Paleolithic hunting and gathering people ate leafy vegetables, fruit, nuts and insects, meat, fish, and shellfish. As there is little direct evidence, it is almost impossible to determine the relative proportions of plant and animal foods. There is a modern diet called paleolithic diet, but it has few things in common with the paleolitic diet of the time. Even the claim that most humans of a given period shared the same diet is problematic. The Paleolithic was an extended period of time. During that time, there were many technological advances, many of which had impact on human dietary structure. For example, humans probably did not possess the control of fire until the Middle Paleolithic, or tools necessary to engage in extensive fishing. On the other hand, both these technologies are generally agreed to have been widely available to humans by the end of the Paleolithic (consequently, allowing humans in some regions of the planet to rely heavily on fishing and hunting). In addition, the Paleolithic involved a substantial geographical expansion of human populations. During the Lower Paleolithic, ancestors of modern humans are thought to have been constrained to Africa east of the Great Rift Valley. During the Middle and Upper Paleolithic, humans greatly expanded their area of settlement, reaching ecosystems as diverse as New Guinea and Alaska. The also needed to adapt their diets to the local resources that were available.