Playing God: What is the problem?

To play God is supposedly to do something morally wrong and is a charge levelled at research and development in new technologies that enable, among other things, human enhancement. An attempt will be made to understand what this charge means in a non-religious context where nature replaces god. From a secular standpoint it usually means that an action is interfering with nature. This raises the possibility of creating a Frankenstein monster that cannot be controlled and is therefore morally wrong. One difficulty is that if humans are part of the natural world then everything that we do is as natural as birds building nests. The argument here, after distinguishing two concepts of nature and using geoengineering as an example, will be that the dramatic technological manipulation of humans, life, and matter is rapidly extending the scope of human control and thus thrusting humans into unfamiliar situations where they do not have the competence to make good decisions. This is playing God with defensible content and moral significance.