# Physics 434, 2015: Project 5

Start with the world human population size data from the textbook web site. Notice that there are also other estimates out there -- maybe it's worthwhile looking for them. A simple model of growth for bacteria (and humans) would be an exponential growth, where ${\displaystyle dn/dt=\gamma n}$. That is each person gives rise to ${\displaystyle \gamma }$ people over a certain time. But humans have two sexes, and the growth rate should be proportional to the rate of pair encounters in the population. Change the model appropriately -- does it fit the data better?