Tuesday, 2 April 2013

Tree of Life

The Girl was looking at a picture where all kinds of animals – owls, mice, turtles and foxes – hid in the corners, and you had to find them.

Can you find the anapsids in the picture? I asked.

“There’s a turtle there?” she asked in surprise.

I talk to her a lot about the living things around us and try to do better than most children’s schools. I was taught the way we all are, that fish evolved into amphibians that evolved into reptiles and so on –a system that seems to form a ladder of progress from primordial ooze to astronauts. The more I learned as a child, though, the more I realised the world was a very different place than that, and the more I wished for someone to teach the world as it was.

For example, as scientist Stephen Jay Gould said after a lifetime studying fish, “There’s no such thing as a fish.” Animals like lampreys, sharks, lungfish and anchovies are much further apart in the family tree of life than we are from, say, frogs or ducks, and our word “fish” reflects our convenience rather than their DNA. Even if we disregard animals that many people regard as fish (whales) or that share the name (shellfish, starfish) and concentrate only on animals with bones and gills that swim, we are still left with more variety than any land vertebrate. To use a metaphor, we know that bees, crows and bats all fly, but we don’t call them all birds.

The same is true of many of the easy categories we use to describe the world; by the same logic, there is no such thing as a reptile, or a bug, or a tree -- no tree family, and no "first tree" which produced all the others.

So I explained when she was very young that when amphibians first became able to lay eggs out of water – making them what we call reptiles – they divided into three groups, which we separate, strange as it might sound, by the number of holes in the skull. The main one at first were the synapsids (one hole), which grew giant and dominated the land for many millions of years, the first large animals to walk the Earth. Few people have any idea these sort-of-reptiles existed, as they have been completely overshadowed by the later dinosaurs – but they were not the ancestors of dinosaurs, or remotely related to them.

They were a fascinating bunch that The Girl loves to draw and talk about, but they almost all disappeared in the largest extinction event in Earth’s history – a series of volcanic tears in the skin of the world, much more destructive than the asteroid strike that killed the dinosaurs. It wiped almost all synapsids – and almost all everything else – off the world, leaving just a few tiny animals left over.

Some, the more obscure diapsids (two holes), grew and became the next great group of animals to dominate the world, the dinosaurs – and later, the birds. The few surviving synapsids laid low, remaining tiny and developing into something else over the eons …. the first mammals.

And anapsids – well, I tell The Girl, it looked like they would take over the world for a while, but they settled for being durable rather than powerful, effectively turning themselves inside-out so that their bones were on the outside and fusing them into armour. They couldn’t outrun anything anymore, but they rarely needed to – they were tortoises and turtles.

This might not seem like the most utilitarian information, but I think most children suffer from not understanding how the living world works. It makes a difference, at least to me, to know that we are not the top rung of a short ladder, but an outermost twig on the tree, cells in the body, a tiny patch of the ultimate work of art.

You might think such a lesson would make you feel small, but I didn’t find it so, nor did The Girl. It pleases us to know that the Creation’s jigsaw pieces fit together.  It liberates us to know that this work of art has survived worse things than our presence. And it’s sobers us to realise how often the artist paints over his work.   


Andy Brown said...

"how often the artist paints over his work." That's a beautiful and evocative phrase.

Brian Kaller said...

Thanks, Andy! Hope your spring is turning out well.