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With a very general statement like this, one first has to define what is understood by 'intelligence'. 'Intelligence' may be defined in many different ways and there is no single absolute definition. It may reflect the speed and ability with which a person can acquire knowledge or a skill or it may measure the ability to use reason and logic in solving problems. The way in which one measures the 'intelligence' of a dog or a bird or a fish will differ from the way the 'intelligence' of a child is measured and the way one measures a child's 'intelligence' will be different from the way one measures that of an adult. Once one has decided what population is being studied and the criteria for determining intelligence, one then has to devise tests which will reliably determine which influences are solely environmental and which are entirely genetic. Although science has mapped the entire human genome, we still know very little about what each genetic component does and still less about the complex and subtle influences which individual genes have on each other and how the environment affects their action. In short, the environment and genetics are so intertwined in their influence on factors such as intelligence that it is probably impossible to either prove or disprove such a generalised statement as the above, let alone to assign any quantitative analysis which says, for example, that 'human intelligence is 80% due to genetic influences and 20% due to purely environmental factors'. In any case, such a statement would be virtually meaningless unless one were comparing the intelligence of two specific populations.