  We introduce a toy model of the "rat race" in which individuals try to better
themselves relative to the rest of the population. An individual is
characterized by a real-valued fitness and each advances at a constant rate by
an amount that depends on its standing in the population. The leader advances
to remain ahead of its nearest neighbor, while all others advance by an amount
that is set by the distance to the leader. A rich dynamics occurs as a function
of the mean jump size of the trailing particles. For small jumps, the leader
maintains its position, while for large jumps, there are long periods of stasis
that are punctuated by episodes of explosive advancement and many lead changes.
Intermediate to these two regimes, agents reach a common fitness and evolution
grinds to a halt.
