The elephant bird's tale
In an exclusive extract from his latest book, a Chaucerian pilgrimage to the remote past, Richard Dawkins roams the lost continent of Gondwana
From the tales of the 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 – 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, lived there, perhaps until as late as the seventeenth century, although more probably around 1000 AD. The elephant bird finally succumbed, perhaps partly through people stealing its eggs, which were up to a metre in circumference and would have provided as much food as 200 chicken eggs. The bird was three metres tall and weighed nearly half a tonne or 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 is a plausible progenitor of the roc.
The elephant bird was probably vegetarian, unlike the fabulously jumbophagous roc, and unlike earlier groups of giant carnivorous birds such as the phorusrhachoid family of the New World. They could grow to the same height as Aepyornis, with a fearsomely hooked beak which, as if in justification of their nickname of 'feathered tyrannosaurs', looks capable of swallowing a medium-sized lawyer whole. These monstrous cranes seem at first sight better casting for the role of the terrifying roc than 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.
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. In life, unlike the reconstruction (right), 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, and they ranged in size from turkey to double-sized ostrich. 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. 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, and belying, not for the first time, the wishful myth of the noble savage living in respectful harmony with his environment. By the time the Europeans arrived, only a few centuries after the Maoris invaded New Zealand, the last moa was gone. Legends and tall stories of sightings persist to this day, but the hope is forlorn. In the words of a plaintive song, to be sung in a mournful New Zealand accent:
No moa, no moa
In old Ao-tea-roa.*
Can't get 'em.
They've et 'em;
They've gone and there ain't no moa!
Elephant birds and moas (but not the carnivorous phorusrhachoids nor various other extinct flightless giants) were ratites, an ancient family of birds, which now includes the rheas of South America, the emus of Australia, the cassowaries of New Guinea and Australia, the kiwis of New Zealand, and the ostrich, now confined to Africa and Arabia but previously common in Asia and even Europe. I take delight in the power of natural selection, and it would have given me satisfaction to report that the ratites evolved their flightlessness separately in different parts of the world, in the same way that the dodo did. In other words, I would have liked the ratites to have been an artificial assemblage, driven to superficial resemblance by parallel pressures in different places. Alas, this is not so. The true tale of the ratites, which I am attributing to the elephant bird, is very different. And I must say that it eventually turns out to be, in its way, even more fascinating The Elephant Bird's Tale is a tale of Gondwana, and of continental drift or, as it is now called, plate tectonics.
The ratites are a truly natural group. Ostriches, emus, cassowaries, rheas, kiwis, moas and elephant birds really are more closely related to each other than they are to any other birds. And their shared ancestor was flightless too. Probably it originally lost its wings after flying to some long-forgotten island off Gondwana. But that was before the ratites divided into the separate forms whose descendants we now find on the different southern continents and islands. Moreover, the split of the ratites from the rest of the birds is extremely old. The ratites are a genuinely ancient group in the following sense. Surviving birds fall into two groups. On the one hand are the ratites and the tinamous (a group of South American birds which can fly). On the other hand are all the rest of the surviving birds put together. So if you are a bird, either you are a ratite/tinamou or you are in with the rest, and the division between these two categories is the oldest split among surviving birds.
The ratites, then, are a natural group, with a common ratite ancestor that was also flightless.This is not to deny that an earlier ancestor of all the ratites flew.Of course it did, for why else would they (most of them) have vestigial wings? But the last common ancestor of all the surviving ratites had already reduced its wings to stubby vestiges long before its descendants branched into the various groups of ratites we see today.This deprives us of the notion of ancestors flying across the sea to distant lands and then each independently losing its wings.The ratites reached their present separated homelands without benefit of flight. How did they get there?
They walked. All the way. How is this possible? It is the whole point of the Elephant Bird's Tale. The sea wasn't there – there was nothing to cross. What we now know as separate continents were joined together, and the great flightless birds walked dry shod.
When I was a small child in Africa my father regaled my little sister and me with bedtime stories, as we lay under our mosquito nets and gazed at his luminous wristwatch, about a 'Broncosaurus' who lived faaaaaaaaaaaar away in a place called Gonwonkyland. I forgot all about this until much later when I learned about the great southern continent of Gondwanaland.
One hundred and fifty million years ago, Gondwanaland, or Gondwana as it is more correctly called, consisted of everything that we now know as South America, Africa, Arabia, Antarctica, Australasia, Madagascar and India. The southern tip of Africa was touching Antarctica, and tilted to the 'right'. There was therefore a triangular gap between the east coast of Africa and the north coast of Antarctica – but it wasn't really a gap because it was filled by India. India was in those days separated from the rest of Asia (Laurasia) by an ocean, the Tethys, whose centre roughly corresponds today to the modern Indian Ocean and whose westernmost reaches turned into today's Mediterranean Sea. Madagascar nestled between India and Africa, joined on both sides. Australia with New Guinea, and the embryonic New Zealand, were also joined to Antarctica, further round the coast from India.
But Gondwana was about to break up. You can see where the tale is going. When the ratite birds first roamed Gondwana, they could walk from any of the places where they later dwelt, to any other. Ratite fossils have even been found in Antarctica, which we know from plant fossils to have been covered with warm, subtropical forest at the time. Ancestral ratites wandered freely over the whole continent of Gondwana with no inkling that their homeland was destined to be broken up into chunks separated by thousands of miles of ocean. When it did break up, the ratites went too. They rafted all right. But their raft was not the proverbial fragment of mangrove. It was the very ground beneath their feet. And there was plenty of time for them to evolve their separate ways, on their separately retreating landmasses.
The legend of the roc, the fabulous great bird with the strength to shift elephants, is a wonder of childhood. But isn't the true story of how the very continents themselves are shifted, through thousands of miles, an even greater wonder, more worthy of the adult imagination?
This article is an extract from Richard Dawkins's book, The Ancestor's Tale, published by Weidenfeld and Nicholson
*Ao-tea-roa is the Maori name for New Zealand