Quotes from David Christian

The modern era is the briefest but most turbulent of the three main eras of human history. Whereas the era of foragers lasted more than 200,000 years and the agrarian era about 10,000 years, the modern era has lasted just 250 years. Yet during this brief era change has been more rapid and more fundamental than ever before; indeed, populations have grown so fast that 20 percent of all humans may have lived during just these two and a half centuries.

Fernandez-Armesto, F. (2007). The world: A history. Upper Saddle River, NJ: Pearson/Prentice Hall.

Brown, C. S. (2007). Big history: From the Big Bang to the present. New York: The New Press.

Between 1750 and 2000 the number of human beings increased from approximately 770 million to almost 6 billion, close to an eightfold increase in just 250 years. This increase is the equivalent of a growth rate of about 0.8 percent per annum and represents a doubling time of about eighty-five years. (Compare this with estimated doubling times of fourteen hundred years during the agrarian era and eight thousand to nine thousand years during the era of foragers.)

Christian, D. (2004). Maps of time: An introduction to big history. Berkeley and Los Angeles: University of California Press.

it takes photons of light just over 8 minutes to reach Earth, 150 million kilometers away.

Diamond, J. (1998). Guns, germs, and steel: The fates of human societies. London: Vintage. Diamond, J. (2004). Collapse: How societies choose to fail or succeed. New York: Viking

From the beginning most of history was a story of divergence: humans' biological and cultural differentiation as they evolved and dispersed across the planet. For the past millennium, history has been dominated by convergent forces, of which globalization is the latest phase. During this era that I call the Great Convergence, human interaction, trade, and intercommunication have increased at a rapid rate.

the universe may, in fact, be bigger than this, because the notion of inflation suggests that in the first second of its existence, the space-time in which the universe is embedded expanded much faster than the speed of light. If so, the real universe may be billions of billions of times larger than the observable universe.

Choices whose outcomes matter even though they are neither deterministic nor completely random surround us all the time. So it is not surprising that in all human societies, entire professions have been based on the making of such predictions—think of astrologers, stockbrokers, professional gamblers, weather forecasters, or . . . politicians.

Earth, for example, is made up of oxygen (almost 50 percent) and smaller amounts of iron (19 percent), silicon (14 percent), magnesium (12.5 percent)

tax. When the star stops generating energy, it will collapse.

No scientific theory can claim absolutely certainty.

All knowledge arises from a relationship between a knower and an object of knowledge.

Living organisms are constructed, for the most part, from compounds of carbon and hydrogen. Carbon is critical because of its astonishing flexibility. Add hydrogen, nitrogen, oxygen, phosphorus, and sulfur and we can account for 99 percent of the dry weight of all living organisms.

there are several distinct types of networks of exchange, each with its own typical range and characteristics. The main types that they identify are bulk-goods networks, prestige-goods networks, political/military networks, and information networks.

The efficiency of information exchanges reflects, above all, the nature and regularity of contacts and exchanges between different communities.

Within a single information network, processes of collective learning may be more or less powerful in different regions; it is thus possible to imagine regions in which more information is pooled, in greater variety and in greater concentrations, than in other regions. These arguments suggest a useful general principle: the size, diversity, and efficiency of information networks should be an important large-scale determinant of rates of ecological innovation.

The universe really is indifferent to our fate. It's a vast ocean of energy for which individual wavelets such as us are ephemeral, passing phenomena.

In the 1990s, global military expenditures declined by perhaps 40 percent, and stocks of weapons of all kinds fell.

thus animals without symbolic language may lack the ability humans have to deliberately think about the past and imagine the future.

as Joel Mokyr has argued, technological innovation is unlikely to happen quickly where those who work lack wealth, education, and prestige, and those who are wealthy, educated, and have prestige know nothing about productive work.

Even in Jericho, the oldest-known farming village, the walls, which were once believed to have been fortifications, are now thought to have been an early form of flood control.

energy is used to pump individual protons from inside the cell (where there is a low concentration of protons) to outside the cell (where there is a high concentration of protons). This is like charging a battery.