Bacteria, not humans, are dominant life-force on Earth

In relation to Emer Sexton’s column on bacteria (Irish Examiner, January 5), the late Stephen Gould, the evolutionary biologist, said that bacteria, not humans, were the dominant life-force on Earth.

Our skin, digestive systems and respiratory tracts are full of bacteria. Those in the gut secrete enzymes that aid digestion. Although we think of bacteria as passengers, they out-number our own cells 10-to-one. Even more impressively, the microbiological genes that each of us harbours outnumber our human genes by 100-to-one. All of this prompts the question: what does it mean to be human?

Gordon Cunningham,