| Tales the dead dodo tells
(`Didus Ineptus' by Clark Ashton Smith, 1893-1961) |
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IT USED to be said that dead men tell no tales. It was on the belief in this saying that the underworld `took out' people who could have divulged sensitive information to the police and the court. This belief may well hold with regard to what the dead man had in his mind, but a study of his remains can still reveal a lot. This of course is the business of the coroner. The mouth of the dead may no longer talk, but the body indeed can. A vivid example of this has just appeared in the 1 March issue of Science. Dr. Alan Cooper and colleagues of Oxford University have analysed the remains of the dodo bird preserved and exhibited at the Natural History Museum of the university. The specimen was placed there in the year 1683, just two years after the last dodo was sighted. `Dead as a dodo' has become an evocative phrase in the English language. Here was a bird that became geographically confined to the islands of Mauritius, Reunion and Rodrigues in the Indian Ocean, just east of Africa. Long long before men set foot and settled in numbers there, these isles were the Garden of Eden for the dodo. Food was in plenty, there were no predators and life was paradise. These islands were formed as a result of volcanic eruptions, and thus were rich in minerals and nutrients. This led to the flourishing of vegetation and insect life. The dodo did not have to exert at all; it just had to totter along, eat to heart's content and procreate- `went forth and multiplied'. As a result, the bird in time grew in size (zoologists impolitely call this gigantism; though how fat it got is debated even today), and lost its need and ability to fly. In 1598, when the Dutchman Admiral Jacob Cornelius van Neck came to Mauritius, he sighted the bird and called it the dodo, a take-off of the Dutch word `dodoor' meaning a sluggard. The Dutch colonised Mauritius in 1638, followed by the French and the British, and before we knew it, the colonisers wiped the bird out of existence. The sad story of its extinction raised the bird to mythological status, making it the avian equivalent of the great Greek warrior and hero of Homer's Iliad, Achilles, who was killed in the Trojan War when Paris wounded him in the heel, his one vulnerable spot. Read the poem by Clark Smith, quoted above, for a feel of the dodo mystique. It is on the evolutionary history of the dodo that the Oxford scientists focused attention in their study. It is a murky affair, with some scholars classifying it as part of the family of preying birds such as the falcon, hawk and eagle, while others holding it as from the family of flat-breast-boned ratities such as the ostrich, emu and rhea. Morphological studies have long linked the dodo, and its presumed close relative, the solitaire bird, with pigeons and doves. But their exact position still remains to be established as to whether they are a part of this family called Columbidae or a group unto themselves. Appearances can be deceptive. You can push morphology thus far and no further. To establish lineage, we can study the DNA of the genes. When Darwin said that we humans evolved from apes, the Bishop of Wilberforce mocked at the idea. Comparison of the DNA sequences tells us that we are 98.5 per cent chimpanzees, and that we both are of the primate family of monkeys. Cooper and colleagues thus undertook to compare the DNA sequences of the dodo and the solitaire birds with those of 35 species of pigeons and doves. Where did they get the DNA of the dodo? From the head, leg and foot remains of a dodo donated to the university's Natural History Museum in 1683. This was the specimen that inspired Lewis Carroll to write about the bird in his `Alice's Adventures in Wonderland' thus: `When they had been running half an hour or so, the dodo suddenly called out `The race is over', and they all crowded round it, panting and asking `But who has won?'— poignant and prescient words from the bird about `race'. The dead may tell no tales but their DNA can be telltale. Fortunately, DNA is a rugged molecule that withstands the ravages of time reasonably well. The researchers compared well-chosen DNA sequences of the birds, based on which they constructed a family tree using the `maximum likelihood' approach. What they found was interesting. `Despite the substantial morphological differences between the dodo, the solitaire, and other pigeons, the maximum likelihood analysis showed them to be nested within the family Columbidae. The closest living relative is the Nicobar pigeon from the Nicobar islands and nearby Southeast Asia, and the sister taxa... . are the Crowned pigeons from New Guinea'. The DNA tree also suggests that the dodo and solitaire dispersed from Southeast Asia to the Mascarene Archipelago at some point in the past. At what point? Mutations in the DNA of mitochondria occur at fairly regular intervals in time, and thus act as a molecular clock. Analysis using this method, and supporting it with fossil records suggests that the dodo/solitaire branch diverged from the parent line in the mid/late Eocene period, around 43 million years ago (Ma). The dodo and the solitaire themselves separated in the late Oligocene period, or 26 Ma. Now, these dates are interesting because they are far older than the islands of Mauritius and Rodrigues, both of which emerged as island masses much later, Mauritius around 6.8-7.8 Ma and Rodrigues around 1.5 Ma. Prior to this, the ridges surrounding the Mascarene plateau were above sea level in the late Oligocene and subsided slowly thereafter. It thus appears likely that the dodo (and the solitaire) used these ridges as stepping-stones for their travel from Southeast Asia into these islands. It is not yet clear whether they hopped it all the way, or actually flew into them, although the isolation and relative youth of Rodrigues make one entertain the possibility that the solitaire might have retained its ability to fly until at least 1.5 million years ago. The fact that DNA has been isolated from the dodo remains raises a tantalising possibility. Can we do a cloning of the dodo and bring it back into the world? Technology for doing so is not beyond our hands! Disappointing answer is no, as it turns out that the DNA isolated from these specimens is not intact but fragmented. It was good enough to construct the family tree and interrelationships, but intact enough for cloning. But as Dr. Malgosia Nowak-kemp, the keeper of the dodo remains at Oxford is reported to have said: "But you can never say never!"
Source: Online edition of India's National Newspaper |
Copyright Dodohaus Berlin 2004