Cavemen suffered from bedbugs, according to a study.

The small insects have been plaguing human sleep for at least 50,000 years, but populations boomed when humans left caves behind and started forming basic cities, around 13,000 years ago.

A study on the genetics of bedbugs found the pest split into two lineages millennia ago, with one staying on bats and the other adapting to target sleeping people.

Both groups saw a decrease in numbers during the last Ice Age around 20,000 years ago, the scientists found.

Analysis of the genes of the two types of bedbugs revealed the bedbugs recovered at different rates depending on what animal they lived on. Bedbugs that lived in human beds fared better than those still living on bats, the scientists discovered.