At least part of the last sentence is demonstrably false since medical research on non-human primates has provided important medical advances over the last century. Helene Guldberg recently wrote a short, informative article for Spiked Science laying out the case against great apes being similar enough to human beings to be granted rights. According to Jane Goodall, 'the higher intelligence and the emotional nature of the great apes sets them apart from non-primate animals', making experiments that cause them suffering entirely illegitimate. Guldberg runs through a lot of the problems with claims that apes are self aware or have other human-like characteristics. It is when thought and speech come together that children's thinking is raised to new heights and they start acquiring truly human characteristics.
Language becomes a tool of thought allowing children increasingly to master their own behavior.
Alex Kirby, The BBC, March 28, 2001. The great ape debate . Helene Guldberg, Spiked-Online. Com, March 29, 2001. Copyright 1998-2001 by Brian Carnell .