Great apes were wiped out in ancient Europe when their environment changed drastically some nine million years ago, scientists say.
A study of fossil teeth from grazing animals sheds light on what Europe was like during Late Miocene times.
Researchers say changes in Europe's climate and environment at the time replaced many forests with grasslands - and great apes with monkeys.
The scientists described their findings in a Royal Society journal.
Ancient relatives of modern orangutans, gorillas, chimpanzees and gibbons were able to survive in Asia and Africa, where those changes were not as drastic.
A team led by Dr Gildas Merceron from Claude Bernard University Lyon 1 in France looked at the fossilised teeth of ancient antelopes that lived alongside apes during the Miocene epoch - in what now is Germany, Hungary and Greece.
The researchers tried to determine what these animals ate millions of years ago.
"The best way to reconstruct the past environment is to determine the diet of vegetarian species. Here we used fossils of antelopes because these animals dominated the fauna in Europe at the time," Dr Merceron told BBC News.
The scientists then analysed "micro scars" - specific patterns of wear that give researchers clues about the animals' dietary habits - on the teeth of these antelopes.
They found that when these mammals shared the land with great apes, the landscape in Europe was quite different from what it gradually became.
The changes didn't happen overnight - it took thousands of years, said Dr Merceron. But as the apes' original habitat changed and forests disappeared, these animals slowly became extinct in Europe.
Eventually, apes were replaced by their smaller cousins - a species of monkey called Mesopithecus, said the researcher.
Danger of extinction
Today, humans can cause much more rapid change to the environment than what was happening millions of years ago. People need to be mindful of their negative impact on the animal world, said Dr Merceron.
"If we dry out our swamps and cut down our forests, in the end we might get a very uniform environment and a decrease in biodiversity," said the scientist.
"Deforestation leads to eventual isolation of different populations of great apes in small forests. When they get isolated, it becomes impossible for them to have a genetic exchange between populations - and the populations start to decline."
Numbers of apes living today have fallen sharply in recent years. Increased levels of poaching and deforestation are thought to be the main factors for the decline.
Many species are critically endangered - only about 6,000 Sumatran orangutans and as few as some 700 mountain gorillas are thought to remain in the wild.
But there is more, says Dr Merceron's colleague, Dr Ellen Schulz from the University of Hamburg in Germany.
"Great apes are in danger of extinction, mostly because of humans destroying their habitat," she said.
"But there's something else - people tend to forget that preserving biodiversity is important for their own survival as well - we never know what awaits us in the future."