When adults learn a language, they tend to change that language, McWhorter says. They simplify it by ignoring many of the complexities, and these simplifications catch on with native speakers. The more adults learning a language, the simpler that language becomes.
England has been conquering or visited by many outsiders over the centuries, including Vikings, Romans and Normans. Then the British Empire spread the English language around the globe. Millions of people learn English as a second language. All these influences make English, as complicated as it may sometimes seem, one of the easiest languages to learn. This, in turn, encourages its spread to still more people.
The English language has no genders. French, Spanish, Latin and some languages have words that are either masculine or feminine. Nasioi, a language spoken by a few people in New Guinea, has about 100 genders. Ket, a language spoken by a handful of people in Siberia, has 11 cases. In English we have the words here and there. To be more precise, we can add modifiers such as up here, down here and over here. In Kikuyu, a language spoken by Eskimos, there are 12 very different words meaning here or there, or more than the seven words McWhorter says Eskimos actually have for snow.
Languages, McWhorter writes, are like bathtub rings. Look at them under a microscope, and you can see that those rings are "complex, teeming slices of biology." Yet all this complexity serves no purpose. It doesn't make your bath any better. In the same way, complexity in language serves no purpose. It doesn't make communication any better, and that is why we have language in the first place. Children don't mind the complexity, but it tends to isolate those who speak these languages because adults have a disincentive to learn them.
Travel and immigration, along with their other virtues, help keep our language simple.