The cratering records on the Moon, Mercury, and Mars are studied to provide constraints on (1) terrestrial conditions prior to about 3.8 Ga, (2) why biology was not extensively established prior to 3.5 Ga, (3) whether impact-induced volcanism can explain some feature of the Cretaceous/Tertiary (K/T) boundary event, and (4) how common large single-impact events are in the inner Solar System. Earth underwent a period of high impact rates and large basin-forming events early in its history, based on the cratering record retained in the lunar, mercurian, and martian highlands. The widespread occurrence of life around 3.5 Ga is linked to the cessation of high impact rates. Impact of a 10-km-diameter object into terrestrial oceans could excavate through crustal material and into mantle reservoirs, creating extended basaltic volcanic activity. Scaling laws, coupled with the record retained on lunar and martian plains, indicate that between one and seven craters of ≥90 km diameter could have formed on Earth in the past 65 m.y.