Rivers never flow uphill

As a youth in my native Grafton, I didn't think of myself as somebody who might be particularly interested in the flow of rivers. That's because I happened to be living alongside the great Clarence River, which I used to see so regularly (usually from afar) that I finished by no longer noticing it. I had grown up in the aftermath of the tragic December 1943 drowning of 13 boys, junior (cub) members of the local troop of Boy Scouts. As a child of ten or so, I had witnessed the damage waged by the waters of the Clarence in a disastrous flood. Later, I rowed in school races (in "fours") in the shadow of the antique double-decker bridge, over which I used to ride my bicycle regularly.

To paraphrase the well-known forest/trees saying, I simply didn't see the river because of the water. Much later, in Paris, I learned that a river has a left bank and a right bank.

The common-sense adjectives "left" and "right" are so much more tangible, for people living alongside a great river, than the theoretical notions of north and south. So, I had passed my childhood in right-bank Waterview (South Grafton) before moving across to our new left-bank residence in Kent Street (Grafton).

Since arriving here at Choranche, on the edge of the French Alps, I've come to appreciate the sense of the adjectives upstream and downstream. The Bourne flows down from Villard-de-Lans.  Choranche is located on the right bank, and Châtelus on the left. And Pont-en-Royans is a little further downstream. It's a bit like seasons. Back in Australia, I hardly knew what they were all about. These days, at Gamone, they determine my daily existence.

There's another realm, of a theoretical kind, in which we must be aware of the direction of flow. I'm referring to the flow of information and scientific knowledge. Just as rivers never flow in an upstream direction, information and knowledge always flow in a unique direction: downwards from X to Y, say, but never upwards from Y to X.

This was one of the great lessons taught by Karl Popper when he demolished the time-honored but absurd notion that an understanding of the laws of the natural universe can be acquired miraculously when knowledge flows spontaneously, indeed magically, from the natural phenomena being examined by a researcher up into the scientist's mind. This mysterious process, referred to as induction, was a part of established science back in my student days. Since Popper, we realize that a new understanding of the ways in which various natural phenomena unfold can arise in the mind of a brilliant scientist. This knowledge then flows down into other human minds, enabling the newly-imagined explanations to be applied to the natural phenomena that inspired the creative scientist, for verification (best possible case) or for rejection (worst-case scenario).

Two centuries ago, in the domain of the evolution of living organisms, a great and ancient "river" of a physiological kind was thought of as capable, from time to time, of flowing uphill.

 Jean-Baptiste Lamarck considered that a living creature could transmit to its offspring various characteristics acquired during the parent's earthly existence. Take the case of a primitive giraffe, many millennia ago, at a time when giraffes still had relatively short necks, since they could find all the leaves they needed quite close to the ground. Let's suppose that a couple of giraffes were having a serious discussion about the idea of having a baby.

Mr Giraffe: There's only one thing that worries me, dear. Due to global warming, there's no longer any grass around. So, we're forced to eat leaves. But there are fewer and fewer leaves at a low level. Soon, to reach the high leaves and survive, giraffes will need to have longer and longer necks.

Mrs Giraffe: My dear husband, I agree with you entirely. But, if our future baby needs an exceptionally long neck to find food, then we must make sure that he's born with such a neck. There are no two ways about it.

Mr Giraffe: OK, but how can we make sure that his neck will be long enough for him to survive?

Mrs Giraffe: We must pray, my dear husband, and implore our Good Giraffe God to perform a miraculous intervention of genetic engineering.

So, that's what they did. And, soon after, biological information from the parched earth flowed up through the tree trunks, past the bare branches at the bottom of the trees, until it reached the level of the luscious greenery. And, from there, this precious information—dealing primarily with the complex procreative question of how to produce giraffe embryos with long necks—was consumed and digested by Mrs Giraffe… who suddenly felt a glowing long-necked warmth in her womb. The miracle was taking place!

We now know that Lamarckism was totally wrong, but it was never, at any stage, a completely crazy belief. Even today, when tourists halt for a moment alongside the lovely old thatched house in Pont-en-Royans [display], and chat with the village blacksmith and his son, they are invariably impressed by their giant strong hands, which have been  photographed in closeup on countless mobile phones.

Blacksmith: My ancestors have been blacksmiths here at Pont-en-Royans for countless generations, and the blacksmiths' sons and daughters have always married the offspring of other blacksmiths in neighboring villages. And the gnarled hands of our kids, today, reveal the traces of all those centuries of hard work at the forge.

Who could possibly doubt the truth of the good man's words? His strong hands have been shaped, over the centuries, by a mysterious process of divinely-ordained genetic engineering that seems to "understand" that future blacksmiths need to inherit the hands, not merely of their forefathers, but of their forefathers' trade! This knowledge has flowed up from the forge to the uterus of every young lady chosen to become the mother of a future blacksmith. It's all a bit like the Nazarene carpenter's wife, who had received knowledge informing her that she would be giving birth to the Lord.

The only flaw in these nice and convincing tales is that knowledge about a future offspring never needs to flow into an embryo, because the zygote formed from the pair of gametes provided by the parents of a future member of the blacksmith dynasty contains all the information that it is required to forge a new human being. And, if the baby blacksmith looks as if he has inherited gnarled hands, that merely means that at least one of his parents had gnarled hands. And that characteristic had nothing to do with their daily occupations. Even if the latest generations of the baby's ancestors had all decided to transform their ancient forges into tourist boutiques, they would still have been born with gnarled hands. Inheritance specifications never flow upwards from a blacksmith's forge to human parents and their babies. They are transmitted, through chromosomes, from parents down to their offspring. Rivers never flow uphill.

This metaphor of information flow applied both to Karl Popper's views on induction and to Lamarck's views on inheritance was developed at length by David Deutsch, of Oxford.

His article Selfish Genes and Information Flow appeared in the collection entitled Richard Dawkins, How a Scientist Changed the Way We Think, Oxford University Press, 2006.