Stochastic Tunnel

If you have two states that require an large amounts of energy/distance to travel between them, it is not likely that state one will become state two. However, if there is enough random fluctuation, state two will eventually be sampled, and if it is a stable minimum, this can lead to conversion from state one to state two in what is termed ‘stochastic tunnelling’. This concept has been used to explain adaptations in evolutionary biology where the intermediate mutations required appear to be unfavourable for fitness.