Different views regarding the invention of the number 'Zero' exist. The ancient Egyptians are believed to have a decimal number system. 'Zero' is also said to be invented independently by different civilisations. India is also considered an independent inventor of 'Zero' and developer of Mathematics around it.
The fact that who invented 'Zero' is not so important to the idea behind what made these civilisations invent it. And if some particular civilisations did, why couldn't others? It seems like a very obvious thing to account for non-existence when one is considering existence in finite terms (1,2,3...).
The key to the invention of the digit in question, lies deeper in the lifestyles of different civilisations.
Lets consider two groups of people at present, 'Indians' and 'Germans'.
Punctuality is a virtue in Germany. It is said that in the German way of life you own time, and you spend it. You are the sole authority of your resources and you use it at your will to achieve certain tasks. Individual is the focus in every situation. An Individual is the owner, doer and the person responsible for everything happening around him.
Now lets consider the Indian style...
Lets make some counteracting points before we dwell deep into this.
Indians are famous for not being punctual. There is a saying in India that everything starts at the 'Indian standard time', which is late than scheduled. Another common dialogue by any devout individual you might hear is, 'The God works through us and he has given us everything'. Also Indian tradition encourages to search for the 'God' (read goodness) in everyone. Thus, an Indian mind does not possess time, nor the resources accessible to him. He/She performs actions and dedicates them to the Higher Authorities.
When Alexander the great meets a naked sage on the banks o river Indus, he offers the sage gold and gems and all the luxury in the world. But the sage replies that he has no use of any such things. Whatever he has or had, he did not acquire it, it did not belong to him nor is he going to retain it. He replies that the universe gives us things and it takes those things away. The existence of an individual does not make some things belong to the individual. Alexander on the contrary came from a different line of thought that a person had to earn everything in his one life and everything that he earned belonged to him. He believed that every person must work to make this one life rich and worth to have lived. While the Sage believed that this life is just a part of a big cycle and it has to do its role on the big canvas.
These contrasting belief systems, according to me determined the invention of zero. Where in some civilisations the idea that the individual holds nothing and does nothing according to his own accord are imbibed. The ideas of ownership and belonging are the key to other. The idea of nothingness, non-existence or not non-possessiveness gave rise to the invention of 'Zero'. And the lack of such a ideology led others to be completely unaware of a digit. Thus, the invention of zero represents more a bridge from philosophy to mathematics and a little less the advanced mathematical concepts it enables the mankind to perform. :)
