By comparing the human genome with that of chimpanzees, people’s closest living relative, scientists have identified a partial list of the genes that make people human.

Because the sequence of DNA units in the two genomes is 98.8 percent identical, just a handful of genes might define the essence of humanity.

Prominent sets of human genes show signs of accelerated evolution, under strong recent pressure of natural selection. These include those involved in governing speech, hearing, brain development (especially EMA3B, which helps guide growing nerve axons to the proper regions in the brain), and recycling amino acids.