If you seem to be better at climbing trees than your friends, you could be having a bone structure more similar to a chimpanzee, a new study has claimed.
One in 13 people have flexible ape-like feet, according to the new study by Boston University scientists.
The team studied the feet of 398 visitors to the Boston Museum of Science and the results show differences in foot bone structure similar to those seen in fossils of a member of the human lineage from two million years ago.
It is hoped the research, published in the American Journal of Physical Anthropology, will establish how that creature moved.
Apes like the chimpanzee spend a lot of their time in trees, so their flexible feet are essential to grip branches and allow them to move around quickly - but how most of us ended up with more rigid feet remains unclear, the BBC reported.
Jeremy DeSilva from Boston University and a colleague asked the museum visitors to walk barefoot and observed how they walked by using a mechanised carpet that was able to analyse several components of the foot.
Most people have very rigid feet, helpful for stability, with stiff ligaments holding the bones in the foot together.
When primates lift their heels off the ground, however, they have a floppy foot with nothing holding their bones together.
This is known as a midtarsal break and is similar to what the Boston team identified in some of their participants.
This makes the middle part of the foot bend more easily as the subject pushes off to propel themselves on to their next step.
Most with this flexibility did not realise they had it and there was no observable difference in the speed of their stride.
In addition, DeSilva found that people with a flexible fold in their feet also roll to the inside of their foot as they walk.
The bone structure of a two-million-year old fossil human relative, Australopithecus sediba, suggests it also had this mobility.
"We are using variation in humans today as a model for understanding what this human creature two million years ago was doing," added DeSilva.
Tracy Kivell, a palaeoanthropologist from the Max Planck Institute for Evolutionary Anthropology, said: "The research has implications for how we interpret the fossil record and the evolution of these features.
"It's good to understand the normal variation among humans before we go figure out what it means in the fossil record," Dr Kivell was quoted as saying in the report.