Here a North American species withdraws blood from the nose of a bat. However bats are not the bedbugs' first hosts and were even colonised several times. Photograph: Mark A. Chappell, University of California, Riverside

Bedbugs – some of the most unwanted human bedfellows - have been parasitic companions with other species asides from humans for more than 100 million years, walking the earth at the same time as dinosaurs.

Work by an international team of scientists, including from the University of Sussex and the University of Sheffield, compared the DNA of dozens of bedbug species in order to understand the evolutionary relationships within the group as well as their relationship with humans.

In research published in Current Biology, the team discovered that bedbugs are older than bats – a mammal that people had previously believed to be their first host 50-60 million years ago. Bedbugs in fact evolved around 50 million years earlier.

Dr Ted Morrow, Senior Research Fellow at the University of Sussex, said: “Bedbugs are a really fascinating group of insects, and despite the fact they are no fun to have in bed they actually show some incredibly interesting biology.

“This study helps us work further on how those biological features evolve and it’s a great step forwards for understanding more about these enigmatic insects.”

Dr Steffen Roth from the University Museum Bergen in Norway, who led the study, said: “The first big surprise we found was that bedbugs are much older than bats, which everyone assumed to be their first host. It was also unexpected to see that evolutionary older bedbugs were already specialised on a single host type, even though we don't know what the host was, at the time when T. rex walked the earth.”

Professor Mike Siva-Jothy, from the University of Sheffield’s Department of Animal and Plant Sciences, added: “To think that the pests that live in our beds today evolved more than 100 million years ago and were walking the earth side-by-side with dinosaurs, was a revelation. It shows that the evolutionary history of bed bugs is far more complex than we previously thought.”

The team spent 15 years collecting samples from wild sites and museums around the world, dodging bats and buffaloes in African caves and climbing cliffs to collect from bird nests in South East Asia.

The study also revealed that a new species of bedbug conquers humans about every half a million years. Furthermore, when bedbugs changed hosts, they didn’t always become specialised, maintaining the ability to jump back to their original hosts.

Co-leader of the study, Professor Klaus Reinhardt, a bedbug researcher from Dresden University, Germany, said: “These species are the ones we can reasonably expect to be the next ones drinking our blood, and it may not even take half a million years given that many more humans, livestock and pets that now live on earth provide lots more opportunities."

The team also found that the two major pests of humans, the common and the tropical bedbug, are much older than us as a species, contradicting the common notion that the split in ancient humans caused the split of the bedbugs into new species.

The researchers hope the findings will help create an evolutionary history of an important group of insects, allowing us to understand how other insects become carriers of disease, how they evolve to use different hosts and how they develop novel traits. The aim is to help control insects effectively and prevent the transmission of insect-vectored disease.