When compared with other animals of a similar size, our brains are extremely large. The human brain has nearly become four times bigger in size in the six million years. However, studies show this trend has reversed in Homo sapiens (智人). In our species, average brain sizes have shrunk over the course of the last 100,000 years.
How can we explain this striking reduction? Ian Tattersall suggests that the shrinkage in brain size began around 100,000 years ago, which corresponds to a period of time in which humans switched from a more intuitive (直觉的) style of thinking to thinking in a more abstract way to better understand your surroundings. Tattersall believes that what caused this change in thinking style was the invention of language. This led to the brain being reorganised in a more efficient way, allowing humans to get more “bang for their buck”.
However, Stibel believes that a changing climate, and not language, could explain our smaller brains. In a 2023 study, he analysed the skulls (头骨) of 298 Homo sapiens over the past 50,000 years. He found that human brains have been shrinking for about the last 17,000 years or so — since the end of the last ice age. When he carefully examined the climate record, he found that decreasing brain sizes were closely linked to periods of climate warming. Smaller brains could have allowed humans to cool down quickly. It’s well known that humans in hot climates have evolved thinner and taller bodies to increase heat loss. It’s possible that our brains could have evolved in a similar fashion.
Perhaps the most well-known theory put forward to explain our shrinking brains is that it began when our ancestors stopped being hunter-gatherers, laid down roots, and began to build complex societies. Jeremy DeSilva suggests that the birth of complex societies meant that knowledge and tasks could be spread out. People no longer had to know everything, and as individuals no longer had to think as much to survive, their brains reduced in size. But not all are convinced.
So where does that leave us?
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1.What does the underlined word “reversed” mean?
A Started.
B Disturbed.
C Completed.
D Exchanged.
解析：选D。D词义猜测题。根据第一段划线单词前文的“The human brain has nearly become four times bigger in size”“However”和后文的“average brain sizes have shrunk”可知，前后意思表示转折，即人类大脑增大的趋势开始“逆转”，人类大脑开始缩小。故选D。
2.What might Tattersall agree with?
A Bigger brains are better organised.
B Smaller brains perform less complex tasks.
C Language was the root cause of smaller brains.
D Humans are thinking in a more and more simple way.
解析：选C。C细节理解题。根据第二段中的“Tattersall believes that what caused this change in thinking style was the invention of language.”塔特萨尔认为，导致这种思维方式变化的原因是语言的发明，即他认为大脑缩小的根源在于语言。故选C。
3.How does the author prove Stibel’s opinion?
A By giving examples.
B By presenting research.
C By analyzing troubles.
D By doing experiments.
解析：选B。B细节理解题。根据第三段中的“In a 2023 study”“It’s well known that humans in hot climates have evolved thinner and taller bodies to increase heat loss.”可知，作者给出了相关的研究来证实斯塔贝尔的观点。故选B。
4.What does the fourth paragraph focus on?
A The rise of complex civilisations.
B The way our ancestors lived.
C A consequence of self-adjustment.
D A way to keep cooler.
解析：选A。A段落大意题。根据第四段关键词“stopped being hunter-gatherers”“began to build complex societies”“the birth of complex societies”可知该段讲的是因为复杂文明的兴起，人类不需要思考更多，从而导致大脑缩小。故选A。
