Earthworm clues - Charles Darwin.
One of Charles Darwin's lesser known scientific contributions was the study of the humble earthworm. But could his work on this underground creature provide valuable clues about the ancient site of Stonehenge?
The earthworm plays a crucial role in improving soil fertility as it burrows beneath the ground.
Its work helps us to live in a green and pleasant land as the worms aerate the soil.
But as Darwin discovered, worms are also surprisingly good friends to archaeologists.
Today this humble beast is providing clues about the history of Stonehenge and its surrounding countryside.
Darwin's studies of earthworms at Stonehenge involved some of the first scientifically recorded excavations at the site.
They're unusual because they were carried out not by an archaeologist, but by a naturalist.
Darwin was interested in the action of earthworms in burying objects.
Earthy solutions - the humble earthworm.
It's the continual processes of burrowing, digesting and excreting the soil by earthworms that gradually leads to objects settling down in the soil.
In some cases they become completely buried by it.
Dr Josh Pollard, one of the directors of the Stonehenge Riverside Project, has been assessing the importance of Darwin's worm experiments at the ancient site.
Pollard thinks he's identified a fallen stone on the outside of the circle, and one that was split in two, as the subject of Darwin's book - "Vegetable Mould and Earthworms".
The book features a picture of the ground which had built up around the fallen stone and describes how the stone had sunk into the soil profile:
"At Stonehenge, some of the outer Druidical stones are now prostrate, and these have become buried to a moderate depth in the ground."
Darwin discovered that earthworms are rather like archaeological JCB diggers.
They eat the earth, it goes through their muscular tube, and comes out the other end as worm casts.
This is where the earthworms interact with archaeology.
Stonehenge - clues in the earth.
The cumulative effect of millions of worms in a field chewing their way through the soil and depositing it on the surface is that they actually raise the surface of the soil.
Darwin worked out that the soil increased in depth by 0.2 of an inch per year.
After 10 years an object in the soil will go down two inches, and after 1,000 years it will reduce down 200 inches.
The result on the ground is that things disappear and gently sink into the soil.
To test this theory Dr Josh Pollard visited the site of one of his old excavations - the remains of a Saxon village on a farm overlooking Cheddar in Somerset.
Since his last visit a decade ago the landscape has changed - and it's down to the efforts of the earthworms which have worked their magic.
Latin name - Lumbricus terrestris.
Play an important role in fertilising the soil by bringing nutrients closer to the surface.
Worms comprise numerous small segments or 'annuli' covered in minute hairs that grip the soil. These enable the worm to move as it contracts its muscles.
Live in soil at depths of up to 2m. Feed on decaying organic matter in the soil.
The worms excrete digested material as worm casts and these can be seen as clumps of mud at the surface of the soil. These are very rich in nutrients.
Earthworms are hermaphrodite and have both male and female reproductive cells.
Source: BBC Nature
Earth shattering clues?
So should archaeologists be worried about the impact of earthworms?
Dr Josh Pollard says:
"When you're finding small objects through the layer, they needn't have started out in that layer, they may have started out higher up in the slightly later layer.
"But worms have gradually taken those small objects or maybe small pieces of charcoal or other material that we might actually use for things like radio carbon dating, down through the layers."
So does this and Darwin's research mean that the dating of Stonehenge, could be completely wrong?
And could the activities of earthworms continue to alter the landscape of Stonehenge in 100 year's time as objects and stones sink deeper into the ground and get covered by soil?
To modern minds Darwin's work on natural selection was far more important than his study of the humble earthworm.
But to archaeologists he founded the modern science of soil, and provided some clues about the changing landscape around Stonehenge.
last updated: 25/02/2009 at 17:54