There are two types of chimpanzees. The common chimp lives in West and Central Africa. Its cousin is the bonobo or pygmy chimp, which comes from the forests of the Democratic Republic of Congo. The Congo River forms a boundary between the two species. Adult male chimps can weigh between 35 to 70 kg. They usually stand 0.9 to 1.2m tall. Females usually weigh 26 to 50kg and stand 0.66 to 1m tall. Chimps rarely live past 40 years old in the wild. But in captivity they have been known to reach the age of 60. In 1859, Darwin's Theory of Evolution was published. This spurred interest in chimps as a link to humans. Observers at the time were interested in the chimp’s behaviour. They were searching for similarities to human behaviour. Their main goal was to discover whether chimps were inherently “good.” Their interest was not grounded in practical science, however. The tendency of the time was to greatly exaggerate the chimp’s intelligence. At one point, plans were made to create a workforce of chimps. The idea was make chimps fill menial labor positions such as factory work. Chimps were treated with much more serious scientific interest in the 20th century. Before 1960, almost nothing was known about chimps’ behaviour in their natural habitat. Then Jane Goodall went to live in Tanzania’s Gombe Forest. There she lived among the chimps and observed their habits. Her discovery of chimps making tools was groundbreaking. It was previously believed that only humans did this. Common chimps sometimes attack humans. In Uganda, many children have been attacked by chimps. These attacks are usually fatal for the children. One reason for these attacks is that the chimps mistake the children for a species of monkey called the Western Red Colobus. It is one of the common chip’s favourite foods. Humans must be careful around chimps. They view humans as their rivals. Also, the average chimp has five times the upper body strength of an adult human male. This was proven when former NASCAR (National Association for Stock Car Automobile Racing) driver Saint James Davis was attacked and almost killed by a chimp.