Towns and cities were established not only as garrisons (military posts) but as centers for the diffusion of Greek language, literature, and thought, particularly through libraries, as at Antioch (in modern Turkey) and the most famous of all, at Alexandria in Egypt, which would be the finest in the world for the next thousand years.

Another flaw of the tiredness theory is that yawning does not raise alertness or physiological activity, as the theory would predict.

In brief, Lazarus contends that emotions are roused when cognitive appraisals of events or circumstances are positive or negative━ but not neutral.

Whether Mithen’s explanation is satisfactory is open to contention, and some authors have recently emphasized the importance of other factors.

Some of the proposed mechanisms required a very brief period during which all extinctions suddenly took place; other mechanisms would be more likely to have taken place more gradually, over an extended period, or at different times on different continents.

The undisputed pre-Columbian presence in Oceania of the sweet potato, which is a New World domesticated plant, has sometimes been used to support Heyerdahl’s “American Indians in the Pacific” theories.

Information transfer can be unintentional though some species make use of special assembly calls or behavior.

Through continuous creation, the steady-state theory is finally compatible with the expanding universe.

The accidental effects obtained by candid photographers were soon copied by artist, such as the French painter Degas

For example, caterpillars that feed on soot-covered leaves did not give rise to dark-colored adults.

Occasionally, a sequence of fossil-rich layers of rock permits a comprehensive look at one type of organism over a long period of time.

Others have blamed extinction on competition from the mammals, which allegedly ate all the dinosaur eggs — except that mammals and dinosaurs appeared at the same time in the Late Triassic, about 190 million years ago, and there is no reason to believe that mammals suddenly acquired a taste for dinosaur eggs after 120 million years of coexistence.

Coral reefs have fascinated scientists for almost 200 years, and some of the most pertinent observations of them were made in the 1830s by Charles Darwin on the voyage of the Beagle.

Sense organs monitor specific stimuli in the environment and send a summation of pertinent stimuli back to central-nervous-system centers, which regulate the amount of exploration.

Commensal associations sometimes involve one species’ obtaining food that is inadvertently exposed by another.

The Maori may have also inadvertently brought pests and disease organisms in fowls, which could have crossed over to eradicate moa populations.

In Jamaica, overfishing removed most of the plant-eating fish from coral reefs. Initially, algal growth was kept in check by grazing sea urchins, but in 1982, a pathogen reduced the population by 99 percent. Without grazers, the algae were able to completely overgrow the coral.

Control of disease, like the checking of smallpox【醫】天花by vaccination may have been important. But of most critical importance was the food supply.

Still, extreme temperatures, in combination with other factors, may have dramatic detrimental effects.

Books became major vehicles for artistic expression, and the artists who produced them, notably calligraphers and painters, enjoyed high status, and their workshops were often sponsored by princes and their courts.