But this concept has certain disadvantages: If too many lifelines are stacked up an overview becomes difficult and a usefull graphic becomes just a vertical list of people without any meaningful association.

That means a selection within any century must be restricted to about twenty concurrent people. The printed chart has to live within this restriction but in the electronic version we have the advantage for an expansion into special lifeline sections for scientists, artists, writers etc.

Important selection criteria for the General Lifeline section were:

1. Did this person have an unusual influence within his (her) own time?  (1)

2. Will this be an enduring influence or will it be not more than temporary fashionable fame?  (2)

3. Was this person a pioneer in his field, or a founder of a nation?  (3)

4. Can this person serve as a landmark for his time around which other persons can be imagined even if they are not shown within the Lifelines?  (4)

5. Would history have evolved differently if this person would not have existed?  (5)

6. Did such a person contribute significantly to the most important ideas of mankind?  (6)

7. Was this person an unusual master of his art or did he (she) initiate a new art form?  (7)

The self imposed rule of twenty person per century leaves not much room to choose. Any selection of the ten most important artists would certainly by hotly challenged, but there will be less controversy for the selection of the single most influential artist of our time, namely Picasso. Likewise, the selection of the foremost scientist is not that difficult: who could disagree with the selection of Einstein. Freud is there, not on account of his theories which become increasingly challenged, but because he was the founder of a new branch of investigation, namely psychoanalysis. The selection of literary figures was a bit more subjective as can be seen. The question of course remains: which writer could be removed to make space for anybody else?

The world wars and the confrontation of communism with the Western world were certainly watershed events of the 20th century. The political antagonists of those events have therefore been included in the political section, with the addition of Gandhi, of whom Einstein once remarked: 'Generations to come will scarcely believe that such a one as this ever in flesh and blood walked upon this earth.'

The notion of landmark people is important because from the exclusive selection of familiar 20th century persons we can assess of how important the selected people of past centuries must have been.