Complex sentence: The Olduvai theory claims that exponential growth of energy production ended in 1979, that energy use per capita will show no growth through 2008, and that after 2008 energy growth will become sharply negative, culminating in a world population of 2 billion circa 2050.
Split into simpler sentences: The Olduvai theory claims that exponential growth of energy production ended in 1979 and will show no growth per capita though 2008. After 2008 energy growth will become sharply negative culminating in a world population of 2 billion circa 2050.