SIMILARITIES between human and insect brains could be the reason why humans are attracted to plant-derived chemicals, such as tea, coffee, tobacco and drugs, according to a new book.

Professor David Kennedy, of Northumbria University, believes his new book, Plants and the Human Brain, answers the question why human brains are affected by plant chemicals.

Prof Kennedy, director of Northumbria University’s Brain Performance and Nutrition Research Centre, believes that similarities between human and insect brains can explain why humans are affected by and, in some cases, attracted to plant-derived chemicals.

Prof Kennedy states that human brains are fundamentally just a more complex version of the insect brain, with many striking similarities and patterns of behaviour. These include the use of exactly the same neurotransmitters, receptors and physiological processes.

He explained: “Plants evolved to interact with the brains of insects, their closest neighbours, in order to survive, by attracting them for pollination, or repelling them or dissuading them from eating plant tissue. Therefore, plant chemicals that have evolved to target the brains of insects then have the same effects on the human brain.

“Humans have a long and close relationship with plant-derived chemicals that alter brain function. Most of us reach for a cup of tea or coffee in the morning, many smoke tobacco; a few consume heavyweight drugs such as cocaine, morphine or cannabis.

“If you give the chemicals we think of as social drugs to insects, the change in behaviour is often strikingly similar to that seen in humans. Plants and humans share about 3,000 ancestral genes, which underlie a host of unexpected similarities. “We are not as different from plants as we would like to think, and our brains are, in most respects, the same as an insect brain – albeit much more complex.”