Paleolithic hunter-gatherers ate leafy vegetables, fruit, nuts, insects, meat, shellfish, and other types of fish. Because there is little direct evidence, it is almost impossible to determine how much of their diet was plant food and how much was meat. Even the idea 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, until the Middle Palaeolithic, humans probably did not have control of fire, or the tools needed to do extensive fishing. On the other hand, archaeologists generally agree that both of these technologies were widely available to humans by the end of the Paleolithic. (This allowed humans in some regions of the planet to rely heavily on fishing and hunting.)