After half a lifetime of hill walking and scientific field trips, Steve Jones decided 10 years ago that it was time to stop confronting the forces of nature and start working with them. "I mean, what's the point of fighting gravity?" he says.
"So rather than climbing up mountains, I decided to come down rivers and, as somebody who was born in Wales and spent years there, I conceived the notion of walking down all the rivers of Wales. I haven't done it yet, but I've done quite a few of them.
"And it's a real pleasure, because you start off in the harsh and difficult neck of the woods, when you're feeling fresh, and you end up at the sea, where there's always a nice pub, rather than at the top of a mountain where you have to walk the whole bloody way down again."
His favourite so far is the Afon Ystwyth, which starts in the Plynlimon massif of mid-Wales, also the source of the Wye and Severn. The area is close to his heart as Professor of Genetics at University College, London, because he has some Y-chromosome genes which show that the Welsh have a common male ances try with people in the Basque country of northern Spain.
The river emerges from a peat bog and works its way down through a little-known area heavily used for lead and silver mining from Roman times until the 19th century.
As a geneticist, Jones takes a special interest in the way local plants have adapted to pollution by heavy metals. "It's nice to think when you're walking through these places with just a bit of scrappy grass on them, that it's all evolved by a process of natural selection. Plants from those mines have been taken and bred together to make a super-strain, which has been used to re-seed mines around the world."
Next comes the social history: this part of Wales was always poor, but many valleys have large and imposing houses where the mine-owners lived. Half-way down the Ystwyth valley is Trawsgoed (Crosswood in English), an elegant Georgian structure that was home to the wealthy Vaughan family before being taken over by the University of Wales.
From there, the river continues through the beautiful, if rainy, Welsh landscape and reaches the sea at Aberystwyth by an Iron Age hill fort called Pen Dinas. Jones was born within a few hundred yards of it and ending the day there has "another kind of resonance".
"The walk starts off gloomy and atmospheric and ends up fairly idyllic. The great strength of many of these Welsh river walks is simply that nobody ever does them. There are honeypots, but people never go more than a few hundred yards from the car, so you can be a whole day without seeing anyone.
"It's not the Lakes or Snowdonia, where there are fantastic features you can point to. It's just the general atmosphere of being relatively unspoilt.
"Rivers are always moving, and their mouths are always moving. As a biologist and a geneticist and an evolutionist, you're aware of this balance between what seems static but is in fact always changing, and a river is the constant image of that. Herodotus said: 'No man can stand in the same river twice'.
"And that's the kind of truth I like to get about walking down rivers. I'm not one of those people who has this false and romantic image of the landscape being unchanging. It's always changing, and it always will."
Hard times in the hills
The Vaughans of Trawsgoed were the greatest landowners of the county of Cardiganshire from the 14th to the 20th century. They owned the local lead and silver mines and used the proceeds to build a mansion surrounded by woods and parkland.
But they were originally from England, and their exploitation of the land and treatment of the local people was rarely enlightened. They declined to learn Welsh or invest in the welfare of their workers and tenants, and Prof Jones calls them "classic grinders of the faces of the poor".
"There are all kinds of legends about them and it was claimed that if they wanted to get rid of an awkward tenant, they would drop a sheep on a rope down his chimney at night, then suddenly attack the house and find the sheep.
"Then the tenant would be found guilty of sheep stealing and hanged. There were various riots as a result, none of which made much impact on history, but which are interesting to me because one side of my own family were small farmers in that area."
The house was taken over in the 20th century by the University of Wales for its Grassland Research Station, which made a major contribution to developing strains of grass for the rehabilitation of mining sites.
The following appology was printed in the Guardian's Corrections and Clarifications column, Tuesday June 27, 2000
In this article, we recommended a book, A Welsh House and its Family: The Vaughans of Trawsgoed, by Gerald Morgan. Mr Morgan has pointed out that the accompanying article included a number of mistakes from which a reading of his book should have saved us.
Among these were our statement that the Vaughans were the largest landowners in Cardiganshire from the 14th to the 20th centuries (that should have been the 17th to 20th centuries); that the Vaughans never learned Welsh (they were a Welsh-speaking family until the 18th century); that their former home was taken over by the University of Wales (it never was); that it became a Grassland Research Station (it did not: it was bought by the government in 1947 and became the Welsh headquarters of the Agricultural Development and Advisory Service).
Part of the farmland originally belonging to Trawsgoed (but not the mansion itself) is now run by IGER (Institute for Grassland and Environmental Research). Apologies for all that.
