Following the discovery of a 47 million year old primate fossil that is set to revolutionize our understanding of human evolution, the full story of this world-changing discovery is told in The Link: Uncovering Our Earliest Ancestor by Colin Tudge, published by Little, Brown, with exclusive access to the first scientists to study her.

"The link they would have said until now is missing... it is no longer missing." Sir David Attenborough

Scientists have announced the discovery of a 47 million year old human ancestor. Discovered in Messel Pit, Germany, the fossil is twenty times older than most fossils that explain human evolution. Known as 'Ida', the fossil is a transitional species showing characteristics from the very primitive non-human evolutionary line (prosimians, such as lemurs), but she is more related to the human evolutionary line (anthropoids, such as monkeys, apes and humans). This places Ida at the very root of anthropoid evolution - when primates were first developing the features that would evolve into our own. The scientists' findings are published today by PLoS One, the open source journal of the Public Library of Science.

For the past two years, an international team of scientists, led by world-renowned Norwegian fossil scientist Dr Jørn Hurum, University of Oslo Natural History Museum, has secretly conducted a detailed forensic analysis of the extraordinary fossil, studying the data to decode humankind's ancient origins. At 95% complete, Ida is set to revolutionize our understanding of human evolution.

Unlike Lucy and other famous primate fossils found in Africa's Cradle of Mankind, Ida is a European fossil, preserved in Germany's Messel Pit; the mile-wide crater and oil-rich shale is a significant site for fossils of the Eocene Epoch. Fossil analysis reveals that the prehistoric primate was a young female. Opposable big toes and nails confirm the fossil is a primate, and a foot bone called the talus bone links Ida directly to humans.

The fossil also features the complete soft body outline as well as the gut contents; a herbivore, Ida feasted on fruits, seeds and leaves before she died. X-rays reveal both baby and adult teeth, and the lack of a 'toothcomb' or a 'toilet claw' which is an attribute of lemurs. The scientists estimate Ida's age when she died to be approximately nine months, and she measured approximately three feet in length.

Ida lived 47 million years ago at a critical period in Earth's history. It fell within the Eocene Epoch, a time when the blueprints for modern mammals were being established. Following the extinction of dinosaurs, early horses, bats, whales and many other creatures including the first primates thrived on a subtropical planet. The Earth was just beginning to take the shape that we know and recognize today - the Himalayas were being formed and modern flora and fauna evolved. Land mammals, including primates, lived amid vast jungle.

Ida was found to be lacking two of the key anatomical features found in lemurs: a grooming claw on the second digit of the foot, and a fused row of teeth in the middle of her lower jaw known as a toothcomb. She has nails rather than the claw typical of non-anthropoid primates such as lemurs, and her teeth are similar to those of monkeys. Her forward facing eyes are like ours - which would have enabled her fields of vision to overlap, allowing 3D vision and an ability to judge distance.

The fossil's hands show a humanlike opposable thumb. Like all primates, Ida has five fingers on each hand. Her opposable thumb would have provided a 'precision grip'. In Ida's case, this is useful for climbing and gathering fruit; in our case, it allows important human functions such as making tools, and writing. Ida would have also had flexible arms, which would have allowed her to use both hands for any task that cannot be done with one - like grabbing a piece of fruit. Like us, Ida also has quite short arms and legs.

Evidence in the talus bone links Ida to us. The bone has the same shape as in humans today. Only the human talus is obviously bigger. Extensive X-rays, CT scanning and computer tomography reveal Ida to be about nine months old when she died, and provide clues to her diet - which included berries and plants. Furthermore the lack of a bacculum (penis bone) means that the fossil was definitely female.

X-rays reveal that a broken wrist may have contributed to Ida's death - her left wrist was healing from a bad fracture. The scientists believe she was overcome by carbon dioxide gas whilst from drinking from the Messel lake: the still waters of the lake were often covered by a low lying blanket of the gas as a result of the volcanic forces that formed the lake and which were still active. Hampered by her broken wrist, Ida slipped into unconsciousness, was washed into the lake, and sunk to the bottom, where unique preservation conditions preserved her for 47 million years.

Author Colin Tudge is a biologist by education and a writer by inclination - on biology, food and agriculture, and the philosophy of science. His books include The Tree, Feeding People is Easy, Consider the Birds, and The Time Before History. For more information about the author, go to www.colintudge.com.

You can also find more information and watch a number of video presentations on the discovery and investigation of the Ida fossil at www.revealingthelink.com and the findings of the two year study will be revealed exclusively by Atlantic Productions in a special documentary film, Uncovering Our Earliest Ancestor: THE LINK, to be screened by BBC One on Tuesday 26th May 2009 at 9pm.