The author presents evidence that evolution is not gradual with many steps over many years to make a significant change, but happens quickly in a generation with the assimilation of a single mutation. For example, in insects the nerve chord runs along the front of the animal facing the ground with the digestive track running along the back facing the sun. Vertebrates have the opposite arrangement. Perhaps one mutation flipped the insect version to the vertebrate version.
The discovery of the Moroto vertebra showed that 21 million years ago a mutation occurred that created a new type of body plan: the hominoid body plan. This allowed hominoids to be bipedal. So our ancestors were bipedal that long ago and some descendants went back to the older way of walking but we didn't.
Although written for the general reader the book does give extensive details.
