We're dabbling in eugenics all the time, breeding ideal crops to replace less aesthetic or nutritious or hardy varieties; leveling forests to graze cattle or erect shopping malls and condos; planting groves of a few familiar trees that homeowners and industries prefer.

Which is crueler, an old man's lost memories of a life lived, or a young man's lost memories of the life he meant to live?

Complexity excites the mind, and order rewards it. In the garden, one finds both, including vanishingly small orders too complex to spot, and orders so vast the mind struggles to embrace them.

Smell brings to mind... a family dinner of pot roast and sweet potatoes during a myrtle-mad August in a Midwestern town. Smells detonate softly in our memory like poignant land mines hidden under the weedy mass of years.

Ecstasy is what everyone craves - not love or sex, but a hot-blooded, soaring intensity, in which being alive is a joy and a thrill. That enravishment doesn't give meaning to life, and yet without it life seems meaningless.

The further we distance ourselves from the spell of the present, explored by our senses, the harder it will be to understand and protect nature's precarious balance, let alone the balance of our own human nature.

As a species, we've somehow survived large and small ice ages, genetic bottlenecks, plagues, world wars and all manner of natural disasters, but I sometimes wonder if we'll survive our own ingenuity.