探索世界奥秘之Life Story(生命物语) Unit9

Millions of years ago, the embryo of a distant ancestor of ours would have shared with us many of these features. As well as giving rise to us, it gave rise to all sorts of other creatures. And in those creatures, these features we're looking at here have evolved quite differently. We can actually see it happening with the ear bones, because those very same grooves that in us would have become our ear bones, in this creature become something else entirely. This is the embryo of a fish. Here is its heart. And it too has a curved spine and the tiny grooves here, just a fraction of a millimeter long, have evolved to become not ear bones, but supports for its gills.

So, sometime long, long ago, this sort and I shared a common ancestor. And like them it too had little bones around its gills which helped it to breathe. But as we evolved, these little bones were adapted for an entirely different job purpose to become the intricate mechanism of our ears.

And our ear bones are not the only things to have been transformed in this way. Such apparent miracles are in fact all around us. The rest of our ears that allow us to balance and walk upright as well as hear, our limbs and hands, our whole body has been shaped by the process of evolution.

Everything about the human body has been inherited and adapted from something our ancestors had a long time ago. Even though they may have used it for something entirely different, we are recycled from the past.

Once we begin to understand the source from which our bodies are derived, the way we look at ourselves can never be quite the same again. So every part of the human body bears a shadow from our distant past. Evolution has adapted our bodies from those of our ancestors, all the way back since life was as simple as that in the steaming pools of three billion years ago. It is incredible...

words and expressions

derive:To issue from a source; originate.起源于，来自