"Imagine a future where lab workers can reprogram human embryos to make our children "smarter" or "more sociable" or "happier. " Some researchers are doing more than imagining this future; having worked such changes on a wide range of other animals, they've begun to plan for what they see as the inevitable transformation of our species. They are joined by other engineers, working in fields like advanced robotics and nanotechnology, who foresee a not-very-distant day when people merge with machines to create a "posthuman" world. " "Enough examines such possibilities, and explains how we can avoid their worst consequences while still enjoying the fruits of our new scientific understandings. More, it confronts the most basic questions that our technological society Will we ever decide that we've grown powerful enough? Can we draw a line and say this far and no further? " McKibben answers yes, and argues that only by staying human can we find the true meaning in our lives. A warning against the gravest dangers humans have ever faced, this wise and eloquent book is also a passionate defense of the world we were born into, and a celebration of our ability to say, "Enough. "