模拟测试卷5-2019-8月新卷 According to the professor, what was a possible result of the selective breeding of crop plants?

[00:00.00]Narrator：Listen to part of a lecture in a history class.[00:05.80]Professor：So we’ve been talking about early civilization, those that existed seven to eight thousand years ago. [00:15.00]And today I’d like to talk about the switch from foraging, or searching for whatever wild foods are available, to farming, intentionally cultivating crops. [00:26.00]Now, the way that switch is frequently portrayed is that it was an improvement. [00:32.30]The development of agriculture is usually portrayed as a good thing. But there are advantages to foraging. [00:40.20]For one thing, it provides a better balance of nutrients and in particular, more protein at least compared to the diet of the farmers. [00:49.70]Foragers end up eating a greater mix of foods, both plants and animals. [00:55.90]But the early farmers and to some extent—this is still true today—the early farmers concentrated on just a few crops. It’s just rice and wheat.[01:07.40] There was less variety and therefore, a smaller range of nutrients and a lot of carbohydrates so the quality of the diet wasn’t as good. And we have evidence of this.[01:20.30] In Greece and Turkey, when comparing skeletons from forager communities to those of early farming communities, we see that height declined when farming was adopted, quite dramatically I might add.[01:34.30] Foragers were on average almost fifteen centimeters taller than the early farmers. That’s a lot. [01:42.10]Furthermore, farming increased one vulnerability to starvation.[01:48.30] It was easier to live off cultivating crops than to live off the wild, partly because it meant living off fewer plants.[01:57.30] I mean, farmers, even modern farmers, only cultivated about twenty different plants on average.[02:04.80] And even then, they really just focus on just three: wheat, rice, and maize.[02:12.00] Modern foragers, on the other hand, depend on over a hundred different plants.[02:17.30] They went with fruits, nuts, berries, roots, beets, and so on.[02:22.60] So if a few cultivated crops failed, if the rice crops failed for example, the farmers were in trouble.[02:31.40] Now of course, wild plants could fail too, but foragers eat so many different plants they always have something to eat.[02:40.50] Also, domesticated plants may be more prone to failure than wild plants.[02:45.80] Don’t forget, agricultural crops are the results of selective breeding.[02:51.70] Farmers choose certain seeds, ones that have the qualities they want refining the crops enchartered.[02:59.40] So, if the seeds of the plumpest potatoes or the whitest white grains are chosen, the hardy strains, the ones that can resist insect attacks or disease or strings of moisture for example, may be eliminated because the farmer hasn’t chosen seeds in plants with these characteristics.[03:20.70]So how did the switch from foraging to agriculture happen? Well, no one is really sure.[03:28.70] Some speculate that during the final stage of the last Ice Age, about ten to thirteen thousand years ago, there was a shift in climate in a number of locations that led to the decrease of food you could forage for.[03:44.30] The failure of wild harvests may have caused people of the different parts of the world to plant some crops to make up for the shortage.[03:54.10] There’s evidence that the practice of cultivation existed at that time.[03:59.20] For example, rice was cultivated in China as long as ten thousand years ago by people who were also still eating wild rice.[04:09.60] By counting the proportion of wild rice in cultivated rice in fossil remains, archaeologists have determined that the switch to farming there was a slow one, taking about four thousand years, so it didn’t happen overnight.[04:28.40] And there’s evidence that other groups of people also cultivated some cereal crops blending both foraging and farming for thousands of years. [04:40.00]So putting people into boxes, classifying them as either foragers or famers, well, we don’t do that anymore.[04:49.20] Of course, there were advantages to farming. Agriculture provided a greater quantity of food.[04:57.30] And when you have the increasing population as was the case in ancient Southwestern Asia, there was an advantage.[05:05.40] Also, with irrigation, crops could be planted in what was until then useless land.[05:12.60] For example, rooted barley didn’t grow naturally on the land between Tigris and Euphrates Rivers in ancient Mesopotamia.[05:22.30] But once that land was irrigated, all of it could become cultivated.[05:27.60] And hectare for hectare, farming was raising more food than foraging.[05:33.80] Farmers needed twenty times less land, a hundred times less if they irrigated, to feed the same number of people as foragers needed.