So what’s wrong with doubling–or more–the human life span?

It’s like stretching out a symphony, playing it at half speed so it goes on longer–it wouldn’t have the same beauty or meaning…..

We get a taste of each relational category–being a child, a parent, and a grandparent. And our direct family lineage is connected by both genetics and personal experience, not so attenuated by time that relatives feel unrelated. If people lived to be 140, as some scientists suggest we will through technological intervention, a child could have 64 great-great-great-great-grandparents whose names he or she could never remember. In our natural lifespan, there is a harmony of proportion between the cycles of birth, ascendancy, and decline–phases of generation, nurture, and dependency that give a sense of meaningful connection within the journey of our lives.

Genes are not Legos; you can’t just plug them in and get a better baby. Genetics is very complicated; most genes affect many traits and most traits are affected by many genes. It’s not like Mr. Potato Head–you can’t just stick on new ears or a better nose or a bigger brain. These schemes amount to a massive human experiment, an imposition of our imagination and ideology onto the next generation–without consulting them and without a deeply considered appreciation for the fragile balance of our natural being–or our natural body. We are the product of nearly 4 billion years of evolutionary refinement. Our minds and the sense of meaning in our lives are wrapped into our very embodied form–our natural body is the fragile frame of our freedom and comprehending consciousness. If we’re not careful, we could write ourselves right out of our own story.

More here.