Top Down, or Bottom Up?

It’s been very warm here in middle England these last few days. So yesterday I went out and bought several trays of little plastic plant pots, 40 per tray, and a GroBag Plus of soil/compost. And today I half filled one tray with GroStuff, and sprinkled two or three of the tobacco seeds Leggy sent me into each pot, and covered them over with more GroStuff, and then watered them all thoroughly with warm water (I just somehow felt that the water needed to be warm). As an afterthought, remembering that Rose said she’d grown peppers from seeds, I planted one row of 5 pots with the seeds of a large red pepper that I’d chopped up yesterday, and another row with the seeds of a green chilli pepper that I’d also chopped up. Unfortunately, I neglected to mark which end of the tray had the pepper seeds in. So if they germinate and grow, I may well end up smoking dried pepper leaves.

I was going to germinate the tobacco seeds separately, on cotton wool or tissue, in a warm box. But I couldn’t find my thermostatic switch. It’s probably somewhere, buried at the bottom of some bag or box, but I don’t know where. But I read that Junican had successfully germinated seeds by just sticking them straight into pots, so I figured I’d try that method, after convincing myself that in the natural world that’s what happens. The tray is sitting indoors in a room at 20° C.  If it gets too chilly, I might put a hot water bottle under it. I’ve no idea how long to wait for green shoots to appear. A week or two is what I imagine.

My only other plant, the basil bush, is showing signs of growth. Tiny leaves have re-appeared on its stem where old leaves fell off, but only where the stem is green. No signs of new leaves on the brown woody stem further down.

It’s set me thinking about plants and animals, and reminded me of a question that was puzzling me last year, which was: do plants have a water circulation system? I know that water goes up from the roots through xylem pipes to the leaves, and sugary water goes down from leaves to roots through phloem pipes. But do the pipes join at top and bottom? I think they must do, but I’ve yet to read anywhere that they do.

After all, living things like animals have a circulation system. And for a long time the bright red blood in arteries was thought to be different from the dark red blood in veins, much like xylem and phloem. It was someone called Harvey who found out that the arteries and veins actually belonged to a single circulation system. That was in 1628, less than 400 years ago.

And water circulates on the surface of the Earth, evaporating by sunlight into the air, condensing into rainfall which flows down streams into wide rivers, which then fan out into deltas when they reach the sea. And since arteries and veins look very like rivers, I’ve been wondering whether they form in the same way as rivers. Nature doesn’t draw up plans of rivers, and drive stakes into the ground where it wants them to go, and then bring in bulldozers.  Rivers aren’t designed in that sort of top-down manner. They emerge out of a bottom-up logic, as individual drops of water roll downhill and merge into streams which carve rivers out of the ground. So why should blood circulation systems, which look just like rivers, emerge in any different way? Perhaps veins and arteries form in exactly the same way as rivers in the inner terrain of a living thing, with blood flowing downhill just like water. But then, rivers don’t have hearts, do they? Hearts are a bit of a puzzle.

I read today that a heart only starts beating in a human embryo 22 days after conception. So how does all the oxygen and glucose and water in blood get to the embryo’s cells before there’s a heart to pump it round? One answer might be that cells are tiny little pumps. After all, they’re little engines, pulling in glucose and oxygen, burning it, and pushing out carbon dioxide and water. And so maybe there’s enough power in all those little pumps to drive a circulation system for the first 22 days.

It’s a bit like boats. If you have a little boat, you can get around with a little outboard motor stuck on the back. And when you’ve got a bigger boat, you can put two outboard motors on it. I’ve seen boats with four outboard motors on the back end, all strapped together. But big ocean-going ships don’t have hundreds or thousands of outboard motors strapped to them. They have just one big engine. And the engine can be as big as a house. It’s more efficient using one big engine. It saves on fuel. Somehow or other, a developing embryo follows the same logic. It starts off with lots of little outboard motors in the form of its cells, and ends up with just one big engine – the heart. And the heart takes over the blood-pumping job from the cells, and relieves them of that work. So they don’t have to work quite so hard.

How many cells are there in an embryo after 22 days? I read somewhere today that human embryo cells divide every 8 hours or so. So they go 1, 2, 4, 8, 16, 32, 64, 128 and so on. And so every day there are 8 times as many of them as there were the previous day. That’s pretty near 10 times, and means that after 22 days, there’d be 10²²  cells. That’s 10,000,000,000,000,000,000,000 cells. But, hang on, I also read today that there are only 10¹³ cells in an adult human body. So embryo cell division rates must slow down a lot if women are to give birth to only 3.5 kg babies after 37 weeks of gestation. If not, pregnant women would simply explode a few weeks after conception. And their first baby would be their last baby. And in my theoretical model of ageing, cells are expected to slow their reproduction rate.

Anyway, today I’ve been toying with the idea that there’s no top-down blueprint design of living things, but instead a bottom-up emergence. Humans design things, but Nature doesn’t.

All this may seem utterly irrelevant, but in thinking about how 10 trillion cells come to form a single human body, with heart, arteries, veins, bones, muscles, etc, one is also thinking about how 7 billion humans might form a single global society or nation. Are human societies best ordered and arranged top-down or bottom-up? Our present lords and masters seem to think it’s done top-down. The EU is a piece of top-down political engineering. AGW is top-down authoritarian science, with the IPCC telling us all that we’ve got to cut our carbon emissions. And the smoking ban is a piece of top-down social engineering too. They have drawn up their blueprint, and we’re all supposed to fit into it.

And signs are these days that their plans are all beginning to go wrong.