When this world consider whether a individual is outstanding or not, the influence of individuals' contribution to the world always put on the priority list. Retrospecting the history, we can easily find that the great individuals share some shinny charicteristics, that is brave, diligence and so on. When contemporaries assess whether a indicidual is great enough or not, they just consider that whether the indicidual earn a much better living standard for the averages or whether the indicidual do some irreplaceable works that push a filed of study to new stage. However, for the prople who live after this indiciduals they will regard them much comprehensivly.
It is ture that a part of persons honered with contemporareis and the people who lived after them. For instance, Martin Luther King as a brave combattant in the war fight aganist slavey, in his live time, he was supported by the native American and when long time after he was murderned, people also consider him as a hero. Because in his live time, he was proper right for the contemporaries and in this way, he can draw a lot of attention from outside world. Meanwhile, as a leader of justicial works, even through long time after his death, some researcheres was doubted his stage in American's role in Viterman war, are accepted by worldwild as a shedstone in American's history.
Simply sum, contemporaries use comtemporary sociaty as a rule to judge whether a individual is great enough. In this way, they may ignore the consequial influence the individual bring to this world, beacause no one can predict the future world precisely. However, a greatness of a people must be eternal which means it cannot be changed by the social stage or other outside environment.
In this way, a greatness of people need and must be determined by the people after them. Mender, father of heredity, is underappraciated for more than 30 years. Mender combined mathmaticals, statisticals and  
botany finally draw a rule of heredity of specices. His dissertation was not catch people's attention since his research was too surrealistic to understand by the contemporaries. In anther word, his great finds was put aside for more than 30 years and about 10 years after his death, three scientists proven Mender heredity theory individly. Until that day, the prestige of Mender in heredity was established.
Another reason for the underappraciate of Mender was from his accentric action in that society. He refused to obey governments' unreasonable recommand and used eight years to plant peas just to draw a conclusion that cannot be accepted by the comtemporaries. In that time, beacause of the publish of Origin Of species, most botanies was fixed their eyes on the process of evolution of species. In this way, it is easily understand Mender's failure in that time.
Nowaday, many individuals who were underestimated in their time is proven to be great individuals. As a going says, the gold will shine. The greatness of individual can be decided only by the people who live after them since this greatness is tested by the time and eventually get it's name.