I learnt that initially (more than 100,000 years ago), Man had no possessions and no need for possessions. So, I guess that there was no need for numbers. However, the basic foundations of numbers was laid at that point of time. Man would hunt animals and eat. Now, Man would have calculated that if he hunted a Mammoth and if his tribe had 20 people in it, then the tribe could survive through the meat from the hunt for say 2 months. This essentially meant that Man would need going out hunting again after about 45 days to keep a reorder level of 15 days of meat.
What seems like an innocuous arithmetics is actually quite an intricate amount of calculations? They would have needed specialised people to determine the right fractions for dividing the meat so that it could last the 2 months and the tribe could rest for this period. If these people messed up, it would mean work for the Men of the tribe; and days of sleeping hungry for the Women and Children.
Gradually, they would have called these people “Mathematicians”. I am now wondering why these people are called “Mathematicians” and why is this process of calculation called “Maths”, rather “Arithmetic”. Why did our Ancestors (I am a Bengali) call this “Onko”?
Image taken from Google Images.
Experiences of Partha Majumdar 
Man would not have known months. I guess he would have known days as he would have seen the Sun rise and set at regular intervals. He may or may not have known about seasons as most of the places where he lived would have been covered by snow.