make it a better habitat for memes. The avenues for entry and departure are modified to suit local conditions, and strengthened by various artificial devices that enhance fidelity and prolixity of replication: native Chinese minds differ dramatically from native French minds, and literate minds differ from illiterate minds.8 It would be Dennett's view that the main difference between anatomically modern brains before the cultural Great Leap Forward and after it is that the latter are swarming with memes. Blackmore goes further. She invokes memes to explain the evolution of the large human brain. It can't be only memes, of course, because we are talking about major anatomical change here. Memes may manifest themselves in the circ.u.mcised p.e.n.i.s phenotype (which sometimes pa.s.ses, in quasi-genetic fashion, from father to son), and they might even manifest themselves in body shape (think of a transmitted fashion for slimming, or elongating the neck with rings). But a doubling in brain size is another matter. This has got to come about through changes in the gene pool. So what role does Blackmore see for memes in the evolutionary expansion of the human brain? This is, again, where s.e.xual selection comes in.

People are most apt to copy their memes from admired models. This is a fact that advertisers bet money on: they pay footballers, film stars and supermodels to recommend products people who have no expertise to judge them. Attractive, admired, talented or otherwise celebrated people are potent meme donors. The same people also tend to be s.e.xually attractive and therefore, at least in the sort of polygamous society in which our ancestors probably lived, potent gene donors. In every generation, the same attractive individuals contribute more than their fair share of both genes and memes to the next generation. Now Blackmore a.s.sumes that part of what makes people attractive is their meme-generating minds: creative, artistic, loquacious, eloquent minds. And genes help to make the kind of brains that are good at generating attractive memes. So, quasi-Darwinian selection of memes in the meme pool goes hand in hand with genuinely Darwinian s.e.xual selection of genes in the gene pool. It is yet another recipe for runaway evolution.

What, on this view, is the exact role of memes in the evolutionary swelling of the human brain? I think the most helpful way to look at it is this. There are genetic variations in brains which would remain unnoticed without memes to bring them out into the open. For example, the evidence is good that there is a genetic component to variation in musical ability. The musical talent of members of the Bach family probably owed much to their genes. In a world full of musical memes, genetic differences in musical ability shine through and are potentially available for s.e.xual selection. In a world before musical memes entered human brains, genetic differences in musical ability would still have been there, but would not have manifested themselves, at least not in the same way. They would have been unavailable for s.e.xual, or natural, selection. Memetic selection cannot change brain size by itself, but it can bring into the open genetic variation that would otherwise have remained under cover. This could be seen as a version of the Baldwin Effect, which we met in the Hippo's Tale.

The Peac.o.c.k's Tale has used Darwin's beautiful theory of s.e.xual selection to pick up a number of questions about human evolution. Why are we naked? Why do we walk on two legs? And why do we have big brains? I do not want to go out on a limb for s.e.xual selection as the universal answer to all outstanding questions about human evolution. In the particular case of bipedalism, I am at least as persuaded by Jonathan Kingdon's 'squat feeding' theory. But I applaud the current vogue for giving s.e.xual selection another serious look, after its long neglect since Darwin first proposed it. And it does provide a ready answer to the supplementary question that so often lurks behind the main questions: why, if bipedalism (or braininess or nakedness) was such a good idea for us, do we not see it in other apes? s.e.xual selection is good at that, because it predicts sudden evolutionary spurts in arbitrary directions. On the other hand, the lack of s.e.xual dimorphism in braininess and in bipedality demands some special pleading. Let's leave the matter there. It needs more thought.

THE DODO'S TALE.

Land animals, for obvious reasons, have a hard time reaching remote oceanic islands such as the Galapagos archipelago, or Mauritius. If, through the much invoked freak accident of rafting inadvertently on a detached mangrove, they do happen to find themselves on an island like Mauritius, an easy life is likely to open up. This is precisely because it is hard to get to the island in the first place, so the compet.i.tion and the predation are usually not so fierce as on the mainland left behind. As we have seen, this is probably how monkeys and rodents arrived in South America.

If I say it is 'hard' to colonise an island, I must hasten to forestall the usual misunderstanding. A drowning individual may try desperately to reach land, but no species ever tries tries to colonise an island. A species is not the kind of ent.i.ty that tries to do anything. Individuals of a species may happen, by luck, to find themselves in a position to colonise an island previously uninhabited by their kind. The individuals concerned can then be expected to take advantage of the vacuum, and the consequence may be that their species, with hindsight, is said to have colonised the island. The descendants of the species may subsequently change their ways, over evolutionary time, to accommodate the unfamiliar island conditions. to colonise an island. A species is not the kind of ent.i.ty that tries to do anything. Individuals of a species may happen, by luck, to find themselves in a position to colonise an island previously uninhabited by their kind. The individuals concerned can then be expected to take advantage of the vacuum, and the consequence may be that their species, with hindsight, is said to have colonised the island. The descendants of the species may subsequently change their ways, over evolutionary time, to accommodate the unfamiliar island conditions.

And now here is the point of the Dodo's Tale. It is hard for land animals to reach an island, but it is a lot easier if they have wings. Like the ancestors of the Galapagos finches ... or the ancestors of the dodo, whoever they were. Flying animals are in a special situation. They don't need the proverbial mangrove raft. Their wings carry them, perhaps as a freak accident, blown on a gale, to a distant island. Having arrived on wings, they find that they no longer need them. Especially because islands often lack predators. This is why island animals, as Darwin noted on the Galapagos, are often remarkably tame. And this is what makes them easy meat for sailors. The most famous example is the dodo, Raphus cucullatus Raphus cucullatus, cruelly named Didus ineptus Didus ineptus by Linnaeus, the father of taxonomy. by Linnaeus, the father of taxonomy.

The very name dodo comes from the Portuguese for stupid. Stupid is unfair. When Portuguese sailors arrived on Mauritius in 1507, the abundant dodos were completely tame, and approached the sailors in a manner which cannot have been far from 'trusting'. Why would they not trust, for their ancestors had not encountered a predator for thousands of years? Alas for trust. The unfortunate dodos were clubbed to death by Portuguese, and later Dutch, sailors even though they were deemed 'unpalatable'. Presumably it was 'sport'. Extinction took less than two centuries. As so often, it came about through a combination of killing and more indirect effects. Humans introduced dogs, pigs, rats, and religious refugees. The first three ate dodo eggs, and the last planted sugar cane and destroyed habitats.

Conservation is a very modern idea. I doubt that extinction, and what it means, entered anybody's head in the seventeenth century. I can hardly bear to tell the story of the Oxford Dodo, the last dodo stuffed in England. Its owner and taxidermist, John Tradescant, was induced to bequeath his large collection of curios and treasures to the infamous (some say) Elias Ashmole, which is why the Ashmolean Museum in Oxford is not called the Tradescantian as (some say) it should be. Ashmole's curators (some say, probably falsely) later decided to burn, as rubbish, all of Tradescant's dodo except the beak and one foot. These are now in my place of work, the University Museum of Natural History, where they memorably inspired Lewis Carroll. Also Hilaire Belloc: The Dodo used to walk aroundAnd take the sun and air.The sun yet warms his native ground The Dodo is not there!The voice, which used to squawk and squeakIs now for ever dumb Yet you may see his bones and beakAll in the Mu-se-um.

The white dodo, Raphus solitarius Raphus solitarius, was alleged to have met the same fate on the neighbouring island of Reunion.9 And Rodriguez, the third island of the Mascarene archipelago, housed, and lost for the same reason, a slightly more distant relative, the Rodriguez solitaire, And Rodriguez, the third island of the Mascarene archipelago, housed, and lost for the same reason, a slightly more distant relative, the Rodriguez solitaire, Pezophaps solitaria Pezophaps solitaria.

The ancestors of the dodos had wings. Their forebears were flying pigeons who arrived on the Mascarene Islands under their own muscle power, perhaps aided by a freak wind. Once there, they had no need to fly any more nothing to flee and so lost their wings. Like Galapagos and Hawaii, these islands are recent volcanic creations, none of them more than seven million years old. Molecular evidence suggests that the dodo and solitaire probably arrived on the Mascarene Islands from the East, not from Africa or Madagascar as we might otherwise have supposed. Perhaps the solitaire did the bulk of its evolutionary divergence before it finally arrived on Rodriguez, retaining enough wing power to get there from Mauritius.

Why bother to lose the wings? They took a long time to evolve, why not hang on to them in case one day they might come in useful again? Alas (for the dodo) that is not the way evolution thinks. Evolution doesn't think at all, and certainly not ahead. If it did, the dodos would have kept their wings, and the Portuguese and Dutch sailors would not have had sitting targets for their vandalism.

The late Douglas Adams was moved by the sad case of the dodo. In one of the episodes of Doctor Who Doctor Who that he wrote in the 1970s, the aged Professor Chronotis's college room in Cambridge serves as a time machine, but he uses it for one purpose only, his secret vice: he obsessively and repeatedly visits seventeenth-century Mauritius in order to that he wrote in the 1970s, the aged Professor Chronotis's college room in Cambridge serves as a time machine, but he uses it for one purpose only, his secret vice: he obsessively and repeatedly visits seventeenth-century Mauritius in order to weep for the dodo weep for the dodo. Because of a strike at the BBC, this episode of Doctor Who Doctor Who was never broadcast, and Douglas Adams later recycled the haunting dodo was never broadcast, and Douglas Adams later recycled the haunting dodo motif motif in his novel in his novel Dirk Gently's Holistic Detective Agency Dirk Gently's Holistic Detective Agency. Call me sentimental, but I must pause for a moment for Douglas, and for Professor Chronotis and what he wept for.

Evolution, or its driving engine natural selection, has no foresight. In every generation within every species, the individuals best equipped to survive and reproduce contribute more than their fair share of genes to the next generation. The consequence, blind as it is, is the nearest approach to foresight that nature admits. Wings might be useful a million years hence when sailors arrive with clubs. But wings will not help a bird contribute offspring and genes to the next generation, in the immediate here and now. On the contrary wings, and especially the ma.s.sive breast muscles needed to power them, are an expensive luxury. Shrink them, and the resources saved can now be spent on something more immediately useful such as eggs: immediately useful for surviving and reproducing the very genes that programmed the shrinkage.

That's the kind of thing natural selection does all the time. It is always tinkering: here shrinking a bit, there expanding a bit, constantly adjusting, putting on and taking off, optimising immediate reproductive success. Survival in future centuries doesn't enter into the calculation, for the good reason that it isn't really a calculation at all. It all happens automatically, as some genes survive in the gene pool and others don't.

The sad end of the Oxford Dodo (Alice's Dodo, Belloc's Dodo) is mitigated by a happier sequel. A group of Oxford scientists in the laboratory of my colleague Alan Cooper obtained permission to take a tiny sample from inside one of the foot bones. They also obtained a thigh bone of a solitaire found in a cave on Rodriguez. These bones yielded enough mitochondrial DNA to allow detailed, letter-by-letter sequence comparisons between the two extinct birds and a wide range of living birds. The results confirm that, as long suspected, dodos were modified pigeons. It is also no surprise that, within the pigeon family, the closest relative of the dodo is the solitaire, and vice versa. What is less expected is that these two extinct flightless giants are nested deep inside the pigeon family tree. In other words, dodos are more closely related to some flying pigeons than those flying pigeons are to other flying pigeons; despite the fact that, to look at them, you'd expect all the flying pigeons to be more closely related to each other, with the dodos out on a limb. Among pigeons, the dodos are most close to the Nicobar, Caloenus nicobarica Caloenus nicobarica, a beautiful pigeon from South-East Asia. In turn, the group consisting of the Nicobar pigeon and the dodos is most closely related to the Victoria crowned pigeon, a splendid bird from New Guinea, and Didunculus Didunculus, a rare Samoan toothbilled pigeon which looks quite like a dodo and whose name even means 'little dodo'.10 The Oxford scientists comment that the nomadic lifestyle of the Nicobar pigeon makes it ideally suited to invade remote islands, and Nicobar-type fossils are known from Pacific islands as far east as the Pitcairns. These crowned and toothbilled pigeons, they go on to point out, are large, ground-dwelling birds who rarely fly. It looks as though this whole subgroup of pigeons habitually colonise islands and then lose their power of flight and become larger and more dodo-like. The dodo itself and the solitaire have pushed the trend to extremes.

Something like the Dodo's Tale has been repeated on islands all over the world. Many different families of birds, most of which are dominated numerically by flying species, have evolved flightless forms on islands. Mauritius itself had a large flightless rail, Aphanapteryx bonasia Aphanapteryx bonasia, also now extinct, which may on occasion have been confused with the dodo. Rodriguez had a related species, A. leguati A. leguati. Rails seem to lend themselves to Dodo's Tale island-hopping followed by flightlessness. In addition to the Indian Ocean forms, there is a flightless rail in the Tristan da Cunha group in the South Atlantic; and most of the Pacific islands have or had their own species of flightless rail. Before man ruined the Hawaiian avifauna, there were more than twelve species of flightless rail in that archipelago. More than a quarter of all the world's 60-odd living species of rail are flightless, and all flightless rails live on islands (if you count large islands like New Guinea and New Zealand). Perhaps as many as 200 species have gone extinct on tropical Pacific islands since human contact.

Again on Mauritius, and also now extinct, was a large parrot Lophopsittacus mauritia.n.u.s Lophopsittacus mauritia.n.u.s. This crested parrot was a poor flyer and may have occupied a niche similar to the still (just) surviving kakapo of New Zealand.11 New Zealand is, or was, home to a large number of flightless birds belonging to many different families. One of the more striking was the so-called adzebill a stout, chunky bird, distantly related to cranes and rails. There were different species of adzebill on the North and South Islands, but neither island had any mammals except (for the obvious reason which underlies the Dodo's Tale) bats, and it is easy to imagine that the adzebills made their living in a rather mammal-like way, filling a gap in the market. New Zealand is, or was, home to a large number of flightless birds belonging to many different families. One of the more striking was the so-called adzebill a stout, chunky bird, distantly related to cranes and rails. There were different species of adzebill on the North and South Islands, but neither island had any mammals except (for the obvious reason which underlies the Dodo's Tale) bats, and it is easy to imagine that the adzebills made their living in a rather mammal-like way, filling a gap in the market.

In all these cases, the evolutionary story is almost certainly a version of the Dodo's Tale. Ancestral flying birds are carried by their wings to a remote island where an absence of mammals opens up opportunities for making a living on the ground. Their wings are no longer useful in the way that they were on the mainland, so the birds give up flying, and their wings and costly wing muscles degenerate. There is one notable exception, one of the oldest and the most famous of all the groups of flightless birds: the rat.i.tes, the ostrich order. The evolutionary story of the rat.i.tes is very different from all the rest of the flightless birds, and they have a tale of their own, the Elephant Bird's Tale.

THE ELEPHANT BIRD'S TALE.

From the tales of the Arabian Nights Arabian Nights, the image that most stirred my childish imagination was the roc encountered by Sinbad the Sailor, who at first thought this monstrous bird was a cloud, come over the sun: I had heard aforetime of pilgrims and travellers, how in a certain island dwelleth a huge bird, called the 'roc', which feedeth its young on elephants.

The legend of the roc (rucke or rukh) surfaces in several stories of the Arabian Nights Arabian Nights two involving Sinbad and two about Abd-al-Rahman. It is mentioned by Marco Polo as living in Madagascar, and envoys from the King of Madagascar were said to have presented the Khan of Cathay with a roc feather. Michael Drayton (15631631) invoked the monstrous bird's name to contrast it with the proverbially tiny wren: two involving Sinbad and two about Abd-al-Rahman. It is mentioned by Marco Polo as living in Madagascar, and envoys from the King of Madagascar were said to have presented the Khan of Cathay with a roc feather. Michael Drayton (15631631) invoked the monstrous bird's name to contrast it with the proverbially tiny wren: All feathered things yet ever knowne to men,From the huge Rucke, unto the little Wren ...

What is the origin of the roc legend? And if it is pure fantasy, whence the recurrent connection with Madagascar?

Fossils from Madagascar tell us that a gigantic bird, the elephant bird Aepyornis maximus Aepyornis maximus, lived there, perhaps until as late as the seventeenth century,12 although more probably around 1000 although more probably around 1000 AD AD. The elephant bird finally succ.u.mbed, perhaps partly through people stealing its eggs which were up to a metre in circ.u.mference13 and would have provided as much food as 200 chicken eggs. The elephant bird was three metres tall and weighed nearly half a tonne as much as five ostriches. Unlike the legendary roc (which used its 16-metre wingspan to carry Sinbad aloft as well as elephants) the real elephant bird could not fly, and its wings were (relatively) small like an ostrich's. But, though a cousin, it would be wrong to imagine it as a scaled-up ostrich: it was a more robust, heavy-set bird, a kind of feathered tank with a big head and neck, unlike the ostrich's slender periscope. Given how legends readily grow and inflate, and would have provided as much food as 200 chicken eggs. The elephant bird was three metres tall and weighed nearly half a tonne as much as five ostriches. Unlike the legendary roc (which used its 16-metre wingspan to carry Sinbad aloft as well as elephants) the real elephant bird could not fly, and its wings were (relatively) small like an ostrich's. But, though a cousin, it would be wrong to imagine it as a scaled-up ostrich: it was a more robust, heavy-set bird, a kind of feathered tank with a big head and neck, unlike the ostrich's slender periscope. Given how legends readily grow and inflate, Aepyornis Aepyornis is a plausible progenitor of the roc. is a plausible progenitor of the roc.

The elephant bird was probably vegetarian, unlike the fabulously jumbo-phagous roc, and unlike earlier groups of giant carnivorous birds such as the phorusrhachoid family of the New World. These could grow to the same height as Aepyornis Aepyornis, with a fearsomely hooked beak which, as if in justification of their nickname of 'feathered tyrannosaurs', looks capable of swallowing a mediumsized lawyer whole. These monstrous cranes seem at first sight better casting for the role of the terrifying roc than Aepyornis Aepyornis, but they went extinct too long ago to have started the legend, and in any case Sinbad (or his real-life Arab counterparts) never visited the Americas.

[image]

They've gone and there ain't no moa. Sir Richard Owen with the skeleton of Sir Richard Owen with the skeleton of Dinornis Dinornis, the giant moa. Owen, to whom we owe the term dinosaur, was the first to describe the moa.

The elephant bird of Madagascar is the heaviest bird known to have lived, but it was not the longest. Some species of moa could reach a height of 3.5 metres, but only if the neck was raised, as in Richard Owen's mounting (see photo). In life, it seems, they normally carried the head only a little way above the back. But the moa cannot have generated the roc legend, for New Zealand, too, was well beyond Sinbad's ken. About ten moa species existed in New Zealand, ranging in size from turkey to double-sized ostrich.14 Moas are extreme among flightless birds in that they have no trace of wings at all, not even buried vestiges of wing bones. They thrived in both the North and South Islands of New Zealand until the recent invasion by the Maori people, about 1250 Moas are extreme among flightless birds in that they have no trace of wings at all, not even buried vestiges of wing bones. They thrived in both the North and South Islands of New Zealand until the recent invasion by the Maori people, about 1250 AD AD. They were easy prey, no doubt for the same reason as the dodo. Except for the (extinct) Haast's eagle, the largest eagle ever to have lived, they had known no predators for tens of millions of years, and the Maoris slaughtered them all, eating the choicer parts and discarding the rest, belying, not for the first time, the wishful myth of the n.o.ble savage living in respectful harmony with his envir