Updating the Origin
Charles Darwin was painfully aware of the gaps in the fossil record, and hoped that they’d be filled by later generations. They have been, in part using techniques that Darwin couldn’t have imagined, while new discoveries have taken the record’s starting point back even further.
Friday February 27th. The major challenge posed to supporters of evolutionary theory has always been to “prove it”. In addressing that issue the BRLSI’s Darwin and Beyond series is very fortunate to have Bristol University’s Earth Sciences department close by. On January 30th Professor Michael Benton took us through the Key Stages in the History Life, telling how we evolved from the ‘sludge’ into today’s complex organisms. Tonight his colleague Dr Phil Donoghue tackled the thorny question of the gaps in the fossil record which, in Darwin’s time, appeared to undermine Darwin’s claim of a continuous ‘tree of life’ linking all current life forms back to the earliest examples.
Dr Donohue began with the good news that the gaps in the fossil records have now, indeed, been filled. Much of this has been done by the method Darwin anticipated, namely to ‘keep hammering away at the rocks’, but the discovery of DNA and advances in embryology, assisted by technology such as the electron microscope and magnetic scanning systems, have also played their part, with many ‘fossils’ still alive today in genetic codes and stages of embryonic development. The result is a 21st century tree of life diagram (stylishly presented in a form reminiscent of the outer reaches of the London Underground map) that shows the intermediate stages between all the fossils known in Darwin’s time.
There is, however, a problem in discovering fossils of really primitive, pre-vertebrate life forms, in that they tend to ‘decay to snot’ (as Dr Donohue delicately put it) leaving no trace behind. But here Dr Donohue had been involved in a remarkable discovery - fossilised embryos, 580 million years old, found in rocks in China and elsewhere. Half a millimetre across and found in tiny quantities (40 tons of Chinese rock yielded less than a gramme of them), non-destructive scanning has revealed fascinating details of their interiors, including one example that had grown to 1,000 cells without any specialised tissue development, a phenomenon unknown in anything alive today.
Embryos normally decompose in a matter of hours, and as yet no-one knows why these ones stayed intact long enough to fossilise, or whether they represent successful life forms of their time (as one questioner put it, they were dead before maturity and thus failed examples of life). They are, however, the earliest preserved life forms yet discovered, and as such a major advance towards the real starting point of life. The search for the full history of life on Earth goes on. •
Friday February 27th. The major challenge posed to supporters of evolutionary theory has always been to “prove it”. In addressing that issue the BRLSI’s Darwin and Beyond series is very fortunate to have Bristol University’s Earth Sciences department close by. On January 30th Professor Michael Benton took us through the Key Stages in the History Life, telling how we evolved from the ‘sludge’ into today’s complex organisms. Tonight his colleague Dr Phil Donoghue tackled the thorny question of the gaps in the fossil record which, in Darwin’s time, appeared to undermine Darwin’s claim of a continuous ‘tree of life’ linking all current life forms back to the earliest examples.
Dr Donohue began with the good news that the gaps in the fossil records have now, indeed, been filled. Much of this has been done by the method Darwin anticipated, namely to ‘keep hammering away at the rocks’, but the discovery of DNA and advances in embryology, assisted by technology such as the electron microscope and magnetic scanning systems, have also played their part, with many ‘fossils’ still alive today in genetic codes and stages of embryonic development. The result is a 21st century tree of life diagram (stylishly presented in a form reminiscent of the outer reaches of the London Underground map) that shows the intermediate stages between all the fossils known in Darwin’s time.
There is, however, a problem in discovering fossils of really primitive, pre-
Embryos normally decompose in a matter of hours, and as yet no-
© Bath Royal Literary and Scientific Institution 2008 • Contact Us
Dr Phil Donohue of Bristol University showing fossilised teeth on a pinhead, photographed through an electron microscope. Modern technology has enabled major advances in fossil research.
LECTURE REPORT - THE IMPERFECTION OF THE FOSSIL RECORD
Dr Donohue (right) with David Cunliffe-Jones, BRLSI’s Science Group Convenor.
It’s all changed since Darwin’s time. The first tree of life diagrams, produced in the 19th century, actually resembled trees. 21st Century trees are more stylish and logical, albeit with a hint of London Underground to them.
