Geological time

MADAM,Your evolution word over my letter of last week was an unneccssary complication which could unfortunately sidetrack my fascinating little salamander into a fruitless argument with all the nuts in Kentucky. In fact, he could teach us a great deal without any need at all of Charles Darwin.

In the past 150 years, the general sequence of rock strata, worldwide, has been established very nearly beyond question. More recently it has become possible to radio-metrically date the intervening lava flows at the various levels.

So we can fairly confidently put a date on, say, the yellow Downton Castle sandstone in the walls of Gorsley chapel, and a slightly earlier date on its Aymestry limestone mortar. Between the two, in the Ludlow area, came what used to be known as the Ludlow Bone Beds; and these represent the remains of a multitude of fish that suddenly ran out of water - about 410 million years ago.

A better bet for the first chap crawling about on land might be 50 million years later - when there was plenty of greenery to feed on. But there is still no need to disturb Darwin.

K Horne, Gorsley