Debate

The fossil record contains many gaps and the quality of sampling can vary immensely over time and among taxa. But, argues Dr Peter Wagner, when constructing phylogenies no source of information should be ignored. The challenge is knowing how to weight such data.

If the fossil record cannot provide definitive answers to evolutionary questions perhaps we should be looking elsewhere. Dr Blair Hedges proposes that investigating gene sequences can reveal what fossils cannot.

Amoung the e-mails sent to the debate in the first week is the following, which asks the question "The fossil record-adequate for what?"

The timing of evolutionary events can be estimated from both fossil and molecular data, but what if these methods do not agree? Dr Jan Pawlowski and Colomban de Vargas argue that it may not always be the fossil record that is inadequate.

Dr Andrew Smith, moderator for this debate, introduces the topic and the conflicting viewpoints that surround it.

Whatever the quality of the fossil record it must contain information about time of a species' genesis and extinction. Professor Charles Marshall holds that we should not ignore this information but rather find ways to incorporate it in a 'total evidence' approach.

The fossil record may not be complete for all groups at all times and in all places. But, argues Dr Paul Pearson, when we have reason to believe that it is, the dates that can be assigned to fossils are invaluable for unravelling the paths of evolution.

Can we identify fossil ancestors of species alive today? Dr Mark Siddall contends that this is impossible and that the use of stratigraphic data when assembling phylogenies is thus unsupportable.

In the final week of this first Nature debate the moderator, Mike Wilkinson, draws together the main threads that have run through the contributions.

To date, the e-mail responses to this debate have represented both sides of the argument. However, very few have raised significant points not already covered by the official contributors. Those that have appear broadly in favour of the technology.

In an area so politically sensitive and publicly emotive as genetic modification ecologists should look before leaping in with slight and inconclusive data, argues Professor Alan Gray. To assess risk we must first look to the hazards...

Alongside the environmental risks of using genetically modified crops are the public health concerns. These may be easier to assess but are of no lesser importance.

The time for discussing possible consequences of GMO releases is over. Instead, the focus of assessment must now be on how and why they are actually being put to use.

Mike Wilkinson, moderator for this, the first of the Nature Debates, surveys the terrains on which conflicting interests will do battle.

Increasingly disturbed by potential risks and sceptical of the claimed benefits, green activists want an end to the scientific uncertainties in risk assessment. But, argues Julie Hill from the UK's Green Alliance, this also requires a broad consensus on what actually constitutes environmental harm.

The answer to the question, "Will this product have an impact on the environment?" is almost always "Yes". But it is not the most important question, says the Ecological Risk Assessment Group from Oxford. Instead we should be asking, "Will it result in more or less harm than the current conventional alternatives?"