How we bring fossils 'back to life'
When you see a drawing or model of a dinosaur, or even a 'live' one in a movie, how do you know that that is what they really looked like? Well, here is how it's done.
The first step in restoring the life appearance of any prehistoric creature is to discover its fossil remains. These fossils are usually made up of just the hard parts such as bone and shell, although special conditions do very rarely preserve soft parts. Once a fossil has been discovered, let's say of a dinosaur, the skeleton must then be reconstructed. This may be very difficult or very easy depending on how complete the remains are. Often only a few scrappy bones are preserved, so missing parts of the skeleton must be reconstructed by looking at close relatives. This gives us a good idea of what the missing parts of the animal looked like. For example we have a large number of complete fossils of Tyrannoaurus. If a new type of tyrannosaur is found with just a few bones, we may not know exactly what it looked like, but based on Tyrannosaurus we will have a very good idea of the shapes, size and numbers of the missing bones.
Sometimes complete skeletons are found, which makes this process much simpler, and if the bones are all articulated (joined together as they were in life so the feet are attached to the legs and the legs to the hips etc.) this is even easier. The natural posture of the animal can be determined by articulating each bone in the skeleton relative to the next. Computer simulations also allow palaeontologists to calculate the most balanced stance.
The skeletal reconstruction can be accomplished in two dimensions such as in an illustration of all the bones, or in three dimensions - the most obvious and striking examples of reconstructed skeletons can be seen on display in museums. Sometimes these mounted skeletons are genuine fossils, but often they are casts taken from the fossil bones - these are much lighter and easier to construct, and this also allows the real bones to be safely stored for protection and scientific investigation.
The next step is to reconstruct the muscles of the body around the skeleton. The position and size of the muscles can be determined by looking at the muscles of living animals, and their position and size is also indicated by scars and bumps on the fossil bones where the muscles once attached. The dinosaur is now ready to put on its skin. The skin texture is sometimes known from rare fossil impressions, but the colour is almost entirely guesswork. However, it is important to think about where the creature lived and how it may have behaved -many animals are camouflaged to their surrounding, so maybe animals from a desert were yellow whereas forest-dwelling animals were green. There are other subtle details to take into account at this stage, such as the type of eye and tongue. These features can be reconstructed with some confidence by looking at the closest living relatives of the prehistoric animal.
It is possible to stop here, but we can go a step further and figure out how the animal moved and sounded. Indeed, the most complete restorations or prehistoric animals are 3D mechanical creations, and computer generated 3D animations, such as those seen in 'Walking with Dinosaurs'. Fossil footprints provide good evidence for gait and posture, and when combined with an understanding of the flexibility and strength of joints, the fossil organisms can finally be brought back to life.