Hominids had upright walking, stone tools, fire, even language but still remained in profound stasis. What led to humanity's global takeoff, Ridley argues, was the invention of exchange about 120,000 years ago. "That's ten times older than agriculture."
The beginnings of trade encouraged specialization and innovation, which encouraged further innovation, specialization, and trade, and the unending virtuous cycle of progress was set in motion. The quality and speed of the progress depends on the size of the population doing the exchanging. "It's not how clever we are but how much in contact we are with each other." Thus the 5,000 Australians who became isolated on Tasmania 10,000 years ago didn't just stop progressing, they forgot how to make and use bone tools and even how to clothe themselves against cold weather. Their individual brains were fine, "but there was something wrong with their collective brains."
What really is being exchanged is ideas. The Pill-cam (for shooting video of your gut) was invented, Ridley points out, when a gastroenterologist had a conversation with guided missile designer.
The acceleration of progess can be measured in objective terms such as the amount of labor it takes to earn an hour of reading light. In 1997, with CF bulbs, it was half a second. In 1950, with incandescent bulbs, eight seconds. In 1880, with kerosene lamps, fifteen minutes. In 1800, with candles, six hours. In every decade various intellectuals keep saying that progress has stopped or is about to stop, but Ridley showed chart after chart chronicling constant improvement in everything we care about. Life expectancy is increasing by five hours a day. IQ keeps going up by three points a decade. Agriculture gets ever more productive, leaving more land to remain wild. Even economic inequality is decreasing, with poor countries getting rich faster than rich countries are getting richer.
On the subject of climate change, Ridley has a similar set of detailed charts showing that sea level has been rising slowly for a long time, but it is not accelerating. The same with the retreat of glaciers. Overall global warming is proceeding slower than was predicted. Humanity has been decarbonizing its energy supply steadily for 150 years as we progressed from wood to coal to oil to natural gas. A few years ago it was thought that only 25 years of natural gas was left, but with the invention of hydrofracking shale gas, the supply is suddenly 250 years worth, and it is a hugely cleaner source than coal. (Among nuclear innovations, Ridley is particularly intrigued by thorium reactors.)
"The story of history is of more for less." Paul Ehrlich's formula (I=PAT--- environmental Impact equals Population times Affluence times Technology) is better stated as I=P/AT--- Impact equals Population divided by Affluence times Techology. As affluence and technology increase, and population levels off, environmental impact can go ever down.
An historian once wrote, 'On what principle is it that when we see nothing but improvement behind us, we are to expect nothing but deterioration before us?" That was English historian Thomas Babington Macaulay in 1830, even before the industrial revolution.