The study of self-control is being increasingly studied by social psychologists, as they have found it to be as important to achievement as intelligence and grit.
In the new study, scientists studied mitochondrial DNA extracted from well-dated fossil bear skeletons to work out how population size changed over time.
In last year's study, the average service time at the McDonald's drive-through studied was 188.83 seconds, compared with 129.75 for industry leader Wendy's Co.