实用英语口语(高级) 25.Studying DNA
PROFESSOR:What do all these different species have in common? Well, to begin with, they are all made of flesh and blood, have organs, bones, skin and hair. And most importantly, they all share the building blocks every creature needs to exist: DNA. 最近，现代科技使得我们可以研究存活至今离我们最近的祖先黑猩猩的DNA，将其与人类DNA进行比较。 A sample of blood was taken from a chimp.
PROFESSOR:The chimp's genome, or genetic sequence, was then compared by scientists to that of a human. The results were astonishing! It was found that 96% of the human genome was identical to chimpanzees! In fact, the number of genetic differences between humans and chimps was ten times smaller than that between a mouse and a rat. This knowledge brings up some interesting philosophical questions.
PROFESSOR:one of them being: If 96% of our DNA is the same as a chimp's, what is in the 4% that makes us different? What makes us human? Why do we have cars, coffee machines, cell phones and computers ... and chimps don't? Well, there are two main reasons. Firstly, we stand upright, and have opposable thumbs.
PROFESSOR:This allows us to get more things done. Because our hands were free, we learned how to make and build things more effectively than any other species. Secondly, and this is perhaps the biggest thing that sets us apart from our monkey cousins, humans can communicate in complex language. Chimpanzee DNA does not contain FOXP2, the gene responsible for speech. Humans have this gene.
PROFESSOR:And as speech helped the human brain evolve at an amazing speed, we quickly became the dominant animal on the planet. That's not to say, however, that no other animals communicate. In fact, all animals communicate in their own way. Biologists have studied the language systems of everything from insects to primates, and have found that most species seem to have some form of basic language. Chimps use language to help them work together on quite complex levels.
PROFESSOR:They make tools, and they hunt together, which shows that chimps can make a plan and carry it out. What's holding them back, however, is that their language is what is called isomorphic. This means that, when chimps - and most other animals - communicate, each sound they make has only one meaning. In other words, one sound means go, one sound means hungry, one sound means eat. This makes their language very limited.
PROFESSOR:Human language, on the other hand, has almost limitless layers of complex meaning, allowing us to communicate on a much higher level. Humans, as far as we know, are the only animal able to discuss the world in an abstract or theoretical way. We can speculate, wish, tell secrets, voice regret, organize, rebel, love and hate in words and sentences which contain layers and layers of meaning! Humans can't run as fast as a cheetah, swim as fast as a shark, or break the branches of a tree as powerfully as a gorilla. But the power of language has made us king.
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