Manipulating this genetic code – a process known as genetic engineering – could allow scientists to produce people with stronger muscles, harder bones and faster brains.Theoretically, it also could create people with gills or webbed hands and feet or even wings – and, as Garreau points out in his book, could lead to “an even greater variety of breeds of humans than there is of dogs.”

In recent years, the prospect of advanced genetic engineering has become much more real, largely due to two developments.First, inexpensive and sophisticated gene mapping technology has given scientists an increasingly more sophisticated understanding of the human genome.The second important development involves the powerful new gene editing technology known as CRISPR.While gene editing itself is not new, CRISPR offers scientists a method that is much faster, cheaper and more accurate.“It’s about 1,000 times cheaper [than existing methods],” says George Church, a geneticist at Harvard Medical School.“It could be a game changer.” CRISPR is so much more efficient and accurate than older gene-editing technology because it uses each cell’s immune system to target and splice out parts of its DNA and replace them with new genetic code.