Our back yard is filled with ancient plants and animals. It’s a mysterious garden of life forms that have mutated and evolved seemingly beyond recognition over eons. In imagining their origins I look into a Past that, like a god, generates all life and consumes all but these present-day versions.

Our dog comes from 40,000 years of creatures–wolves initially–that became friendly enough to live with, and off of, humans.

My wife and I, whom the dog learned to play with and be fed by, go back longer, to about 200,000 years ago. We are Homo sapiens, “wise” creatures, who still carry some DNA of the chimps from whom we separated genetically about 7 million years earlier. Along the way there have been other species of Homo–Homo erectus, Home habilis, Homo neanderthalensis, others–but, chillingly, they have all disappeared, all except us, so far, the “wise” ones.

The squirrels date from 36 million years ago, part of a huge group of rodents with big, continually growing teeth, all the better to chew the nuts and the trees they came from.

But all of us animals here are much younger than even the youngest plant, the grass, which appeared about 50 million years ago among the plants adapting to a warming climate. One of the grasses’ secrets to success is that they grow from the bottom of the stalk, so they recover quickly from grazing or damage to their tops.

An oak tree dominates the yard. It, like the grasses, belongs to the spread of flowering plants around the planet, blooming around 160 million years ago. So do the current insects—flies, butterflies, wasps, bees, ants—that feed on and pollinate the flowers. Other insects, like the beetles, spiders, and dragonflies, appeared much earlier.

The pine trees and cedars around the house pre-date the oak. They arose 300 million years ago as early trees took root farther from the water. So did the ferns, one of the earliest land plants with a stalk and a stem that lifted it towards the light. Here in the crowded yard, the ferns still find room.

The birds in the yard are our dinosaurs, walking on two legs, with the abrupt turns of their heads, feathered for warmth, as were their dinosaur predecessors 180 million years ago.

So it is an ancient back yard if you look at it in this way. Of course these dates are approximate, in part because the “birth” of these groups of organisms was more evolutionary process than eventful arrival: the age of a rose depends on whether you count it strictly as a rose or a seed-bearing plant or a land plant.

Still, I savor the history here, the parade of lives.