Manual labour (manual labor in American English) or manual work is physical work done by people, most especially in contrast to that done by machines, and to that done by working animals. It is most literally work done with the hands (the word "manual" comes from the ), and, by figurative extension, it is work done with any of the muscles and bones of the body. For most of human prehistory and history, manual labour and its close cousin, animal labour, have been the primary ways that physical work has been accomplished. Mechanisation and automation, which reduce the need for human and animal labour in production, have existed for centuries, but it was only starting in the 19th century that they began to significantly expand and to change human culture. To be implemented, they require that sufficient technology exist and that its capital costs be justified by the amount of future wages that they will .