Is smooching fundamentally weird? Kissing is older than humanity. Yet scientists are divided on why we do it and where it came from. Locking lips might be much stranger than it seems.
First kiss ‘was 21 million years ago’
Kissing cousins: The Barbary macaque, also known as the Berber monkey, frequently engages in lip-to-lip contact that resembles kissing, primarily as a form of social greeting and affectionate bonding. Glossary
Mesopotamia - A historical region of the Middle East, mostly centred on modern-day Iraq, Kuwait and parts of Syria and Turkey. The name "Mesopotamia" in Greek means "between rivers" because of the Tigris and Euphrates that run through it.
Evolutionary - Relating to evolution, a process of gradual change that takes place over many generations, during which species of animals, plants, or insects slowly change some of their physical characteristics.
Neanderthals - An extinct hominid species that lived alongside Homo sapiens until around 40,000 years ago. Their ancestry began in Africa, like ours, but neanderthals migrated to Europe and Asia long before humans. They looked like us but were shorter and stockier with angled cheekbones, prominent brows and wide noses.
Microbe - A tiny living organism that is too small to be seen with the naked eye and requires a microscope to be seen.
Calorific - Foods rich in fat or carbohydrates, which provide a large amount of energy to the body.
Great apes - The Hominidae or Hominid family of primates, including orangutans, gorillas, chimpanzees, bonobos and humans.
Albatrosses - A type of very large seabird.
Familial - Relating to a family.
Hormone - Chemicals carried in the bloodstream that alter the way your body's systems act.
Anthropologist - Someone who studies human beings and societies. The word "anthropology" comes from the Greek "anthropos", meaning "human". It developed as a subject in Europe in the 19th century, although some regard the Arab historian Ibn Khaldun as the first anthropologist.
Indigenous - Ethnic groups who are the original or earliest-known inhabitants of an area or country: for example, Native Americans in the USA.