【英语时差8,16】饮食与大脑进化

Don: Our development of larger brains had much to do with our evolution as a species.      But the question is what fueled the development of those larger brains?

Ya?l: Isn't it that our ancestors switched from a herbivorous diet to an omnivorous¹ diet?

D: That's the most popular theory among anthropologists. Our ancestors are believed to      have evolved in a less forested, more open grassland² environment than our cousins,      the chimpanzees. This would have given them a clear view of large herbivores. Cut      marks on animal bones suggest that around 2.5 million years ago our ancestors did      indeed begin hunting. Because meat is rich in nutrients³, including essential amino      acids, it may have spurred the increase in brain size.

Y: Sounds reasonable.

D: The trouble is that the big increase in brain size occurred with Homo erectus, which      appeared just 1.8 million years ago. If meat was largely responsible for the change,      then why are there cut marks on bones nearly a million years earlier?

Y: That is strange.

D: Other anthropologists think it's because meat-eating isn't the key at all, that the real      key is cooked tubers.

Y: As in baked yams?

D: Yep. They say an increase in calories is what's important when it comes to the      development of larger brains, and that cooked tubers would have provided just such      a boost. And root vegetables are believed to have been plentiful⁴ in the environment      where humans evolvedY: And I guess that cooking would have made the tubers easier to digest.

D: Right, and therefore richer in calories. Cooking's the target of major criticism though.      Most archaeologists believe humans didn't begin cooking until about 250,000 years      ago.

Y: Oh. That is a problem, but then again, perhaps we started cooking earlier than      scientists think.

D: Time may tell.  

1 omnivorous   

adj.杂食的

参考例句：

• Brown bears are omnivorous,eating anything that they can get their paws on.棕熊是杂食性动物，抓到什么吃什么。
• Man is an omnivorous animal.人是肉类与蔬菜均食用的动物。

2 grassland   

n.牧场，草地，草原

参考例句：

• There is a reach of grassland in the distance.远处是连绵一片的草原。
• The snowstorm swept the vast expanse of grassland.暴风雪袭击了辽阔的草原。

3 nutrients   

n.（食品或化学品）营养物，营养品( nutrient的名词复数 )

参考例句：

• a lack of essential nutrients 基本营养的缺乏
• Nutrients are absorbed into the bloodstream. 营养素被吸收进血液。 来自《简明英汉词典》

4 plentiful   

adj.富裕的，丰富的

参考例句：

• Their family has a plentiful harvest this year.他们家今年又丰收了。
• Rainfall is plentiful in the area.这个地区雨量充足。