Science shuts its eyes to evidence

Stephen Rothman is a cell biologist who has been dedicated to understanding how cells function since the early 1960s. At Harvard Medical School and the University of California, San Francisco, he and his students were at the heart of one of the most exciting epochs in 20th-century biology: the era of molecular biology, roughly 1960-90, after which we enter the age of the genome. In this period, biology was rewritten in terms of the basic molecular processes and constituents of cells: DNA replication, transcription, translation of genes to produce proteins, assembly of proteins and other macromolecules into organelles, and the formation of biological membranes with their remarkable properties of selective transport of molecules into and out of the cell.

It was questions about the transport of proteins through cells from their sites of synthesis near the nucleus to their secretion across the cell membrane that preoccupied Rothman. And it was in this arena that he learnt that science is not practised according to the principles that he and most scientists believe to characterise it as the unique achievement of modernity. The story of his rude awakening is told in Lessons from the Living Cell .

Young scientists are encouraged to believe that experimental evidence always comes first in scientific judgements; that the evidence is scrutinised for consistency with any current working hypothesis, which is abandoned and replaced by another if serious anomalies are repeatedly observed. Science is also portrayed as being free of irrational dogma. Rothman found that this is not the case. Experimental science is pursued in accordance with "paradigms", models that put together a selected set of "facts" into coherent, logical stories. These guide research and the interpretation of evidence. The dominant tendency is not to test models and see if they hold up to new evidence but to fit the evidence into the accepted models. Evidence is interpreted to save the model, not to test it.

Rothman gives copious examples from his research to show this. He and his colleagues produced evidence that the dominant theory of protein transport through cells and its secretion across membranes, the vesicle theory, was inconsistent with their observations that proteins can cross membranes independently of enclosure in vesicles. They also found evidence that rates of protein secretion did not correlate with vesicle number, as expected by the accepted theory, among other observations that put the theory in question. But there are many ways to save a hypothesis, and Rothman encountered these repeatedly from the dominant theory's proponents.

Rothman's most scathing criticism of dogma in biology focuses on what he calls the "strong micro-reductionist principle": the belief that all the properties of living cells can be accounted for by a knowledge of their molecular components and their interactions. There is no evidence for this. No one has succeeded in reassembling a living cell from its molecular constituents. What is missing? The cells' organisation in space and time. However, organisation cannot be isolated and bottled. Understanding it requires close attention to the living cell: biology must be done on life - cells and organisms - not on the cells' dead parts. And where does this organisation come from? We have to go back to the origin of life, Rothman says. The organisation of the living state arose accidentally and spontaneously with the first cells and has been transmitted from cell to cell ever since.

I have reservations about this book's presentation and organisation. After every bit of conflicting evidence is presented, Rothman rehearses the strong micro-reductionist principle and the logical dangers of paradigms and fashions ad nauseam . He knows about Thomas Kuhn and the role of paradigms in "normal science". However, he did not expect biologists to be quite so irrationally committed to them. The book has an air of complaint and frustration that gets tiresome after 200 pages or so. Science is about stories, models that help people explore the world and make a career out of their work. It is also about power and authority. Rothman failed to tell a consistent story about protein transport and secretion that allowed others to make a living out of its exploration.

The amazing thing is that, despite the failings of its human practitioners, science works. It is, eventually, self-correcting. We just have to give reductionists and genetic determinists enough rope and they will hang themselves on self-contradictions. Then biologists will again focus on the living state and understand their parts within this organised context. Just hang in a little longer, Dr Rothman, and things will end up closer to your biological convictions.

Brian Goodwin is a visiting scholar, Schumacher College, Dartington, Devon.