| One of the most famous cases of extinction is that of a bird known as the dodo. |
| In fact there's even a saying in English, 'as dead as the dodo', |
| used to refer to something which no longer exists. |
| But for many centuries the dodo was alive and well, |
| although it could only be found in one place, |
| the island of Mauritius in the Indian Ocean. |
| It was a very large bird, about one metre tall, |
| and over the centuries it had lost the ability to fly, |
| but it survived happily under the trees that covered the island. |
| Then in the year 1507, |
| the first Portuguese ships stopped at the island. |
| The sailors were carrying spices back to Europe, |
| and found the island a convenient stopping place |
| where they could stock up with food and water for the rest of the voyage, |
| but they didn't settle on Mauritius. |
| However, in 1638 |
| the Dutch arrived and set up a colony there. |
| These first human inhabitants of the island |
| found the dodo birds a convenient source of meat, |
| although not everyone liked the taste. |
| It's hard to get an accurate description of what the dodo actually looked like. |
| We do have some written records from sailors, |
| and a few pictures, |
| but we don't know how reliable these are. |
| The best-known picture is a Dutch painting, |
| in which the bird appears to be extremely fat, |
| but this may not be accurate - |
| an Indian painting done at the same time shows a much thinner bird. |
| Although attempts were made to preserve the bodies of some of the birds, |
| no complete specimen survives. |
| In the early 17th century |
| four dried parts of a bird were known to exist - |
| of these, three have disappeared, |
| so only one example of soft tissue from the dodo survives, |
| a dodo head. |
| Bones have also been found, |
| but there's only one complete skeleton in existence. |
| This single dodo skeleton has recently been the subject of scientific research |
| which suggests that many of the earlier beliefs about dodos |
| may have been incorrect. |
| For example, |
| early accounts of the birds mention how slow and clumsy it was, |
| but scientists now believe |
| the bird's strong knee joints would have made it capable of movement which was not slow, |
| but actually quite fast. |
| In fact, one 17th century sailor wrote that he found the birds hard to catch. |
| It's true that the dodo's small wings wouldn't have allowed it to leave the ground, |
| but the scientists suggest that these were probably employed for balance |
| while going over uneven ground. |
| Another group of scientists carried out analysis of the dodo's skull. |
| They found that the reports of the lack of intelligence of the dodo |
| were not borne out by their research, |
| which suggested the bird's brain was not small, |
| but average in size. |
| In fact, in relation to its body size, |
| it was similar to that of the pigeon, |
| which is known to be a highly intelligent bird. |
| The researchers also found that the structure of the bird's skull |
| suggested that one sense which was particularly well-developed was that of smell. |
| So the dodo may also have been particularly good at locating ripe fruit |
| and other food in the island's thick vegetation. |
| So it looks as if the dodo was better able to survive and defend itself than was originally believed. |
| Yet less than 200 years after Europeans first arrived on the island, |
| they had become extinct. |
| So what was the reason for this? |
| For a long time, it was believed that the dodos were hunted to extinction, |
| but scientists now believe the situation was more complicated than this. |
| Another factor may have been the new species brought to the island by the sailors. |
| These included dogs, which would have been a threat to the dodos, |
| and also monkeys, |
| which ate the fruit that was the main part of the dodos' diet. |
| These were brought to the island deliberately, |
| but the ships also brought another type of creature - rats, |
| which came to land from the ships and rapidly overran the island. |
| These upset the ecology of the island, |
| not just the dodos but other species too. |
| However, |
| they were a particular danger to the dodos |
| because they consumed their eggs, |
| and since each dodo only laid one at a time, |
| this probably had a devastating effect on populations. |
| However, |
| we now think that probably the main cause of the birds' extinction |
| was not the introduction of non-native species, |
| but the introduction of agriculture. |
| This meant that the forest that had once covered all the island, |
| and that had provided a perfect home for the dodo, |
| was cut down so that crops such as sugar could be grown. |
| So although the dodo had survived for thousands of years, |
| suddenly it was gone. |