Researchers have recently suggested that the developments in human lineage may be linked to the changes in the environment over certain periods that lead to human evolution.

To get deep into the fact of evolution of the human race, researchers investigated samples of the leaf waxes that were preserved in lake sediments at Olduvai Gorge. Olduvai Gorge is a site in Africa, where excavations helped to find that it was base of human evolution.

The scientists studied that plants that existed and dominated the local environment about two million years ago. It was the time when the human ancestors used some advanced tools made from stones. They looked into leaf waxes which they say survived well in sediments.

After four years of research into same, the scientists now looked into carbon isotopes in the samples of leaves which helped to reveal which plants were dominant in the area. Hey found out that Olduvai Gorge frequently varied between grasslands and damp forests for about five to six times during 200,000 years.

"I was surprised by the magnitude of changes and the rapid pace of the changes we found. I've worked on carbon isotopes my whole career, and I've never seen anything like this before", said Katherine Freeman, a Biogeochemist at Pennsylvania State University who was involved in the research.