(A) The domestication of animals occurred some 10,000 years ago and represented a milestone for the history of human civilization. The origin and sequence of domestication is a hotly debated topic among anthropologists and historians. Richard Bulliet, professor of history at Columbia University, argues that animals were probably first kept in captivity for use in sacrificial rites. This practice allowed ancient civilizations to observe which species were tame enough for use as work animals. Animals, notably cattle, provided labor and locomotion when they were harnessed to plows, sledges, and wagons beginning in about 4000 BC. Thus, animal agriculture ①was indispensable to accelerate the development of crop agriculture. The flesh and hides of sacrificial animals were routinely consumed by those in the royal house or the priesthood. Eventually, the habit of having the animals under human control at all times provided a constant and consistent food supply ready at hand. It also thereby created the leisure time necessary to societal progress.
(B) Much of what we know about the population processes of animals comes from studies on birds. The reasons are not hard to find, for comparing to many other animals, birds are relatively easy to study. Most species are active by day; they are conspicuous and can be recognised by their appearance, songs or calls, which makes them easy to detect and count. In addition, most birds can be trapped and marked with leg rings or other tags. They then become identifiable as individuals, ②enabling their movements and life histories to follow. Many species, too, are large enough to carry radio-transmitters or other electronic devices, so that their day-to-day activities and movements can be recorded. When tracked using satellites or geolocator tags, individuals can also be followed on their migrations, wherever on earth they travel. ③Hardly do any other kinds of animals show such an obliging combination of characteristics.
(C) Children learn to walk, run, climb, whistle, ride a bike, skate, play games, and jump rope without adult teachers. They compare their own performance with what more skilled people do, and slowly make the needed changes. In the same way, a child learning to talk compares a thousand times a day the differences between the language he uses and the language those around him use. Bit by bit, he makes the necessary changes to make his language like other people's. But in school we teachers rarely give a child such a chance. We don't let him detect his mistakes for himself, ④let alone correcting them. Instead, we do it all for him. We incessantly point out his mistakes and correct him almost all the time. Before long he becomes completely dependent on the teacher.
