My Million-Year-Old Back Yard

I like knowing the age of living things—not the age of the individual organism but of the lineage, of how long a plant or animal has been different from other lineages. The dates give me a glimpse of a Past that, like a god, generates and then consumes everything.

So here are the ages, youngest first, of the plants and animals in my suburban yard. Dates are approximate by millions or tens of millions of years!

The youngest creature in the yard is our dog, an animal that separated from its wolf-like ancestors about 40,000 years ago.

Next is me and my wife. Our species, Homo sapiens, separated from our Homo ancestors about 200,000 years ago. Before that, our genus, Homo, split off from the genus that chimps belong to about 7 million years ago. All our ancestors in our genus have died off and we are the only member left, a strange isolation. We are probably the only species in the yard in that situation.

The youngest plant is the grass, appearing about 40 million years ago among plants that adapted to a warming climate.

Back yardThe first squirrel fossil dates from 36 mya. Squirrels are part of a huge group of rodents with big, continually growing teeth. The chipmunks are in the same category.

An oak tree dominates the yard. Although trees in general have been around for much longer, the oak was part of the spread of flowering plants, at very roughly 70 million years.

There’s a holly tree. The several hundred species of holly emerged about 80 million years ago.

Other flowering plants and trees come next. Their ancestors began diverging from flowerless plants around 240 mya, they were blooming 160 mya, and they became widespread and then dominant among plants during the 100 million years after that.

Insects originated about 600 million years ago, but the modern insects in the yard—flies, butterflies, wasps, bees, ants— co-evolved along with the flowering plants from 146 to 66 mya.

The birds are thought to have evolved from certain dinosaurs that carried feathers for warmth, about 180 million years ago.

The pine trees and cedars around the house are among the conifers that date back 300 million years when early trees began to live away from the water. Conifers reproduce through exposed seeds (on pine cones) and pollen. Protected seeds, enclosed in nuts and fruits, came later.

Two other back-yard inhabitants go back as far as the conifers: Ferns, not so different 350 million years ago, with their tiny, single-cell spores, another predecessor of the modern seed. And spiders, spinning their silk about 300 million years ago.

I’m realizing, as I finish hunting through Wikipedia for these dates, that my intentions have become a little muddled. The “birth” of these species was more process than event, a long interweaving with their early kin. The age of a rose depends on whether you look at it as a rose or a seed-bearing plant or a land plant.

Still, I savor the majestic history here, the story of life.

Dinosaurs in the Backyard

utahraptor

Utahraptor, up to 7 feet long, with early feathers
(palaeocritti.com)

Not dinosaurs exactly, but their descendants for sure. Look outside for the creatures that lay eggs and walk semi-upright on two legs, with a stiffened tail. Imagine that that robin is many times larger, without feathers but with scales, with a large jaw instead of a beak, with long forearms instead of full wings, and you have a creature out of Jurassic Park. A topic of speculation since Darwin’s time, the descent of birds from dinosaurs has been confirmed by recent fossil discoveries. Natural selection works in wondrous ways.

How did the dinosaurs of 200 million years ago get feathers? The feathers first appeared because they helped a dinosaur stay warm. But they had a second, accidental benefit. When a dinosaur was running, its feathers provided balance and lift. Eventually, according to the most widely accepted theory, lift became lift-off. (The familiar Pterodactyl flew on wings of skin and membrane; it was neither bird nor, officially, a dinosaur.)

archaeopteryx

From dinosaur to bird. Archaeopteryx lived 150 million years ago and was about the size of a crow. It had both a dinosaur’s sharp teeth and a bird’s feathers. This 1880 photo shows feathers that were later removed. (wikipedia)

And where were our own ancestors, the mammals, while all this was going on? Early mammals were small and stayed  out of the way of the meat-eating reptiles. They bore young that had grown inside the mother instead of inside eggs, reptilian style.

early mammal

Juramala, a mouse-size mammal living 160 millions year ago. Like humans, it had a neo-cortex and nourished its young until birth through an umbilical chord. (physorg.com)

And they carried a brain more complex than the old “lizard brain.” The bigger brain, with its neo-cortex, improved their sensory perception and movement. We also use it to think and imagine.

Feathers and wings, and the new brain—all of them selected for survival and adapted for soaring.