There is evidence that between 6,000,000 – 10,000,000 (6 million – 10 million) years ago, grasslands expanded across landscapes, creating vast open savannas, whilst tall grasses continued to remain dominant within wetter environments. These novel environments influenced the movement and adaptation of early human beings. It is theorized by scientists that human beings walked out of these evolving landscapes and adapted to the ground as humans were not evolved and/or adapted to take advantage of tall grasses the way other species are (e.g. snakes, mice, large cats etc.). It is also theorized by scientists that human beings needed to stand upright because the forests around them were thinning and with that, the canopy disappearing, making it virtually impossible to move from treetop to treetop as time moved forward. With the discovery of the hominid Anamensis, it is now clear to scientists that the tree of human ancestry follows its evolutionary order from Australopithecus Anamensis 4,200,000 (4.2 million) years ago, to Kenyanthropus Platyops, to Homo Habilis within the past 2,300,000 (2.3 million) years, to Homo Erectus, and finally to Homo Sapiens, the species to which modern day human beings belong to. Anamensis allows scientists to definitively state that bipedalism occurred 500,000 years earlier than what was previously believed as the tibia bone from Anamensis clearly demonstrates that Anamensis walked upright on both legs