D
As evolution tends to remove waste, how come we evolved such large, energyconsuming brains? The dominant hypothesis(假设) suggests that tough social interactions are the driving force. But our new study done in an unusual way shows that human brain expansion is likely driven by ecology(生态)．
Scientists have tested the ecological and social hypotheses before. The common approach is to look at many species and investigate whether large brains are associated with specific problems. For example, do primates or other animals with large brains have a diet that is challenging to find but nutritionally rewarding? This would indicate an ecological origin. Or do they live in large groups where they face lots of social problems?
While many studies have found such associations, there is a problem. It cannot tell whether large brains evolved to solve the difficult problems or whether they evolved for other reasons and then enabled their bearers to deal with the hard problems.
To find out the causes of brain expansion, we recreated the scenarios(情景) of the two hypotheses using a mathematical model. We found that a combination of ecological and social challenges does produce the brain size we see in humans. But it was ecological challenges that expanded brains. In contrast to the dominant view and our own expectation, we found that social challenges contributed by decreasing brain size. But you need both factors to get the brain size we see today,if there were no social challenges our brains would have been even larger but likely poorly suited to social life. Bigger isn’t necessarily better.
But many animals face hard ecological problems. Why don’t they all have large brains? We found that ecological problems only lead to humansized brains when individuals can keep learning hard skills as they grow. So our results and those of others’ suggest that hard ecology and the accumulation of cultural knowledge could act together to produce a humansized brain.
Will the human brain expand further? The complexity of the systems involved makes it impossible to say much with certainty at present.
12．In most people’s view, what makes human evolve large brains?
A．Social challenges.
B．Social and ecological challenges.
C．Ecological challenges.
D．Competition with other large animals.
13．What’s the problem of the common approach?
A．Its model is not reliable enough.
B．It doesn’t tell the cause and effect clearly.
C．Its hypothesis cannot be proved effectively.
D．It doesn’t find brain size is connected with problems.
14．Why don’t many animals have large brains?
A．They don’t learn from each other.
B．They don’t face hard ecological problems.
C．They don’t need to cooperate with each other.
D．They don’t keep learning tough skills as they grow.
15．Which of the following do the researchers find most surprising?
A．Animals don’t have large brains.
B．Social challenges decrease brain size.
C．Ecological challenges increase brain size.
D．It’s unclear whether human brains will expand further.
阅读理解D
As evolution tends to remove waste, how come we evolved such large, energyconsuming brains? The dominant hypothesis(假设) suggests that tough social interactions are the driving force. But our new study done in an unusual way shows that human brain expansion is likely driven by ecology(生态)．
Scientists have tested the ecological and social hypotheses before. The common approach is to look at many species and investigate whether large brains are associated with specific problems. For example, do primates or other animals with large brains have a diet that is challenging to find but nutritionally rewarding? This would indicate an ecological origin. Or do they live in large groups where they face lots of social problems?
While many studies have found such associations, there is a problem. It cannot tell whether large brains evolved to solve the difficult problems or whether they evolved for other reasons and then enabled their bearers to deal with the hard problems.
To find out the causes of brain expansion, we recreated the scenarios(情景) of the two hypotheses using a mathematical model. We found that a combination of ecological and social challenges does produce the brain size we see in humans. But it was ecological challenges that expanded brains. In contrast to the dominant view and our own expectation, we found that social challenges contributed by decreasing brain size. But you need both factors to get the brain size we see today,if there were no social challenges our brains would have been even larger but likely poorly suited to social life. Bigger isn’t necessarily better.
But many animals face hard ecological problems. Why don’t they all have large brains? We found that ecological problems only lead to humansized brains when individuals can keep learning hard skills as they grow. So our results and those of others’ suggest that hard ecology and the accumulation of cultural knowledge could act together to produce a humansized brain.
Will the human brain expand further? The complexity of the systems involved makes it impossible to say much with certainty at present.
12．In most people’s view, what makes human evolve large brains?
A．Social challenges.
B．Social and ecological challenges.
C．Ecological challenges.
D．Competition with other large animals.
13．What’s the problem of the common approach?
A．Its model is not reliable enough.
B．It doesn’t tell the cause and effect clearly.
C．Its hypothesis cannot be proved effectively.
D．It doesn’t find brain size is connected with problems.
14．Why don’t many animals have large brains?
A．They don’t learn from each other.
B．They don’t face hard ecological problems.
C．They don’t need to cooperate with each other.
D．They don’t keep learning tough skills as they grow.
15．Which of the following do the researchers find most surprising?
A．Animals don’t have large brains.
B．Social challenges decrease brain size.
C．Ecological challenges increase brain size.
D．It’s unclear whether human brains will expand further.
阅读理解D
