Millions of years ago, the species of mankind that once spent their lives swinging around the trees began to start walking on the ground instead.
And it appears as though the same process of evolution has a chance of happening again, according to new research.
Species of monkeys and lemurs that have spent thousands of years living in the trees have been spending more and more time walking around on the forest floor due to circumstances like deforestation and climate change, the Daily Star reports.
A study based on more than 150,000 hours of observations of 47 tree-dwelling primate species living across almost 70 sites in Madagascar and the Americas has shown the change in habitat is a global trend.
Giuseppe Donati from Oxford Brookes University says the the tree-dwelling animals are being forced to the ground to seek shade and water as temperatures in the forest continue to rise.
He told New Scientist : "In most tropical countries where these species live, humans log the forest.
"This creates gaps and it opens the canopy of the forest. That causes an increase in temperature."
He added that deforestation "is working together with climate change" to drive the animals into seeking out new places to live.
One species that Giuseppe identified was the bamboo lemur from Madagascar. Like most species of lemur, they spend most of their time up in the trees.
But in south Madagascar, where the forest canopy is becoming increasingly thinner, he says bamboo lemurs have started grazing on the grasslands – “a bit like little cows”.
While it's not 100% confirmed what caused our ancestors to ditch the trees for good and start walking around on land, the change in habitat is widely believed to have been driven by climate change.
But these changes are happening very quickly now compared to the natural fluctuations in the Earth's climate historically, and monkeys will struggle to adapt with these.
Timothy Eppley, from the San Diego Zoo Wildlife Alliance, says: "None of the species we studied are likely to fully transition to a terrestrial lifestyle. It’s simply not a viable long-term outcome to happen in such a short period of time.”
He says if tree-dwelling monkeys like lemurs are to be saved from the new mass extinction currently killing the planet's biodiversity, "we need to actively protect the forest habitat that we currently have".
Don't miss the latest news from around Scotland and beyond - Sign up to our daily newsletter here.
