【英语时差8,16】人类大脑的进化（上）

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? The most popular theory among anthropologists is that we switched to an omnivorous¹ diet. 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. 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?

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》